net/ipv4/bpf_tcp_ca.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Copyright (c) 2019 Facebook  */
   3
   4 #include <linux/init.h>
   5 #include <linux/types.h>
   6 #include <linux/bpf_verifier.h>
   7 #include <linux/bpf.h>
   8 #include <linux/btf.h>
   9 #include <linux/btf_ids.h>
  10 #include <linux/filter.h>
  11 #include <net/tcp.h>
  12 #include <net/bpf_sk_storage.h>
  13
  14 /* "extern" is to avoid sparse warning.  It is only used in bpf_struct_ops.c. */
  15 extern struct bpf_struct_ops bpf_tcp_congestion_ops;
  16
  17 static u32 unsupported_ops[] = {
  18         offsetof(struct tcp_congestion_ops, get_info),
  19 };
  20
  21 static const struct btf_type *tcp_sock_type;
  22 static u32 tcp_sock_id, sock_id;
  23
  24 static int bpf_tcp_ca_init(struct btf *btf)
  25 {
  26         s32 type_id;
  27
  28         type_id = btf_find_by_name_kind(btf, "sock", BTF_KIND_STRUCT);
  29         if (type_id < 0)
  30                 return -EINVAL;
  31         sock_id = type_id;
  32
  33         type_id = btf_find_by_name_kind(btf, "tcp_sock", BTF_KIND_STRUCT);
  34         if (type_id < 0)
  35                 return -EINVAL;
  36         tcp_sock_id = type_id;
  37         tcp_sock_type = btf_type_by_id(btf, tcp_sock_id);
  38
  39         return 0;
  40 }
  41
  42 static bool is_unsupported(u32 member_offset)
  43 {
  44         unsigned int i;
  45
  46         for (i = 0; i < ARRAY_SIZE(unsupported_ops); i++) {
  47                 if (member_offset == unsupported_ops[i])
  48                         return true;
  49         }
  50
  51         return false;
  52 }
  53
  54 static bool bpf_tcp_ca_is_valid_access(int off, int size,
  55                                        enum bpf_access_type type,
  56                                        const struct bpf_prog *prog,
  57                                        struct bpf_insn_access_aux *info)
  58 {
  59         if (!bpf_tracing_btf_ctx_access(off, size, type, prog, info))
  60                 return false;
  61
  62         if (base_type(info->reg_type) == PTR_TO_BTF_ID &&
  63             !bpf_type_has_unsafe_modifiers(info->reg_type) &&
  64             info->btf_id == sock_id)
  65                 /* promote it to tcp_sock */
  66                 info->btf_id = tcp_sock_id;
  67
  68         return true;
  69 }
  70
  71 static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
  72                                         const struct bpf_reg_state *reg,
  73                                         int off, int size)
  74 {
  75         const struct btf_type *t;
  76         size_t end;
  77
  78         t = btf_type_by_id(reg->btf, reg->btf_id);
  79         if (t != tcp_sock_type) {
  80                 bpf_log(log, "only read is supported\n");
  81                 return -EACCES;
  82         }
  83
  84         switch (off) {
  85         case offsetof(struct sock, sk_pacing_rate):
  86                 end = offsetofend(struct sock, sk_pacing_rate);
  87                 break;
  88         case offsetof(struct sock, sk_pacing_status):
  89                 end = offsetofend(struct sock, sk_pacing_status);
  90                 break;
  91         case bpf_ctx_range(struct inet_connection_sock, icsk_ca_priv):
  92                 end = offsetofend(struct inet_connection_sock, icsk_ca_priv);
  93                 break;
  94         case offsetof(struct inet_connection_sock, icsk_ack.pending):
  95                 end = offsetofend(struct inet_connection_sock,
  96                                   icsk_ack.pending);
  97                 break;
  98         case offsetof(struct tcp_sock, snd_cwnd):
