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 (off < 0 || off >= sizeof(__u64) * MAX_BPF_FUNC_ARGS)
  85                return false;
  86        if (type != BPF_READ)
  87                return false;
  88        if (off % size != 0)
  89                return false;
  90
  91        if (!btf_ctx_access(off, size, type, prog, info))
  92                return false;
  93
  94        if (info->reg_type == PTR_TO_BTF_ID && info->btf_id == sock_id)
  95                /* promote it to tcp_sock */
  96                info->btf_id = tcp_sock_id;
  97
  98        return true;
  99}
 100
 101static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
 102                                        const struct btf *btf,
 103                                        const struct btf_type *t, int off,
 104                                        int size, enum bpf_access_type atype,
 105                                        u32 *next_btf_id)
 106{
 107        size_t end;
 108
 109        if (atype == BPF_READ)
 110                return btf_struct_access(log, btf, t, off, size, atype, next_btf_id);
 111
 112        if (t != tcp_sock_type) {
 113                bpf_log(log, "only read is supported\n");
 114                return -EACCES;
 115        }
 116
 117        switch (off) {
 118        case bpf_ctx_range(struct inet_connection_sock, icsk_ca_priv):
 119                end = offsetofend(struct inet_connection_sock, icsk_ca_priv);
 120                break;
 121        case offsetof(struct inet_connection_sock, icsk_ack.pending):
 122                end = offsetofend(struct inet_connection_sock,
 123                                  icsk_ack.pending);
 124                break;
 125        case offsetof(struct tcp_sock, snd_cwnd):
 126                end = offsetofend(struct tcp_sock, snd_cwnd);
 127                break;
 128        case offsetof(struct tcp_sock, snd_cwnd_cnt):
 129                end = offsetofend(struct tcp_sock, snd_cwnd_cnt);
 130                break;
 131        case offsetof(struct tcp_sock, snd_ssthresh):
 132                end = offsetofend(struct tcp_sock, snd_ssthresh);
 133                break;
 134        case offsetof(struct tcp_sock, ecn_flags):
 135                end = offsetofend(struct tcp_sock, ecn_flags);
 136                break;
 137        default:
 138                bpf_log(log, "no write support to tcp_sock at off %d\n", off);
 139                return -EACCES;
 140        }
 141
 142        if (off + size > end) {
 143                bpf_log(log,
 144                        "write access at off %d with size %d beyond the member of tcp_sock ended at %zu\n",
 145                        off, size, end);
 146                return -EACCES;
 147        }
 148
 149        return NOT_INIT;
 150}
 151
 152BPF_CALL_2(bpf_tcp_send_ack, struct tcp_sock *, tp, u32, rcv_nxt)
 153{
 154        /* bpf_tcp_ca prog cannot have NULL tp */
 155        __tcp_send_ack((struct sock *)tp, rcv_nxt);
 156        return 0;
 157}
 158
 159static const struct bpf_func_proto bpf_tcp_send_ack_proto = {
 160        .func           = bpf_tcp_send_ack,
 161        .gpl_only       = false,
 162        /* In case we want to report error later */
 163        .ret_type       = RET_INTEGER,
 164        .arg1_type      = ARG_PTR_TO_BTF_ID,
 165        .arg1_btf_id    = &tcp_sock_id,
 166        .arg2_type      = ARG_ANYTHING,
 167};
 168
 169static u32 prog_ops_moff(const struct bpf_prog *prog)
 170{
 171        const struct btf_member *m;
 172        const struct btf_type *t;
 173        u32 midx;
 174
 175        midx = prog->expected_attach_type;
 176        t = bpf_tcp_congestion_ops.type;
 177        m = &btf_type_member(t)[midx];
 178
 179        return btf_member_bit_offset(t, m) / 8;
 180}
 181
 182static const struct bpf_func_proto *
 183bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
 184                          const struct bpf_prog *prog)
 185{
 186        switch (func_id) {
 187        case BPF_FUNC_tcp_send_ack:
 188                return &bpf_tcp_send_ack_proto;
 189        case BPF_FUNC_sk_storage_get:
 190                return &bpf_sk_storage_get_proto;
 191        case BPF_FUNC_sk_storage_delete:
 192                return &bpf_sk_storage_delete_proto;
 193        case BPF_FUNC_setsockopt:
 194                /* Does not allow release() to call setsockopt.
 195                 * release() is called when the current bpf-tcp-cc
 196                 * is retiring.  It is not allowed to call
 197                 * setsockopt() to make further changes which
 198                 * may potentially allocate new resources.
 199                 */
 200                if (prog_ops_moff(prog) !=
 201                    offsetof(struct tcp_congestion_ops, release))
 202                        return &bpf_sk_setsockopt_proto;
 203                return NULL;
 204        case BPF_FUNC_getsockopt:
 205                /* Since get/setsockopt is usually expected to
 206                 * be available together, disable getsockopt for
 207                 * release also to avoid usage surprise.
 208                 * The bpf-tcp-cc already has a more powerful way
 209                 * to read tcp_sock from the PTR_TO_BTF_ID.
