// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Linux Socket Filter - Kernel level socket filtering
 *
 * Based on the design of the Berkeley Packet Filter. The new
 * internal format has been designed by PLUMgrid:
 *
 *      Copyright (c) 2011 - 2014 PLUMgrid, http://plumgrid.com
 *
 * Authors:
 *
 *      Jay Schulist <jschlst@samba.org>
 *      Alexei Starovoitov <ast@plumgrid.com>
 *      Daniel Borkmann <dborkman@redhat.com>
 *
 * Andi Kleen - Fix a few bad bugs and races.
 * Kris Katterjohn - Added many additional checks in bpf_check_classic()
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/fcntl.h>
#include <linux/socket.h>
#include <linux/sock_diag.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/if_packet.h>
#include <linux/if_arp.h>
#include <linux/gfp.h>
#include <net/inet_common.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/netlink.h>
#include <linux/skbuff.h>
#include <linux/skmsg.h>
#include <net/sock.h>
#include <net/flow_dissector.h>
#include <linux/errno.h>
#include <linux/timer.h>
#include <linux/uaccess.h>
#include <asm/unaligned.h>
#include <asm/cmpxchg.h>
#include <linux/filter.h>
#include <linux/ratelimit.h>
#include <linux/seccomp.h>
#include <linux/if_vlan.h>
#include <linux/bpf.h>
#include <net/sch_generic.h>
#include <net/cls_cgroup.h>
#include <net/dst_metadata.h>
#include <net/dst.h>
#include <net/sock_reuseport.h>
#include <net/busy_poll.h>
#include <net/tcp.h>
#include <net/xfrm.h>
#include <net/udp.h>
#include <linux/bpf_trace.h>
#include <net/xdp_sock.h>
#include <linux/inetdevice.h>
#include <net/inet_hashtables.h>
#include <net/inet6_hashtables.h>
#include <net/ip_fib.h>
#include <net/flow.h>
#include <net/arp.h>
#include <net/ipv6.h>
#include <net/net_namespace.h>
#include <linux/seg6_local.h>
#include <net/seg6.h>
#include <net/seg6_local.h>
#include <net/lwtunnel.h>
#include <net/ipv6_stubs.h>
#include <net/bpf_sk_storage.h>

/**
 *      sk_filter_trim_cap - run a packet through a socket filter
 *      @sk: sock associated with &sk_buff
 *      @skb: buffer to filter
 *      @cap: limit on how short the eBPF program may trim the packet
 *
 * Run the eBPF program and then cut skb->data to correct size returned by
 * the program. If pkt_len is 0 we toss packet. If skb->len is smaller
 * than pkt_len we keep whole skb->data. This is the socket level
 * wrapper to BPF_PROG_RUN. It returns 0 if the packet should
 * be accepted or -EPERM if the packet should be tossed.
 *
 */
int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap)
{
        int err;
        struct sk_filter *filter;

        /*
         * If the skb was allocated from pfmemalloc reserves, only
         * allow SOCK_MEMALLOC sockets to use it as this socket is
         * helping free memory
         */
        if (skb_pfmemalloc(skb) && !sock_flag(sk, SOCK_MEMALLOC)) {
                NET_INC_STATS(sock_net(sk), LINUX_MIB_PFMEMALLOCDROP);
                return -ENOMEM;
        }
        err = BPF_CGROUP_RUN_PROG_INET_INGRESS(sk, skb);
        if (err)
                return err;

        err = security_sock_rcv_skb(sk, skb);
        if (err)
                return err;

        rcu_read_lock();
        filter = rcu_dereference(sk->sk_filter);
        if (filter) {
                struct sock *save_sk = skb->sk;
                unsigned int pkt_len;

                skb->sk = sk;
                pkt_len = bpf_prog_run_save_cb(filter->prog, skb);
                skb->sk = save_sk;
                err = pkt_len ? pskb_trim(skb, max(cap, pkt_len)) : -EPERM;
        }
        rcu_read_unlock();

        return err;
}
EXPORT_SYMBOL(sk_filter_trim_cap);

BPF_CALL_1(bpf_skb_get_pay_offset, struct sk_buff *, skb)
{
        return skb_get_poff(skb);
}

BPF_CALL_3(bpf_skb_get_nlattr, struct sk_buff *, skb, u32, a, u32, x)
{
        struct nlattr *nla;

        if (skb_is_nonlinear(skb))
                return 0;

        if (skb->len < sizeof(struct nlattr))
                return 0;

        if (a > skb->len - sizeof(struct nlattr))
                return 0;

        nla = nla_find((struct nlattr *) &skb->data[a], skb->len - a, x);
        if (nla)
                return (void *) nla - (void *) skb->data;

        return 0;
}

BPF_CALL_3(bpf_skb_get_nlattr_nest, struct sk_buff *, skb, u32, a, u32, x)
{
        struct nlattr *nla;

        if (skb_is_nonlinear(skb))
                return 0;

        if (skb->len < sizeof(struct nlattr))
                return 0;

        if (a > skb->len - sizeof(struct nlattr))
                return 0;

        nla = (struct nlattr *) &skb->data[a];
        if (nla->nla_len > skb->len - a)
                return 0;

        nla = nla_find_nested(nla, x);
        if (nla)
                return (void *) nla - (void *) skb->data;

        return 0;
}

BPF_CALL_4(bpf_skb_load_helper_8, const struct sk_buff *, skb, const void *,
           data, int, headlen, int, offset)
{
        u8 tmp, *ptr;
        const int len = sizeof(tmp);

        if (offset >= 0) {
                if (headlen - offset >= len)
                        return *(u8 *)(data + offset);
                if (!skb_copy_bits(skb, offset, &tmp, sizeof(tmp)))
                        return tmp;
        } else {
                ptr = bpf_internal_load_pointer_neg_helper(skb, offset, len);
                if (likely(ptr))
                        return *(u8 *)ptr;
        }

        return -EFAULT;
}

BPF_CALL_2(bpf_skb_load_helper_8_no_cache, const struct sk_buff *, skb,
           int, offset)
{
        return ____bpf_skb_load_helper_8(skb, skb->data, skb->len - skb->data_len,
                                         offset);
}

BPF_CALL_4(bpf_skb_load_helper_16, const struct sk_buff *, skb, const void *,
           data, int, headlen, int, offset)
{
        u16 tmp, *ptr;
        const int len = sizeof(tmp);

        if (offset >= 0) {
                if (headlen - offset >= len)
                        return get_unaligned_be16(data + offset);
                if (!skb_copy_bits(skb, offset, &tmp, sizeof(tmp)))
                        return be16_to_cpu(tmp);
        } else {
                ptr = bpf_internal_load_pointer_neg_helper(skb, offset, len);
                if (likely(ptr))
                        return get_unaligned_be16(ptr);
        }

        return -EFAULT;
}

BPF_CALL_2(bpf_skb_load_helper_16_no_cache, const struct sk_buff *, skb,
           int, offset)
{
        return ____bpf_skb_load_helper_16(skb, skb->data, skb->len - skb->data_len,
                                          offset);
}

BPF_CALL_4(bpf_skb_load_helper_32, const struct sk_buff *, skb, const void *,
           data, int, headlen, int, offset)
{
        u32 tmp, *ptr;
        const int len = sizeof(tmp);

        if (likely(offset >= 0)) {
                if (headlen - offset >= len)
                        return get_unaligned_be32(data + offset);
                if (!skb_copy_bits(skb, offset, &tmp, sizeof(tmp)))
                        return be32_to_cpu(tmp);
        } else {
                ptr = bpf_internal_load_pointer_neg_helper(skb, offset, len);
                if (likely(ptr))
                        return get_unaligned_be32(ptr);
        }

        return -EFAULT;
}

BPF_CALL_2(bpf_skb_load_helper_32_no_cache, const struct sk_buff *, skb,
           int, offset)
{
        return ____bpf_skb_load_helper_32(skb, skb->data, skb->len - skb->data_len,
                                          offset);
}

BPF_CALL_0(bpf_get_raw_cpu_id)
{
        return raw_smp_processor_id();
}

static const struct bpf_func_proto bpf_get_raw_smp_processor_id_proto = {
        .func           = bpf_get_raw_cpu_id,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
};

static u32 convert_skb_access(int skb_field, int dst_reg, int src_reg,
                              struct bpf_insn *insn_buf)
{
        struct bpf_insn *insn = insn_buf;

        switch (skb_field) {
        case SKF_AD_MARK:
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);

                *insn++ = BPF_LDX_MEM(BPF_W, dst_reg, src_reg,
                                      offsetof(struct sk_buff, mark));
                break;

        case SKF_AD_PKTTYPE:
                *insn++ = BPF_LDX_MEM(BPF_B, dst_reg, src_reg, PKT_TYPE_OFFSET());
                *insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg, PKT_TYPE_MAX);
#ifdef __BIG_ENDIAN_BITFIELD
                *insn++ = BPF_ALU32_IMM(BPF_RSH, dst_reg, 5);
#endif
                break;

        case SKF_AD_QUEUE:
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, queue_mapping) != 2);

                *insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
                                      offsetof(struct sk_buff, queue_mapping));
                break;

        case SKF_AD_VLAN_TAG:
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);

                /* dst_reg = *(u16 *) (src_reg + offsetof(vlan_tci)) */
                *insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
                                      offsetof(struct sk_buff, vlan_tci));
                break;
        case SKF_AD_VLAN_TAG_PRESENT:
                *insn++ = BPF_LDX_MEM(BPF_B, dst_reg, src_reg, PKT_VLAN_PRESENT_OFFSET());
                if (PKT_VLAN_PRESENT_BIT)
                        *insn++ = BPF_ALU32_IMM(BPF_RSH, dst_reg, PKT_VLAN_PRESENT_BIT);
                if (PKT_VLAN_PRESENT_BIT < 7)
                        *insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg, 1);
                break;
        }

        return insn - insn_buf;
}

static bool convert_bpf_extensions(struct sock_filter *fp,
                                   struct bpf_insn **insnp)
{
        struct bpf_insn *insn = *insnp;
        u32 cnt;

        switch (fp->k) {
        case SKF_AD_OFF + SKF_AD_PROTOCOL:
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);

                /* A = *(u16 *) (CTX + offsetof(protocol)) */
                *insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
                                      offsetof(struct sk_buff, protocol));
                /* A = ntohs(A) [emitting a nop or swap16] */
                *insn = BPF_ENDIAN(BPF_FROM_BE, BPF_REG_A, 16);
                break;

        case SKF_AD_OFF + SKF_AD_PKTTYPE:
                cnt = convert_skb_access(SKF_AD_PKTTYPE, BPF_REG_A, BPF_REG_CTX, insn);
                insn += cnt - 1;
                break;

        case SKF_AD_OFF + SKF_AD_IFINDEX:
        case SKF_AD_OFF + SKF_AD_HATYPE:
                BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4);
                BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, type) != 2);

                *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, dev),
                                      BPF_REG_TMP, BPF_REG_CTX,
                                      offsetof(struct sk_buff, dev));
                /* if (tmp != 0) goto pc + 1 */
                *insn++ = BPF_JMP_IMM(BPF_JNE, BPF_REG_TMP, 0, 1);
                *insn++ = BPF_EXIT_INSN();
                if (fp->k == SKF_AD_OFF + SKF_AD_IFINDEX)
                        *insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_TMP,
                                            offsetof(struct net_device, ifindex));
                else
                        *insn = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_TMP,
                                            offsetof(struct net_device, type));
                break;

        case SKF_AD_OFF + SKF_AD_MARK:
                cnt = convert_skb_access(SKF_AD_MARK, BPF_REG_A, BPF_REG_CTX, insn);
                insn += cnt - 1;
                break;

        case SKF_AD_OFF + SKF_AD_RXHASH:
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);

                *insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_CTX,
                                    offsetof(struct sk_buff, hash));
                break;

        case SKF_AD_OFF + SKF_AD_QUEUE:
                cnt = convert_skb_access(SKF_AD_QUEUE, BPF_REG_A, BPF_REG_CTX, insn);
                insn += cnt - 1;
                break;

        case SKF_AD_OFF + SKF_AD_VLAN_TAG:
                cnt = convert_skb_access(SKF_AD_VLAN_TAG,
                                         BPF_REG_A, BPF_REG_CTX, insn);
                insn += cnt - 1;
                break;

        case SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT:
                cnt = convert_skb_access(SKF_AD_VLAN_TAG_PRESENT,
                                         BPF_REG_A, BPF_REG_CTX, insn);
                insn += cnt - 1;
                break;

        case SKF_AD_OFF + SKF_AD_VLAN_TPID:
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_proto) != 2);

