From 17b2063077a7478e5fd3c34b04a059dbb8474638 Mon Sep 17 00:00:00 2001 From: Jon Paul Maloy Date: Thu, 20 Aug 2015 02:12:54 -0400 Subject: [PATCH] tipc: eliminate risk of premature link setup during failover When a link goes down, and there is still a working link towards its destination node, a failover is initiated, and the failed link is not allowed to re-establish until that procedure is finished. To ensure this, the concerned link endpoints are set to state LINK_FAILINGOVER, and the node endpoints to NODE_FAILINGOVER during the failover period. However, if the link reset is due to a disabled bearer, the corres- ponding link endpoint is deleted, and only the node endpoint knows about the ongoing failover. Now, if the disabled bearer is re-enabled during the failover period, the discovery mechanism may create a new link endpoint that is ready to be established, despite that this is not permitted. This situation may cause both the ongoing failover and any subsequent link synchronization to fail. In this commit, we ensure that a newly created link goes directly to state LINK_FAILINGOVER if the corresponding node state is NODE_FAILINGOVER. This eliminates the problem described above. Furthermore, we tighten the criteria for which packets are allowed to end a failover state in the function tipc_node_check_state(). By checking that the receiving link is up and running, instead of just checking that it is not in failover mode, we eliminate the risk that protocol packets from the re-created link may cause the failover to be prematurely terminated. Reviewed-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller --- net/tipc/node.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/tipc/node.c b/net/tipc/node.c index 7c191641b44f..004834bd1605 100644 --- a/net/tipc/node.c +++ b/net/tipc/node.c @@ -565,6 +565,8 @@ void tipc_node_check_dest(struct net *net, u32 onode, goto exit; } tipc_link_reset(l); + if (n->state == NODE_FAILINGOVER) + tipc_link_fsm_evt(l, LINK_FAILOVER_BEGIN_EVT); le->link = l; n->link_cnt++; tipc_node_calculate_timer(n, l); @@ -1129,7 +1131,7 @@ static bool tipc_node_check_state(struct tipc_node *n, struct sk_buff *skb, } /* Open parallel link when tunnel link reaches synch point */ - if ((n->state == NODE_FAILINGOVER) && !tipc_link_is_failingover(l)) { + if ((n->state == NODE_FAILINGOVER) && tipc_link_is_up(l)) { if (!more(rcv_nxt, n->sync_point)) return true; tipc_node_fsm_evt(n, NODE_FAILOVER_END_EVT);