LXR linux/net/ipv4/bpf_tcp

   1// SPDX-License-Identifier: GPL-2.0
   2/* Copyright (c) 2019 Facebook  */
   3
   4#include <linux/types.h>
   5#include <linux/bpf_verifier.h>
   6#include <linux/bpf.h>
   7#include <linux/btf.h>
   8#include <linux/btf_ids.h>
   9#include <linux/filter.h>
  10#include <net/tcp.h>
  11#include <net/bpf_sk_storage.h>
  12
  13/* "extern" is to avoid sparse warning.  It is only used in bpf_struct_ops.c. */
  14extern struct bpf_struct_ops bpf_tcp_congestion_ops;
  15
  16static u32 optional_ops[] = {
  17        offsetof(struct tcp_congestion_ops, init),
  18        offsetof(struct tcp_congestion_ops, release),
  19        offsetof(struct tcp_congestion_ops, set_state),
  20        offsetof(struct tcp_congestion_ops, cwnd_event),
  21        offsetof(struct tcp_congestion_ops, in_ack_event),
  22        offsetof(struct tcp_congestion_ops, pkts_acked),
  23        offsetof(struct tcp_congestion_ops, min_tso_segs),
  24        offsetof(struct tcp_congestion_ops, sndbuf_expand),
  25        offsetof(struct tcp_congestion_ops, cong_control),
  26};
  27
  28static u32 unsupported_ops[] = {
  29        offsetof(struct tcp_congestion_ops, get_info),
  30};
  31
  32static const struct btf_type *tcp_sock_type;
  33static u32 tcp_sock_id, sock_id;
  34
  35static int bpf_tcp_ca_init(struct btf *btf)
  36{
  37        s32 type_id;
  38
  39        type_id = btf_find_by_name_kind(btf, "sock", BTF_KIND_STRUCT);
  40        if (type_id < 0)
  41                return -EINVAL;
  42        sock_id = type_id;
  43
  44        type_id = btf_find_by_name_kind(btf, "tcp_sock", BTF_KIND_STRUCT);
  45        if (type_id < 0)
  46                return -EINVAL;
  47        tcp_sock_id = type_id;
  48        tcp_sock_type = btf_type_by_id(btf, tcp_sock_id);
  49
  50        return 0;
  51}
  52
  53static bool is_optional(u32 member_offset)
  54{
  55        unsigned int i;
  56
  57        for (i = 0; i < ARRAY_SIZE(optional_ops); i++) {
  58                if (member_offset == optional_ops[i])
  59                        return true;
  60        }
  61
  62        return false;
  63}
  64
  65static bool is_unsupported(u32 member_offset)
  66{
  67        unsigned int i;
  68
  69        for (i = 0; i < ARRAY_SIZE(unsupported_ops); i++) {
  70                if (member_offset == unsupported_ops[i])
  71                        return true;
  72        }
  73
  74        return false;
  75}
  76
  77extern struct btf *btf_vmlinux;
  78
  79static bool bpf_tcp_ca_is_valid_access(int off, int size,
  80                                       enum bpf_access_type type,
  81                                       const struct bpf_prog *prog,
  82                                       struct bpf_insn_access_aux *info)
  83{
  84        if (!bpf_tracing_btf_ctx_access(off, size, type, prog, info))
  85                return false;
  86
  87        if (info->reg_type == PTR_TO_BTF_ID && info->btf_id == sock_id)
  88                /* promote it to tcp_sock */
  89                info->btf_id = tcp_sock_id;
  90
  91        return true;
  92}
  93
  94static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
  95                                        const struct btf *btf,
  96                                        const struct btf_type *t, int off,
  97                                        int size, enum bpf_access_type atype,
  98                                        u32 *next_btf_id)
  99{
 100        size_t end;
 101
 102        if (atype == BPF_READ)
 103                return btf_struct_access(log, btf, t, off, size, atype, next_btf_id);
 104
 105        if (t != tcp_sock_type) {
 106                bpf_log(log, "only read is supported\n");
 107                return -EACCES;
 108        }
 109
 110        switch (off) {
 111        case bpf_ctx_range(struct inet_connection_sock, icsk_ca_priv):