                /* A = *(u16 *) (CTX + offsetof(vlan_proto)) */
                *insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
                                      offsetof(struct sk_buff, vlan_proto));
                /* A = ntohs(A) [emitting a nop or swap16] */
                *insn = BPF_ENDIAN(BPF_FROM_BE, BPF_REG_A, 16);
                break;

        case SKF_AD_OFF + SKF_AD_PAY_OFFSET:
        case SKF_AD_OFF + SKF_AD_NLATTR:
        case SKF_AD_OFF + SKF_AD_NLATTR_NEST:
        case SKF_AD_OFF + SKF_AD_CPU:
        case SKF_AD_OFF + SKF_AD_RANDOM:
                /* arg1 = CTX */
                *insn++ = BPF_MOV64_REG(BPF_REG_ARG1, BPF_REG_CTX);
                /* arg2 = A */
                *insn++ = BPF_MOV64_REG(BPF_REG_ARG2, BPF_REG_A);
                /* arg3 = X */
                *insn++ = BPF_MOV64_REG(BPF_REG_ARG3, BPF_REG_X);
                /* Emit call(arg1=CTX, arg2=A, arg3=X) */
                switch (fp->k) {
                case SKF_AD_OFF + SKF_AD_PAY_OFFSET:
                        *insn = BPF_EMIT_CALL(bpf_skb_get_pay_offset);
                        break;
                case SKF_AD_OFF + SKF_AD_NLATTR:
                        *insn = BPF_EMIT_CALL(bpf_skb_get_nlattr);
                        break;
                case SKF_AD_OFF + SKF_AD_NLATTR_NEST:
                        *insn = BPF_EMIT_CALL(bpf_skb_get_nlattr_nest);
                        break;
                case SKF_AD_OFF + SKF_AD_CPU:
                        *insn = BPF_EMIT_CALL(bpf_get_raw_cpu_id);
                        break;
                case SKF_AD_OFF + SKF_AD_RANDOM:
                        *insn = BPF_EMIT_CALL(bpf_user_rnd_u32);
                        bpf_user_rnd_init_once();
                        break;
                }
                break;

        case SKF_AD_OFF + SKF_AD_ALU_XOR_X:
                /* A ^= X */
                *insn = BPF_ALU32_REG(BPF_XOR, BPF_REG_A, BPF_REG_X);
                break;

        default:
                /* This is just a dummy call to avoid letting the compiler
                 * evict __bpf_call_base() as an optimization. Placed here
                 * where no-one bothers.
                 */
                BUG_ON(__bpf_call_base(0, 0, 0, 0, 0) != 0);
                return false;
        }

        *insnp = insn;
        return true;
}

static bool convert_bpf_ld_abs(struct sock_filter *fp, struct bpf_insn **insnp)
{
        const bool unaligned_ok = IS_BUILTIN(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS);
        int size = bpf_size_to_bytes(BPF_SIZE(fp->code));
        bool endian = BPF_SIZE(fp->code) == BPF_H ||
                      BPF_SIZE(fp->code) == BPF_W;
        bool indirect = BPF_MODE(fp->code) == BPF_IND;
        const int ip_align = NET_IP_ALIGN;
        struct bpf_insn *insn = *insnp;
        int offset = fp->k;

        if (!indirect &&
            ((unaligned_ok && offset >= 0) ||
             (!unaligned_ok && offset >= 0 &&
              offset + ip_align >= 0 &&
              offset + ip_align % size == 0))) {
                bool ldx_off_ok = offset <= S16_MAX;

                *insn++ = BPF_MOV64_REG(BPF_REG_TMP, BPF_REG_H);
                if (offset)
                        *insn++ = BPF_ALU64_IMM(BPF_SUB, BPF_REG_TMP, offset);
                *insn++ = BPF_JMP_IMM(BPF_JSLT, BPF_REG_TMP,
                                      size, 2 + endian + (!ldx_off_ok * 2));
                if (ldx_off_ok) {
                        *insn++ = BPF_LDX_MEM(BPF_SIZE(fp->code), BPF_REG_A,
                                              BPF_REG_D, offset);
                } else {
                        *insn++ = BPF_MOV64_REG(BPF_REG_TMP, BPF_REG_D);
                        *insn++ = BPF_ALU64_IMM(BPF_ADD, BPF_REG_TMP, offset);
                        *insn++ = BPF_LDX_MEM(BPF_SIZE(fp->code), BPF_REG_A,
                                              BPF_REG_TMP, 0);
                }
                if (endian)
                        *insn++ = BPF_ENDIAN(BPF_FROM_BE, BPF_REG_A, size * 8);
                *insn++ = BPF_JMP_A(8);
        }

        *insn++ = BPF_MOV64_REG(BPF_REG_ARG1, BPF_REG_CTX);
        *insn++ = BPF_MOV64_REG(BPF_REG_ARG2, BPF_REG_D);
        *insn++ = BPF_MOV64_REG(BPF_REG_ARG3, BPF_REG_H);
        if (!indirect) {
                *insn++ = BPF_MOV64_IMM(BPF_REG_ARG4, offset);
        } else {
                *insn++ = BPF_MOV64_REG(BPF_REG_ARG4, BPF_REG_X);
                if (fp->k)
                        *insn++ = BPF_ALU64_IMM(BPF_ADD, BPF_REG_ARG4, offset);
        }

        switch (BPF_SIZE(fp->code)) {
        case BPF_B:
                *insn++ = BPF_EMIT_CALL(bpf_skb_load_helper_8);
                break;
        case BPF_H:
                *insn++ = BPF_EMIT_CALL(bpf_skb_load_helper_16);
                break;
        case BPF_W:
                *insn++ = BPF_EMIT_CALL(bpf_skb_load_helper_32);
                break;
        default:
                return false;
        }

        *insn++ = BPF_JMP_IMM(BPF_JSGE, BPF_REG_A, 0, 2);
        *insn++ = BPF_ALU32_REG(BPF_XOR, BPF_REG_A, BPF_REG_A);
        *insn   = BPF_EXIT_INSN();

        *insnp = insn;
        return true;
}

/**
 *      bpf_convert_filter - convert filter program
 *      @prog: the user passed filter program
 *      @len: the length of the user passed filter program
 *      @new_prog: allocated 'struct bpf_prog' or NULL
 *      @new_len: pointer to store length of converted program
 *      @seen_ld_abs: bool whether we've seen ld_abs/ind
 *
 * Remap 'sock_filter' style classic BPF (cBPF) instruction set to 'bpf_insn'
 * style extended BPF (eBPF).
 * Conversion workflow:
 *
 * 1) First pass for calculating the new program length:
 *   bpf_convert_filter(old_prog, old_len, NULL, &new_len, &seen_ld_abs)
 *
 * 2) 2nd pass to remap in two passes: 1st pass finds new
 *    jump offsets, 2nd pass remapping:
 *   bpf_convert_filter(old_prog, old_len, new_prog, &new_len, &seen_ld_abs)
 */
static int bpf_convert_filter(struct sock_filter *prog, int len,
                              struct bpf_prog *new_prog, int *new_len,
                              bool *seen_ld_abs)
{
        int new_flen = 0, pass = 0, target, i, stack_off;
        struct bpf_insn *new_insn, *first_insn = NULL;
        struct sock_filter *fp;
        int *addrs = NULL;
        u8 bpf_src;

        BUILD_BUG_ON(BPF_MEMWORDS * sizeof(u32) > MAX_BPF_STACK);
        BUILD_BUG_ON(BPF_REG_FP + 1 != MAX_BPF_REG);

        if (len <= 0 || len > BPF_MAXINSNS)
                return -EINVAL;

        if (new_prog) {
                first_insn = new_prog->insnsi;
                addrs = kcalloc(len, sizeof(*addrs),
                                GFP_KERNEL | __GFP_NOWARN);
                if (!addrs)
                        return -ENOMEM;
        }

do_pass:
        new_insn = first_insn;
        fp = prog;

        /* Classic BPF related prologue emission. */
        if (new_prog) {
                /* Classic BPF expects A and X to be reset first. These need
                 * to be guaranteed to be the first two instructions.
                 */
                *new_insn++ = BPF_ALU32_REG(BPF_XOR, BPF_REG_A, BPF_REG_A);
                *new_insn++ = BPF_ALU32_REG(BPF_XOR, BPF_REG_X, BPF_REG_X);

                /* All programs must keep CTX in callee saved BPF_REG_CTX.
                 * In eBPF case it's done by the compiler, here we need to
                 * do this ourself. Initial CTX is present in BPF_REG_ARG1.
                 */
                *new_insn++ = BPF_MOV64_REG(BPF_REG_CTX, BPF_REG_ARG1);
                if (*seen_ld_abs) {
                        /* For packet access in classic BPF, cache skb->data
                         * in callee-saved BPF R8 and skb->len - skb->data_len
                         * (headlen) in BPF R9. Since classic BPF is read-only
                         * on CTX, we only need to cache it once.
                         */
                        *new_insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, data),
                                                  BPF_REG_D, BPF_REG_CTX,
                                                  offsetof(struct sk_buff, data));
                        *new_insn++ = BPF_LDX_MEM(BPF_W, BPF_REG_H, BPF_REG_CTX,
                                                  offsetof(struct sk_buff, len));
                        *new_insn++ = BPF_LDX_MEM(BPF_W, BPF_REG_TMP, BPF_REG_CTX,
                                                  offsetof(struct sk_buff, data_len));
                        *new_insn++ = BPF_ALU32_REG(BPF_SUB, BPF_REG_H, BPF_REG_TMP);
                }
        } else {
                new_insn += 3;
        }

        for (i = 0; i < len; fp++, i++) {
                struct bpf_insn tmp_insns[32] = { };
                struct bpf_insn *insn = tmp_insns;

                if (addrs)
                        addrs[i] = new_insn - first_insn;

                switch (fp->code) {
                /* All arithmetic insns and skb loads map as-is. */
                case BPF_ALU | BPF_ADD | BPF_X:
                case BPF_ALU | BPF_ADD | BPF_K:
                case BPF_ALU | BPF_SUB | BPF_X:
                case BPF_ALU | BPF_SUB | BPF_K:
                case BPF_ALU | BPF_AND | BPF_X:
                case BPF_ALU | BPF_AND | BPF_K:
                case BPF_ALU | BPF_OR | BPF_X:
                case BPF_ALU | BPF_OR | BPF_K:
                case BPF_ALU | BPF_LSH | BPF_X:
                case BPF_ALU | BPF_LSH | BPF_K:
                case BPF_ALU | BPF_RSH | BPF_X:
                case BPF_ALU | BPF_RSH | BPF_K:
                case BPF_ALU | BPF_XOR | BPF_X:
                case BPF_ALU | BPF_XOR | BPF_K:
                case BPF_ALU | BPF_MUL | BPF_X:
                case BPF_ALU | BPF_MUL | BPF_K:
                case BPF_ALU | BPF_DIV | BPF_X:
                case BPF_ALU | BPF_DIV | BPF_K:
                case BPF_ALU | BPF_MOD | BPF_X:
                case BPF_ALU | BPF_MOD | BPF_K:
                case BPF_ALU | BPF_NEG:
                case BPF_LD | BPF_ABS | BPF_W:
                case BPF_LD | BPF_ABS | BPF_H:
                case BPF_LD | BPF_ABS | BPF_B:
                case BPF_LD | BPF_IND | BPF_W:
                case BPF_LD | BPF_IND | BPF_H:
                case BPF_LD | BPF_IND | BPF_B:
                        /* Check for overloaded BPF extension and
                         * directly convert it if found, otherwise
                         * just move on with mapping.
                         */
                        if (BPF_CLASS(fp->code) == BPF_LD &&
                            BPF_MODE(fp->code) == BPF_ABS &&
                            convert_bpf_extensions(fp, &insn))
                                break;
                        if (BPF_CLASS(fp->code) == BPF_LD &&
                            convert_bpf_ld_abs(fp, &insn)) {
                                *seen_ld_abs = true;
                                break;
                        }