 210                 */
 211                if (prog_ops_moff(prog) !=
 212                    offsetof(struct tcp_congestion_ops, release))
 213                        return &bpf_sk_getsockopt_proto;
 214                return NULL;
 215        default:
 216                return bpf_base_func_proto(func_id);
 217        }
 218}
 219
 220BTF_SET_START(bpf_tcp_ca_kfunc_ids)
 221BTF_ID(func, tcp_reno_ssthresh)
 222BTF_ID(func, tcp_reno_cong_avoid)
 223BTF_ID(func, tcp_reno_undo_cwnd)
 224BTF_ID(func, tcp_slow_start)
 225BTF_ID(func, tcp_cong_avoid_ai)
 226#ifdef CONFIG_X86
 227#ifdef CONFIG_DYNAMIC_FTRACE
 228#if IS_BUILTIN(CONFIG_TCP_CONG_CUBIC)
 229BTF_ID(func, cubictcp_init)
 230BTF_ID(func, cubictcp_recalc_ssthresh)
 231BTF_ID(func, cubictcp_cong_avoid)
 232BTF_ID(func, cubictcp_state)
 233BTF_ID(func, cubictcp_cwnd_event)
 234BTF_ID(func, cubictcp_acked)
 235#endif
 236#if IS_BUILTIN(CONFIG_TCP_CONG_DCTCP)
 237BTF_ID(func, dctcp_init)
 238BTF_ID(func, dctcp_update_alpha)
 239BTF_ID(func, dctcp_cwnd_event)
 240BTF_ID(func, dctcp_ssthresh)
 241BTF_ID(func, dctcp_cwnd_undo)
 242BTF_ID(func, dctcp_state)
 243#endif
 244#if IS_BUILTIN(CONFIG_TCP_CONG_BBR)
 245BTF_ID(func, bbr_init)
 246BTF_ID(func, bbr_main)
 247BTF_ID(func, bbr_sndbuf_expand)
 248BTF_ID(func, bbr_undo_cwnd)
 249BTF_ID(func, bbr_cwnd_event)
 250BTF_ID(func, bbr_ssthresh)
 251BTF_ID(func, bbr_min_tso_segs)
 252BTF_ID(func, bbr_set_state)
 253#endif
 254#endif  /* CONFIG_DYNAMIC_FTRACE */
 255#endif  /* CONFIG_X86 */
 256BTF_SET_END(bpf_tcp_ca_kfunc_ids)
 257
 258static bool bpf_tcp_ca_check_kfunc_call(u32 kfunc_btf_id)
 259{
 260        return btf_id_set_contains(&bpf_tcp_ca_kfunc_ids, kfunc_btf_id);
 261}
 262
 263static const struct bpf_verifier_ops bpf_tcp_ca_verifier_ops = {
 264        .get_func_proto         = bpf_tcp_ca_get_func_proto,
 265        .is_valid_access        = bpf_tcp_ca_is_valid_access,
 266        .btf_struct_access      = bpf_tcp_ca_btf_struct_access,
 267        .check_kfunc_call       = bpf_tcp_ca_check_kfunc_call,
 268};
 269
 270static int bpf_tcp_ca_init_member(const struct btf_type *t,
 271                                  const struct btf_member *member,
 272                                  void *kdata, const void *udata)
 273{
 274        const struct tcp_congestion_ops *utcp_ca;
 275        struct tcp_congestion_ops *tcp_ca;
 276        int prog_fd;
 277        u32 moff;
 278
 279        utcp_ca = (const struct tcp_congestion_ops *)udata;
 280        tcp_ca = (struct tcp_congestion_ops *)kdata;
 281
 282        moff = btf_member_bit_offset(t, member) / 8;
 283        switch (moff) {
 284        case offsetof(struct tcp_congestion_ops, flags):
 285                if (utcp_ca->flags & ~TCP_CONG_MASK)
 286                        return -EINVAL;
 287                tcp_ca->flags = utcp_ca->flags;
 288                return 1;
 289        case offsetof(struct tcp_congestion_ops, name):
 290                if (bpf_obj_name_cpy(tcp_ca->name, utcp_ca->name,
 291                                     sizeof(tcp_ca->name)) <= 0)
 292                        return -EINVAL;
 293                if (tcp_ca_find(utcp_ca->name))
 294                        return -EEXIST;
 295                return 1;
 296        }
 297
 298        if (!btf_type_resolve_func_ptr(btf_vmlinux, member->type, NULL))
 299                return 0;
 300
 301        /* Ensure bpf_prog is provided for compulsory func ptr */
 302        prog_fd = (int)(*(unsigned long *)(udata + moff));
 303        if (!prog_fd && !is_optional(moff) && !is_unsupported(moff))
 304                return -EINVAL;
 305
 306        return 0;
 307}
 308
 309static int bpf_tcp_ca_check_member(const struct btf_type *t,
 310                                   const struct btf_member *member)
 311{
 312        if (is_unsupported(btf_member_bit_offset(t, member) / 8))
 313                return -ENOTSUPP;
 314        return 0;
 315}
 316
 317static int bpf_tcp_ca_reg(void *kdata)
 318{
 319        return tcp_register_congestion_control(kdata);
 320}
 321
 322static void bpf_tcp_ca_unreg(void *kdata)
 323{
 324        tcp_unregister_congestion_control(kdata);
 325}
 326
 327struct bpf_struct_ops bpf_tcp_congestion_ops = {
 328        .verifier_ops = &bpf_tcp_ca_verifier_ops,
 329        .reg = bpf_tcp_ca_reg,
 330        .unreg = bpf_tcp_ca_unreg,
 331        .check_member = bpf_tcp_ca_check_member,
 332        .init_member = bpf_tcp_ca_init_member,
 333        .init = bpf_tcp_ca_init,
 334        .name = "tcp_congestion_ops",
 335};
 336