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 btf_sk_storage_get_ids[5];
  32 static struct bpf_func_proto btf_sk_storage_get_proto __read_mostly;
  33
  34 static int btf_sk_storage_delete_ids[5];
  35 static struct bpf_func_proto btf_sk_storage_delete_proto __read_mostly;
  36
  37 static void convert_sk_func_proto(struct bpf_func_proto *to, int *to_btf_ids,
  38                                   const struct bpf_func_proto *from)
  39 {
  40         int i;
  41
  42         *to = *from;
  43         to->btf_id = to_btf_ids;
  44         for (i = 0; i < ARRAY_SIZE(to->arg_type); i++) {
  45                 if (to->arg_type[i] == ARG_PTR_TO_SOCKET) {
  46                         to->arg_type[i] = ARG_PTR_TO_BTF_ID;
  47                         to->btf_id[i] = tcp_sock_id;
  48                 }
  49         }
  50 }
  51
  52 static int bpf_tcp_ca_init(struct btf *btf)
  53 {
  54         s32 type_id;
  55
  56         type_id = btf_find_by_name_kind(btf, "sock", BTF_KIND_STRUCT);
  57         if (type_id < 0)
  58                 return -EINVAL;
  59         sock_id = type_id;
  60
  61         type_id = btf_find_by_name_kind(btf, "tcp_sock", BTF_KIND_STRUCT);
  62         if (type_id < 0)
  63                 return -EINVAL;
  64         tcp_sock_id = type_id;
  65         tcp_sock_type = btf_type_by_id(btf, tcp_sock_id);
  66
  67         convert_sk_func_proto(&btf_sk_storage_get_proto,
  68                               btf_sk_storage_get_ids,
  69                               &bpf_sk_storage_get_proto);
  70         convert_sk_func_proto(&btf_sk_storage_delete_proto,
  71                               btf_sk_storage_delete_ids,
  72                               &bpf_sk_storage_delete_proto);
  73
  74         return 0;
  75 }
  76
  77 static bool is_optional(u32 member_offset)
  78 {
  79         unsigned int i;
  80
  81         for (i = 0; i < ARRAY_SIZE(optional_ops); i++) {
  82                 if (member_offset == optional_ops[i])
  83                         return true;
  84         }
  85
  86         return false;
  87 }
  88
  89 static bool is_unsupported(u32 member_offset)
  90 {
  91         unsigned int i;
  92
  93         for (i = 0; i < ARRAY_SIZE(unsupported_ops); i++) {
  94                 if (member_offset == unsupported_ops[i])
  95                         return true;
  96         }
  97
  98         return false;
  99 }
 100
 101 extern struct btf *btf_vmlinux;
 102
 103 static bool bpf_tcp_ca_is_valid_access(int off, int size,
 104                                        enum bpf_access_type type,
 105                                        const struct bpf_prog *prog,
 106                                        struct bpf_insn_access_aux *info)
 107 {
 108         if (off < 0 || off >= sizeof(__u64) * MAX_BPF_FUNC_ARGS)
 109                 return false;
 110         if (type != BPF_READ)
 111                 return false;
 112         if (off % size != 0)
 113                 return false;
 114
 115         if (!btf_ctx_access(off, size, type, prog, info))
 116                 return false;
 117
 118         if (info->reg_type == PTR_TO_BTF_ID && info->btf_id == sock_id)
 119                 /* promote it to tcp_sock */
 120                 info->btf_id = tcp_sock_id;
 121
 122         return true;
 123 }
 124
 125 static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
 126                                         const struct btf_type *t, int off,
 127                                         int size, enum bpf_access_type atype,
 128                                         u32 *next_btf_id)
 129 {
 130         size_t end;
 131
 132         if (atype == BPF_READ)
 133                 return btf_struct_access(log, t, off, size, atype, next_btf_id);
 134
 135         if (t != tcp_sock_type) {
 136                 bpf_log(log, "only read is supported\n");
 137                 return -EACCES;
 138         }
 139
 140         switch (off) {
 141         case bpf_ctx_range(struct inet_connection_sock, icsk_ca_priv):
 142                 end = offsetofend(struct inet_connection_sock, icsk_ca_priv);
 143                 break;
 144         case offsetof(struct inet_connection_sock, icsk_ack.pending):
 145                 end = offsetofend(struct inet_connection_sock,
 146                                   icsk_ack.pending);
 147                 break;
 148         case offsetof(struct tcp_sock, snd_cwnd):
 149                 end = offsetofend(struct tcp_sock, snd_cwnd);
 150                 break;
 151         case offsetof(struct tcp_sock, snd_cwnd_cnt):
 152                 end = offsetofend(struct tcp_sock, snd_cwnd_cnt);
 153                 break;
 154         case offsetof(struct tcp_sock, snd_ssthresh):
