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// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2022 Bobby Eshleman <bobby.eshleman@bytedance.com>
*
* Based off of net/unix/unix_bpf.c
*/
#include <linux/bpf.h>
#include <linux/module.h>
#include <linux/skmsg.h>
#include <linux/socket.h>
#include <linux/wait.h>
#include <net/af_vsock.h>
#include <net/sock.h>
#define vsock_sk_has_data(__sk, __psock) \
({ !skb_queue_empty(&(__sk)->sk_receive_queue) || \
!skb_queue_empty(&(__psock)->ingress_skb) || \
!list_empty(&(__psock)->ingress_msg); \
})
static struct proto *vsock_prot_saved __read_mostly;
static DEFINE_SPINLOCK(vsock_prot_lock);
static struct proto vsock_bpf_prot;
static bool vsock_has_data(struct sock *sk, struct sk_psock *psock)
{
struct vsock_sock *vsk = vsock_sk(sk);
s64 ret;
ret = vsock_connectible_has_data(vsk);
if (ret > 0)
return true;
return vsock_sk_has_data(sk, psock);
}
static bool vsock_msg_wait_data(struct sock *sk, struct sk_psock *psock, long timeo)
{
bool ret;
DEFINE_WAIT_FUNC(wait, woken_wake_function);
if (sk->sk_shutdown & RCV_SHUTDOWN)
return true;
if (!timeo)
return false;
add_wait_queue(sk_sleep(sk), &wait);
sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
ret = vsock_has_data(sk, psock);
if (!ret) {
wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);
ret = vsock_has_data(sk, psock);
}
sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
remove_wait_queue(sk_sleep(sk), &wait);
return ret;
}
static int __vsock_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int flags)
{
struct socket *sock = sk->sk_socket;
int err;
if (sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET)
err = vsock_connectible_recvmsg(sock, msg, len, flags);
else if (sk->sk_type == SOCK_DGRAM)
err = vsock_dgram_recvmsg(sock, msg, len, flags);
else
err = -EPROTOTYPE;
return err;
}
static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr *msg,
size_t len, int flags, int *addr_len)
{
struct sk_psock *psock;
int copied;
psock = sk_psock_get(sk);
if (unlikely(!psock))
return __vsock_recvmsg(sk, msg, len, flags);
lock_sock(sk);
if (vsock_has_data(sk, psock) && sk_psock_queue_empty(psock)) {
release_sock(sk);
sk_psock_put(sk, psock);
return __vsock_recvmsg(sk, msg, len, flags);
}
copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
while (copied == 0) {
long timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
if (!vsock_msg_wait_data(sk, psock, timeo)) {
copied = -EAGAIN;
break;
}
if (sk_psock_queue_empty(psock)) {
release_sock(sk);
sk_psock_put(sk, psock);
return __vsock_recvmsg(sk, msg, len, flags);
}
copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
}
release_sock(sk);
sk_psock_put(sk, psock);
return copied;
}
/* Copy of original proto with updated sock_map methods */
static struct proto vsock_bpf_prot = {
.close = sock_map_close,
.recvmsg = vsock_bpf_recvmsg,
.sock_is_readable = sk_msg_is_readable,
.unhash = sock_map_unhash,
};
static void vsock_bpf_rebuild_protos(struct proto *prot, const struct proto *base)
{
*prot = *base;
prot->close = sock_map_close;
prot->recvmsg = vsock_bpf_recvmsg;
prot->sock_is_readable = sk_msg_is_readable;
}
static void vsock_bpf_check_needs_rebuild(struct proto *ops)
{
/* Paired with the smp_store_release() below. */
if (unlikely(ops != smp_load_acquire(&vsock_prot_saved))) {
spin_lock_bh(&vsock_prot_lock);
if (likely(ops != vsock_prot_saved)) {
vsock_bpf_rebuild_protos(&vsock_bpf_prot, ops);
/* Make sure proto function pointers are updated before publishing the
* pointer to the struct.
*/
smp_store_release(&vsock_prot_saved, ops);
}
spin_unlock_bh(&vsock_prot_lock);
}
}
int vsock_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
{
struct vsock_sock *vsk;
if (restore) {
sk->sk_write_space = psock->saved_write_space;
sock_replace_proto(sk, psock->sk_proto);
return 0;
}
vsk = vsock_sk(sk);
if (!vsk->transport)
return -ENODEV;
if (!vsk->transport->read_skb)
return -EOPNOTSUPP;
vsock_bpf_check_needs_rebuild(psock->sk_proto);
sock_replace_proto(sk, &vsock_bpf_prot);
return 0;
}
void __init vsock_bpf_build_proto(void)
{
vsock_bpf_rebuild_protos(&vsock_bpf_prot, &vsock_proto);
}
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