                        if (fp->code == (BPF_ALU | BPF_DIV | BPF_X) ||
                            fp->code == (BPF_ALU | BPF_MOD | BPF_X)) {
                                *insn++ = BPF_MOV32_REG(BPF_REG_X, BPF_REG_X);
                                /* Error with exception code on div/mod by 0.
                                 * For cBPF programs, this was always return 0.
                                 */
                                *insn++ = BPF_JMP_IMM(BPF_JNE, BPF_REG_X, 0, 2);
                                *insn++ = BPF_ALU32_REG(BPF_XOR, BPF_REG_A, BPF_REG_A);
                                *insn++ = BPF_EXIT_INSN();
                        }

                        *insn = BPF_RAW_INSN(fp->code, BPF_REG_A, BPF_REG_X, 0, fp->k);
                        break;

                /* Jump transformation cannot use BPF block macros
                 * everywhere as offset calculation and target updates
                 * require a bit more work than the rest, i.e. jump
                 * opcodes map as-is, but offsets need adjustment.
                 */

#define BPF_EMIT_JMP                                                    \
        do {                                                            \
                const s32 off_min = S16_MIN, off_max = S16_MAX;         \
                s32 off;                                                \
                                                                        \
                if (target >= len || target < 0)                        \
                        goto err;                                       \
                off = addrs ? addrs[target] - addrs[i] - 1 : 0;         \
                /* Adjust pc relative offset for 2nd or 3rd insn. */    \
                off -= insn - tmp_insns;                                \
                /* Reject anything not fitting into insn->off. */       \
                if (off < off_min || off > off_max)                     \
                        goto err;                                       \
                insn->off = off;                                        \
        } while (0)

                case BPF_JMP | BPF_JA:
                        target = i + fp->k + 1;
                        insn->code = fp->code;
                        BPF_EMIT_JMP;
                        break;

                case BPF_JMP | BPF_JEQ | BPF_K:
                case BPF_JMP | BPF_JEQ | BPF_X:
                case BPF_JMP | BPF_JSET | BPF_K:
                case BPF_JMP | BPF_JSET | BPF_X:
                case BPF_JMP | BPF_JGT | BPF_K:
                case BPF_JMP | BPF_JGT | BPF_X:
                case BPF_JMP | BPF_JGE | BPF_K:
                case BPF_JMP | BPF_JGE | BPF_X:
                        if (BPF_SRC(fp->code) == BPF_K && (int) fp->k < 0) {
                                /* BPF immediates are signed, zero extend
                                 * immediate into tmp register and use it
                                 * in compare insn.
                                 */
                                *insn++ = BPF_MOV32_IMM(BPF_REG_TMP, fp->k);

                                insn->dst_reg = BPF_REG_A;
                                insn->src_reg = BPF_REG_TMP;
                                bpf_src = BPF_X;
                        } else {
                                insn->dst_reg = BPF_REG_A;
                                insn->imm = fp->k;
                                bpf_src = BPF_SRC(fp->code);
                                insn->src_reg = bpf_src == BPF_X ? BPF_REG_X : 0;
                        }

                        /* Common case where 'jump_false' is next insn. */
                        if (fp->jf == 0) {
                                insn->code = BPF_JMP | BPF_OP(fp->code) | bpf_src;
                                target = i + fp->jt + 1;
                                BPF_EMIT_JMP;
                                break;
                        }

                        /* Convert some jumps when 'jump_true' is next insn. */
                        if (fp->jt == 0) {
                                switch (BPF_OP(fp->code)) {
                                case BPF_JEQ:
                                        insn->code = BPF_JMP | BPF_JNE | bpf_src;
                                        break;
                                case BPF_JGT:
                                        insn->code = BPF_JMP | BPF_JLE | bpf_src;
                                        break;
                                case BPF_JGE:
                                        insn->code = BPF_JMP | BPF_JLT | bpf_src;
                                        break;
                                default:
                                        goto jmp_rest;
                                }

                                target = i + fp->jf + 1;
                                BPF_EMIT_JMP;
                                break;
                        }
jmp_rest:
                        /* Other jumps are mapped into two insns: Jxx and JA. */
                        target = i + fp->jt + 1;
                        insn->code = BPF_JMP | BPF_OP(fp->code) | bpf_src;
                        BPF_EMIT_JMP;
                        insn++;

                        insn->code = BPF_JMP | BPF_JA;
                        target = i + fp->jf + 1;
                        BPF_EMIT_JMP;
                        break;

                /* ldxb 4 * ([14] & 0xf) is remaped into 6 insns. */
                case BPF_LDX | BPF_MSH | BPF_B: {
                        struct sock_filter tmp = {
                                .code   = BPF_LD | BPF_ABS | BPF_B,
                                .k      = fp->k,
                        };

                        *seen_ld_abs = true;

                        /* X = A */
                        *insn++ = BPF_MOV64_REG(BPF_REG_X, BPF_REG_A);
                        /* A = BPF_R0 = *(u8 *) (skb->data + K) */
                        convert_bpf_ld_abs(&tmp, &insn);
                        insn++;
                        /* A &= 0xf */
                        *insn++ = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, 0xf);
                        /* A <<= 2 */
                        *insn++ = BPF_ALU32_IMM(BPF_LSH, BPF_REG_A, 2);
                        /* tmp = X */
                        *insn++ = BPF_MOV64_REG(BPF_REG_TMP, BPF_REG_X);
                        /* X = A */
                        *insn++ = BPF_MOV64_REG(BPF_REG_X, BPF_REG_A);
                        /* A = tmp */
                        *insn = BPF_MOV64_REG(BPF_REG_A, BPF_REG_TMP);
                        break;
                }
                /* RET_K is remaped into 2 insns. RET_A case doesn't need an
                 * extra mov as BPF_REG_0 is already mapped into BPF_REG_A.
                 */
                case BPF_RET | BPF_A:
                case BPF_RET | BPF_K:
                        if (BPF_RVAL(fp->code) == BPF_K)
                                *insn++ = BPF_MOV32_RAW(BPF_K, BPF_REG_0,
                                                        0, fp->k);
                        *insn = BPF_EXIT_INSN();
                        break;

                /* Store to stack. */
                case BPF_ST:
                case BPF_STX:
                        stack_off = fp->k * 4  + 4;
                        *insn = BPF_STX_MEM(BPF_W, BPF_REG_FP, BPF_CLASS(fp->code) ==
                                            BPF_ST ? BPF_REG_A : BPF_REG_X,
                                            -stack_off);
                        /* check_load_and_stores() verifies that classic BPF can
                         * load from stack only after write, so tracking
                         * stack_depth for ST|STX insns is enough
                         */
                        if (new_prog && new_prog->aux->stack_depth < stack_off)
                                new_prog->aux->stack_depth = stack_off;
                        break;

                /* Load from stack. */
                case BPF_LD | BPF_MEM:
                case BPF_LDX | BPF_MEM:
                        stack_off = fp->k * 4  + 4;
                        *insn = BPF_LDX_MEM(BPF_W, BPF_CLASS(fp->code) == BPF_LD  ?
                                            BPF_REG_A : BPF_REG_X, BPF_REG_FP,
                                            -stack_off);
                        break;

                /* A = K or X = K */
                case BPF_LD | BPF_IMM:
                case BPF_LDX | BPF_IMM:
                        *insn = BPF_MOV32_IMM(BPF_CLASS(fp->code) == BPF_LD ?
                                              BPF_REG_A : BPF_REG_X, fp->k);
                        break;

                /* X = A */
                case BPF_MISC | BPF_TAX:
                        *insn = BPF_MOV64_REG(BPF_REG_X, BPF_REG_A);
                        break;

                /* A = X */
                case BPF_MISC | BPF_TXA:
                        *insn = BPF_MOV64_REG(BPF_REG_A, BPF_REG_X);
                        break;

                /* A = skb->len or X = skb->len */
                case BPF_LD | BPF_W | BPF_LEN:
                case BPF_LDX | BPF_W | BPF_LEN:
                        *insn = BPF_LDX_MEM(BPF_W, BPF_CLASS(fp->code) == BPF_LD ?
                                            BPF_REG_A : BPF_REG_X, BPF_REG_CTX,
                                            offsetof(struct sk_buff, len));
                        break;

                /* Access seccomp_data fields. */
                case BPF_LDX | BPF_ABS | BPF_W:
                        /* A = *(u32 *) (ctx + K) */
                        *insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_CTX, fp->k);
                        break;

                /* Unknown instruction. */
                default:
                        goto err;
                }

                insn++;
                if (new_prog)
                        memcpy(new_insn, tmp_insns,
                               sizeof(*insn) * (insn - tmp_insns));
                new_insn += insn - tmp_insns;
        }

        if (!new_prog) {
                /* Only calculating new length. */
                *new_len = new_insn - first_insn;
                if (*seen_ld_abs)
                        *new_len += 4; /* Prologue bits. */
                return 0;
        }

        pass++;
        if (new_flen != new_insn - first_insn) {
                new_flen = new_insn - first_insn;
                if (pass > 2)
                        goto err;
                goto do_pass;
        }

        kfree(addrs);
        BUG_ON(*new_len != new_flen);
        return 0;
err:
        kfree(addrs);
        return -EINVAL;
}

/* Security:
 *
 * As we dont want to clear mem[] array for each packet going through
 * __bpf_prog_run(), we check that filter loaded by user never try to read
 * a cell if not previously written, and we check all branches to be sure
 * a malicious user doesn't try to abuse us.
 */
static int check_load_and_stores(const struct sock_filter *filter, int flen)
{
        u16 *masks, memvalid = 0; /* One bit per cell, 16 cells */
        int pc, ret = 0;

        BUILD_BUG_ON(BPF_MEMWORDS > 16);

        masks = kmalloc_array(flen, sizeof(*masks), GFP_KERNEL);
        if (!masks)
                return -ENOMEM;

        memset(masks, 0xff, flen * sizeof(*masks));

        for (pc = 0; pc < flen; pc++) {
                memvalid &= masks[pc];

                switch (filter[pc].code) {
                case BPF_ST:
                case BPF_STX:
                        memvalid |= (1 << filter[pc].k);
                        break;
                case BPF_LD | BPF_MEM:
                case BPF_LDX | BPF_MEM:
                        if (!(memvalid & (1 << filter[pc].k))) {
                                ret = -EINVAL;
                                goto error;
                        }
                        break;
                case BPF_JMP | BPF_JA:
                        /* A jump must set masks on target */
                        masks[pc + 1 + filter[pc].k] &= memvalid;
                        memvalid = ~0;
                        break;
                case BPF_JMP | BPF_JEQ | BPF_K:
                case BPF_JMP | BPF_JEQ | BPF_X:
                case BPF_JMP | BPF_JGE | BPF_K:
                case BPF_JMP | BPF_JGE | BPF_X:
                case BPF_JMP | BPF_JGT | BPF_K:
                case BPF_JMP | BPF_JGT | BPF_X:
                case BPF_JMP | BPF_JSET | BPF_K:
                case BPF_JMP | BPF_JSET | BPF_X:
                        /* A jump must set masks on targets */
                        masks[pc + 1 + filter[pc].jt] &= memvalid;
                        masks[pc + 1 + filter[pc].jf] &= memvalid;
                        memvalid = ~0;
                        break;
                }
        }
error:
        kfree(masks);
        return ret;
}

