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 /* "extern" is to avoid sparse warning.  It is only used in bpf_struct_ops.c. */
  14 extern struct bpf_struct_ops bpf_tcp_congestion_ops;
  15
  16 static 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
  28 static u32 unsupported_ops[] = {
  29         offsetof(struct tcp_congestion_ops, get_info),
  30 };
  31
  32 static const struct btf_type *tcp_sock_type;
  33 static u32 tcp_sock_id, sock_id;
  34
  35 static 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
  53 static 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
  65 static 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
  77 extern struct btf *btf_vmlinux;
  78
  79 static 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
 101 static 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
 152 BPF_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
 159 static 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
 169 static 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
 182 static const struct bpf_func_proto *
 183 bpf_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
 220 BTF_SET_START(bpf_tcp_ca_kfunc_ids)
 221 BTF_ID(func, tcp_reno_ssthresh)
 222 BTF_ID(func, tcp_reno_cong_avoid)
 223 BTF_ID(func, tcp_reno_undo_cwnd)
 224 BTF_ID(func, tcp_slow_start)
 225 BTF_ID(func, tcp_cong_avoid_ai)
 226 #ifdef CONFIG_X86
 227 #ifdef CONFIG_DYNAMIC_FTRACE
 228 #if IS_BUILTIN(CONFIG_TCP_CONG_CUBIC)
 229 BTF_ID(func, cubictcp_init)
 230 BTF_ID(func, cubictcp_recalc_ssthresh)
 231 BTF_ID(func, cubictcp_cong_avoid)
 232 BTF_ID(func, cubictcp_state)
 233 BTF_ID(func, cubictcp_cwnd_event)
 234 BTF_ID(func, cubictcp_acked)
 235 #endif
 236 #if IS_BUILTIN(CONFIG_TCP_CONG_DCTCP)
 237 BTF_ID(func, dctcp_init)
 238 BTF_ID(func, dctcp_update_alpha)
 239 BTF_ID(func, dctcp_cwnd_event)
 240 BTF_ID(func, dctcp_ssthresh)
 241 BTF_ID(func, dctcp_cwnd_undo)
 242 BTF_ID(func, dctcp_state)
 243 #endif
 244 #if IS_BUILTIN(CONFIG_TCP_CONG_BBR)
 245 BTF_ID(func, bbr_init)
 246 BTF_ID(func, bbr_main)
 247 BTF_ID(func, bbr_sndbuf_expand)
 248 BTF_ID(func, bbr_undo_cwnd)
 249 BTF_ID(func, bbr_cwnd_event)
 250 BTF_ID(func, bbr_ssthresh)
 251 BTF_ID(func, bbr_min_tso_segs)
 252 BTF_ID(func, bbr_set_state)
 253 #endif
 254 #endif  /* CONFIG_DYNAMIC_FTRACE */
 255 #endif  /* CONFIG_X86 */
 256 BTF_SET_END(bpf_tcp_ca_kfunc_ids)
 257
 258 static 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
 263 static 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
 270 static 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
 309 static 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
 317 static int bpf_tcp_ca_reg(void *kdata)
 318 {
 319         return tcp_register_congestion_control(kdata);
 320 }
 321
 322 static void bpf_tcp_ca_unreg(void *kdata)
 323 {
 324         tcp_unregister_congestion_control(kdata);
 325 }
 326
 327 struct 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 };