 155                 end = offsetofend(struct tcp_sock, snd_ssthresh);
 156                 break;
 157         case offsetof(struct tcp_sock, ecn_flags):
 158                 end = offsetofend(struct tcp_sock, ecn_flags);
 159                 break;
 160         default:
 161                 bpf_log(log, "no write support to tcp_sock at off %d\n", off);
 162                 return -EACCES;
 163         }
 164
 165         if (off + size > end) {
 166                 bpf_log(log,
 167                         "write access at off %d with size %d beyond the member of tcp_sock ended at %zu\n",
 168                         off, size, end);
 169                 return -EACCES;
 170         }
 171
 172         return NOT_INIT;
 173 }
 174
 175 BPF_CALL_2(bpf_tcp_send_ack, struct tcp_sock *, tp, u32, rcv_nxt)
 176 {
 177         /* bpf_tcp_ca prog cannot have NULL tp */
 178         __tcp_send_ack((struct sock *)tp, rcv_nxt);
 179         return 0;
 180 }
 181
 182 static const struct bpf_func_proto bpf_tcp_send_ack_proto = {
 183         .func           = bpf_tcp_send_ack,
 184         .gpl_only       = false,
 185         /* In case we want to report error later */
 186         .ret_type       = RET_INTEGER,
 187         .arg1_type      = ARG_PTR_TO_BTF_ID,
 188         .arg2_type      = ARG_ANYTHING,
 189         .btf_id         = &tcp_sock_id,
 190 };
 191
 192 static const struct bpf_func_proto *
 193 bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
 194                           const struct bpf_prog *prog)
 195 {
 196         switch (func_id) {
 197         case BPF_FUNC_tcp_send_ack:
 198                 return &bpf_tcp_send_ack_proto;
 199         case BPF_FUNC_sk_storage_get:
 200                 return &btf_sk_storage_get_proto;
 201         case BPF_FUNC_sk_storage_delete:
 202                 return &btf_sk_storage_delete_proto;
 203         default:
 204                 return bpf_base_func_proto(func_id);
 205         }
 206 }
 207
 208 static const struct bpf_verifier_ops bpf_tcp_ca_verifier_ops = {
 209         .get_func_proto         = bpf_tcp_ca_get_func_proto,
 210         .is_valid_access        = bpf_tcp_ca_is_valid_access,
 211         .btf_struct_access      = bpf_tcp_ca_btf_struct_access,
 212 };
 213
 214 static int bpf_tcp_ca_init_member(const struct btf_type *t,
 215                                   const struct btf_member *member,
 216                                   void *kdata, const void *udata)
 217 {
 218         const struct tcp_congestion_ops *utcp_ca;
 219         struct tcp_congestion_ops *tcp_ca;
 220         int prog_fd;
 221         u32 moff;
 222
 223         utcp_ca = (const struct tcp_congestion_ops *)udata;
 224         tcp_ca = (struct tcp_congestion_ops *)kdata;
 225
 226         moff = btf_member_bit_offset(t, member) / 8;
 227         switch (moff) {
 228         case offsetof(struct tcp_congestion_ops, flags):
 229                 if (utcp_ca->flags & ~TCP_CONG_MASK)
 230                         return -EINVAL;
 231                 tcp_ca->flags = utcp_ca->flags;
 232                 return 1;
 233         case offsetof(struct tcp_congestion_ops, name):
 234                 if (bpf_obj_name_cpy(tcp_ca->name, utcp_ca->name,
 235                                      sizeof(tcp_ca->name)) <= 0)
 236                         return -EINVAL;
 237                 if (tcp_ca_find(utcp_ca->name))
 238                         return -EEXIST;
 239                 return 1;
 240         }
 241
 242         if (!btf_type_resolve_func_ptr(btf_vmlinux, member->type, NULL))
 243                 return 0;
 244
 245         /* Ensure bpf_prog is provided for compulsory func ptr */
 246         prog_fd = (int)(*(unsigned long *)(udata + moff));
 247         if (!prog_fd && !is_optional(moff) && !is_unsupported(moff))
 248                 return -EINVAL;
 249
 250         return 0;
 251 }
 252
 253 static int bpf_tcp_ca_check_member(const struct btf_type *t,
 254                                    const struct btf_member *member)
 255 {
 256         if (is_unsupported(btf_member_bit_offset(t, member) / 8))
 257                 return -ENOTSUPP;
 258         return 0;
 259 }
 260
 261 static int bpf_tcp_ca_reg(void *kdata)
 262 {
 263         return tcp_register_congestion_control(kdata);
 264 }
 265
 266 static void bpf_tcp_ca_unreg(void *kdata)
 267 {
 268         tcp_unregister_congestion_control(kdata);
 269 }
 270
 271 /* Avoid sparse warning.  It is only used in bpf_struct_ops.c. */
 272 extern struct bpf_struct_ops bpf_tcp_congestion_ops;
 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         .check_member = bpf_tcp_ca_check_member,
 279         .init_member = bpf_tcp_ca_init_member,
 280         .init = bpf_tcp_ca_init,
 281         .name = "tcp_congestion_ops",
 282 };