static bool chk_code_allowed(u16 code_to_probe)
{
        static const bool codes[] = {
                /* 32 bit ALU operations */
                [BPF_ALU | BPF_ADD | BPF_K] = true,
                [BPF_ALU | BPF_ADD | BPF_X] = true,
                [BPF_ALU | BPF_SUB | BPF_K] = true,
                [BPF_ALU | BPF_SUB | BPF_X] = true,
                [BPF_ALU | BPF_MUL | BPF_K] = true,
                [BPF_ALU | BPF_MUL | BPF_X] = true,
                [BPF_ALU | BPF_DIV | BPF_K] = true,
                [BPF_ALU | BPF_DIV | BPF_X] = true,
                [BPF_ALU | BPF_MOD | BPF_K] = true,
                [BPF_ALU | BPF_MOD | BPF_X] = true,
                [BPF_ALU | BPF_AND | BPF_K] = true,
                [BPF_ALU | BPF_AND | BPF_X] = true,
                [BPF_ALU | BPF_OR | BPF_K] = true,
                [BPF_ALU | BPF_OR | BPF_X] = true,
                [BPF_ALU | BPF_XOR | BPF_K] = true,
                [BPF_ALU | BPF_XOR | BPF_X] = true,
                [BPF_ALU | BPF_LSH | BPF_K] = true,
                [BPF_ALU | BPF_LSH | BPF_X] = true,
                [BPF_ALU | BPF_RSH | BPF_K] = true,
                [BPF_ALU | BPF_RSH | BPF_X] = true,
                [BPF_ALU | BPF_NEG] = true,
                /* Load instructions */
                [BPF_LD | BPF_W | BPF_ABS] = true,
                [BPF_LD | BPF_H | BPF_ABS] = true,
                [BPF_LD | BPF_B | BPF_ABS] = true,
                [BPF_LD | BPF_W | BPF_LEN] = true,
                [BPF_LD | BPF_W | BPF_IND] = true,
                [BPF_LD | BPF_H | BPF_IND] = true,
                [BPF_LD | BPF_B | BPF_IND] = true,
                [BPF_LD | BPF_IMM] = true,
                [BPF_LD | BPF_MEM] = true,
                [BPF_LDX | BPF_W | BPF_LEN] = true,
                [BPF_LDX | BPF_B | BPF_MSH] = true,
                [BPF_LDX | BPF_IMM] = true,
                [BPF_LDX | BPF_MEM] = true,
                /* Store instructions */
                [BPF_ST] = true,
                [BPF_STX] = true,
                /* Misc instructions */
                [BPF_MISC | BPF_TAX] = true,
                [BPF_MISC | BPF_TXA] = true,
                /* Return instructions */
                [BPF_RET | BPF_K] = true,
                [BPF_RET | BPF_A] = true,
                /* Jump instructions */
                [BPF_JMP | BPF_JA] = true,
                [BPF_JMP | BPF_JEQ | BPF_K] = true,
                [BPF_JMP | BPF_JEQ | BPF_X] = true,
                [BPF_JMP | BPF_JGE | BPF_K] = true,
                [BPF_JMP | BPF_JGE | BPF_X] = true,
                [BPF_JMP | BPF_JGT | BPF_K] = true,
                [BPF_JMP | BPF_JGT | BPF_X] = true,
                [BPF_JMP | BPF_JSET | BPF_K] = true,
                [BPF_JMP | BPF_JSET | BPF_X] = true,
        };

        if (code_to_probe >= ARRAY_SIZE(codes))

                return false;

        return codes[code_to_probe];
}

static bool bpf_check_basics_ok(const struct sock_filter *filter,
                                unsigned int flen)
{
        if (filter == NULL)
                return false;
        if (flen == 0 || flen > BPF_MAXINSNS)
                return false;

        return true;
}

/**
 *      bpf_check_classic - verify socket filter code
 *      @filter: filter to verify
 *      @flen: length of filter
 *
 * Check the user's filter code. If we let some ugly
 * filter code slip through kaboom! The filter must contain
 * no references or jumps that are out of range, no illegal
 * instructions, and must end with a RET instruction.
 *
 * All jumps are forward as they are not signed.
 *
 * Returns 0 if the rule set is legal or -EINVAL if not.
 */
static int bpf_check_classic(const struct sock_filter *filter,
                             unsigned int flen)
{
        bool anc_found;
        int pc;

        /* Check the filter code now */
        for (pc = 0; pc < flen; pc++) {
                const struct sock_filter *ftest = &filter[pc];

                /* May we actually operate on this code? */
                if (!chk_code_allowed(ftest->code))
                        return -EINVAL;

                /* Some instructions need special checks */
                switch (ftest->code) {
                case BPF_ALU | BPF_DIV | BPF_K:
                case BPF_ALU | BPF_MOD | BPF_K:
                        /* Check for division by zero */
                        if (ftest->k == 0)
                                return -EINVAL;
                        break;
                case BPF_ALU | BPF_LSH | BPF_K:
                case BPF_ALU | BPF_RSH | BPF_K:
                        if (ftest->k >= 32)
                                return -EINVAL;
                        break;
                case BPF_LD | BPF_MEM:
                case BPF_LDX | BPF_MEM:
                case BPF_ST:
                case BPF_STX:
                        /* Check for invalid memory addresses */
                        if (ftest->k >= BPF_MEMWORDS)
                                return -EINVAL;
                        break;
                case BPF_JMP | BPF_JA:
                        /* Note, the large ftest->k might cause loops.
                         * Compare this with conditional jumps below,
                         * where offsets are limited. --ANK (981016)
                         */
                        if (ftest->k >= (unsigned int)(flen - pc - 1))
                                return -EINVAL;
                        break;
                case BPF_JMP | BPF_JEQ | BPF_K:
                case BPF_JMP | BPF_JEQ | BPF_X:
                case BPF_JMP | BPF_JGE | BPF_K:
                case BPF_JMP | BPF_JGE | BPF_X:
                case BPF_JMP | BPF_JGT | BPF_K:
                case BPF_JMP | BPF_JGT | BPF_X:
                case BPF_JMP | BPF_JSET | BPF_K:
                case BPF_JMP | BPF_JSET | BPF_X:
                        /* Both conditionals must be safe */
                        if (pc + ftest->jt + 1 >= flen ||
                            pc + ftest->jf + 1 >= flen)
                                return -EINVAL;
                        break;
                case BPF_LD | BPF_W | BPF_ABS:
                case BPF_LD | BPF_H | BPF_ABS:
                case BPF_LD | BPF_B | BPF_ABS:
                        anc_found = false;
                        if (bpf_anc_helper(ftest) & BPF_ANC)
                                anc_found = true;
                        /* Ancillary operation unknown or unsupported */
                        if (anc_found == false && ftest->k >= SKF_AD_OFF)
                                return -EINVAL;
                }
        }

        /* Last instruction must be a RET code */
        switch (filter[flen - 1].code) {
        case BPF_RET | BPF_K:
        case BPF_RET | BPF_A:
                return check_load_and_stores(filter, flen);
        }

        return -EINVAL;
}

static int bpf_prog_store_orig_filter(struct bpf_prog *fp,
                                      const struct sock_fprog *fprog)
{
        unsigned int fsize = bpf_classic_proglen(fprog);
        struct sock_fprog_kern *fkprog;

        fp->orig_prog = kmalloc(sizeof(*fkprog), GFP_KERNEL);
        if (!fp->orig_prog)
                return -ENOMEM;

        fkprog = fp->orig_prog;
        fkprog->len = fprog->len;

        fkprog->filter = kmemdup(fp->insns, fsize,
                                 GFP_KERNEL | __GFP_NOWARN);
        if (!fkprog->filter) {
                kfree(fp->orig_prog);
                return -ENOMEM;
        }

        return 0;
}

static void bpf_release_orig_filter(struct bpf_prog *fp)
{
        struct sock_fprog_kern *fprog = fp->orig_prog;

        if (fprog) {
                kfree(fprog->filter);
                kfree(fprog);
        }
}

static void __bpf_prog_release(struct bpf_prog *prog)
{
        if (prog->type == BPF_PROG_TYPE_SOCKET_FILTER) {
                bpf_prog_put(prog);
        } else {
                bpf_release_orig_filter(prog);
                bpf_prog_free(prog);
        }
}

static void __sk_filter_release(struct sk_filter *fp)
{
        __bpf_prog_release(fp->prog);
        kfree(fp);
}

/**
 *      sk_filter_release_rcu - Release a socket filter by rcu_head
 *      @rcu: rcu_head that contains the sk_filter to free
 */
static void sk_filter_release_rcu(struct rcu_head *rcu)
{
        struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu);

        __sk_filter_release(fp);
}

/**
 *      sk_filter_release - release a socket filter
 *      @fp: filter to remove
 *
 *      Remove a filter from a socket and release its resources.
 */
static void sk_filter_release(struct sk_filter *fp)
{
        if (refcount_dec_and_test(&fp->refcnt))
                call_rcu(&fp->rcu, sk_filter_release_rcu);
}

void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp)
{
        u32 filter_size = bpf_prog_size(fp->prog->len);

        atomic_sub(filter_size, &sk->sk_omem_alloc);
        sk_filter_release(fp);
}

/* try to charge the socket memory if there is space available
 * return true on success
 */
static bool __sk_filter_charge(struct sock *sk, struct sk_filter *fp)
{
        u32 filter_size = bpf_prog_size(fp->prog->len);

        /* same check as in sock_kmalloc() */
        if (filter_size <= sysctl_optmem_max &&
            atomic_read(&sk->sk_omem_alloc) + filter_size < sysctl_optmem_max) {
                atomic_add(filter_size, &sk->sk_omem_alloc);
                return true;
        }
        return false;
}

bool sk_filter_charge(struct sock *sk, struct sk_filter *fp)
{
        if (!refcount_inc_not_zero(&fp->refcnt))
                return false;

        if (!__sk_filter_charge(sk, fp)) {
                sk_filter_release(fp);
                return false;
        }
        return true;
}

static struct bpf_prog *bpf_migrate_filter(struct bpf_prog *fp)
{
        struct sock_filter *old_prog;
        struct bpf_prog *old_fp;
        int err, new_len, old_len = fp->len;
        bool seen_ld_abs = false;

        /* We are free to overwrite insns et al right here as it
         * won't be used at this point in time anymore internally
         * after the migration to the internal BPF instruction
         * representation.
         */
        BUILD_BUG_ON(sizeof(struct sock_filter) !=
                     sizeof(struct bpf_insn));

        /* Conversion cannot happen on overlapping memory areas,
         * so we need to keep the user BPF around until the 2nd
         * pass. At this time, the user BPF is stored in fp->insns.
         */
        old_prog = kmemdup(fp->insns, old_len * sizeof(struct sock_filter),
                           GFP_KERNEL | __GFP_NOWARN);
        if (!old_prog) {
                err = -ENOMEM;
                goto out_err;
        }

        /* 1st pass: calculate the new program length. */
        err = bpf_convert_filter(old_prog, old_len, NULL, &new_len,
                                 &seen_ld_abs);
        if (err)
                goto out_err_free;

        /* Expand fp for appending the new filter representation. */
        old_fp = fp;
        fp = bpf_prog_realloc(old_fp, bpf_prog_size(new_len), 0);
        if (!fp) {
                /* The old_fp is still around in case we couldn't
                 * allocate new memory, so uncharge on that one.
                 */
                fp = old_fp;
                err = -ENOMEM;
                goto out_err_free;
        }

        fp->len = new_len;

        /* 2nd pass: remap sock_filter insns into bpf_insn insns. */
        err = bpf_convert_filter(old_prog, old_len, fp, &new_len,
                                 &seen_ld_abs);
        if (err)
                /* 2nd bpf_convert_filter() can fail only if it fails
                 * to allocate memory, remapping must succeed. Note,
                 * that at this time old_fp has already been released
                 * by krealloc().
                 */
                goto out_err_free;

        fp = bpf_prog_select_runtime(fp, &err);
        if (err)
                goto out_err_free;

        kfree(old_prog);
        return fp;

out_err_free:
        kfree(old_prog);
out_err:
        __bpf_prog_release(fp);
        return ERR_PTR(err);
}

static struct bpf_prog *bpf_prepare_filter(struct bpf_prog *fp,
                                           bpf_aux_classic_check_t trans)
{
        int err;

        fp->bpf_func = NULL;
        fp->jited = 0;

        err = bpf_check_classic(fp->insns, fp->len);
        if (err) {
                __bpf_prog_release(fp);
                return ERR_PTR(err);
        }

        /* There might be additional checks and transformations
         * needed on classic filters, f.e. in case of seccomp.
         */
        if (trans) {
                err = trans(fp->insns, fp->len);
                if (err) {
                        __bpf_prog_release(fp);
                        return ERR_PTR(err);
                }
        }

        /* Probe if we can JIT compile the filter and if so, do
         * the compilation of the filter.
         */
        bpf_jit_compile(fp);

        /* JIT compiler couldn't process this filter, so do the
         * internal BPF translation for the optimized interpreter.
         */
        if (!fp->jited)
                fp = bpf_migrate_filter(fp);

        return fp;
}

/**
 *      bpf_prog_create - create an unattached filter
 *      @pfp: the unattached filter that is created
 *      @fprog: the filter program
 *
 * Create a filter independent of any socket. We first run some
 * sanity checks on it to make sure it does not explode on us later.
 * If an error occurs or there is insufficient memory for the filter
 * a negative errno code is returned. On success the return is zero.
 */
int bpf_prog_create(struct bpf_prog **pfp, struct sock_fprog_kern *fprog)
{
        unsigned int fsize = bpf_classic_proglen(fprog);
        struct bpf_prog *fp;

