[PATCH v1 net-next 04/16] af_unix: Save listener for embryo socket.

[Kuniyuki Iwashima <kuniyu@amazon.com>]

This is a prep patch for the following change, where we need to
fetch the listening socket from an embryo socket in sendmsg().

We add a new field to struct unix_sock to save a pointer to a
listening socket.

We set it when connect() creates a new socket, and clear it when
accept() is called.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 include/net/af_unix.h | 1 +
 net/unix/af_unix.c    | 5 ++++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index 54d62467a70b..438d2a18ba2e 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -79,6 +79,7 @@ struct unix_sock {
 	struct path		path;
 	struct mutex		iolock, bindlock;
 	struct sock		*peer;
+	struct sock		*listener;
 	struct unix_vertex	vertex;
 	struct list_head	link;
 	unsigned long		inflight;
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index ea7bac18a781..1ebc3c15f972 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -992,6 +992,7 @@ static struct sock *unix_create1(struct net *net, struct socket *sock, int kern,
 	sk->sk_max_ack_backlog	= net->unx.sysctl_max_dgram_qlen;
 	sk->sk_destruct		= unix_sock_destructor;
 	u = unix_sk(sk);
+	u->listener = NULL;
 	u->inflight = 0;
 	u->path.dentry = NULL;
 	u->path.mnt = NULL;
@@ -1611,6 +1612,7 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 	newsk->sk_type		= sk->sk_type;
 	init_peercred(newsk);
 	newu = unix_sk(newsk);
+	newu->listener = other;
 	RCU_INIT_POINTER(newsk->sk_wq, &newu->peer_wq);
 	otheru = unix_sk(other);
 
@@ -1706,8 +1708,8 @@ static int unix_accept(struct socket *sock, struct socket *newsock, int flags,
 		       bool kern)
 {
 	struct sock *sk = sock->sk;
-	struct sock *tsk;
 	struct sk_buff *skb;
+	struct sock *tsk;
 	int err;
 
 	err = -EOPNOTSUPP;
@@ -1732,6 +1734,7 @@ static int unix_accept(struct socket *sock, struct socket *newsock, int flags,
 	}
 
 	tsk = skb->sk;
+	unix_sk(tsk)->listener = NULL;
 	skb_free_datagram(sk, skb);
 	wake_up_interruptible(&unix_sk(sk)->peer_wait);
 
-- 
2.30.2