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 extern struct btf *btf_vmlinux;
  55
  56 static bool bpf_tcp_ca_is_valid_access(int off, int size,
  57                                        enum bpf_access_type type,
  58                                        const struct bpf_prog *prog,
  59                                        struct bpf_insn_access_aux *info)
  60 {
  61         if (!bpf_tracing_btf_ctx_access(off, size, type, prog, info))
  62                 return false;
  63
  64         if (base_type(info->reg_type) == PTR_TO_BTF_ID &&
  65             !bpf_type_has_unsafe_modifiers(info->reg_type) &&
  66             info->btf_id == sock_id)
  67                 /* promote it to tcp_sock */
  68                 info->btf_id = tcp_sock_id;
  69
  70         return true;
  71 }
  72
  73 static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
  74                                         const struct bpf_reg_state *reg,
  75                                         int off, int size)
  76 {
  77         const struct btf_type *t;
  78         size_t end;
  79
  80         t = btf_type_by_id(reg->btf, reg->btf_id);
  81         if (t != tcp_sock_type) {
  82                 bpf_log(log, "only read is supported\n");
  83                 return -EACCES;
  84         }
  85
  86         switch (off) {
  87         case offsetof(struct sock, sk_pacing_rate):
  88                 end = offsetofend(struct sock, sk_pacing_rate);
  89                 break;
  90         case offsetof(struct sock, sk_pacing_status):
  91                 end = offsetofend(struct sock, sk_pacing_status);
  92                 break;
  93         case bpf_ctx_range(struct inet_connection_sock, icsk_ca_priv):
  94                 end = offsetofend(struct inet_connection_sock, icsk_ca_priv);
  95                 break;
  96         case offsetof(struct inet_connection_sock, icsk_ack.pending):
  97                 end = offsetofend(struct inet_connection_sock,
  98                                   icsk_ack.pending);
  99                 break;
 100         case offsetof(struct tcp_sock, snd_cwnd):
 101                 end = offsetofend(struct tcp_sock, snd_cwnd);
 102                 break;
 103         case offsetof(struct tcp_sock, snd_cwnd_cnt):
 104                 end = offsetofend(struct tcp_sock, snd_cwnd_cnt);
 105                 break;
 106         case offsetof(struct tcp_sock, snd_ssthresh):
 107                 end = offsetofend(struct tcp_sock, snd_ssthresh);
 108                 break;
 109         case offsetof(struct tcp_sock, ecn_flags):
 110                 end = offsetofend(struct tcp_sock, ecn_flags);
 111                 break;
 112         case offsetof(struct tcp_sock, app_limited):
 113                 end = offsetofend(struct tcp_sock, app_limited);
 114                 break;
 115         default:
 116                 bpf_log(log, "no write support to tcp_sock at off %d\n", off);
 117                 return -EACCES;
 118         }
 119
 120         if (off + size > end) {
 121                 bpf_log(log,
 122                         "write access at off %d with size %d beyond the member of tcp_sock ended at %zu\n",
 123                         off, size, end);
 124                 return -EACCES;
 125         }
 126
 127         return 0;
 128 }
 129
 130 BPF_CALL_2(bpf_tcp_send_ack, struct tcp_sock *, tp, u32, rcv_nxt)
 131 {
 132         /* bpf_tcp_ca prog cannot have NULL tp */
 133         __tcp_send_ack((struct sock *)tp, rcv_nxt);
 134         return 0;
 135 }
 136
 137 static const struct bpf_func_proto bpf_tcp_send_ack_proto = {
 138         .func           = bpf_tcp_send_ack,
 139         .gpl_only       = false,
 140         /* In case we want to report error later */
 141         .ret_type       = RET_INTEGER,
 142         .arg1_type      = ARG_PTR_TO_BTF_ID,
 143         .arg1_btf_id    = &tcp_sock_id,
 144         .arg2_type      = ARG_ANYTHING,
 145 };
 146
 147 static u32 prog_ops_moff(const struct bpf_prog *prog)
 148 {
 149         const struct btf_member *m;
 150         const struct btf_type *t;
 151         u32 midx;
 152
 153         midx = prog->expected_attach_type;
 154         t = bpf_tcp_congestion_ops.type;
 155         m = &btf_type_member(t)[midx];
 156
 157         return __btf_member_bit_offset(t, m) / 8;
 158 }
 159
 160 static const struct bpf_func_proto *
 161 bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
 162                           const struct bpf_prog *prog)
 163 {
 164         switch (func_id) {
 165         case BPF_FUNC_tcp_send_ack:
 166                 return &bpf_tcp_send_ack_proto;
 167         case BPF_FUNC_sk_storage_get:
 168                 return &bpf_sk_storage_get_proto;
 169         case BPF_FUNC_sk_storage_delete:
 170                 return &bpf_sk_storage_delete_proto;
 171         case BPF_FUNC_setsockopt:
 172                 /* Does not allow release() to call setsockopt.
 173                  * release() is called when the current bpf-tcp-cc
 174                  * is retiring.  It is not allowed to call
 175                  * setsockopt() to make further changes which
 176                  * may potentially allocate new resources.
