sch_sfb: use skb_flow_dissect()

Current SFB double hashing is not fulfilling SFB theory, if two flows
share same rxhash value.

Using skb_flow_dissect() permits to really have better hash dispersion,
and get tunnelling support as well.

Double hashing point was mentioned by Florian Westphal

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_sfb.c b/net/sched/sch_sfb.c
index e83c272..96e42ca 100644 (file)
--- a/net/sched/sch_sfb.c
+++ b/net/sched/sch_sfb.c
@@ -26,6 +26,7 @@
 #include <net/ip.h>
 #include <net/pkt_sched.h>
 #include <net/inet_ecn.h>
+#include <net/flow_keys.h>
 
 /*
  * SFB uses two B[l][n] : L x N arrays of bins (L levels, N bins per level)
@@ -286,6 +287,7 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch)
        u32 minqlen = ~0;
        u32 r, slot, salt, sfbhash;
        int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
+       struct flow_keys keys;
 
        if (unlikely(sch->q.qlen >= q->limit)) {
                sch->qstats.overlimits++;
@@ -309,13 +311,19 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch)
                /* If using external classifiers, get result and record it. */
                if (!sfb_classify(skb, q, &ret, &salt))
                        goto other_drop;
+               keys.src = salt;
+               keys.dst = 0;
+               keys.ports = 0;
        } else {
-               salt = skb_get_rxhash(skb);
+               skb_flow_dissect(skb, &keys);
        }
 
        slot = q->slot;
 
-       sfbhash = jhash_1word(salt, q->bins[slot].perturbation);
+       sfbhash = jhash_3words((__force u32)keys.dst,
+                              (__force u32)keys.src,
+                              (__force u32)keys.ports,
+                              q->bins[slot].perturbation);
        if (!sfbhash)
                sfbhash = 1;
        sfb_skb_cb(skb)->hashes[slot] = sfbhash;
@@ -347,7 +355,10 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch)
        if (unlikely(p_min >= SFB_MAX_PROB)) {
                /* Inelastic flow */
                if (q->double_buffering) {
-                       sfbhash = jhash_1word(salt, q->bins[slot].perturbation);
+                       sfbhash = jhash_3words((__force u32)keys.dst,
+                                              (__force u32)keys.src,
+                                              (__force u32)keys.ports,
+                                              q->bins[slot].perturbation);
                        if (!sfbhash)
                                sfbhash = 1;
                        sfb_skb_cb(skb)->hashes[slot] = sfbhash;