From ed43594aede9719e56eca72fc6a9a200c60b60e6 Mon Sep 17 00:00:00 2001 From: Jon Paul Maloy Date: Tue, 8 Aug 2017 22:23:56 +0200 Subject: [PATCH] tipc: remove premature ESTABLISH FSM event at link synchronization When a link between two nodes come up, both endpoints will initially send out a STATE message to the peer, to increase the probability that the peer endpoint also is up when the first traffic message arrives. Thereafter, if the establishing link is the second link between two nodes, this first "traffic" message is a TUNNEL_PROTOCOL/SYNCH message, helping the peer to perform initial synchronization between the two links. However, the initial STATE message may be lost, in which case the SYNCH message will be the first one arriving at the peer. This should also work, as the SYNCH message itself will be used to take up the link endpoint before initializing synchronization. Unfortunately the code for this case is broken. Currently, the link is brought up through a tipc_link_fsm_evt(ESTABLISHED) when a SYNCH arrives, whereupon __tipc_node_link_up() is called to distribute the link slots and take the link into traffic. But, __tipc_node_link_up() is itself starting with a test for whether the link is up, and if true, returns without action. Clearly, the tipc_link_fsm_evt(ESTABLISHED) call is unnecessary, since tipc_node_link_up() is itself issuing such an event, but also harmful, since it inhibits tipc_node_link_up() to perform the test of its tasks, and the link endpoint in question hence is never taken into traffic. This problem has been exposed when we set up dual links between pre- and post-4.4 kernels, because the former ones don't send out the initial STATE message described above. We fix this by removing the unnecessary event call. Signed-off-by: Jon Maloy Signed-off-by: David S. Miller --- net/tipc/node.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/net/tipc/node.c b/net/tipc/node.c index aeef8011ac7d..9b4dcb6a16b5 100644 --- a/net/tipc/node.c +++ b/net/tipc/node.c @@ -1455,10 +1455,8 @@ static bool tipc_node_check_state(struct tipc_node *n, struct sk_buff *skb, /* Initiate synch mode if applicable */ if ((usr == TUNNEL_PROTOCOL) && (mtyp == SYNCH_MSG) && (oseqno == 1)) { syncpt = iseqno + exp_pkts - 1; - if (!tipc_link_is_up(l)) { - tipc_link_fsm_evt(l, LINK_ESTABLISH_EVT); + if (!tipc_link_is_up(l)) __tipc_node_link_up(n, bearer_id, xmitq); - } if (n->state == SELF_UP_PEER_UP) { n->sync_point = syncpt; tipc_link_fsm_evt(l, LINK_SYNCH_BEGIN_EVT); -- 2.20.1