tipc: don't reset stale broadcast send link

When the broadcast send link after 100 attempts has failed to
transfer a packet to all peers, we consider it stale, and reset
it. Thereafter it needs to re-synchronize with the peers, something
currently done by just resetting and re-establishing all links to
all peers. This has turned out to be overkill, with potentially
unwanted consequences for the remaining cluster.

A closer analysis reveals that this can be done much simpler. When
this kind of failure happens, for reasons that may lie outside the
TIPC protocol, it is typically only one peer which is failing to
receive and acknowledge packets. It is hence sufficient to identify
and reset the links only to that peer to resolve the situation, without
having to reset the broadcast link at all. This solution entails a much
lower risk of negative consequences for the own node as well as for
the overall cluster.

We implement this change in this commit.

Reviewed-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 10 deletions

diff --git a/net/tipc/link.c b/net/tipc/link.c
index 60820dc35a08..ac0144f532aa 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -978,15 +978,15 @@ static void link_retransmit_failure(struct tipc_link *l, struct sk_buff *skb)
 	struct tipc_msg *hdr = buf_msg(skb);
 
 	pr_warn("Retransmission failure on link <%s>\n", l->name);
-	link_print(l, "Resetting link ");
+	link_print(l, "State of link ");
 	pr_info("Failed msg: usr %u, typ %u, len %u, err %u\n",
 		msg_user(hdr), msg_type(hdr), msg_size(hdr), msg_errcode(hdr));
 	pr_info("sqno %u, prev: %x, src: %x\n",
 		msg_seqno(hdr), msg_prevnode(hdr), msg_orignode(hdr));
 }
 
-int tipc_link_retrans(struct tipc_link *l, u16 from, u16 to,
-		      struct sk_buff_head *xmitq)
+int tipc_link_retrans(struct tipc_link *l, struct tipc_link *nacker,
+		      u16 from, u16 to, struct sk_buff_head *xmitq)
 {
 	struct sk_buff *_skb, *skb = skb_peek(&l->transmq);
 	struct tipc_msg *hdr;
@@ -997,11 +997,14 @@ int tipc_link_retrans(struct tipc_link *l, u16 from, u16 to,
 		return 0;
 
 	/* Detect repeated retransmit failures on same packet */
-	if (likely(l->last_retransm != buf_seqno(skb))) {
-		l->last_retransm = buf_seqno(skb);
-		l->stale_count = 1;
-	} else if (++l->stale_count > 100) {
+	if (nacker->last_retransm != buf_seqno(skb)) {
+		nacker->last_retransm = buf_seqno(skb);
+		nacker->stale_count = 1;
+	} else if (++nacker->stale_count > 100) {
 		link_retransmit_failure(l, skb);
+		nacker->stale_count = 0;
+		if (link_is_bc_sndlink(l))
+			return TIPC_LINK_DOWN_EVT;
 		return tipc_link_fsm_evt(l, LINK_FAILURE_EVT);
 	}
 
@@ -1528,7 +1531,7 @@ static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,
 
 		/* If NACK, retransmit will now start at right position */
 		if (gap) {
-			rc = tipc_link_retrans(l, ack + 1, ack + gap, xmitq);
+			rc = tipc_link_retrans(l, l, ack + 1, ack + gap, xmitq);
 			l->stats.recv_nacks++;
 		}
 
@@ -1680,7 +1683,7 @@ int tipc_link_bc_sync_rcv(struct tipc_link *l, struct tipc_msg *hdr,
 		return rc;
 
 	if (link_bc_retr_eval(snd_l, &from, &to))
-		rc = tipc_link_retrans(snd_l, from, to, xmitq);
+		rc = tipc_link_retrans(snd_l, l, from, to, xmitq);
 
 	l->snd_nxt = peers_snd_nxt;
 	if (link_bc_rcv_gap(l))
@@ -1775,7 +1778,7 @@ int tipc_link_bc_nack_rcv(struct tipc_link *l, struct sk_buff *skb,
 
 	if (dnode == tipc_own_addr(l->net)) {
 		tipc_link_bc_ack_rcv(l, acked, xmitq);
-		rc = tipc_link_retrans(l->bc_sndlink, from, to, xmitq);
+		rc = tipc_link_retrans(l->bc_sndlink, l, from, to, xmitq);
 		l->stats.recv_nacks++;
 		return rc;
 	}