        /* Make sure new filter is there and in the right amounts. */
        if (!bpf_check_basics_ok(fprog->filter, fprog->len))
                return -EINVAL;

        fp = bpf_prog_alloc(bpf_prog_size(fprog->len), 0);
        if (!fp)
                return -ENOMEM;

        memcpy(fp->insns, fprog->filter, fsize);

        fp->len = fprog->len;
        /* Since unattached filters are not copied back to user
         * space through sk_get_filter(), we do not need to hold
         * a copy here, and can spare us the work.
         */
        fp->orig_prog = NULL;

        /* bpf_prepare_filter() already takes care of freeing
         * memory in case something goes wrong.
         */
        fp = bpf_prepare_filter(fp, NULL);
        if (IS_ERR(fp))
                return PTR_ERR(fp);

        *pfp = fp;
        return 0;
}
EXPORT_SYMBOL_GPL(bpf_prog_create);

/**
 *      bpf_prog_create_from_user - create an unattached filter from user buffer
 *      @pfp: the unattached filter that is created
 *      @fprog: the filter program
 *      @trans: post-classic verifier transformation handler
 *      @save_orig: save classic BPF program
 *
 * This function effectively does the same as bpf_prog_create(), only
 * that it builds up its insns buffer from user space provided buffer.
 * It also allows for passing a bpf_aux_classic_check_t handler.
 */
int bpf_prog_create_from_user(struct bpf_prog **pfp, struct sock_fprog *fprog,
                              bpf_aux_classic_check_t trans, bool save_orig)
{
        unsigned int fsize = bpf_classic_proglen(fprog);
        struct bpf_prog *fp;
        int err;

        /* Make sure new filter is there and in the right amounts. */
        if (!bpf_check_basics_ok(fprog->filter, fprog->len))
                return -EINVAL;

        fp = bpf_prog_alloc(bpf_prog_size(fprog->len), 0);
        if (!fp)
                return -ENOMEM;

        if (copy_from_user(fp->insns, fprog->filter, fsize)) {
                __bpf_prog_free(fp);
                return -EFAULT;
        }

        fp->len = fprog->len;
        fp->orig_prog = NULL;

        if (save_orig) {
                err = bpf_prog_store_orig_filter(fp, fprog);
                if (err) {
                        __bpf_prog_free(fp);
                        return -ENOMEM;
                }
        }

        /* bpf_prepare_filter() already takes care of freeing
         * memory in case something goes wrong.
         */
        fp = bpf_prepare_filter(fp, trans);
        if (IS_ERR(fp))
                return PTR_ERR(fp);

        *pfp = fp;
        return 0;
}
EXPORT_SYMBOL_GPL(bpf_prog_create_from_user);

void bpf_prog_destroy(struct bpf_prog *fp)
{
        __bpf_prog_release(fp);
}
EXPORT_SYMBOL_GPL(bpf_prog_destroy);

static int __sk_attach_prog(struct bpf_prog *prog, struct sock *sk)
{
        struct sk_filter *fp, *old_fp;

        fp = kmalloc(sizeof(*fp), GFP_KERNEL);
        if (!fp)
                return -ENOMEM;

        fp->prog = prog;

        if (!__sk_filter_charge(sk, fp)) {
                kfree(fp);
                return -ENOMEM;
        }
        refcount_set(&fp->refcnt, 1);

        old_fp = rcu_dereference_protected(sk->sk_filter,
                                           lockdep_sock_is_held(sk));
        rcu_assign_pointer(sk->sk_filter, fp);

        if (old_fp)
                sk_filter_uncharge(sk, old_fp);

        return 0;
}

static
struct bpf_prog *__get_filter(struct sock_fprog *fprog, struct sock *sk)
{
        unsigned int fsize = bpf_classic_proglen(fprog);
        struct bpf_prog *prog;
        int err;

        if (sock_flag(sk, SOCK_FILTER_LOCKED))
                return ERR_PTR(-EPERM);

        /* Make sure new filter is there and in the right amounts. */
        if (!bpf_check_basics_ok(fprog->filter, fprog->len))
                return ERR_PTR(-EINVAL);

        prog = bpf_prog_alloc(bpf_prog_size(fprog->len), 0);
        if (!prog)
                return ERR_PTR(-ENOMEM);

        if (copy_from_user(prog->insns, fprog->filter, fsize)) {
                __bpf_prog_free(prog);
                return ERR_PTR(-EFAULT);
        }

        prog->len = fprog->len;

        err = bpf_prog_store_orig_filter(prog, fprog);
        if (err) {
                __bpf_prog_free(prog);
                return ERR_PTR(-ENOMEM);
        }

        /* bpf_prepare_filter() already takes care of freeing
         * memory in case something goes wrong.
         */
        return bpf_prepare_filter(prog, NULL);
}

/**
 *      sk_attach_filter - attach a socket filter
 *      @fprog: the filter program
 *      @sk: the socket to use
 *
 * Attach the user's filter code. We first run some sanity checks on
 * it to make sure it does not explode on us later. If an error
 * occurs or there is insufficient memory for the filter a negative
 * errno code is returned. On success the return is zero.
 */
int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
{
        struct bpf_prog *prog = __get_filter(fprog, sk);
        int err;

        if (IS_ERR(prog))
                return PTR_ERR(prog);

        err = __sk_attach_prog(prog, sk);
        if (err < 0) {
                __bpf_prog_release(prog);
                return err;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(sk_attach_filter);

int sk_reuseport_attach_filter(struct sock_fprog *fprog, struct sock *sk)
{
        struct bpf_prog *prog = __get_filter(fprog, sk);
        int err;

        if (IS_ERR(prog))
                return PTR_ERR(prog);

        if (bpf_prog_size(prog->len) > sysctl_optmem_max)
                err = -ENOMEM;
        else
                err = reuseport_attach_prog(sk, prog);

        if (err)
                __bpf_prog_release(prog);

        return err;
}

static struct bpf_prog *__get_bpf(u32 ufd, struct sock *sk)
{
        if (sock_flag(sk, SOCK_FILTER_LOCKED))
                return ERR_PTR(-EPERM);

        return bpf_prog_get_type(ufd, BPF_PROG_TYPE_SOCKET_FILTER);
}

int sk_attach_bpf(u32 ufd, struct sock *sk)
{
        struct bpf_prog *prog = __get_bpf(ufd, sk);
        int err;

        if (IS_ERR(prog))
                return PTR_ERR(prog);

        err = __sk_attach_prog(prog, sk);
        if (err < 0) {
                bpf_prog_put(prog);
                return err;
        }

        return 0;
}

int sk_reuseport_attach_bpf(u32 ufd, struct sock *sk)
{
        struct bpf_prog *prog;
        int err;

        if (sock_flag(sk, SOCK_FILTER_LOCKED))
                return -EPERM;

        prog = bpf_prog_get_type(ufd, BPF_PROG_TYPE_SOCKET_FILTER);
        if (IS_ERR(prog) && PTR_ERR(prog) == -EINVAL)
                prog = bpf_prog_get_type(ufd, BPF_PROG_TYPE_SK_REUSEPORT);
        if (IS_ERR(prog))
                return PTR_ERR(prog);

        if (prog->type == BPF_PROG_TYPE_SK_REUSEPORT) {
                /* Like other non BPF_PROG_TYPE_SOCKET_FILTER
                 * bpf prog (e.g. sockmap).  It depends on the
                 * limitation imposed by bpf_prog_load().
                 * Hence, sysctl_optmem_max is not checked.
                 */
                if ((sk->sk_type != SOCK_STREAM &&
                     sk->sk_type != SOCK_DGRAM) ||
                    (sk->sk_protocol != IPPROTO_UDP &&
                     sk->sk_protocol != IPPROTO_TCP) ||
                    (sk->sk_family != AF_INET &&
                     sk->sk_family != AF_INET6)) {
                        err = -ENOTSUPP;
                        goto err_prog_put;
                }
        } else {
                /* BPF_PROG_TYPE_SOCKET_FILTER */
                if (bpf_prog_size(prog->len) > sysctl_optmem_max) {
                        err = -ENOMEM;
                        goto err_prog_put;
                }
        }

        err = reuseport_attach_prog(sk, prog);
err_prog_put:
        if (err)
                bpf_prog_put(prog);

        return err;
}

void sk_reuseport_prog_free(struct bpf_prog *prog)
{
        if (!prog)
                return;

        if (prog->type == BPF_PROG_TYPE_SK_REUSEPORT)
                bpf_prog_put(prog);
        else
                bpf_prog_destroy(prog);
}

struct bpf_scratchpad {
        union {
                __be32 diff[MAX_BPF_STACK / sizeof(__be32)];
                u8     buff[MAX_BPF_STACK];
        };
};

static DEFINE_PER_CPU(struct bpf_scratchpad, bpf_sp);

static inline int __bpf_try_make_writable(struct sk_buff *skb,
                                          unsigned int write_len)
{
        return skb_ensure_writable(skb, write_len);
}

static inline int bpf_try_make_writable(struct sk_buff *skb,
                                        unsigned int write_len)
{
        int err = __bpf_try_make_writable(skb, write_len);

        bpf_compute_data_pointers(skb);
        return err;
}

static int bpf_try_make_head_writable(struct sk_buff *skb)
{
        return bpf_try_make_writable(skb, skb_headlen(skb));
}

static inline void bpf_push_mac_rcsum(struct sk_buff *skb)
{
        if (skb_at_tc_ingress(skb))
                skb_postpush_rcsum(skb, skb_mac_header(skb), skb->mac_len);
}

static inline void bpf_pull_mac_rcsum(struct sk_buff *skb)
{
        if (skb_at_tc_ingress(skb))
                skb_postpull_rcsum(skb, skb_mac_header(skb), skb->mac_len);
}

BPF_CALL_5(bpf_skb_store_bytes, struct sk_buff *, skb, u32, offset,
           const void *, from, u32, len, u64, flags)
{
        void *ptr;

        if (unlikely(flags & ~(BPF_F_RECOMPUTE_CSUM | BPF_F_INVALIDATE_HASH)))
                return -EINVAL;
        if (unlikely(offset > 0xffff))
                return -EFAULT;
        if (unlikely(bpf_try_make_writable(skb, offset + len)))
                return -EFAULT;

        ptr = skb->data + offset;
        if (flags & BPF_F_RECOMPUTE_CSUM)
                __skb_postpull_rcsum(skb, ptr, len, offset);

        memcpy(ptr, from, len);

        if (flags & BPF_F_RECOMPUTE_CSUM)
                __skb_postpush_rcsum(skb, ptr, len, offset);
        if (flags & BPF_F_INVALIDATE_HASH)
                skb_clear_hash(skb);

        return 0;
}

static const struct bpf_func_proto bpf_skb_store_bytes_proto = {
        .func           = bpf_skb_store_bytes,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
        .arg3_type      = ARG_PTR_TO_MEM,
        .arg4_type      = ARG_CONST_SIZE,
        .arg5_type      = ARG_ANYTHING,
};

BPF_CALL_4(bpf_skb_load_bytes, const struct sk_buff *, skb, u32, offset,
           void *, to, u32, len)
{
        void *ptr;

        if (unlikely(offset > 0xffff))
                goto err_clear;

        ptr = skb_header_pointer(skb, offset, len, to);
        if (unlikely(!ptr))
                goto err_clear;
        if (ptr != to)
                memcpy(to, ptr, len);

        return 0;
err_clear:
        memset(to, 0, len);
        return -EFAULT;
}

static const struct bpf_func_proto bpf_skb_load_bytes_proto = {
        .func           = bpf_skb_load_bytes,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
        .arg3_type      = ARG_PTR_TO_UNINIT_MEM,
        .arg4_type      = ARG_CONST_SIZE,
};

BPF_CALL_4(bpf_flow_dissector_load_bytes,
           const struct bpf_flow_dissector *, ctx, u32, offset,
           void *, to, u32, len)
{
        void *ptr;

        if (unlikely(offset > 0xffff))
                goto err_clear;

        if (unlikely(!ctx->skb))
                goto err_clear;

        ptr = skb_header_pointer(ctx->skb, offset, len, to);
        if (unlikely(!ptr))
                goto err_clear;
        if (ptr != to)
                memcpy(to, ptr, len);

        return 0;
err_clear:
        memset(to, 0, len);
        return -EFAULT;
}

static const struct bpf_func_proto bpf_flow_dissector_load_bytes_proto = {
        .func           = bpf_flow_dissector_load_bytes,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
        .arg3_type      = ARG_PTR_TO_UNINIT_MEM,
        .arg4_type      = ARG_CONST_SIZE,
};

