net/ipv4/bpf_tcp_ca.c

   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 static u32 optional_ops[] = {
  14         offsetof(struct tcp_congestion_ops, init),
  15         offsetof(struct tcp_congestion_ops, release),
  16         offsetof(struct tcp_congestion_ops, set_state),
  17         offsetof(struct tcp_congestion_ops, cwnd_event),
  18         offsetof(struct tcp_congestion_ops, in_ack_event),
  19         offsetof(struct tcp_congestion_ops, pkts_acked),
  20         offsetof(struct tcp_congestion_ops, min_tso_segs),
  21         offsetof(struct tcp_congestion_ops, sndbuf_expand),
  22         offsetof(struct tcp_congestion_ops, cong_control),
  23 };
  24
  25 static u32 unsupported_ops[] = {
  26         offsetof(struct tcp_congestion_ops, get_info),
  27 };
  28
  29 static const struct btf_type *tcp_sock_type;
  30 static u32 tcp_sock_id, sock_id;
  31
  32 static int bpf_tcp_ca_init(struct btf *btf)
  33 {
  34         s32 type_id;
  35
  36         type_id = btf_find_by_name_kind(btf, "sock", BTF_KIND_STRUCT);
  37         if (type_id < 0)
  38                 return -EINVAL;
  39         sock_id = type_id;
  40
  41         type_id = btf_find_by_name_kind(btf, "tcp_sock", BTF_KIND_STRUCT);
  42         if (type_id < 0)
  43                 return -EINVAL;
  44         tcp_sock_id = type_id;
  45         tcp_sock_type = btf_type_by_id(btf, tcp_sock_id);
  46
  47         return 0;
  48 }
  49
  50 static bool is_optional(u32 member_offset)
  51 {
  52         unsigned int i;
  53
  54         for (i = 0; i < ARRAY_SIZE(optional_ops); i++) {
  55                 if (member_offset == optional_ops[i])
  56                         return true;
  57         }
  58
  59         return false;
  60 }
  61
  62 static bool is_unsupported(u32 member_offset)
  63 {
  64         unsigned int i;
  65
  66         for (i = 0; i < ARRAY_SIZE(unsupported_ops); i++) {
  67                 if (member_offset == unsupported_ops[i])
  68                         return true;
  69         }
  70
  71         return false;
  72 }
  73
  74 extern struct btf *btf_vmlinux;
  75
  76 static bool bpf_tcp_ca_is_valid_access(int off, int size,
  77                                        enum bpf_access_type type,
  78                                        const struct bpf_prog *prog,
  79                                        struct bpf_insn_access_aux *info)
  80 {
  81         if (off < 0 || off >= sizeof(__u64) * MAX_BPF_FUNC_ARGS)
  82                 return false;
  83         if (type != BPF_READ)
  84                 return false;
  85         if (off % size != 0)
  86                 return false;
  87
  88         if (!btf_ctx_access(off, size, type, prog, info))
  89                 return false;
  90
  91         if (info->reg_type == PTR_TO_BTF_ID && info->btf_id == sock_id)
  92                 /* promote it to tcp_sock */
  93                 info->btf_id = tcp_sock_id;
  94
  95         return true;
  96 }
  97
  98 static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
  99                                         const struct btf *btf,
 100                                         const struct btf_type *t, int off,
 101                                         int size, enum bpf_access_type atype,
 102                                         u32 *next_btf_id)
 103 {
 104         size_t end;
 105
 106         if (atype == BPF_READ)
 107                 return btf_struct_access(log, btf, t, off, size, atype, next_btf_id);
 108
 109         if (t != tcp_sock_type) {
 110                 bpf_log(log, "only read is supported\n");
