tipc: set default MTU for UDP media

GhantaKrishnamurthy MohanKrishna · davem330 · commit a4dfa72d0acd · 2018-04-20T11:04:05.000-04:00
Currently, all bearers are configured with MTU value same as the
underlying L2 device. However, in case of bearers with media type
UDP, higher throughput is possible with a fixed and higher emulated
MTU value than adapting to the underlying L2 MTU.

In this commit, we introduce a parameter mtu in struct tipc_media
and a default value is set for UDP. A default value of 14k
was determined by experimentation and found to have a higher throughput
than 16k. MTU for UDP bearers are assigned the above set value of
media MTU.

Acked-by: Ying Xue &lt;ying.xue@windriver.com&gt;
Acked-by: Jon Maloy &lt;jon.maloy@ericsson.com&gt;
Signed-off-by: GhantaKrishnamurthy MohanKrishna &lt;mohan.krishna.ghanta.krishnamurthy@ericsson.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
diff --git a/include/uapi/linux/tipc_config.h b/include/uapi/linux/tipc_config.h
@@ -185,6 +185,11 @@
 #define TIPC_DEF_LINK_WIN 50
 #define TIPC_MAX_LINK_WIN 8191
 
+/*
+ * Default MTU for UDP media
+ */
+
+#define TIPC_DEF_LINK_UDP_MTU 14000
 
 struct tipc_node_info {
 	__be32 addr;			/* network address of node */
diff --git a/net/tipc/udp_media.c b/net/tipc/udp_media.c
@@ -713,8 +713,7 @@ static int tipc_udp_enable(struct net *net, struct tipc_bearer *b,
 			err = -EINVAL;
 			goto err;
 		}
-		b->mtu = dev->mtu - sizeof(struct iphdr)
-			- sizeof(struct udphdr);
+		b->mtu = b->media->mtu;
 #if IS_ENABLED(CONFIG_IPV6)
 	} else if (local.proto == htons(ETH_P_IPV6)) {
 		udp_conf.family = AF_INET6;
@@ -803,6 +802,7 @@ struct tipc_media udp_media_info = {
 	.priority	= TIPC_DEF_LINK_PRI,
 	.tolerance	= TIPC_DEF_LINK_TOL,
 	.window		= TIPC_DEF_LINK_WIN,
+	.mtu		= TIPC_DEF_LINK_UDP_MTU,
 	.type_id	= TIPC_MEDIA_TYPE_UDP,
 	.hwaddr_len	= 0,
 	.name		= "udp"