 112                end = offsetofend(struct inet_connection_sock, icsk_ca_priv);
 113                break;
 114        case offsetof(struct inet_connection_sock, icsk_ack.pending):
 115                end = offsetofend(struct inet_connection_sock,
 116                                  icsk_ack.pending);
 117                break;
 118        case offsetof(struct tcp_sock, snd_cwnd):
 119                end = offsetofend(struct tcp_sock, snd_cwnd);
 120                break;
 121        case offsetof(struct tcp_sock, snd_cwnd_cnt):
 122                end = offsetofend(struct tcp_sock, snd_cwnd_cnt);
 123                break;
 124        case offsetof(struct tcp_sock, snd_ssthresh):
 125                end = offsetofend(struct tcp_sock, snd_ssthresh);
 126                break;
 127        case offsetof(struct tcp_sock, ecn_flags):
 128                end = offsetofend(struct tcp_sock, ecn_flags);
 129                break;
 130        default:
 131                bpf_log(log, "no write support to tcp_sock at off %d\n", off);
 132                return -EACCES;
 133        }
 134
 135        if (off + size > end) {
 136                bpf_log(log,
 137                        "write access at off %d with size %d beyond the member of tcp_sock ended at %zu\n",
 138                        off, size, end);
 139                return -EACCES;
 140        }
 141
 142        return NOT_INIT;
 143}
 144
 145BPF_CALL_2(bpf_tcp_send_ack, struct tcp_sock *, tp, u32, rcv_nxt)
 146{
 147        /* bpf_tcp_ca prog cannot have NULL tp */
 148        __tcp_send_ack((struct sock *)tp, rcv_nxt);
 149        return 0;
 150}
 151
 152static const struct bpf_func_proto bpf_tcp_send_ack_proto = {
 153        .func           = bpf_tcp_send_ack,
 154        .gpl_only       = false,
 155        /* In case we want to report error later */
 156        .ret_type       = RET_INTEGER,
 157        .arg1_type      = ARG_PTR_TO_BTF_ID,
 158        .arg1_btf_id    = &tcp_sock_id,
 159        .arg2_type      = ARG_ANYTHING,
 160};
 161
 162static u32 prog_ops_moff(const struct bpf_prog *prog)
 163{
 164        const struct btf_member *m;
 165        const struct btf_type *t;
 166        u32 midx;
 167
 168        midx = prog->expected_attach_type;
 169        t = bpf_tcp_congestion_ops.type;
 170        m = &btf_type_member(t)[midx];
 171
 172        return btf_member_bit_offset(t, m) / 8;
 173}
 174
 175static const struct bpf_func_proto *
 176bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
 177                          const struct bpf_prog *prog)
 178{
 179        switch (func_id) {
 180        case BPF_FUNC_tcp_send_ack:
 181                return &bpf_tcp_send_ack_proto;
 182        case BPF_FUNC_sk_storage_get:
 183                return &bpf_sk_storage_get_proto;
 184        case BPF_FUNC_sk_storage_delete:
 185                return &bpf_sk_storage_delete_proto;
 186        case BPF_FUNC_setsockopt:
 187                /* Does not allow release() to call setsockopt.
 188                 * release() is called when the current bpf-tcp-cc
 189                 * is retiring.  It is not allowed to call
 190                 * setsockopt() to make further changes which
 191                 * may potentially allocate new resources.
 192                 */
 193                if (prog_ops_moff(prog) !=
 194                    offsetof(struct tcp_congestion_ops, release))
 195                        return &bpf_sk_setsockopt_proto;
 196                return NULL;
 197        case BPF_FUNC_getsockopt:
 198                /* Since get/setsockopt is usually expected to
 199                 * be available together, disable getsockopt for
 200                 * release also to avoid usage surprise.
 201                 * The bpf-tcp-cc already has a more powerful way
 202                 * to read tcp_sock from the PTR_TO_BTF_ID.
