netdev - [net 1/1] tipc: remove joining group member from congested list

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Date:   Wed, 20 Dec 2017 11:03:15 +0100
From:   Jon Maloy <jon.maloy@...csson.com>
To:     <davem@...emloft.net>, <netdev@...r.kernel.org>
CC:     <mohan.krishna.ghanta.krishnamurthy@...csson.com>,
        <tung.q.nguyen@...tech.com.au>, <hoang.h.le@...tech.com.au>,
        <jon.maloy@...csson.com>, <canh.d.luu@...tech.com.au>,
        <ying.xue@...driver.com>, <tipc-discussion@...ts.sourceforge.net>
Subject: [net  1/1] tipc: remove joining group member from congested list

When we receive a JOIN message from a peer member, the message may
contain an advertised window value ADV_IDLE that permits removing the
member in question from the tipc_group::congested list. However, since
the removal has been made conditional on that the advertised window is
*not* ADV_IDLE, we miss this case. This has the effect that a sender
sometimes may enter a state of permanent, false, broadcast congestion.

We fix this by unconditinally removing the member from the congested
list before calling tipc_member_update(), which might potentially sort
it into the list again.

Signed-off-by: Jon Maloy <jon.maloy@...csson.com>
---
 net/tipc/group.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/tipc/group.c b/net/tipc/group.c
index bbc004e..7ebbdeb 100644
--- a/net/tipc/group.c
+++ b/net/tipc/group.c
@@ -689,10 +689,8 @@ void tipc_group_proto_rcv(struct tipc_group *grp, bool *usr_wakeup,
 			msg_set_grp_bc_seqno(ehdr, m->bc_syncpt);
 			__skb_queue_tail(inputq, m->event_msg);
 		}
-		if (m->window < ADV_IDLE)
-			tipc_group_update_member(m, 0);
-		else
-			list_del_init(&m->congested);
+		list_del_init(&m->congested);
+		tipc_group_update_member(m, 0);
 		return;
 	case GRP_LEAVE_MSG:
 		if (!m)
-- 
2.1.4