  99                 end = offsetofend(struct tcp_sock, snd_cwnd);
 100                 break;
 101         case offsetof(struct tcp_sock, snd_cwnd_cnt):
 102                 end = offsetofend(struct tcp_sock, snd_cwnd_cnt);
 103                 break;
 104         case offsetof(struct tcp_sock, snd_ssthresh):
 105                 end = offsetofend(struct tcp_sock, snd_ssthresh);
 106                 break;
 107         case offsetof(struct tcp_sock, ecn_flags):
 108                 end = offsetofend(struct tcp_sock, ecn_flags);
 109                 break;
 110         case offsetof(struct tcp_sock, app_limited):
 111                 end = offsetofend(struct tcp_sock, app_limited);
 112                 break;
 113         default:
 114                 bpf_log(log, "no write support to tcp_sock at off %d\n", off);
 115                 return -EACCES;
 116         }
 117
 118         if (off + size > end) {
 119                 bpf_log(log,
 120                         "write access at off %d with size %d beyond the member of tcp_sock ended at %zu\n",
 121                         off, size, end);
 122                 return -EACCES;
 123         }
 124
 125         return 0;
 126 }
 127
 128 BPF_CALL_2(bpf_tcp_send_ack, struct tcp_sock *, tp, u32, rcv_nxt)
 129 {
 130         /* bpf_tcp_ca prog cannot have NULL tp */
 131         __tcp_send_ack((struct sock *)tp, rcv_nxt);
 132         return 0;
 133 }
 134
 135 static const struct bpf_func_proto bpf_tcp_send_ack_proto = {
 136         .func           = bpf_tcp_send_ack,
 137         .gpl_only       = false,
 138         /* In case we want to report error later */
 139         .ret_type       = RET_INTEGER,
 140         .arg1_type      = ARG_PTR_TO_BTF_ID,
 141         .arg1_btf_id    = &tcp_sock_id,
 142         .arg2_type      = ARG_ANYTHING,
 143 };
 144
 145 static u32 prog_ops_moff(const struct bpf_prog *prog)
 146 {
 147         const struct btf_member *m;
 148         const struct btf_type *t;
 149         u32 midx;
 150
 151         midx = prog->expected_attach_type;
 152         t = bpf_tcp_congestion_ops.type;
 153         m = &btf_type_member(t)[midx];
 154
 155         return __btf_member_bit_offset(t, m) / 8;
 156 }
 157
 158 static const struct bpf_func_proto *
 159 bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
 160                           const struct bpf_prog *prog)
 161 {
 162         switch (func_id) {
 163         case BPF_FUNC_tcp_send_ack:
 164                 return &bpf_tcp_send_ack_proto;
 165         case BPF_FUNC_sk_storage_get:
 166                 return &bpf_sk_storage_get_proto;
 167         case BPF_FUNC_sk_storage_delete:
 168                 return &bpf_sk_storage_delete_proto;
 169         case BPF_FUNC_setsockopt:
 170                 /* Does not allow release() to call setsockopt.
 171                  * release() is called when the current bpf-tcp-cc
 172                  * is retiring.  It is not allowed to call
 173                  * setsockopt() to make further changes which
 174                  * may potentially allocate new resources.
 175                  */
 176                 if (prog_ops_moff(prog) !=
 177                     offsetof(struct tcp_congestion_ops, release))
 178                         return &bpf_sk_setsockopt_proto;
 179                 return NULL;
 180         case BPF_FUNC_getsockopt:
 181                 /* Since get/setsockopt is usually expected to
 182                  * be available together, disable getsockopt for
 183                  * release also to avoid usage surprise.
 184                  * The bpf-tcp-cc already has a more powerful way
 185                  * to read tcp_sock from the PTR_TO_BTF_ID.