 203                 */
 204                if (prog_ops_moff(prog) !=
 205                    offsetof(struct tcp_congestion_ops, release))
 206                        return &bpf_sk_getsockopt_proto;
 207                return NULL;
 208        case BPF_FUNC_ktime_get_coarse_ns:
 209                return &bpf_ktime_get_coarse_ns_proto;
 210        default:
 211                return bpf_base_func_proto(func_id);
 212        }
 213}
 214
 215BTF_SET_START(bpf_tcp_ca_kfunc_ids)
 216BTF_ID(func, tcp_reno_ssthresh)
 217BTF_ID(func, tcp_reno_cong_avoid)
 218BTF_ID(func, tcp_reno_undo_cwnd)
 219BTF_ID(func, tcp_slow_start)
 220BTF_ID(func, tcp_cong_avoid_ai)
 221BTF_SET_END(bpf_tcp_ca_kfunc_ids)
 222
 223static bool bpf_tcp_ca_check_kfunc_call(u32 kfunc_btf_id, struct module *owner)
 224{
 225        if (btf_id_set_contains(&bpf_tcp_ca_kfunc_ids, kfunc_btf_id))
 226                return true;
 227        return bpf_check_mod_kfunc_call(&bpf_tcp_ca_kfunc_list, kfunc_btf_id, owner);
 228}
 229
 230static const struct bpf_verifier_ops bpf_tcp_ca_verifier_ops = {
 231        .get_func_proto         = bpf_tcp_ca_get_func_proto,
 232        .is_valid_access        = bpf_tcp_ca_is_valid_access,
 233        .btf_struct_access      = bpf_tcp_ca_btf_struct_access,
 234        .check_kfunc_call       = bpf_tcp_ca_check_kfunc_call,
 235};
 236
 237static int bpf_tcp_ca_init_member(const struct btf_type *t,
 238                                  const struct btf_member *member,
 239                                  void *kdata, const void *udata)
 240{
 241        const struct tcp_congestion_ops *utcp_ca;
 242        struct tcp_congestion_ops *tcp_ca;
 243        int prog_fd;
 244        u32 moff;
 245
 246        utcp_ca = (const struct tcp_congestion_ops *)udata;
 247        tcp_ca = (struct tcp_congestion_ops *)kdata;
 248
 249        moff = btf_member_bit_offset(t, member) / 8;
 250        switch (moff) {
 251        case offsetof(struct tcp_congestion_ops, flags):
 252                if (utcp_ca->flags & ~TCP_CONG_MASK)
 253                        return -EINVAL;
 254                tcp_ca->flags = utcp_ca->flags;
 255                return 1;
 256        case offsetof(struct tcp_congestion_ops, name):
 257                if (bpf_obj_name_cpy(tcp_ca->name, utcp_ca->name,
 258                                     sizeof(tcp_ca->name)) <= 0)
 259                        return -EINVAL;
 260                if (tcp_ca_find(utcp_ca->name))
 261                        return -EEXIST;
 262                return 1;
 263        }
 264
 265        if (!btf_type_resolve_func_ptr(btf_vmlinux, member->type, NULL))
 266                return 0;
 267
 268        /* Ensure bpf_prog is provided for compulsory func ptr */
 269        prog_fd = (int)(*(unsigned long *)(udata + moff));
 270        if (!prog_fd && !is_optional(moff) && !is_unsupported(moff))
 271                return -EINVAL;
 272
 273        return 0;
 274}
 275
 276static int bpf_tcp_ca_check_member(const struct btf_type *t,
 277                                   const struct btf_member *member)
 278{
 279        if (is_unsupported(btf_member_bit_offset(t, member) / 8))
 280                return -ENOTSUPP;
 281        return 0;
 282}
 283
 284static int bpf_tcp_ca_reg(void *kdata)
 285{
 286        return tcp_register_congestion_control(kdata);
 287}
 288
 289static void bpf_tcp_ca_unreg(void *kdata)
 290{
 291        tcp_unregister_congestion_control(kdata);
 292}
 293
 294struct bpf_struct_ops bpf_tcp_congestion_ops = {
 295        .verifier_ops = &bpf_tcp_ca_verifier_ops,
 296        .reg = bpf_tcp_ca_reg,
 297        .unreg = bpf_tcp_ca_unreg,
 298        .check_member = bpf_tcp_ca_check_member,
 299        .init_member = bpf_tcp_ca_init_member,
 300        .init = bpf_tcp_ca_init,
 301        .name = "tcp_congestion_ops",
 302};
 303