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/filter.h>
   9 #include <net/tcp.h>
  10 #include <net/bpf_sk_storage.h>
  11
  12 static u32 optional_ops[] = {
  13         offsetof(struct tcp_congestion_ops, init),
  14         offsetof(struct tcp_congestion_ops, release),
  15         offsetof(struct tcp_congestion_ops, set_state),
  16         offsetof(struct tcp_congestion_ops, cwnd_event),
  17         offsetof(struct tcp_congestion_ops, in_ack_event),
  18         offsetof(struct tcp_congestion_ops, pkts_acked),
  19         offsetof(struct tcp_congestion_ops, min_tso_segs),
  20         offsetof(struct tcp_congestion_ops, sndbuf_expand),
  21         offsetof(struct tcp_congestion_ops, cong_control),
  22 };
  23
  24 static u32 unsupported_ops[] = {
  25         offsetof(struct tcp_congestion_ops, get_info),
  26 };
  27
  28 static const struct btf_type *tcp_sock_type;
  29 static u32 tcp_sock_id, sock_id;
  30
  31 static int bpf_tcp_ca_init(struct btf *btf)
  32 {
  33         s32 type_id;
  34
  35         type_id = btf_find_by_name_kind(btf, "sock", BTF_KIND_STRUCT);
  36         if (type_id < 0)
  37                 return -EINVAL;
  38         sock_id = type_id;
  39
  40         type_id = btf_find_by_name_kind(btf, "tcp_sock", BTF_KIND_STRUCT);
  41         if (type_id < 0)
  42                 return -EINVAL;
  43         tcp_sock_id = type_id;
  44         tcp_sock_type = btf_type_by_id(btf, tcp_sock_id);
  45
  46         return 0;
  47 }
  48
  49 static bool is_optional(u32 member_offset)
  50 {
  51         unsigned int i;
  52
  53         for (i = 0; i < ARRAY_SIZE(optional_ops); i++) {
  54                 if (member_offset == optional_ops[i])
  55                         return true;
  56         }
  57
  58         return false;
  59 }
  60
  61 static bool is_unsupported(u32 member_offset)
  62 {
  63         unsigned int i;
  64
  65         for (i = 0; i < ARRAY_SIZE(unsupported_ops); i++) {
  66                 if (member_offset == unsupported_ops[i])
  67                         return true;
  68         }
  69
  70         return false;
  71 }
  72
  73 extern struct btf *btf_vmlinux;
  74
  75 static bool bpf_tcp_ca_is_valid_access(int off, int size,
  76                                        enum bpf_access_type type,
  77                                        const struct bpf_prog *prog,
  78                                        struct bpf_insn_access_aux *info)
  79 {
  80         if (off < 0 || off >= sizeof(__u64) * MAX_BPF_FUNC_ARGS)
  81                 return false;
  82         if (type != BPF_READ)
  83                 return false;
  84         if (off % size != 0)
  85                 return false;
  86
  87         if (!btf_ctx_access(off, size, type, prog, info))
  88                 return false;
  89
  90         if (info->reg_type == PTR_TO_BTF_ID && info->btf_id == sock_id)
  91                 /* promote it to tcp_sock */
  92                 info->btf_id = tcp_sock_id;
  93
  94         return true;
  95 }
  96
  97 static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
  98                                         const struct btf *btf,
  99                                         const struct btf_type *t, int off,
 100                                         int size, enum bpf_access_type atype,
 101                                         u32 *next_btf_id)
 102 {
 103         size_t end;
 104
 105         if (atype == BPF_READ)
 106                 return btf_struct_access(log, btf, t, off, size, atype, next_btf_id);
 107
 108         if (t != tcp_sock_type) {
 109                 bpf_log(log, "only read is supported\n");
 110                 return -EACCES;
 111         }
 112
 113         switch (off) {
 114         case bpf_ctx_range(struct inet_connection_sock, icsk_ca_priv):
 115                 end = offsetofend(struct inet_connection_sock, icsk_ca_priv);
 116                 break;
 117         case offsetof(struct inet_connection_sock, icsk_ack.pending):
 118                 end = offsetofend(struct inet_connection_sock,
 119                                   icsk_ack.pending);
 120                 break;
 121         case offsetof(struct tcp_sock, snd_cwnd):
 122                 end = offsetofend(struct tcp_sock, snd_cwnd);
 123                 break;
 124         case offsetof(struct tcp_sock, snd_cwnd_cnt):
 125                 end = offsetofend(struct tcp_sock, snd_cwnd_cnt);
 126                 break;
 127         case offsetof(struct tcp_sock, snd_ssthresh):
 128                 end = offsetofend(struct tcp_sock, snd_ssthresh);
 129                 break;
 130         case offsetof(struct tcp_sock, ecn_flags):
 131                 end = offsetofend(struct tcp_sock, ecn_flags);
