tipc: confgiure and apply UDP bearer MTU on running links

Currently, we have option to configure MTU of UDP media. The configured
MTU takes effect on the links going up after that moment. I.e, a user
has to reset bearer to have new value applied across its links. This is
confusing and disturbing on a running cluster.

We now introduce the functionality to change the default UDP bearer MTU
in struct tipc_bearer. Additionally, the links are updated dynamically,
without any need for a reset, when bearer value is changed. We leverage
the existing per-link functionality and the design being symetrical to
the confguration of link tolerance.

Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: GhantaKrishnamurthy MohanKrishna <mohan.krishna.ghanta.krishnamurthy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/bearer.c

@@ -697,6 +697,9 @@ static int __tipc_nl_add_bearer(struct tipc_nl_msg *msg,
 		goto prop_msg_full;
 	if (nla_put_u32(msg->skb, TIPC_NLA_PROP_WIN, bearer->window))
 		goto prop_msg_full;
+	if (bearer->media->type_id == TIPC_MEDIA_TYPE_UDP)
+		if (nla_put_u32(msg->skb, TIPC_NLA_PROP_MTU, bearer->mtu))
+			goto prop_msg_full;
 
 	nla_nest_end(msg->skb, prop);
 
@@ -979,12 +982,23 @@ int __tipc_nl_bearer_set(struct sk_buff *skb, struct genl_info *info)
 
 		if (props[TIPC_NLA_PROP_TOL]) {
 			b->tolerance = nla_get_u32(props[TIPC_NLA_PROP_TOL]);
-			tipc_node_apply_tolerance(net, b);
+			tipc_node_apply_property(net, b, TIPC_NLA_PROP_TOL);
 		}
 		if (props[TIPC_NLA_PROP_PRIO])
 			b->priority = nla_get_u32(props[TIPC_NLA_PROP_PRIO]);
 		if (props[TIPC_NLA_PROP_WIN])
 			b->window = nla_get_u32(props[TIPC_NLA_PROP_WIN]);
+		if (props[TIPC_NLA_PROP_MTU]) {
+			if (b->media->type_id != TIPC_MEDIA_TYPE_UDP)
+				return -EINVAL;
+#ifdef CONFIG_TIPC_MEDIA_UDP
+			if (tipc_udp_mtu_bad(nla_get_u32
+					     (props[TIPC_NLA_PROP_MTU])))
+				return -EINVAL;
+			b->mtu = nla_get_u32(props[TIPC_NLA_PROP_MTU]);
+			tipc_node_apply_property(net, b, TIPC_NLA_PROP_MTU);
+#endif
+		}
 	}
 
 	return 0;

net/tipc/node.c

@@ -1681,7 +1681,8 @@ void tipc_rcv(struct net *net, struct sk_buff *skb, struct tipc_bearer *b)
 	kfree_skb(skb);
 }
 
-void tipc_node_apply_tolerance(struct net *net, struct tipc_bearer *b)
+void tipc_node_apply_property(struct net *net, struct tipc_bearer *b,
+			      int prop)
 {
 	struct tipc_net *tn = tipc_net(net);
 	int bearer_id = b->identity;
@@ -1696,8 +1697,13 @@ void tipc_node_apply_tolerance(struct net *net, struct tipc_bearer *b)
 	list_for_each_entry_rcu(n, &tn->node_list, list) {
 		tipc_node_write_lock(n);
 		e = &n->links[bearer_id];
-		if (e->link)
-			tipc_link_set_tolerance(e->link, b->tolerance, &xmitq);
+		if (e->link) {
+			if (prop == TIPC_NLA_PROP_TOL)
+				tipc_link_set_tolerance(e->link, b->tolerance,
+							&xmitq);
+			else if (prop == TIPC_NLA_PROP_MTU)
+				tipc_link_set_mtu(e->link, b->mtu);
+		}
 		tipc_node_write_unlock(n);
 		tipc_bearer_xmit(net, bearer_id, &xmitq, &e->maddr);
 	}

net/tipc/node.h

@@ -67,7 +67,7 @@ void tipc_node_check_dest(struct net *net, u32 onode, u8 *peer_id128,
 			  struct tipc_media_addr *maddr,
 			  bool *respond, bool *dupl_addr);
 void tipc_node_delete_links(struct net *net, int bearer_id);
-void tipc_node_apply_tolerance(struct net *net, struct tipc_bearer *b);
+void tipc_node_apply_property(struct net *net, struct tipc_bearer *b, int prop);
 int tipc_node_get_linkname(struct net *net, u32 bearer_id, u32 node,
 			   char *linkname, size_t len);
 int tipc_node_xmit(struct net *net, struct sk_buff_head *list, u32 dnode,