From 2d18ac4ba7454a4260473e68be7e485ae71e7948 Mon Sep 17 00:00:00 2001 From: Jon Paul Maloy Date: Mon, 11 Jul 2016 16:08:35 -0400 Subject: tipc: extend broadcast link initialization criteria At first contact between two nodes, an endpoint might sometimes have time to send out a LINK_PROTOCOL/STATE packet before it has received the broadcast initialization packet from the peer, i.e., before it has received a valid broadcast packet number to add to the 'bc_ack' field of the protocol message. This means that the peer endpoint will receive a protocol packet with an invalid broadcast acknowledge value of 0. Under unlucky circumstances this may lead to the original, already received acknowledge value being overwritten, so that the whole broadcast link goes stale after a while. We fix this by delaying the setting of the link field 'bc_peer_is_up' until we know that the peer really has received our own broadcast initialization message. The latter is always sent out as the first unicast message on a link, and always with seqeunce number 1. Because of this, we only need to look for a non-zero unicast acknowledge value in the arriving STATE messages, and once that is confirmed we know we are safe and can set the mentioned field. Before this moment, we must ignore all broadcast acknowledges from the peer. Acked-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller --- net/tipc/link.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'net/tipc/link.c') diff --git a/net/tipc/link.c b/net/tipc/link.c index 67b6ab9f4c8d..6483dc4333fb 100644 --- a/net/tipc/link.c +++ b/net/tipc/link.c @@ -1559,7 +1559,12 @@ void tipc_link_bc_sync_rcv(struct tipc_link *l, struct tipc_msg *hdr, if (!msg_peer_node_is_up(hdr)) return; - l->bc_peer_is_up = true; + /* Open when peer ackowledges our bcast init msg (pkt #1) */ + if (msg_ack(hdr)) + l->bc_peer_is_up = true; + + if (!l->bc_peer_is_up) + return; /* Ignore if peers_snd_nxt goes beyond receive window */ if (more(peers_snd_nxt, l->rcv_nxt + l->window)) -- cgit v1.2.3-70-g09d2 From a71eb720355c28eaeb2de0c4d960247c69bb2c6f Mon Sep 17 00:00:00 2001 From: Jon Paul Maloy Date: Mon, 11 Jul 2016 16:08:36 -0400 Subject: tipc: ensure correct broadcast send buffer release when peer is lost After a new receiver peer has been added to the broadcast transmission link, we allow immediate transmission of new broadcast packets, trusting that the new peer will not accept the packets until it has received the previously sent unicast broadcast initialiation message. In the same way, the sender must not accept any acknowledges until it has itself received the broadcast initialization from the peer, as well as confirmation of the reception of its own initialization message. Furthermore, when a receiver peer goes down, the sender has to produce the missing acknowledges from the lost peer locally, in order ensure correct release of the buffers that were expected to be acknowledged by the said peer. In a highly stressed system we have observed that contact with a peer may come up and be lost before the above mentioned broadcast initial- ization and confirmation have been received. This leads to the locally produced acknowledges being rejected, and the non-acknowledged buffers to linger in the broadcast link transmission queue until it fills up and the link goes into permanent congestion. In this commit, we remedy this by temporarily setting the corresponding broadcast receive link state to ESTABLISHED and the 'bc_peer_is_up' state to true before we issue the local acknowledges. This ensures that those acknowledges will always be accepted. The mentioned state values are restored immediately afterwards when the link is reset. Acked-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller --- net/tipc/link.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'net/tipc/link.c') diff --git a/net/tipc/link.c b/net/tipc/link.c index 6483dc4333fb..7d89f8713d49 100644 --- a/net/tipc/link.c +++ b/net/tipc/link.c @@ -349,6 +349,8 @@ void tipc_link_remove_bc_peer(struct tipc_link *snd_l, u16 ack = snd_l->snd_nxt - 1; snd_l->ackers--; + rcv_l->bc_peer_is_up = true; + rcv_l->state = LINK_ESTABLISHED; tipc_link_bc_ack_rcv(rcv_l, ack, xmitq); tipc_link_reset(rcv_l); rcv_l->state = LINK_RESET; -- cgit v1.2.3-70-g09d2