 186                  */
 187                 if (prog_ops_moff(prog) !=
 188                     offsetof(struct tcp_congestion_ops, release))
 189                         return &bpf_sk_getsockopt_proto;
 190                 return NULL;
 191         case BPF_FUNC_ktime_get_coarse_ns:
 192                 return &bpf_ktime_get_coarse_ns_proto;
 193         default:
 194                 return bpf_base_func_proto(func_id);
 195         }
 196 }
 197
 198 BTF_SET8_START(bpf_tcp_ca_check_kfunc_ids)
 199 BTF_ID_FLAGS(func, tcp_reno_ssthresh)
 200 BTF_ID_FLAGS(func, tcp_reno_cong_avoid)
 201 BTF_ID_FLAGS(func, tcp_reno_undo_cwnd)
 202 BTF_ID_FLAGS(func, tcp_slow_start)
 203 BTF_ID_FLAGS(func, tcp_cong_avoid_ai)
 204 BTF_SET8_END(bpf_tcp_ca_check_kfunc_ids)
 205
 206 static const struct btf_kfunc_id_set bpf_tcp_ca_kfunc_set = {
 207         .owner = THIS_MODULE,
 208         .set   = &bpf_tcp_ca_check_kfunc_ids,
 209 };
 210
 211 static const struct bpf_verifier_ops bpf_tcp_ca_verifier_ops = {
 212         .get_func_proto         = bpf_tcp_ca_get_func_proto,
 213         .is_valid_access        = bpf_tcp_ca_is_valid_access,
 214         .btf_struct_access      = bpf_tcp_ca_btf_struct_access,
 215 };
 216
 217 static int bpf_tcp_ca_init_member(const struct btf_type *t,
 218                                   const struct btf_member *member,
 219                                   void *kdata, const void *udata)
 220 {
 221         const struct tcp_congestion_ops *utcp_ca;
 222         struct tcp_congestion_ops *tcp_ca;
 223         u32 moff;
 224
 225         utcp_ca = (const struct tcp_congestion_ops *)udata;
 226         tcp_ca = (struct tcp_congestion_ops *)kdata;
 227
 228         moff = __btf_member_bit_offset(t, member) / 8;
 229         switch (moff) {
 230         case offsetof(struct tcp_congestion_ops, flags):
 231                 if (utcp_ca->flags & ~TCP_CONG_MASK)
 232                         return -EINVAL;
 233                 tcp_ca->flags = utcp_ca->flags;
 234                 return 1;
 235         case offsetof(struct tcp_congestion_ops, name):
 236                 if (bpf_obj_name_cpy(tcp_ca->name, utcp_ca->name,
 237                                      sizeof(tcp_ca->name)) <= 0)
 238                         return -EINVAL;
 239                 return 1;
 240         }
 241
 242         return 0;
 243 }
 244
 245 static int bpf_tcp_ca_check_member(const struct btf_type *t,
 246                                    const struct btf_member *member,
 247                                    const struct bpf_prog *prog)
 248 {
 249         if (is_unsupported(__btf_member_bit_offset(t, member) / 8))
 250                 return -ENOTSUPP;
 251         return 0;
 252 }
 253
 254 static int bpf_tcp_ca_reg(void *kdata)
 255 {
 256         return tcp_register_congestion_control(kdata);
 257 }
 258
 259 static void bpf_tcp_ca_unreg(void *kdata)
 260 {
 261         tcp_unregister_congestion_control(kdata);
 262 }
 263
 264 static int bpf_tcp_ca_update(void *kdata, void *old_kdata)
 265 {
 266         return tcp_update_congestion_control(kdata, old_kdata);
 267 }
 268
 269 static int bpf_tcp_ca_validate(void *kdata)
 270 {
 271         return tcp_validate_congestion_control(kdata);
 272 }
 273
 274 struct bpf_struct_ops bpf_tcp_congestion_ops = {
 275         .verifier_ops = &bpf_tcp_ca_verifier_ops,
 276         .reg = bpf_tcp_ca_reg,
 277         .unreg = bpf_tcp_ca_unreg,
 278         .update = bpf_tcp_ca_update,
 279         .check_member = bpf_tcp_ca_check_member,
 280         .init_member = bpf_tcp_ca_init_member,
 281         .init = bpf_tcp_ca_init,
 282         .validate = bpf_tcp_ca_validate,
 283         .name = "tcp_congestion_ops",
 284 };
 285
 286 static int __init bpf_tcp_ca_kfunc_init(void)
 287 {
 288         return register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &bpf_tcp_ca_kfunc_set);
 289 }
 290 late_initcall(bpf_tcp_ca_kfunc_init);