 111                 return -EACCES;
 112         }
 113
 114         switch (off) {
 115         case bpf_ctx_range(struct inet_connection_sock, icsk_ca_priv):
 116                 end = offsetofend(struct inet_connection_sock, icsk_ca_priv);
 117                 break;
 118         case offsetof(struct inet_connection_sock, icsk_ack.pending):
 119                 end = offsetofend(struct inet_connection_sock,
 120                                   icsk_ack.pending);
 121                 break;
 122         case offsetof(struct tcp_sock, snd_cwnd):
 123                 end = offsetofend(struct tcp_sock, snd_cwnd);
 124                 break;
 125         case offsetof(struct tcp_sock, snd_cwnd_cnt):
 126                 end = offsetofend(struct tcp_sock, snd_cwnd_cnt);
 127                 break;
 128         case offsetof(struct tcp_sock, snd_ssthresh):
 129                 end = offsetofend(struct tcp_sock, snd_ssthresh);
 130                 break;
 131         case offsetof(struct tcp_sock, ecn_flags):
 132                 end = offsetofend(struct tcp_sock, ecn_flags);
 133                 break;
 134         default:
 135                 bpf_log(log, "no write support to tcp_sock at off %d\n", off);
 136                 return -EACCES;
 137         }
 138
 139         if (off + size > end) {
 140                 bpf_log(log,
 141                         "write access at off %d with size %d beyond the member of tcp_sock ended at %zu\n",
 142                         off, size, end);
 143                 return -EACCES;
 144         }
 145
 146         return NOT_INIT;
 147 }
 148
 149 BPF_CALL_2(bpf_tcp_send_ack, struct tcp_sock *, tp, u32, rcv_nxt)
 150 {
 151         /* bpf_tcp_ca prog cannot have NULL tp */
 152         __tcp_send_ack((struct sock *)tp, rcv_nxt);
 153         return 0;
 154 }
 155
 156 static const struct bpf_func_proto bpf_tcp_send_ack_proto = {
 157         .func           = bpf_tcp_send_ack,
 158         .gpl_only       = false,
 159         /* In case we want to report error later */
 160         .ret_type       = RET_INTEGER,
 161         .arg1_type      = ARG_PTR_TO_BTF_ID,
 162         .arg1_btf_id    = &tcp_sock_id,
 163         .arg2_type      = ARG_ANYTHING,
 164 };
 165
 166 static const struct bpf_func_proto *
 167 bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
 168                           const struct bpf_prog *prog)
 169 {
 170         switch (func_id) {
 171         case BPF_FUNC_tcp_send_ack:
 172                 return &bpf_tcp_send_ack_proto;
 173         case BPF_FUNC_sk_storage_get:
 174                 return &bpf_sk_storage_get_proto;
 175         case BPF_FUNC_sk_storage_delete:
 176                 return &bpf_sk_storage_delete_proto;
 177         default:
 178                 return bpf_base_func_proto(func_id);
 179         }
 180 }
 181
 182 BTF_SET_START(bpf_tcp_ca_kfunc_ids)
 183 BTF_ID(func, tcp_reno_ssthresh)
 184 BTF_ID(func, tcp_reno_cong_avoid)
 185 BTF_ID(func, tcp_reno_undo_cwnd)
 186 BTF_ID(func, tcp_slow_start)
 187 BTF_ID(func, tcp_cong_avoid_ai)
 188 #ifdef CONFIG_DYNAMIC_FTRACE
 189 #if IS_BUILTIN(CONFIG_TCP_CONG_CUBIC)
 190 BTF_ID(func, cubictcp_init)
 191 BTF_ID(func, cubictcp_recalc_ssthresh)
 192 BTF_ID(func, cubictcp_cong_avoid)
 193 BTF_ID(func, cubictcp_state)
 194 BTF_ID(func, cubictcp_cwnd_event)
 195 BTF_ID(func, cubictcp_acked)
 196 #endif
 197 #if IS_BUILTIN(CONFIG_TCP_CONG_DCTCP)
 198 BTF_ID(func, dctcp_init)
 199 BTF_ID(func, dctcp_update_alpha)
 200 BTF_ID(func, dctcp_cwnd_event)
 201 BTF_ID(func, dctcp_ssthresh)
 202 BTF_ID(func, dctcp_cwnd_undo)
 203 BTF_ID(func, dctcp_state)
