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af_unix: Implement unix_dgram_bpf_recvmsg()

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We have to implement unix_dgram_bpf_recvmsg() to replace the
original ->recvmsg() to retrieve skmsg from ingress_msg.

AF_UNIX is again special here because the lack of
sk_prot->recvmsg(). I simply add a special case inside
unix_dgram_recvmsg() to call sk->sk_prot->recvmsg() directly.

Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210704190252.11866-8-xiyou.wangcong@gmail.com
This commit is contained in:
Cong Wang 2021-07-04 12:02:48 -07:00 committed by Alexei Starovoitov
parent c63829182c
commit 9825d866ce
3 changed files with 93 additions and 3 deletions
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2
include/net/af_unix.h
View file

@ -82,6 +82,8 @@ static inline struct unix_sock *unix_sk(const struct sock *sk)
long unix_inq_len(struct sock *sk);
long unix_outq_len(struct sock *sk);
int __unix_dgram_recvmsg(struct sock *sk, struct msghdr *msg, size_t size,
int flags);
#ifdef CONFIG_SYSCTL
int unix_sysctl_register(struct net *net);
void unix_sysctl_unregister(struct net *net);

19
net/unix/af_unix.c
View file

@ -2098,11 +2098,11 @@ static void unix_copy_addr(struct msghdr *msg, struct sock *sk)
}
}
static int unix_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
size_t size, int flags)
int __unix_dgram_recvmsg(struct sock *sk, struct msghdr *msg, size_t size,
int flags)
{
struct scm_cookie scm;
struct sock *sk = sock->sk;
struct socket *sock = sk->sk_socket;
struct unix_sock *u = unix_sk(sk);
struct sk_buff *skb, *last;
long timeo;
@ -2205,6 +2205,19 @@ static int unix_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
return err;
}
static int unix_dgram_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
int flags)
{
struct sock *sk = sock->sk;
#ifdef CONFIG_BPF_SYSCALL
if (sk->sk_prot != &unix_proto)
return sk->sk_prot->recvmsg(sk, msg, size, flags & MSG_DONTWAIT,
flags & ~MSG_DONTWAIT, NULL);
#endif
return __unix_dgram_recvmsg(sk, msg, size, flags);
}
static int unix_read_sock(struct sock *sk, read_descriptor_t *desc,
sk_read_actor_t recv_actor)
{

75
net/unix/unix_bpf.c
View file

@ -6,6 +6,80 @@
#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, ret;
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)) {
ret = __unix_dgram_recvmsg(sk, msg, len, flags);
goto out;
}
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;
ret = __unix_dgram_recvmsg(sk, msg, len, flags);
goto out;
}
copied = -EAGAIN;
}
ret = copied;
out:
mutex_unlock(&u->iolock);
sk_psock_put(sk, psock);
return ret;
}
static struct proto *unix_prot_saved __read_mostly;
static DEFINE_SPINLOCK(unix_prot_lock);
static struct proto unix_bpf_prot;
@ -14,6 +88,7 @@ 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)