 132                 break;
 133         default:
 134                 bpf_log(log, "no write support to tcp_sock at off %d\n", off);
 135                 return -EACCES;
 136         }
 137
 138         if (off + size > end) {
 139                 bpf_log(log,
 140                         "write access at off %d with size %d beyond the member of tcp_sock ended at %zu\n",
 141                         off, size, end);
 142                 return -EACCES;
 143         }
 144
 145         return NOT_INIT;
 146 }
 147
 148 BPF_CALL_2(bpf_tcp_send_ack, struct tcp_sock *, tp, u32, rcv_nxt)
 149 {
 150         /* bpf_tcp_ca prog cannot have NULL tp */
 151         __tcp_send_ack((struct sock *)tp, rcv_nxt);
 152         return 0;
 153 }
 154
 155 static const struct bpf_func_proto bpf_tcp_send_ack_proto = {
 156         .func           = bpf_tcp_send_ack,
 157         .gpl_only       = false,
 158         /* In case we want to report error later */
 159         .ret_type       = RET_INTEGER,
 160         .arg1_type      = ARG_PTR_TO_BTF_ID,
 161         .arg1_btf_id    = &tcp_sock_id,
 162         .arg2_type      = ARG_ANYTHING,
 163 };
 164
 165 static const struct bpf_func_proto *
 166 bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
 167                           const struct bpf_prog *prog)
 168 {
 169         switch (func_id) {
 170         case BPF_FUNC_tcp_send_ack:
 171                 return &bpf_tcp_send_ack_proto;
 172         case BPF_FUNC_sk_storage_get:
 173                 return &bpf_sk_storage_get_proto;
 174         case BPF_FUNC_sk_storage_delete:
 175                 return &bpf_sk_storage_delete_proto;
 176         default:
 177                 return bpf_base_func_proto(func_id);
 178         }
 179 }
 180
 181 static const struct bpf_verifier_ops bpf_tcp_ca_verifier_ops = {
 182         .get_func_proto         = bpf_tcp_ca_get_func_proto,
 183         .is_valid_access        = bpf_tcp_ca_is_valid_access,
 184         .btf_struct_access      = bpf_tcp_ca_btf_struct_access,
 185 };
 186
 187 static int bpf_tcp_ca_init_member(const struct btf_type *t,
 188                                   const struct btf_member *member,
 189                                   void *kdata, const void *udata)
 190 {
 191         const struct tcp_congestion_ops *utcp_ca;
 192         struct tcp_congestion_ops *tcp_ca;
 193         int prog_fd;
 194         u32 moff;
 195
 196         utcp_ca = (const struct tcp_congestion_ops *)udata;
 197         tcp_ca = (struct tcp_congestion_ops *)kdata;
 198
 199         moff = btf_member_bit_offset(t, member) / 8;
 200         switch (moff) {
 201         case offsetof(struct tcp_congestion_ops, flags):
 202                 if (utcp_ca->flags & ~TCP_CONG_MASK)
 203                         return -EINVAL;
 204                 tcp_ca->flags = utcp_ca->flags;
 205                 return 1;
 206         case offsetof(struct tcp_congestion_ops, name):
 207                 if (bpf_obj_name_cpy(tcp_ca->name, utcp_ca->name,
 208                                      sizeof(tcp_ca->name)) <= 0)
 209                         return -EINVAL;
 210                 if (tcp_ca_find(utcp_ca->name))
 211                         return -EEXIST;
 212                 return 1;
 213         }
 214
 215         if (!btf_type_resolve_func_ptr(btf_vmlinux, member->type, NULL))
 216                 return 0;
 217
 218         /* Ensure bpf_prog is provided for compulsory func ptr */
 219         prog_fd = (int)(*(unsigned long *)(udata + moff));
 220         if (!prog_fd && !is_optional(moff) && !is_unsupported(moff))
 221                 return -EINVAL;
 222
 223         return 0;
 224 }
 225
 226 static int bpf_tcp_ca_check_member(const struct btf_type *t,
 227                                    const struct btf_member *member)
 228 {
 229         if (is_unsupported(btf_member_bit_offset(t, member) / 8))
 230                 return -ENOTSUPP;
 231         return 0;
 232 }
 233
 234 static int bpf_tcp_ca_reg(void *kdata)
 235 {
 236         return tcp_register_congestion_control(kdata);
 237 }
 238
 239 static void bpf_tcp_ca_unreg(void *kdata)
 240 {
 241         tcp_unregister_congestion_control(kdata);
 242 }
 243
 244 /* Avoid sparse warning.  It is only used in bpf_struct_ops.c. */
 245 extern struct bpf_struct_ops bpf_tcp_congestion_ops;
 246
 247 struct bpf_struct_ops bpf_tcp_congestion_ops = {
 248         .verifier_ops = &bpf_tcp_ca_verifier_ops,
 249         .reg = bpf_tcp_ca_reg,
 250         .unreg = bpf_tcp_ca_unreg,
 251         .check_member = bpf_tcp_ca_check_member,
 252         .init_member = bpf_tcp_ca_init_member,
 253         .init = bpf_tcp_ca_init,
 254         .name = "tcp_congestion_ops",
 255 };