BPF_CALL_5(bpf_skb_load_bytes_relative, const struct sk_buff *, skb,
           u32, offset, void *, to, u32, len, u32, start_header)
{
        u8 *end = skb_tail_pointer(skb);
        u8 *net = skb_network_header(skb);
        u8 *mac = skb_mac_header(skb);
        u8 *ptr;

        if (unlikely(offset > 0xffff || len > (end - mac)))
                goto err_clear;

        switch (start_header) {
        case BPF_HDR_START_MAC:
                ptr = mac + offset;
                break;
        case BPF_HDR_START_NET:
                ptr = net + offset;
                break;
        default:
                goto err_clear;
        }

        if (likely(ptr >= mac && ptr + len <= end)) {
                memcpy(to, ptr, len);
                return 0;
        }

err_clear:
        memset(to, 0, len);
        return -EFAULT;
}

static const struct bpf_func_proto bpf_skb_load_bytes_relative_proto = {
        .func           = bpf_skb_load_bytes_relative,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
        .arg3_type      = ARG_PTR_TO_UNINIT_MEM,
        .arg4_type      = ARG_CONST_SIZE,
        .arg5_type      = ARG_ANYTHING,
};

BPF_CALL_2(bpf_skb_pull_data, struct sk_buff *, skb, u32, len)
{
        /* Idea is the following: should the needed direct read/write
         * test fail during runtime, we can pull in more data and redo
         * again, since implicitly, we invalidate previous checks here.
         *
         * Or, since we know how much we need to make read/writeable,
         * this can be done once at the program beginning for direct
         * access case. By this we overcome limitations of only current
         * headroom being accessible.
         */
        return bpf_try_make_writable(skb, len ? : skb_headlen(skb));
}

static const struct bpf_func_proto bpf_skb_pull_data_proto = {
        .func           = bpf_skb_pull_data,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
};

BPF_CALL_1(bpf_sk_fullsock, struct sock *, sk)
{
        return sk_fullsock(sk) ? (unsigned long)sk : (unsigned long)NULL;
}

static const struct bpf_func_proto bpf_sk_fullsock_proto = {
        .func           = bpf_sk_fullsock,
        .gpl_only       = false,
        .ret_type       = RET_PTR_TO_SOCKET_OR_NULL,
        .arg1_type      = ARG_PTR_TO_SOCK_COMMON,
};

static inline int sk_skb_try_make_writable(struct sk_buff *skb,
                                           unsigned int write_len)
{
        int err = __bpf_try_make_writable(skb, write_len);

        bpf_compute_data_end_sk_skb(skb);
        return err;
}

BPF_CALL_2(sk_skb_pull_data, struct sk_buff *, skb, u32, len)
{
        /* Idea is the following: should the needed direct read/write
         * test fail during runtime, we can pull in more data and redo
         * again, since implicitly, we invalidate previous checks here.
         *
         * Or, since we know how much we need to make read/writeable,
         * this can be done once at the program beginning for direct
         * access case. By this we overcome limitations of only current
         * headroom being accessible.
         */
        return sk_skb_try_make_writable(skb, len ? : skb_headlen(skb));
}

static const struct bpf_func_proto sk_skb_pull_data_proto = {
        .func           = sk_skb_pull_data,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
};

BPF_CALL_5(bpf_l3_csum_replace, struct sk_buff *, skb, u32, offset,
           u64, from, u64, to, u64, flags)
{
        __sum16 *ptr;

        if (unlikely(flags & ~(BPF_F_HDR_FIELD_MASK)))
                return -EINVAL;
        if (unlikely(offset > 0xffff || offset & 1))
                return -EFAULT;
        if (unlikely(bpf_try_make_writable(skb, offset + sizeof(*ptr))))
                return -EFAULT;

        ptr = (__sum16 *)(skb->data + offset);
        switch (flags & BPF_F_HDR_FIELD_MASK) {
        case 0:
                if (unlikely(from != 0))
                        return -EINVAL;

                csum_replace_by_diff(ptr, to);
                break;
        case 2:
                csum_replace2(ptr, from, to);
                break;
        case 4:
                csum_replace4(ptr, from, to);
                break;
        default:
                return -EINVAL;
        }

        return 0;
}

static const struct bpf_func_proto bpf_l3_csum_replace_proto = {
        .func           = bpf_l3_csum_replace,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
        .arg3_type      = ARG_ANYTHING,
        .arg4_type      = ARG_ANYTHING,
        .arg5_type      = ARG_ANYTHING,
};

BPF_CALL_5(bpf_l4_csum_replace, struct sk_buff *, skb, u32, offset,
           u64, from, u64, to, u64, flags)
{
        bool is_pseudo = flags & BPF_F_PSEUDO_HDR;
        bool is_mmzero = flags & BPF_F_MARK_MANGLED_0;
        bool do_mforce = flags & BPF_F_MARK_ENFORCE;
        __sum16 *ptr;

        if (unlikely(flags & ~(BPF_F_MARK_MANGLED_0 | BPF_F_MARK_ENFORCE |
                               BPF_F_PSEUDO_HDR | BPF_F_HDR_FIELD_MASK)))
                return -EINVAL;
        if (unlikely(offset > 0xffff || offset & 1))
                return -EFAULT;
        if (unlikely(bpf_try_make_writable(skb, offset + sizeof(*ptr))))
                return -EFAULT;

        ptr = (__sum16 *)(skb->data + offset);
        if (is_mmzero && !do_mforce && !*ptr)
                return 0;

        switch (flags & BPF_F_HDR_FIELD_MASK) {
        case 0:
                if (unlikely(from != 0))
                        return -EINVAL;

                inet_proto_csum_replace_by_diff(ptr, skb, to, is_pseudo);
                break;
        case 2:
                inet_proto_csum_replace2(ptr, skb, from, to, is_pseudo);
                break;
        case 4:
                inet_proto_csum_replace4(ptr, skb, from, to, is_pseudo);
                break;
        default:
                return -EINVAL;
        }

        if (is_mmzero && !*ptr)
                *ptr = CSUM_MANGLED_0;
        return 0;
}

static const struct bpf_func_proto bpf_l4_csum_replace_proto = {
        .func           = bpf_l4_csum_replace,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
        .arg3_type      = ARG_ANYTHING,
        .arg4_type      = ARG_ANYTHING,
        .arg5_type      = ARG_ANYTHING,
};

BPF_CALL_5(bpf_csum_diff, __be32 *, from, u32, from_size,
           __be32 *, to, u32, to_size, __wsum, seed)
{
        struct bpf_scratchpad *sp = this_cpu_ptr(&bpf_sp);
        u32 diff_size = from_size + to_size;
        int i, j = 0;

        /* This is quite flexible, some examples:
         *
         * from_size == 0, to_size > 0,  seed := csum --> pushing data
         * from_size > 0,  to_size == 0, seed := csum --> pulling data
         * from_size > 0,  to_size > 0,  seed := 0    --> diffing data
         *
         * Even for diffing, from_size and to_size don't need to be equal.
         */
        if (unlikely(((from_size | to_size) & (sizeof(__be32) - 1)) ||
                     diff_size > sizeof(sp->diff)))
                return -EINVAL;

        for (i = 0; i < from_size / sizeof(__be32); i++, j++)
                sp->diff[j] = ~from[i];
        for (i = 0; i <   to_size / sizeof(__be32); i++, j++)
                sp->diff[j] = to[i];

        return csum_partial(sp->diff, diff_size, seed);
}

static const struct bpf_func_proto bpf_csum_diff_proto = {
        .func           = bpf_csum_diff,
        .gpl_only       = false,
        .pkt_access     = true,
        .ret_type       = RET_INTEGER,

        .arg1_type      = ARG_PTR_TO_MEM_OR_NULL,
        .arg2_type      = ARG_CONST_SIZE_OR_ZERO,
        .arg3_type      = ARG_PTR_TO_MEM_OR_NULL,
        .arg4_type      = ARG_CONST_SIZE_OR_ZERO,
        .arg5_type      = ARG_ANYTHING,
};

BPF_CALL_2(bpf_csum_update, struct sk_buff *, skb, __wsum, csum)
{
        /* The interface is to be used in combination with bpf_csum_diff()
         * for direct packet writes. csum rotation for alignment as well
         * as emulating csum_sub() can be done from the eBPF program.
         */
        if (skb->ip_summed == CHECKSUM_COMPLETE)
                return (skb->csum = csum_add(skb->csum, csum));

        return -ENOTSUPP;
}

static const struct bpf_func_proto bpf_csum_update_proto = {
        .func           = bpf_csum_update,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
};

static inline int __bpf_rx_skb(struct net_device *dev, struct sk_buff *skb)
{
        return dev_forward_skb(dev, skb);
}

static inline int __bpf_rx_skb_no_mac(struct net_device *dev,
                                      struct sk_buff *skb)
{
        int ret = ____dev_forward_skb(dev, skb);

        if (likely(!ret)) {
                skb->dev = dev;
                ret = netif_rx(skb);
        }

        return ret;
}

static inline int __bpf_tx_skb(struct net_device *dev, struct sk_buff *skb)
{
        int ret;

        if (dev_xmit_recursion()) {
                net_crit_ratelimited("bpf: recursion limit reached on datapath, buggy bpf program?\n");
                kfree_skb(skb);
                return -ENETDOWN;
        }

        skb->dev = dev;

        dev_xmit_recursion_inc();
        ret = dev_queue_xmit(skb);
        dev_xmit_recursion_dec();

        return ret;
}

static int __bpf_redirect_no_mac(struct sk_buff *skb, struct net_device *dev,
                                 u32 flags)
{
        unsigned int mlen = skb_network_offset(skb);

        if (mlen) {
                __skb_pull(skb, mlen);

                /* At ingress, the mac header has already been pulled once.
                 * At egress, skb_pospull_rcsum has to be done in case that
                 * the skb is originated from ingress (i.e. a forwarded skb)
                 * to ensure that rcsum starts at net header.
                 */
                if (!skb_at_tc_ingress(skb))
                        skb_postpull_rcsum(skb, skb_mac_header(skb), mlen);
        }
        skb_pop_mac_header(skb);
        skb_reset_mac_len(skb);
        return flags & BPF_F_INGRESS ?
               __bpf_rx_skb_no_mac(dev, skb) : __bpf_tx_skb(dev, skb);
}

static int __bpf_redirect_common(struct sk_buff *skb, struct net_device *dev,
                                 u32 flags)
{
        /* Verify that a link layer header is carried */
        if (unlikely(skb->mac_header >= skb->network_header)) {
                kfree_skb(skb);
                return -ERANGE;
        }

        bpf_push_mac_rcsum(skb);
        return flags & BPF_F_INGRESS ?
               __bpf_rx_skb(dev, skb) : __bpf_tx_skb(dev, skb);
}

static int __bpf_redirect(struct sk_buff *skb, struct net_device *dev,
                          u32 flags)
{
        if (dev_is_mac_header_xmit(dev))
                return __bpf_redirect_common(skb, dev, flags);
        else
                return __bpf_redirect_no_mac(skb, dev, flags);
}

BPF_CALL_3(bpf_clone_redirect, struct sk_buff *, skb, u32, ifindex, u64, flags)
{
        struct net_device *dev;
        struct sk_buff *clone;
        int ret;

        if (unlikely(flags & ~(BPF_F_INGRESS)))
                return -EINVAL;

        dev = dev_get_by_index_rcu(dev_net(skb->dev), ifindex);
        if (unlikely(!dev))
                return -EINVAL;

        clone = skb_clone(skb, GFP_ATOMIC);
        if (unlikely(!clone))
                return -ENOMEM;

        /* For direct write, we need to keep the invariant that the skbs
         * we're dealing with need to be uncloned. Should uncloning fail
         * here, we need to free the just generated clone to unclone once
         * again.
         */
        ret = bpf_try_make_head_writable(skb);
        if (unlikely(ret)) {
                kfree_skb(clone);
                return -ENOMEM;
        }

        return __bpf_redirect(clone, dev, flags);
}

static const struct bpf_func_proto bpf_clone_redirect_proto = {
        .func           = bpf_clone_redirect,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
        .arg3_type      = ARG_ANYTHING,
};

