[RFC net-next af_unix v1 0/1] Allow delivery of SIGURG on AF_UNIX streams socket

[RFC net-next af_unix v1 0/1] Allow delivery of SIGURG on AF_UNIX streams socket

[rao.shoaib]

From: Rao Shoaib <rao.shoaib@oracle.com>

The use of AF_UNIX sockets is on the rise. We have a case where thousands
of processes connect locally to a database and issue queries that are
serviced by a pool of threads. Communication is done over AF_UNIX
sockets. Currently, there is no way for the submitter to signal the
servicing thread about an urgent condition such as abandoning
the query. This patch addresses that requirement by adding support for
MSG_OOB flag for AF_UNIX sockets. On receipt of such a flag,
the kernel sends a SIGURG to the peer.

Rao Shoaib (1):
  af_unix: Allow delivery of SIGURG on AF_UNIX streams socket

 net/unix/af_unix.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

-- 
1.8.3.1

[RFC net-next af_unix v1 1/1] af_unix: Allow delivery of SIGURG on AF_UNIX streams socket

[rao.shoaib]

From: Rao Shoaib <rao.shoaib@oracle.com>

For AF_UNIX stream socket send SIGURG to the peer if
the msg has MSG_OOB flag set.

Signed-off-by: Rao Shoaib <rao.shoaib@oracle.com>
---
 net/unix/af_unix.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 92784e5..4f01d74 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1840,8 +1840,6 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,
 		return err;
 
 	err = -EOPNOTSUPP;
-	if (msg->msg_flags&MSG_OOB)
-		goto out_err;
 
 	if (msg->msg_namelen) {
 		err = sk->sk_state == TCP_ESTABLISHED ? -EISCONN : -EOPNOTSUPP;
@@ -1906,6 +1904,9 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,
 		sent += size;
 	}
 
+	if (msg->msg_flags & MSG_OOB)
+		sk_send_sigurg(other);
+
 	scm_destroy(&scm);
 
 	return sent;
-- 
1.8.3.1

Re: [RFC net-next af_unix v1 0/1] Allow delivery of SIGURG on AF_UNIX streams socket

[Jakub Kicinski]

On Sat, 14 Nov 2020 18:58:04 -0800 rao.shoaib@oracle.com wrote:
> From: Rao Shoaib <rao.shoaib@oracle.com>
> 
> The use of AF_UNIX sockets is on the rise. We have a case where thousands
> of processes connect locally to a database and issue queries that are
> serviced by a pool of threads. Communication is done over AF_UNIX
> sockets. Currently, there is no way for the submitter to signal the
> servicing thread about an urgent condition such as abandoning
> the query. This patch addresses that requirement by adding support for
> MSG_OOB flag for AF_UNIX sockets. On receipt of such a flag,
> the kernel sends a SIGURG to the peer.

You need to widen the CC list on this, I doubt anyone paid much
attention.

[RFC net-next af_unix v1 0/1] Allow delivery of SIGURG on AF_UNIX streams socket

[rao.shoaib]

From: Rao Shoaib <rao.shoaib@oracle.com>

The use of AF_UNIX sockets is on the rise. We have a case where thousands
of processes connect locally to a database and issue queries that are
serviced by a pool of threads. Communication is done over AF_UNIX
sockets. Currently, there is no way for the submitter to signal the
servicing thread about an urgent condition such as abandoning
the query. This patch addresses that requirement by adding support for
MSG_OOB flag for AF_UNIX sockets. On receipt of such a flag,
the kernel sends a SIGURG to the peer.

Rao Shoaib (1):
  af_unix: Allow delivery of SIGURG on AF_UNIX streams socket

 net/unix/af_unix.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

-- 
1.8.3.1