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[Cluster-devel] [PATCH] dlm: bind connections from known local address when using TCP

From: Lon Hohberger <lhh redhat com>

A common problem occurs when multiple IP addresses within the same
subnet are assigned to the same NIC.  If we make a connection attempt to
another address on the same subnet as one of those addresses, the
connection attempt will not necessarily be routed from the address we

In the case of the DLM, the other nodes will quickly drop the connection
attempt, causing problems.

This patch makes the DLM bind to the local address it acquired from the
cluster manager when using TCP prior to making a connection, obviating
the need for administrators to "fix" their systems or use clever routing

Signed-off-by: Lon Hohberger <lhh redhat com>
Signed-off-by: Patrick Caulfield <pcaulfie redhat com>
Signed-off-by: David Teigland <teigland redhat com>
 fs/dlm/lowcomms.c |   13 ++++++++++++-
 1 files changed, 12 insertions(+), 1 deletions(-)

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index e9923ca..0bea802 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -864,7 +864,7 @@ static void sctp_init_assoc(struct connection *con)
 static void tcp_connect_to_sock(struct connection *con)
 	int result = -EHOSTUNREACH;
-	struct sockaddr_storage saddr;
+	struct sockaddr_storage saddr, src_addr;
 	int addr_len;
 	struct socket *sock;
@@ -898,6 +898,17 @@ static void tcp_connect_to_sock(struct connection *con)
 	con->connect_action = tcp_connect_to_sock;
 	add_sock(sock, con);
+	/* Bind to our cluster-known address connecting to avoid
+	   routing problems */
+	memcpy(&src_addr, dlm_local_addr[0], sizeof(src_addr));
+	make_sockaddr(&src_addr, 0, &addr_len);
+	result = sock->ops->bind(sock, (struct sockaddr *) &src_addr,
+				 addr_len);
+	if (result < 0) {
+		printk("dlm: could not bind for connect: %d\n", result);
+		/* This *may* not indicate a critical error */
+	}
 	make_sockaddr(&saddr, dlm_config.ci_tcp_port, &addr_len);
 	log_print("connecting to %d", con->nodeid);

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