[PATCH mptcp-next v2 1/2] mptcp: propagate fastclose error.

* [PATCH mptcp-next v2 1/2] mptcp: propagate fastclose error.
@ 2022-08-31 10:47 Paolo Abeni
  2022-08-31 10:47 ` [PATCH mptcp-next v2 2/2] mptcp: use fastclose on more edge scenarios Paolo Abeni
  0 siblings, 1 reply; 2+ messages in thread
From: Paolo Abeni @ 2022-08-31 10:47 UTC (permalink / raw)
  To: mptcp

When an mptcp socket is closed due to an incoming FASTCLOSE
option, so specific sk_err is set and later syscall will
fail usually with EPIPE.

Align the current fastclose error handling with TCP reset,
properly setting the socket error according to the current
msk state and propagating such error.

Additionally sendmsg() is currently not handling properly
the sk_err, always returning EPIPE.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 net/mptcp/protocol.c | 45 ++++++++++++++++++++++++++++++++++----------
 1 file changed, 35 insertions(+), 10 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index f4891db86217..b04f184695e4 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1685,9 +1685,13 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	if ((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) {
 		ret = sk_stream_wait_connect(sk, &timeo);
 		if (ret)
-			goto out;
+			goto do_error;
 	}
 
+	ret = -EPIPE;
+	if (unlikely(sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN)))
+		goto do_error;
+
 	pfrag = sk_page_frag(sk);
 
 	while (msg_data_left(msg)) {
@@ -1696,11 +1700,6 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		bool dfrag_collapsed;
 		size_t psize, offset;
 
-		if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN)) {
-			ret = -EPIPE;
-			goto out;
-		}
-
 		/* reuse tail pfrag, if possible, or carve a new one from the
 		 * page allocator
 		 */
@@ -1732,7 +1731,7 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		if (copy_page_from_iter(dfrag->page, offset, psize,
 					&msg->msg_iter) != psize) {
 			ret = -EFAULT;
-			goto out;
+			goto do_error;
 		}
 
 		/* data successfully copied into the write queue */
@@ -1764,7 +1763,7 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		__mptcp_push_pending(sk, msg->msg_flags);
 		ret = sk_stream_wait_memory(sk, &timeo);
 		if (ret)
-			goto out;
+			goto do_error;
 	}
 
 	if (copied)
@@ -1772,7 +1771,14 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 
 out:
 	release_sock(sk);
-	return copied ? : ret;
+	return copied;
+
+do_error:
+	if (copied)
+		goto out;
+
+	copied = sk_stream_error(sk, msg->msg_flags, ret);
+	goto out;
 }
 
 static int __mptcp_recvmsg_mskq(struct mptcp_sock *msk,
@@ -2404,12 +2410,31 @@ static void mptcp_check_fastclose(struct mptcp_sock *msk)
 		unlock_sock_fast(tcp_sk, slow);
 	}
 
+	/* Mirror the tcp_reset() error propagation */
+	switch (sk->sk_state) {
+	case TCP_SYN_SENT:
+		sk->sk_err = ECONNREFUSED;
+		break;
+	case TCP_CLOSE_WAIT:
+		sk->sk_err = EPIPE;
+		break;
+	case TCP_CLOSE:
+		return;
+	default:
+		sk->sk_err = ECONNRESET;
+	}
+
 	inet_sk_state_store(sk, TCP_CLOSE);
 	sk->sk_shutdown = SHUTDOWN_MASK;
 	smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
 	set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags);
 
-	mptcp_close_wake_up(sk);
+	/* the calling mptcp_worker will properly destroy the socket */
+	if (sock_flag(sk, SOCK_DEAD))
+		return;
+
+	sk->sk_state_change(sk);
+	sk_error_report(sk);
 }
 
 static void __mptcp_retrans(struct sock *sk)
-- 
2.37.2


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