1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2022 Bobby Eshleman <bobby.eshleman@bytedance.com>
3 *
4 * Based off of net/unix/unix_bpf.c
5 */
6
7 #include <linux/bpf.h>
8 #include <linux/module.h>
9 #include <linux/skmsg.h>
10 #include <linux/socket.h>
11 #include <linux/wait.h>
12 #include <net/af_vsock.h>
13 #include <net/sock.h>
14
15 #define vsock_sk_has_data(__sk, __psock) \
16 ({ !skb_queue_empty(&(__sk)->sk_receive_queue) || \
17 !skb_queue_empty(&(__psock)->ingress_skb) || \
18 !list_empty(&(__psock)->ingress_msg); \
19 })
20
21 static struct proto *vsock_prot_saved __read_mostly;
22 static DEFINE_SPINLOCK(vsock_prot_lock);
23 static struct proto vsock_bpf_prot;
24
25 static bool vsock_has_data(struct sock *sk, struct sk_psock *psock)
26 {
27 struct vsock_sock *vsk = vsock_sk(sk);
28 s64 ret;
29
30 ret = vsock_connectible_has_data(vsk);
31 if (ret > 0)
32 return true;
33
34 return vsock_sk_has_data(sk, psock);
35 }
36
37 static bool vsock_msg_wait_data(struct sock *sk, struct sk_psock *psock, long timeo)
38 {
39 bool ret;
40
41 DEFINE_WAIT_FUNC(wait, woken_wake_function);
42
43 if (sk->sk_shutdown & RCV_SHUTDOWN)
44 return true;
45
46 if (!timeo)
47 return false;
48
49 add_wait_queue(sk_sleep(sk), &wait);
50 sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
51 ret = vsock_has_data(sk, psock);
52 if (!ret) {
53 wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);
54 ret = vsock_has_data(sk, psock);
55 }
56 sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
57 remove_wait_queue(sk_sleep(sk), &wait);
58 return ret;
59 }
60
61 static int __vsock_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int flags)
62 {
63 struct socket *sock = sk->sk_socket;
64 int err;
65
66 if (sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET)
67 err = vsock_connectible_recvmsg(sock, msg, len, flags);
68 else if (sk->sk_type == SOCK_DGRAM)
69 err = vsock_dgram_recvmsg(sock, msg, len, flags);
70 else
71 err = -EPROTOTYPE;
72
73 return err;
74 }
75
76 static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr *msg,
77 size_t len, int flags, int *addr_len)
78 {
79 struct sk_psock *psock;
80 int copied;
81
82 psock = sk_psock_get(sk);
83 if (unlikely(!psock))
84 return __vsock_recvmsg(sk, msg, len, flags);
85
86 lock_sock(sk);
87 if (vsock_has_data(sk, psock) && sk_psock_queue_empty(psock)) {
88 release_sock(sk);
89 sk_psock_put(sk, psock);
90 return __vsock_recvmsg(sk, msg, len, flags);
91 }
92
93 copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
94 while (copied == 0) {
95 long timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
96
97 if (!vsock_msg_wait_data(sk, psock, timeo)) {
98 copied = -EAGAIN;
99 break;
100 }
101
102 if (sk_psock_queue_empty(psock)) {
103 release_sock(sk);
104 sk_psock_put(sk, psock);
105 return __vsock_recvmsg(sk, msg, len, flags);
106 }
107
108 copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
109 }
110
111 release_sock(sk);
112 sk_psock_put(sk, psock);
113
114 return copied;
115 }
116
117 /* Copy of original proto with updated sock_map methods */
118 static struct proto vsock_bpf_prot = {
119 .close = sock_map_close,
120 .recvmsg = vsock_bpf_recvmsg,
121 .sock_is_readable = sk_msg_is_readable,
122 .unhash = sock_map_unhash,
123 };
124
125 static void vsock_bpf_rebuild_protos(struct proto *prot, const struct proto *base)
126 {
127 *prot = *base;
128 prot->close = sock_map_close;
129 prot->recvmsg = vsock_bpf_recvmsg;
130 prot->sock_is_readable = sk_msg_is_readable;
131 }
132
133 static void vsock_bpf_check_needs_rebuild(struct proto *ops)
134 {
135 /* Paired with the smp_store_release() below. */
136 if (unlikely(ops != smp_load_acquire(&vsock_prot_saved))) {
137 spin_lock_bh(&vsock_prot_lock);
138 if (likely(ops != vsock_prot_saved)) {
139 vsock_bpf_rebuild_protos(&vsock_bpf_prot, ops);
140 /* Make sure proto function pointers are updated before publishing the
141 * pointer to the struct.
142 */
143 smp_store_release(&vsock_prot_saved, ops);
144 }
145 spin_unlock_bh(&vsock_prot_lock);
146 }
147 }
148
149 int vsock_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
150 {
151 struct vsock_sock *vsk;
152
153 if (restore) {
154 sk->sk_write_space = psock->saved_write_space;
155 sock_replace_proto(sk, psock->sk_proto);
156 return 0;
157 }
158
159 vsk = vsock_sk(sk);
160 if (!vsk->transport)
161 return -ENODEV;
162
163 if (!vsk->transport->read_skb)
164 return -EOPNOTSUPP;
165
166 vsock_bpf_check_needs_rebuild(psock->sk_proto);
167 sock_replace_proto(sk, &vsock_bpf_prot);
168 return 0;
169 }
170
171 void __init vsock_bpf_build_proto(void)
172 {
173 vsock_bpf_rebuild_protos(&vsock_bpf_prot, &vsock_proto);
174 }
175
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