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// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2021 Cong Wang <cong.wang@bytedance.com> */
#include <linux/skmsg.h>
#include <linux/bpf.h>
#include <net/sock.h>
#include <net/af_unix.h>
#define unix_sk_has_data(__sk, __psock) \
({ !skb_queue_empty(&__sk->sk_receive_queue) || \
!skb_queue_empty(&__psock->ingress_skb) || \
!list_empty(&__psock->ingress_msg); \
})
static int unix_msg_wait_data(struct sock *sk, struct sk_psock *psock,
long timeo)
{
DEFINE_WAIT_FUNC(wait, woken_wake_function);
struct unix_sock *u = unix_sk(sk);
int ret = 0;
if (sk->sk_shutdown & RCV_SHUTDOWN)
return 1;
if (!timeo)
return ret;
add_wait_queue(sk_sleep(sk), &wait);
sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
if (!unix_sk_has_data(sk, psock)) {
mutex_unlock(&u->iolock);
wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);
mutex_lock(&u->iolock);
ret = unix_sk_has_data(sk, psock);
}
sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
remove_wait_queue(sk_sleep(sk), &wait);
return ret;
}
static int unix_dgram_bpf_recvmsg(struct sock *sk, struct msghdr *msg,
size_t len, int nonblock, int flags,
int *addr_len)
{
struct unix_sock *u = unix_sk(sk);
struct sk_psock *psock;
int copied;
psock = sk_psock_get(sk);
if (unlikely(!psock))
return __unix_dgram_recvmsg(sk, msg, len, flags);
mutex_lock(&u->iolock);
if (!skb_queue_empty(&sk->sk_receive_queue) &&
sk_psock_queue_empty(psock)) {
mutex_unlock(&u->iolock);
sk_psock_put(sk, psock);
return __unix_dgram_recvmsg(sk, msg, len, flags);
}
msg_bytes_ready:
copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
if (!copied) {
long timeo;
int data;
timeo = sock_rcvtimeo(sk, nonblock);
data = unix_msg_wait_data(sk, psock, timeo);
if (data) {
if (!sk_psock_queue_empty(psock))
goto msg_bytes_ready;
mutex_unlock(&u->iolock);
sk_psock_put(sk, psock);
return __unix_dgram_recvmsg(sk, msg, len, flags);
}
copied = -EAGAIN;
}
mutex_unlock(&u->iolock);
sk_psock_put(sk, psock);
return copied;
}
static struct proto *unix_prot_saved __read_mostly;
static DEFINE_SPINLOCK(unix_prot_lock);
static struct proto unix_bpf_prot;
static void unix_bpf_rebuild_protos(struct proto *prot, const struct proto *base)
{
*prot = *base;
prot->close = sock_map_close;
prot->recvmsg = unix_dgram_bpf_recvmsg;
}
static void unix_bpf_check_needs_rebuild(struct proto *ops)
{
if (unlikely(ops != smp_load_acquire(&unix_prot_saved))) {
spin_lock_bh(&unix_prot_lock);
if (likely(ops != unix_prot_saved)) {
unix_bpf_rebuild_protos(&unix_bpf_prot, ops);
smp_store_release(&unix_prot_saved, ops);
}
spin_unlock_bh(&unix_prot_lock);
}
}
int unix_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
{
if (sk->sk_type != SOCK_DGRAM)
return -EOPNOTSUPP;
if (restore) {
sk->sk_write_space = psock->saved_write_space;
WRITE_ONCE(sk->sk_prot, psock->sk_proto);
return 0;
}
unix_bpf_check_needs_rebuild(psock->sk_proto);
WRITE_ONCE(sk->sk_prot, &unix_bpf_prot);
return 0;
}
void __init unix_bpf_build_proto(void)
{
unix_bpf_rebuild_protos(&unix_bpf_prot, &unix_proto);
}
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