DEFINE_PER_CPU(struct bpf_redirect_info, bpf_redirect_info);
EXPORT_PER_CPU_SYMBOL_GPL(bpf_redirect_info);

BPF_CALL_2(bpf_redirect, u32, ifindex, u64, flags)
{
        struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);

        if (unlikely(flags & ~(BPF_F_INGRESS)))
                return TC_ACT_SHOT;

        ri->ifindex = ifindex;
        ri->flags = flags;

        return TC_ACT_REDIRECT;
}

int skb_do_redirect(struct sk_buff *skb)
{
        struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
        struct net_device *dev;

        dev = dev_get_by_index_rcu(dev_net(skb->dev), ri->ifindex);
        ri->ifindex = 0;
        if (unlikely(!dev)) {
                kfree_skb(skb);
                return -EINVAL;
        }

        return __bpf_redirect(skb, dev, ri->flags);
}

static const struct bpf_func_proto bpf_redirect_proto = {
        .func           = bpf_redirect,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_ANYTHING,
        .arg2_type      = ARG_ANYTHING,
};

BPF_CALL_2(bpf_msg_apply_bytes, struct sk_msg *, msg, u32, bytes)
{
        msg->apply_bytes = bytes;
        return 0;
}

static const struct bpf_func_proto bpf_msg_apply_bytes_proto = {
        .func           = bpf_msg_apply_bytes,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
};

BPF_CALL_2(bpf_msg_cork_bytes, struct sk_msg *, msg, u32, bytes)
{
        msg->cork_bytes = bytes;
        return 0;
}

static const struct bpf_func_proto bpf_msg_cork_bytes_proto = {
        .func           = bpf_msg_cork_bytes,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
};

BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
           u32, end, u64, flags)
{
        u32 len = 0, offset = 0, copy = 0, poffset = 0, bytes = end - start;
        u32 first_sge, last_sge, i, shift, bytes_sg_total;
        struct scatterlist *sge;
        u8 *raw, *to, *from;
        struct page *page;

        if (unlikely(flags || end <= start))
                return -EINVAL;

        /* First find the starting scatterlist element */
        i = msg->sg.start;
        do {
                len = sk_msg_elem(msg, i)->length;
                if (start < offset + len)
                        break;
                offset += len;
                sk_msg_iter_var_next(i);
        } while (i != msg->sg.end);

        if (unlikely(start >= offset + len))
                return -EINVAL;

        first_sge = i;
        /* The start may point into the sg element so we need to also
         * account for the headroom.
         */
        bytes_sg_total = start - offset + bytes;
        if (!msg->sg.copy[i] && bytes_sg_total <= len)
                goto out;

        /* At this point we need to linearize multiple scatterlist
         * elements or a single shared page. Either way we need to
         * copy into a linear buffer exclusively owned by BPF. Then
         * place the buffer in the scatterlist and fixup the original
         * entries by removing the entries now in the linear buffer
         * and shifting the remaining entries. For now we do not try
         * to copy partial entries to avoid complexity of running out
         * of sg_entry slots. The downside is reading a single byte
         * will copy the entire sg entry.
         */
        do {
                copy += sk_msg_elem(msg, i)->length;
                sk_msg_iter_var_next(i);
                if (bytes_sg_total <= copy)
                        break;
        } while (i != msg->sg.end);
        last_sge = i;

        if (unlikely(bytes_sg_total > copy))
                return -EINVAL;

        page = alloc_pages(__GFP_NOWARN | GFP_ATOMIC | __GFP_COMP,
                           get_order(copy));
        if (unlikely(!page))
                return -ENOMEM;

        raw = page_address(page);
        i = first_sge;
        do {
                sge = sk_msg_elem(msg, i);
                from = sg_virt(sge);
                len = sge->length;
                to = raw + poffset;

                memcpy(to, from, len);
                poffset += len;
                sge->length = 0;
                put_page(sg_page(sge));

                sk_msg_iter_var_next(i);
        } while (i != last_sge);

        sg_set_page(&msg->sg.data[first_sge], page, copy, 0);

        /* To repair sg ring we need to shift entries. If we only
         * had a single entry though we can just replace it and
         * be done. Otherwise walk the ring and shift the entries.
         */
        WARN_ON_ONCE(last_sge == first_sge);
        shift = last_sge > first_sge ?
                last_sge - first_sge - 1 :
                MAX_SKB_FRAGS - first_sge + last_sge - 1;
        if (!shift)
                goto out;

        i = first_sge;
        sk_msg_iter_var_next(i);
        do {
                u32 move_from;

                if (i + shift >= MAX_MSG_FRAGS)
                        move_from = i + shift - MAX_MSG_FRAGS;
                else
                        move_from = i + shift;
                if (move_from == msg->sg.end)
                        break;

                msg->sg.data[i] = msg->sg.data[move_from];
                msg->sg.data[move_from].length = 0;
                msg->sg.data[move_from].page_link = 0;
                msg->sg.data[move_from].offset = 0;
                sk_msg_iter_var_next(i);
        } while (1);

        msg->sg.end = msg->sg.end - shift > msg->sg.end ?
                      msg->sg.end - shift + MAX_MSG_FRAGS :
                      msg->sg.end - shift;
out:
        msg->data = sg_virt(&msg->sg.data[first_sge]) + start - offset;
        msg->data_end = msg->data + bytes;
        return 0;
}

static const struct bpf_func_proto bpf_msg_pull_data_proto = {
        .func           = bpf_msg_pull_data,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
        .arg3_type      = ARG_ANYTHING,
        .arg4_type      = ARG_ANYTHING,
};

BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start,
           u32, len, u64, flags)
{
        struct scatterlist sge, nsge, nnsge, rsge = {0}, *psge;
        u32 new, i = 0, l, space, copy = 0, offset = 0;
        u8 *raw, *to, *from;
        struct page *page;

        if (unlikely(flags))
                return -EINVAL;

        /* First find the starting scatterlist element */
        i = msg->sg.start;
        do {
                l = sk_msg_elem(msg, i)->length;

                if (start < offset + l)
                        break;
                offset += l;
                sk_msg_iter_var_next(i);
        } while (i != msg->sg.end);

        if (start >= offset + l)
                return -EINVAL;

        space = MAX_MSG_FRAGS - sk_msg_elem_used(msg);

        /* If no space available will fallback to copy, we need at
         * least one scatterlist elem available to push data into
         * when start aligns to the beginning of an element or two
         * when it falls inside an element. We handle the start equals
         * offset case because its the common case for inserting a
         * header.
         */
        if (!space || (space == 1 && start != offset))
                copy = msg->sg.data[i].length;

        page = alloc_pages(__GFP_NOWARN | GFP_ATOMIC | __GFP_COMP,
                           get_order(copy + len));
        if (unlikely(!page))
                return -ENOMEM;

        if (copy) {
                int front, back;

                raw = page_address(page);

                psge = sk_msg_elem(msg, i);
                front = start - offset;
                back = psge->length - front;
                from = sg_virt(psge);

                if (front)
                        memcpy(raw, from, front);

                if (back) {
                        from += front;
                        to = raw + front + len;

                        memcpy(to, from, back);
                }

                put_page(sg_page(psge));
        } else if (start - offset) {
                psge = sk_msg_elem(msg, i);
                rsge = sk_msg_elem_cpy(msg, i);

                psge->length = start - offset;
                rsge.length -= psge->length;
                rsge.offset += start;

                sk_msg_iter_var_next(i);
                sg_unmark_end(psge);
                sk_msg_iter_next(msg, end);
        }

        /* Slot(s) to place newly allocated data */
        new = i;

        /* Shift one or two slots as needed */
        if (!copy) {
                sge = sk_msg_elem_cpy(msg, i);

                sk_msg_iter_var_next(i);
                sg_unmark_end(&sge);
                sk_msg_iter_next(msg, end);

                nsge = sk_msg_elem_cpy(msg, i);
                if (rsge.length) {
                        sk_msg_iter_var_next(i);
                        nnsge = sk_msg_elem_cpy(msg, i);
                }

                while (i != msg->sg.end) {
                        msg->sg.data[i] = sge;
                        sge = nsge;
                        sk_msg_iter_var_next(i);
                        if (rsge.length) {
                                nsge = nnsge;
                                nnsge = sk_msg_elem_cpy(msg, i);
                        } else {
                                nsge = sk_msg_elem_cpy(msg, i);
                        }
                }
        }

        /* Place newly allocated data buffer */
        sk_mem_charge(msg->sk, len);
        msg->sg.size += len;
        msg->sg.copy[new] = false;
        sg_set_page(&msg->sg.data[new], page, len + copy, 0);
        if (rsge.length) {
                get_page(sg_page(&rsge));
                sk_msg_iter_var_next(new);
                msg->sg.data[new] = rsge;
        }

        sk_msg_compute_data_pointers(msg);
        return 0;
}

static const struct bpf_func_proto bpf_msg_push_data_proto = {
        .func           = bpf_msg_push_data,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
        .arg3_type      = ARG_ANYTHING,
        .arg4_type      = ARG_ANYTHING,
};

static void sk_msg_shift_left(struct sk_msg *msg, int i)
{
        int prev;

        do {
                prev = i;
                sk_msg_iter_var_next(i);
                msg->sg.data[prev] = msg->sg.data[i];
        } while (i != msg->sg.end);

        sk_msg_iter_prev(msg, end);
}

static void sk_msg_shift_right(struct sk_msg *msg, int i)
{
        struct scatterlist tmp, sge;

        sk_msg_iter_next(msg, end);
        sge = sk_msg_elem_cpy(msg, i);
        sk_msg_iter_var_next(i);
        tmp = sk_msg_elem_cpy(msg, i);

        while (i != msg->sg.end) {
                msg->sg.data[i] = sge;
                sk_msg_iter_var_next(i);
                sge = tmp;
                tmp = sk_msg_elem_cpy(msg, i);
        }
}

BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
           u32, len, u64, flags)
{
        u32 i = 0, l, space, offset = 0;
        u64 last = start + len;
        int pop;

        if (unlikely(flags))
                return -EINVAL;

        /* First find the starting scatterlist element */
        i = msg->sg.start;
        do {
                l = sk_msg_elem(msg, i)->length;

                if (start < offset + l)
                        break;
                offset += l;
                sk_msg_iter_var_next(i);
        } while (i != msg->sg.end);

        /* Bounds checks: start and pop must be inside message */
        if (start >= offset + l || last >= msg->sg.size)
                return -EINVAL;

        space = MAX_MSG_FRAGS - sk_msg_elem_used(msg);

        pop = len;
        /* --------------| offset
         * -| start      |-------- len -------|
         *
         *  |----- a ----|-------- pop -------|----- b ----|
         *  |______________________________________________| length
         *
         *
         * a:   region at front of scatter element to save
         * b:   region at back of scatter element to save when length > A + pop
         * pop: region to pop from element, same as input 'pop' here will be
         *      decremented below per iteration.
         *
         * Two top-level cases to handle when start != offset, first B is non
         * zero and second B is zero corresponding to when a pop includes more
         * than one element.
         *
         * Then if B is non-zero AND there is no space allocate space and
         * compact A, B regions into page. If there is space shift ring to
         * the rigth free'ing the next element in ring to place B, leaving
         * A untouched except to reduce length.
         */
        if (start != offset) {
                struct scatterlist *nsge, *sge = sk_msg_elem(msg, i);
                int a = start;
                int b = sge->length - pop - a;

                sk_msg_iter_var_next(i);

                if (pop < sge->length - a) {
                        if (space) {
                                sge->length = a;
                                sk_msg_shift_right(msg, i);
                                nsge = sk_msg_elem(msg, i);
                                get_page(sg_page(sge));
                                sg_set_page(nsge,
                                            sg_page(sge),
                                            b, sge->offset + pop + a);
                        } else {
                                struct page *page, *orig;
                                u8 *to, *from;

                                page = alloc_pages(__GFP_NOWARN |
                                                   __GFP_COMP   | GFP_ATOMIC,
                                                   get_order(a + b));
                                if (unlikely(!page))
                                        return -ENOMEM;

