Commit 55612ddb authored by Alexander Aring's avatar Alexander Aring Committed by David Teigland
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dlm: use SHUT_RDWR for SCTP shutdown 



Currently SCTP shutdown() call gets stuck because there is no incoming
EOF indicator on its socket. On the peer side the EOF indicator as
recvmsg() returns 0 will be triggered as mechanism to flush the socket
queue on the receive side. In SCTP recvmsg() function sctp_recvmsg() we
can see that only if sk_shutdown has the bit RCV_SHUTDOWN set SCTP will
recvmsg() will return EOF. The RCV_SHUTDOWN bit will only be set when
shutdown with SHUT_RD is called. We use now SHUT_RDWR to also get a EOF
indicator from recvmsg() call on the shutdown() initiator.

SCTP does not support half closed sockets and the semantic of SHUT_WR is
different here, it seems that calling SHUT_WR on sctp sockets keeps the
socket open to have the possibility to do some specific SCTP operations on
it that we don't do here.

There exists still a difference in the limitations of TCP vs SCTP in
case if we are required to have a half closed socket functionality. This
was tried to archieve with DLM protocol changes in the past and
hopefully we really don't require half closed socket functionality.

Signed-off-by: default avatarAlexander Aring <aahringo@redhat.com>
Tested-by: default avatarHeming zhao <heming.zhao@suse.com>
Reviewed-by: default avatarHeming zhao <heming.zhao@suse.com>
Signed-off-by: default avatarDavid Teigland <teigland@redhat.com>
parent 8a856fde

fs/dlm/lowcomms.c

+4 −1
Original line number Diff line number Diff line
@@ -160,6 +160,7 @@ struct dlm_proto_ops { 
	bool try_new_addr;

	const char *name;

	int proto;

	int how;



	void (*sockopts)(struct socket *sock);

	int (*bind)(struct socket *sock);
@@ -810,7 +811,7 @@ static void shutdown_connection(struct connection *con, bool and_other) 
		return;

	}



	ret = kernel_sock_shutdown(con->sock, SHUT_WR);

	ret = kernel_sock_shutdown(con->sock, dlm_proto_ops->how);

	up_read(&con->sock_lock);

	if (ret) {

		log_print("Connection %p failed to shutdown: %d will force close",
@@ -1858,6 +1859,7 @@ static int dlm_tcp_listen_bind(struct socket *sock) 
static const struct dlm_proto_ops dlm_tcp_ops = {

	.name = "TCP",

	.proto = IPPROTO_TCP,

	.how = SHUT_WR,

	.sockopts = dlm_tcp_sockopts,

	.bind = dlm_tcp_bind,

	.listen_validate = dlm_tcp_listen_validate,
@@ -1896,6 +1898,7 @@ static void dlm_sctp_sockopts(struct socket *sock) 
static const struct dlm_proto_ops dlm_sctp_ops = {

	.name = "SCTP",

	.proto = IPPROTO_SCTP,

	.how = SHUT_RDWR,

	.try_new_addr = true,

	.sockopts = dlm_sctp_sockopts,

	.bind = dlm_sctp_bind,