[PATCH 20/23] netfilter: labels: don't emit ct event if labels were not changed

[Pablo Neira Ayuso]

From: Florian Westphal <f...@strlen.de>

make the replace function only send a ctnetlink event if the contents
of the new set is different.

Otherwise 'ct label set ct label | bar'

will cause netlink event storm since we "replace" labels for each packet.

Signed-off-by: Florian Westphal <f...@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org>
---
 net/netfilter/nf_conntrack_labels.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/net/netfilter/nf_conntrack_labels.c 
b/net/netfilter/nf_conntrack_labels.c
index 3a30900..bd7f26b 100644
--- a/net/netfilter/nf_conntrack_labels.c
+++ b/net/netfilter/nf_conntrack_labels.c
@@ -33,14 +33,18 @@ int nf_connlabel_set(struct nf_conn *ct, u16 bit)
 }
 EXPORT_SYMBOL_GPL(nf_connlabel_set);
 
-static void replace_u32(u32 *address, u32 mask, u32 new)
+static int replace_u32(u32 *address, u32 mask, u32 new)
 {
        u32 old, tmp;
 
        do {
                old = *address;
                tmp = (old & mask) ^ new;
+               if (old == tmp)
+                       return 0;
        } while (cmpxchg(address, old, tmp) != old);
+
+       return 1;
 }
 
 int nf_connlabels_replace(struct nf_conn *ct,
@@ -49,6 +53,7 @@ int nf_connlabels_replace(struct nf_conn *ct,
 {
        struct nf_conn_labels *labels;
        unsigned int size, i;
+       int changed = 0;
        u32 *dst;
 
        labels = nf_ct_labels_find(ct);
@@ -60,16 +65,15 @@ int nf_connlabels_replace(struct nf_conn *ct,
                words32 = size / sizeof(u32);
 
        dst = (u32 *) labels->bits;
-       if (words32) {
-               for (i = 0; i < words32; i++)
-                       replace_u32(&dst[i], mask ? ~mask[i] : 0, data[i]);
-       }
+       for (i = 0; i < words32; i++)
+               changed |= replace_u32(&dst[i], mask ? ~mask[i] : 0, data[i]);
 
        size /= sizeof(u32);
        for (i = words32; i < size; i++) /* pad */
                replace_u32(&dst[i], 0, 0);
 
-       nf_conntrack_event_cache(IPCT_LABEL, ct);
+       if (changed)
+               nf_conntrack_event_cache(IPCT_LABEL, ct);
        return 0;
 }
 EXPORT_SYMBOL_GPL(nf_connlabels_replace);
-- 
2.1.4