net/ipv4/udp_bpf.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Copyright (c) 2020 Cloudflare Ltd https://cloudflare.com */
   3
   4 #include <linux/skmsg.h>
   5 #include <net/sock.h>
   6 #include <net/udp.h>
   7 #include <net/inet_common.h>
   8
   9 #include "udp_impl.h"
  10
  11 static struct proto *udpv6_prot_saved __read_mostly;
  12
  13 static int sk_udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
  14                           int flags, int *addr_len)
  15 {
  16 #if IS_ENABLED(CONFIG_IPV6)
  17         if (sk->sk_family == AF_INET6)
  18                 return udpv6_prot_saved->recvmsg(sk, msg, len, flags, addr_len);
  19 #endif
  20         return udp_prot.recvmsg(sk, msg, len, flags, addr_len);
  21 }
  22
  23 static bool udp_sk_has_data(struct sock *sk)
  24 {
  25         return !skb_queue_empty(&udp_sk(sk)->reader_queue) ||
  26                !skb_queue_empty(&sk->sk_receive_queue);
  27 }
  28
  29 static bool psock_has_data(struct sk_psock *psock)
  30 {
  31         return !skb_queue_empty(&psock->ingress_skb) ||
  32                !sk_psock_queue_empty(psock);
  33 }
  34
  35 #define udp_msg_has_data(__sk, __psock) \
  36                 ({ udp_sk_has_data(__sk) || psock_has_data(__psock); })
  37
  38 static int udp_msg_wait_data(struct sock *sk, struct sk_psock *psock,
  39                              long timeo)
  40 {
  41         DEFINE_WAIT_FUNC(wait, woken_wake_function);
  42         int ret = 0;
  43
  44         if (sk->sk_shutdown & RCV_SHUTDOWN)
  45                 return 1;
  46
  47         if (!timeo)
  48                 return ret;
  49
  50         add_wait_queue(sk_sleep(sk), &wait);
  51         sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
  52         ret = udp_msg_has_data(sk, psock);
  53         if (!ret) {
  54                 wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);
  55                 ret = udp_msg_has_data(sk, psock);
  56         }
  57         sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
  58         remove_wait_queue(sk_sleep(sk), &wait);
  59         return ret;
  60 }
  61
  62 static int udp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
  63                            int flags, int *addr_len)
  64 {
  65         struct sk_psock *psock;
  66         int copied, ret;
  67
  68         if (unlikely(flags & MSG_ERRQUEUE))
  69                 return inet_recv_error(sk, msg, len, addr_len);
  70
  71         psock = sk_psock_get(sk);
  72         if (unlikely(!psock))
  73                 return sk_udp_recvmsg(sk, msg, len, flags, addr_len);
  74
  75         if (!psock_has_data(psock)) {
  76                 ret = sk_udp_recvmsg(sk, msg, len, flags, addr_len);
  77                 goto out;
  78         }
  79
  80 msg_bytes_ready:
  81         copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
  82         if (!copied) {
  83                 long timeo;
  84                 int data;
  85
  86                 timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
  87                 data = udp_msg_wait_data(sk, psock, timeo);
  88                 if (data) {
  89                         if (psock_has_data(psock))
  90                                 goto msg_bytes_ready;
  91                         ret = sk_udp_recvmsg(sk, msg, len, flags, addr_len);
  92                         goto out;
  93                 }
  94                 copied = -EAGAIN;
  95         }
  96         ret = copied;
  97 out:
  98         sk_psock_put(sk, psock);
  99         return ret;
 100 }
 101
 102 enum {
 103         UDP_BPF_IPV4,
 104         UDP_BPF_IPV6,
 105         UDP_BPF_NUM_PROTS,
 106 };
 107
 108 static DEFINE_SPINLOCK(udpv6_prot_lock);
 109 static struct proto udp_bpf_prots[UDP_BPF_NUM_PROTS];
 110
 111 static void udp_bpf_rebuild_protos(struct proto *prot, const struct proto *base)
 112 {
 113         *prot        = *base;
 114         prot->close  = sock_map_close;
 115         prot->recvmsg = udp_bpf_recvmsg;
 116         prot->sock_is_readable = sk_msg_is_readable;
 117 }
 118
 119 static void udp_bpf_check_v6_needs_rebuild(struct proto *ops)
 120 {
 121         if (unlikely(ops != smp_load_acquire(&udpv6_prot_saved))) {
 122                 spin_lock_bh(&udpv6_prot_lock);
 123                 if (likely(ops != udpv6_prot_saved)) {
 124                         udp_bpf_rebuild_protos(&udp_bpf_prots[UDP_BPF_IPV6], ops);
 125                         smp_store_release(&udpv6_prot_saved, ops);
 126                 }
 127                 spin_unlock_bh(&udpv6_prot_lock);
 128         }
 129 }
 130
 131 static int __init udp_bpf_v4_build_proto(void)
 132 {
 133         udp_bpf_rebuild_protos(&udp_bpf_prots[UDP_BPF_IPV4], &udp_prot);
 134         return 0;
 135 }
 136 late_initcall(udp_bpf_v4_build_proto);
 137
 138 int udp_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
 139 {
 140         int family = sk->sk_family == AF_INET ? UDP_BPF_IPV4 : UDP_BPF_IPV6;
 141
 142         if (restore) {
 143                 sk->sk_write_space = psock->saved_write_space;
 144                 WRITE_ONCE(sk->sk_prot, psock->sk_proto);
 145                 return 0;
 146         }
 147
 148         if (sk->sk_family == AF_INET6)
 149                 udp_bpf_check_v6_needs_rebuild(psock->sk_proto);
 150
 151         WRITE_ONCE(sk->sk_prot, &udp_bpf_prots[family]);
 152         return 0;
 153 }
 154 EXPORT_SYMBOL_GPL(udp_bpf_update_proto);