                                sge->length = a;
                                orig = sg_page(sge);
                                from = sg_virt(sge);
                                to = page_address(page);
                                memcpy(to, from, a);
                                memcpy(to + a, from + a + pop, b);
                                sg_set_page(sge, page, a + b, 0);
                                put_page(orig);
                        }
                        pop = 0;
                } else if (pop >= sge->length - a) {
                        sge->length = a;
                        pop -= (sge->length - a);
                }
        }

        /* From above the current layout _must_ be as follows,
         *
         * -| offset
         * -| start
         *
         *  |---- pop ---|---------------- b ------------|
         *  |____________________________________________| length
         *
         * Offset and start of the current msg elem are equal because in the
         * previous case we handled offset != start and either consumed the
         * entire element and advanced to the next element OR pop == 0.
         *
         * Two cases to handle here are first pop is less than the length
         * leaving some remainder b above. Simply adjust the element's layout
         * in this case. Or pop >= length of the element so that b = 0. In this
         * case advance to next element decrementing pop.
         */
        while (pop) {
                struct scatterlist *sge = sk_msg_elem(msg, i);

                if (pop < sge->length) {
                        sge->length -= pop;
                        sge->offset += pop;
                        pop = 0;
                } else {
                        pop -= sge->length;
                        sk_msg_shift_left(msg, i);
                }
                sk_msg_iter_var_next(i);
        }

        sk_mem_uncharge(msg->sk, len - pop);
        msg->sg.size -= (len - pop);
        sk_msg_compute_data_pointers(msg);
        return 0;
}

static const struct bpf_func_proto bpf_msg_pop_data_proto = {
        .func           = bpf_msg_pop_data,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
        .arg3_type      = ARG_ANYTHING,
        .arg4_type      = ARG_ANYTHING,
};

BPF_CALL_1(bpf_get_cgroup_classid, const struct sk_buff *, skb)
{
        return task_get_classid(skb);
}

static const struct bpf_func_proto bpf_get_cgroup_classid_proto = {
        .func           = bpf_get_cgroup_classid,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
};

BPF_CALL_1(bpf_get_route_realm, const struct sk_buff *, skb)
{
        return dst_tclassid(skb);
}

static const struct bpf_func_proto bpf_get_route_realm_proto = {
        .func           = bpf_get_route_realm,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
};

BPF_CALL_1(bpf_get_hash_recalc, struct sk_buff *, skb)
{
        /* If skb_clear_hash() was called due to mangling, we can
         * trigger SW recalculation here. Later access to hash
         * can then use the inline skb->hash via context directly
         * instead of calling this helper again.
         */
        return skb_get_hash(skb);
}

static const struct bpf_func_proto bpf_get_hash_recalc_proto = {
        .func           = bpf_get_hash_recalc,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
};

BPF_CALL_1(bpf_set_hash_invalid, struct sk_buff *, skb)
{
        /* After all direct packet write, this can be used once for
         * triggering a lazy recalc on next skb_get_hash() invocation.
         */
        skb_clear_hash(skb);
        return 0;
}

static const struct bpf_func_proto bpf_set_hash_invalid_proto = {
        .func           = bpf_set_hash_invalid,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
};

BPF_CALL_2(bpf_set_hash, struct sk_buff *, skb, u32, hash)
{
        /* Set user specified hash as L4(+), so that it gets returned
         * on skb_get_hash() call unless BPF prog later on triggers a
         * skb_clear_hash().
         */
        __skb_set_sw_hash(skb, hash, true);
        return 0;
}

static const struct bpf_func_proto bpf_set_hash_proto = {
        .func           = bpf_set_hash,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
};

BPF_CALL_3(bpf_skb_vlan_push, struct sk_buff *, skb, __be16, vlan_proto,
           u16, vlan_tci)
{
        int ret;

        if (unlikely(vlan_proto != htons(ETH_P_8021Q) &&
                     vlan_proto != htons(ETH_P_8021AD)))
                vlan_proto = htons(ETH_P_8021Q);

        bpf_push_mac_rcsum(skb);
        ret = skb_vlan_push(skb, vlan_proto, vlan_tci);
        bpf_pull_mac_rcsum(skb);

        bpf_compute_data_pointers(skb);
        return ret;
}

static const struct bpf_func_proto bpf_skb_vlan_push_proto = {
        .func           = bpf_skb_vlan_push,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
        .arg3_type      = ARG_ANYTHING,
};

BPF_CALL_1(bpf_skb_vlan_pop, struct sk_buff *, skb)
{
        int ret;

        bpf_push_mac_rcsum(skb);
        ret = skb_vlan_pop(skb);
        bpf_pull_mac_rcsum(skb);

        bpf_compute_data_pointers(skb);
        return ret;
}

static const struct bpf_func_proto bpf_skb_vlan_pop_proto = {
        .func           = bpf_skb_vlan_pop,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
};

static int bpf_skb_generic_push(struct sk_buff *skb, u32 off, u32 len)
{
        /* Caller already did skb_cow() with len as headroom,
         * so no need to do it here.
         */
        skb_push(skb, len);
        memmove(skb->data, skb->data + len, off);
        memset(skb->data + off, 0, len);

        /* No skb_postpush_rcsum(skb, skb->data + off, len)
         * needed here as it does not change the skb->csum
         * result for checksum complete when summing over
         * zeroed blocks.
         */
        return 0;
}

static int bpf_skb_generic_pop(struct sk_buff *skb, u32 off, u32 len)
{
        /* skb_ensure_writable() is not needed here, as we're
         * already working on an uncloned skb.
         */
        if (unlikely(!pskb_may_pull(skb, off + len)))
                return -ENOMEM;

        skb_postpull_rcsum(skb, skb->data + off, len);
        memmove(skb->data + len, skb->data, off);
        __skb_pull(skb, len);

        return 0;
}

static int bpf_skb_net_hdr_push(struct sk_buff *skb, u32 off, u32 len)
{
        bool trans_same = skb->transport_header == skb->network_header;
        int ret;

        /* There's no need for __skb_push()/__skb_pull() pair to
         * get to the start of the mac header as we're guaranteed
         * to always start from here under eBPF.
         */
        ret = bpf_skb_generic_push(skb, off, len);
        if (likely(!ret)) {
                skb->mac_header -= len;
                skb->network_header -= len;
                if (trans_same)
                        skb->transport_header = skb->network_header;
        }

        return ret;
}

static int bpf_skb_net_hdr_pop(struct sk_buff *skb, u32 off, u32 len)
{
        bool trans_same = skb->transport_header == skb->network_header;
        int ret;

        /* Same here, __skb_push()/__skb_pull() pair not needed. */
        ret = bpf_skb_generic_pop(skb, off, len);
        if (likely(!ret)) {
                skb->mac_header += len;
                skb->network_header += len;
                if (trans_same)
                        skb->transport_header = skb->network_header;
        }

        return ret;
}

static int bpf_skb_proto_4_to_6(struct sk_buff *skb)
{
        const u32 len_diff = sizeof(struct ipv6hdr) - sizeof(struct iphdr);
        u32 off = skb_mac_header_len(skb);
        int ret;

        if (skb_is_gso(skb) && !skb_is_gso_tcp(skb))
                return -ENOTSUPP;

        ret = skb_cow(skb, len_diff);
        if (unlikely(ret < 0))
                return ret;

        ret = bpf_skb_net_hdr_push(skb, off, len_diff);
        if (unlikely(ret < 0))
                return ret;

        if (skb_is_gso(skb)) {
                struct skb_shared_info *shinfo = skb_shinfo(skb);

                /* SKB_GSO_TCPV4 needs to be changed into
                 * SKB_GSO_TCPV6.
                 */
                if (shinfo->gso_type & SKB_GSO_TCPV4) {
                        shinfo->gso_type &= ~SKB_GSO_TCPV4;
                        shinfo->gso_type |=  SKB_GSO_TCPV6;
                }

                /* Due to IPv6 header, MSS needs to be downgraded. */
                skb_decrease_gso_size(shinfo, len_diff);
                /* Header must be checked, and gso_segs recomputed. */
                shinfo->gso_type |= SKB_GSO_DODGY;
                shinfo->gso_segs = 0;
        }

        skb->protocol = htons(ETH_P_IPV6);
        skb_clear_hash(skb);

        return 0;
}

static int bpf_skb_proto_6_to_4(struct sk_buff *skb)
{
        const u32 len_diff = sizeof(struct ipv6hdr) - sizeof(struct iphdr);
        u32 off = skb_mac_header_len(skb);
        int ret;

        if (skb_is_gso(skb) && !skb_is_gso_tcp(skb))
                return -ENOTSUPP;

        ret = skb_unclone(skb, GFP_ATOMIC);
        if (unlikely(ret < 0))
                return ret;

        ret = bpf_skb_net_hdr_pop(skb, off, len_diff);
        if (unlikely(ret < 0))
                return ret;

        if (skb_is_gso(skb)) {
                struct skb_shared_info *shinfo = skb_shinfo(skb);

                /* SKB_GSO_TCPV6 needs to be changed into
                 * SKB_GSO_TCPV4.
                 */
                if (shinfo->gso_type & SKB_GSO_TCPV6) {
                        shinfo->gso_type &= ~SKB_GSO_TCPV6;
                        shinfo->gso_type |=  SKB_GSO_TCPV4;
                }

                /* Due to IPv4 header, MSS can be upgraded. */
                skb_increase_gso_size(shinfo, len_diff);
                /* Header must be checked, and gso_segs recomputed. */
                shinfo->gso_type |= SKB_GSO_DODGY;
                shinfo->gso_segs = 0;
        }

        skb->protocol = htons(ETH_P_IP);
        skb_clear_hash(skb);

        return 0;
}

static int bpf_skb_proto_xlat(struct sk_buff *skb, __be16 to_proto)
{
        __be16 from_proto = skb->protocol;

        if (from_proto == htons(ETH_P_IP) &&
              to_proto == htons(ETH_P_IPV6))
                return bpf_skb_proto_4_to_6(skb);

        if (from_proto == htons(ETH_P_IPV6) &&
              to_proto == htons(ETH_P_IP))
                return bpf_skb_proto_6_to_4(skb);

        return -ENOTSUPP;
}

BPF_CALL_3(bpf_skb_change_proto, struct sk_buff *, skb, __be16, proto,
           u64, flags)
{
        int ret;

        if (unlikely(flags))
                return -EINVAL;

        /* General idea is that this helper does the basic groundwork
         * needed for changing the protocol, and eBPF program fills the
         * rest through bpf_skb_store_bytes(), bpf_lX_csum_replace()
         * and other helpers, rather than passing a raw buffer here.
         *
         * The rationale is to keep this minimal and without a need to
         * deal with raw packet data. F.e. even if we would pass buffers
         * here, the program still needs to call the bpf_lX_csum_replace()
         * helpers anyway. Plus, this way we keep also separation of
         * concerns, since f.e. bpf_skb_store_bytes() should only take
         * care of stores.
         *
         * Currently, additional options and extension header space are
         * not supported, but flags register is reserved so we can adapt
         * that. For offloads, we mark packet as dodgy, so that headers
         * need to be verified first.
         */
        ret = bpf_skb_proto_xlat(skb, proto);
        bpf_compute_data_pointers(skb);
        return ret;
}

static const struct bpf_func_proto bpf_skb_change_proto_proto = {
        .func           = bpf_skb_change_proto,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
        .arg3_type      = ARG_ANYTHING,
};

BPF_CALL_2(bpf_skb_change_type, struct sk_buff *, skb, u32, pkt_type)
{
        /* We only allow a restricted subset to be changed for now. */
        if (unlikely(!skb_pkt_type_ok(skb->pkt_type) ||
                     !skb_pkt_type_ok(pkt_type)))
                return -EINVAL;

        skb->pkt_type = pkt_type;
        return 0;
}

static const struct bpf_func_proto bpf_skb_change_type_proto = {
        .func           = bpf_skb_change_type,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
};

static u32 bpf_skb_net_base_len(const struct sk_buff *skb)
{
        switch (skb->protocol) {
        case htons(ETH_P_IP):
                return sizeof(struct iphdr);
        case htons(ETH_P_IPV6):
                return sizeof(struct ipv6hdr);
        default:
                return ~0U;
        }
}

#define BPF_F_ADJ_ROOM_ENCAP_L3_MASK    (BPF_F_ADJ_ROOM_ENCAP_L3_IPV4 | \
                                         BPF_F_ADJ_ROOM_ENCAP_L3_IPV6)