 177                  */
 178                 if (prog_ops_moff(prog) !=
 179                     offsetof(struct tcp_congestion_ops, release))
 180                         return &bpf_sk_setsockopt_proto;
 181                 return NULL;
 182         case BPF_FUNC_getsockopt:
 183                 /* Since get/setsockopt is usually expected to
 184                  * be available together, disable getsockopt for
 185                  * release also to avoid usage surprise.
 186                  * The bpf-tcp-cc already has a more powerful way
 187                  * to read tcp_sock from the PTR_TO_BTF_ID.
 188                  */
 189                 if (prog_ops_moff(prog) !=
 190                     offsetof(struct tcp_congestion_ops, release))
 191                         return &bpf_sk_getsockopt_proto;
 192                 return NULL;
 193         case BPF_FUNC_ktime_get_coarse_ns:
 194                 return &bpf_ktime_get_coarse_ns_proto;
 195         default:
 196                 return bpf_base_func_proto(func_id);
 197         }
 198 }
 199
 200 BTF_SET8_START(bpf_tcp_ca_check_kfunc_ids)
 201 BTF_ID_FLAGS(func, tcp_reno_ssthresh)
 202 BTF_ID_FLAGS(func, tcp_reno_cong_avoid)
 203 BTF_ID_FLAGS(func, tcp_reno_undo_cwnd)
 204 BTF_ID_FLAGS(func, tcp_slow_start)
 205 BTF_ID_FLAGS(func, tcp_cong_avoid_ai)
 206 BTF_SET8_END(bpf_tcp_ca_check_kfunc_ids)
 207
 208 static const struct btf_kfunc_id_set bpf_tcp_ca_kfunc_set = {
 209         .owner = THIS_MODULE,
 210         .set   = &bpf_tcp_ca_check_kfunc_ids,
 211 };
 212
 213 static const struct bpf_verifier_ops bpf_tcp_ca_verifier_ops = {
 214         .get_func_proto         = bpf_tcp_ca_get_func_proto,
 215         .is_valid_access        = bpf_tcp_ca_is_valid_access,
 216         .btf_struct_access      = bpf_tcp_ca_btf_struct_access,
 217 };
 218
 219 static int bpf_tcp_ca_init_member(const struct btf_type *t,
 220                                   const struct btf_member *member,
 221                                   void *kdata, const void *udata)
 222 {
 223         const struct tcp_congestion_ops *utcp_ca;
 224         struct tcp_congestion_ops *tcp_ca;
 225         u32 moff;
 226
 227         utcp_ca = (const struct tcp_congestion_ops *)udata;
 228         tcp_ca = (struct tcp_congestion_ops *)kdata;
 229
 230         moff = __btf_member_bit_offset(t, member) / 8;
 231         switch (moff) {
 232         case offsetof(struct tcp_congestion_ops, flags):
 233                 if (utcp_ca->flags & ~TCP_CONG_MASK)
 234                         return -EINVAL;
 235                 tcp_ca->flags = utcp_ca->flags;
 236                 return 1;
 237         case offsetof(struct tcp_congestion_ops, name):
 238                 if (bpf_obj_name_cpy(tcp_ca->name, utcp_ca->name,
 239                                      sizeof(tcp_ca->name)) <= 0)
 240                         return -EINVAL;
 241                 return 1;
 242         }
 243
 244         return 0;
 245 }
 246
 247 static int bpf_tcp_ca_check_member(const struct btf_type *t,
 248                                    const struct btf_member *member,
 249                                    const struct bpf_prog *prog)
 250 {
 251         if (is_unsupported(__btf_member_bit_offset(t, member) / 8))
 252                 return -ENOTSUPP;
 253         return 0;
 254 }
 255
 256 static int bpf_tcp_ca_reg(void *kdata)
 257 {
 258         return tcp_register_congestion_control(kdata);
 259 }
 260
 261 static void bpf_tcp_ca_unreg(void *kdata)
 262 {
 263         tcp_unregister_congestion_control(kdata);
 264 }
 265
 266 static int bpf_tcp_ca_update(void *kdata, void *old_kdata)
 267 {
 268         return tcp_update_congestion_control(kdata, old_kdata);
 269 }
 270
 271 static int bpf_tcp_ca_validate(void *kdata)
 272 {
 273         return tcp_validate_congestion_control(kdata);
 274 }
 275
 276 struct bpf_struct_ops bpf_tcp_congestion_ops = {
 277         .verifier_ops = &bpf_tcp_ca_verifier_ops,
 278         .reg = bpf_tcp_ca_reg,
 279         .unreg = bpf_tcp_ca_unreg,
 280         .update = bpf_tcp_ca_update,
 281         .check_member = bpf_tcp_ca_check_member,
 282         .init_member = bpf_tcp_ca_init_member,
 283         .init = bpf_tcp_ca_init,
 284         .validate = bpf_tcp_ca_validate,
 285         .name = "tcp_congestion_ops",
 286 };
 287
 288 static int __init bpf_tcp_ca_kfunc_init(void)
 289 {
 290         return register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &bpf_tcp_ca_kfunc_set);
 291 }
 292 late_initcall(bpf_tcp_ca_kfunc_init);