linux-kernel - [PATCH net-next v20 14/25] ovpn: add support for MSG_NOSIGNAL in tcp

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Message-Id: <20250227-b4-ovpn-v20-14-93f363310834@openvpn.net>
Date: Thu, 27 Feb 2025 02:21:39 +0100
From: Antonio Quartulli <antonio@...nvpn.net>
To: netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Donald Hunter <donald.hunter@...il.com>, 
 Antonio Quartulli <antonio@...nvpn.net>, Shuah Khan <shuah@...nel.org>, 
 sd@...asysnail.net, ryazanov.s.a@...il.com, 
 Andrew Lunn <andrew+netdev@...n.ch>
Cc: Simon Horman <horms@...nel.org>, linux-kernel@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, Xiao Liang <shaw.leon@...il.com>
Subject: [PATCH net-next v20 14/25] ovpn: add support for MSG_NOSIGNAL in
 tcp_sendmsg

Userspace may want to pass the MSG_NOSIGNAL flag to
tcp_sendmsg() in order to avoid generating a SIGPIPE.

To pass this flag down the TCP stack a new skb sending API
accepting a flags argument is introduced.

Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Paolo Abeni <pabeni@...hat.com>
Signed-off-by: Antonio Quartulli <antonio@...nvpn.net>
---
 drivers/net/ovpn/skb.h |  1 +
 drivers/net/ovpn/tcp.c | 12 ++++++++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ovpn/skb.h b/drivers/net/ovpn/skb.h
index bd3cbcfc770d2c28d234fcdd081b4d02e6496ea0..64430880f1dae33a41f698d713cf151be5b38577 100644
--- a/drivers/net/ovpn/skb.h
+++ b/drivers/net/ovpn/skb.h
@@ -25,6 +25,7 @@ struct ovpn_cb {
 	struct scatterlist *sg;
 	u8 *iv;
 	unsigned int payload_offset;
+	bool nosignal;
 };
 
 static inline struct ovpn_cb *ovpn_skb_cb(struct sk_buff *skb)
diff --git a/drivers/net/ovpn/tcp.c b/drivers/net/ovpn/tcp.c
index 2d343bce477156a9f60ce92d18c815b7c832d2af..10cb0493290c9c4b90fb2734bcc208853d77dfd3 100644
--- a/drivers/net/ovpn/tcp.c
+++ b/drivers/net/ovpn/tcp.c
@@ -215,6 +215,7 @@ void ovpn_tcp_socket_wait_finish(struct ovpn_socket *sock)
 static void ovpn_tcp_send_sock(struct ovpn_peer *peer, struct sock *sk)
 {
 	struct sk_buff *skb = peer->tcp.out_msg.skb;
+	int ret, flags;
 
 	if (!skb)
 		return;
@@ -225,9 +226,11 @@ static void ovpn_tcp_send_sock(struct ovpn_peer *peer, struct sock *sk)
 	peer->tcp.tx_in_progress = true;
 
 	do {
-		int ret = skb_send_sock_locked(sk, skb,
-					       peer->tcp.out_msg.offset,
-					       peer->tcp.out_msg.len);
+		flags = ovpn_skb_cb(skb)->nosignal ? MSG_NOSIGNAL : 0;
+		ret = skb_send_sock_locked_with_flags(sk, skb,
+						      peer->tcp.out_msg.offset,
+						      peer->tcp.out_msg.len,
+						      flags);
 		if (unlikely(ret < 0)) {
 			if (ret == -EAGAIN)
 				goto out;
@@ -370,7 +373,7 @@ static int ovpn_tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
 	rcu_read_unlock();
 	peer = sock->peer;
 
-	if (msg->msg_flags & ~MSG_DONTWAIT) {
+	if (msg->msg_flags & ~(MSG_DONTWAIT | MSG_NOSIGNAL)) {
 		ret = -EOPNOTSUPP;
 		goto peer_free;
 	}
@@ -403,6 +406,7 @@ static int ovpn_tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
 		goto peer_free;
 	}
 
+	ovpn_skb_cb(skb)->nosignal = msg->msg_flags & MSG_NOSIGNAL;
 	ovpn_tcp_send_sock_skb(peer, sk, skb);
 	ret = size;
 peer_free:

-- 
2.45.3