tipc: improve link resiliency when rps is activated

Currently, the TIPC RPS dissector is based only on the incoming packets'
source node address, hence steering all traffic from a node to the same
core. We have seen that this makes the links vulnerable to starvation
and unnecessary resets when we turn down the link tolerance to very low
values.

To reduce the risk of this happening, we exempt probe and probe replies
packets from the convergence to one core per source node. Instead, we do
the opposite, - we try to diverge those packets across as many cores as
possible, by randomizing the flow selector key.

To make such packets identifiable to the dissector, we add a new
'is_keepalive' bit to word 0 of the LINK_PROTOCOL header. This bit is
set both for PROBE and PROBE_REPLY messages, and only for those.

It should be noted that these packets are not part of any flow anyway,
and only constitute a minuscule fraction of all packets sent across a
link. Hence, there is no risk that this will affect overall performance.

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, 15 insertions, 15 deletions

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 1f5caaf..15ce300 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -10,6 +10,7 @@
 #include <net/ipv6.h>
 #include <net/gre.h>
 #include <net/pptp.h>
+#include <net/tipc.h>
 #include <linux/igmp.h>
 #include <linux/icmp.h>
 #include <linux/sctp.h>
@@ -772,23 +773,22 @@ proto_again:
 		break;
 	}
 	case htons(ETH_P_TIPC): {
-		struct {
-			__be32 pre[3];
-			__be32 srcnode;
-		} *hdr, _hdr;
-		hdr = __skb_header_pointer(skb, nhoff, sizeof(_hdr), data, hlen, &_hdr);
+		struct tipc_basic_hdr *hdr, _hdr;
+
+		hdr = __skb_header_pointer(skb, nhoff, sizeof(_hdr),
+					   data, hlen, &_hdr);
 		if (!hdr) {
 			fdret = FLOW_DISSECT_RET_OUT_BAD;
 			break;
 		}
 
 		if (dissector_uses_key(flow_dissector,
-				       FLOW_DISSECTOR_KEY_TIPC_ADDRS)) {
+				       FLOW_DISSECTOR_KEY_TIPC)) {
 			key_addrs = skb_flow_dissector_target(flow_dissector,
-							      FLOW_DISSECTOR_KEY_TIPC_ADDRS,
+							      FLOW_DISSECTOR_KEY_TIPC,
 							      target_container);
-			key_addrs->tipcaddrs.srcnode = hdr->srcnode;
-			key_control->addr_type = FLOW_DISSECTOR_KEY_TIPC_ADDRS;
+			key_addrs->tipckey.key = tipc_hdr_rps_key(hdr);
+			key_control->addr_type = FLOW_DISSECTOR_KEY_TIPC;
 		}
 		fdret = FLOW_DISSECT_RET_OUT_GOOD;
 		break;
@@ -1024,8 +1024,8 @@ static inline size_t flow_keys_hash_length(const struct flow_keys *flow)
 	case FLOW_DISSECTOR_KEY_IPV6_ADDRS:
 		diff -= sizeof(flow->addrs.v6addrs);
 		break;
-	case FLOW_DISSECTOR_KEY_TIPC_ADDRS:
-		diff -= sizeof(flow->addrs.tipcaddrs);
+	case FLOW_DISSECTOR_KEY_TIPC:
+		diff -= sizeof(flow->addrs.tipckey);
 		break;
 	}
 	return (sizeof(*flow) - diff) / sizeof(u32);
@@ -1039,8 +1039,8 @@ __be32 flow_get_u32_src(const struct flow_keys *flow)
 	case FLOW_DISSECTOR_KEY_IPV6_ADDRS:
 		return (__force __be32)ipv6_addr_hash(
 			&flow->addrs.v6addrs.src);
-	case FLOW_DISSECTOR_KEY_TIPC_ADDRS:
-		return flow->addrs.tipcaddrs.srcnode;
+	case FLOW_DISSECTOR_KEY_TIPC:
+		return flow->addrs.tipckey.key;
 	default:
 		return 0;
 	}
@@ -1321,8 +1321,8 @@ static const struct flow_dissector_key flow_keys_dissector_keys[] = {
 		.offset = offsetof(struct flow_keys, addrs.v6addrs),
 	},
 	{
-		.key_id = FLOW_DISSECTOR_KEY_TIPC_ADDRS,
-		.offset = offsetof(struct flow_keys, addrs.tipcaddrs),
+		.key_id = FLOW_DISSECTOR_KEY_TIPC,
+		.offset = offsetof(struct flow_keys, addrs.tipckey),
 	},
 	{
 		.key_id = FLOW_DISSECTOR_KEY_PORTS,