 204 #endif
 205 #if IS_BUILTIN(CONFIG_TCP_CONG_BBR)
 206 BTF_ID(func, bbr_init)
 207 BTF_ID(func, bbr_main)
 208 BTF_ID(func, bbr_sndbuf_expand)
 209 BTF_ID(func, bbr_undo_cwnd)
 210 BTF_ID(func, bbr_cwnd_event)
 211 BTF_ID(func, bbr_ssthresh)
 212 BTF_ID(func, bbr_min_tso_segs)
 213 BTF_ID(func, bbr_set_state)
 214 #endif
 215 #endif  /* CONFIG_DYNAMIC_FTRACE */
 216 BTF_SET_END(bpf_tcp_ca_kfunc_ids)
 217
 218 static bool bpf_tcp_ca_check_kfunc_call(u32 kfunc_btf_id)
 219 {
 220         return btf_id_set_contains(&bpf_tcp_ca_kfunc_ids, kfunc_btf_id);
 221 }
 222
 223 static const struct bpf_verifier_ops bpf_tcp_ca_verifier_ops = {
 224         .get_func_proto         = bpf_tcp_ca_get_func_proto,
 225         .is_valid_access        = bpf_tcp_ca_is_valid_access,
 226         .btf_struct_access      = bpf_tcp_ca_btf_struct_access,
 227         .check_kfunc_call       = bpf_tcp_ca_check_kfunc_call,
 228 };
 229
 230 static int bpf_tcp_ca_init_member(const struct btf_type *t,
 231                                   const struct btf_member *member,
 232                                   void *kdata, const void *udata)
 233 {
 234         const struct tcp_congestion_ops *utcp_ca;
 235         struct tcp_congestion_ops *tcp_ca;
 236         int prog_fd;
 237         u32 moff;
 238
 239         utcp_ca = (const struct tcp_congestion_ops *)udata;
 240         tcp_ca = (struct tcp_congestion_ops *)kdata;
 241
 242         moff = btf_member_bit_offset(t, member) / 8;
 243         switch (moff) {
 244         case offsetof(struct tcp_congestion_ops, flags):
 245                 if (utcp_ca->flags & ~TCP_CONG_MASK)
 246                         return -EINVAL;
 247                 tcp_ca->flags = utcp_ca->flags;
 248                 return 1;
 249         case offsetof(struct tcp_congestion_ops, name):
 250                 if (bpf_obj_name_cpy(tcp_ca->name, utcp_ca->name,
 251                                      sizeof(tcp_ca->name)) <= 0)
 252                         return -EINVAL;
 253                 if (tcp_ca_find(utcp_ca->name))
 254                         return -EEXIST;
 255                 return 1;
 256         }
 257
 258         if (!btf_type_resolve_func_ptr(btf_vmlinux, member->type, NULL))
 259                 return 0;
 260
 261         /* Ensure bpf_prog is provided for compulsory func ptr */
 262         prog_fd = (int)(*(unsigned long *)(udata + moff));
 263         if (!prog_fd && !is_optional(moff) && !is_unsupported(moff))
 264                 return -EINVAL;
 265
 266         return 0;
 267 }
 268
 269 static int bpf_tcp_ca_check_member(const struct btf_type *t,
 270                                    const struct btf_member *member)
 271 {
 272         if (is_unsupported(btf_member_bit_offset(t, member) / 8))
 273                 return -ENOTSUPP;
 274         return 0;
 275 }
 276
 277 static int bpf_tcp_ca_reg(void *kdata)
 278 {
 279         return tcp_register_congestion_control(kdata);
 280 }
 281
 282 static void bpf_tcp_ca_unreg(void *kdata)
 283 {
 284         tcp_unregister_congestion_control(kdata);
 285 }
 286
 287 /* Avoid sparse warning.  It is only used in bpf_struct_ops.c. */
 288 extern struct bpf_struct_ops bpf_tcp_congestion_ops;
 289
 290 struct bpf_struct_ops bpf_tcp_congestion_ops = {
 291         .verifier_ops = &bpf_tcp_ca_verifier_ops,
 292         .reg = bpf_tcp_ca_reg,
 293         .unreg = bpf_tcp_ca_unreg,
 294         .check_member = bpf_tcp_ca_check_member,
 295         .init_member = bpf_tcp_ca_init_member,
 296         .init = bpf_tcp_ca_init,
 297         .name = "tcp_congestion_ops",
 298 };