filter: add SKF_AD_RXHASH and SKF_AD_CPU

Add SKF_AD_RXHASH and SKF_AD_CPU to filter ancillary mechanism,
to be able to build advanced filters.

This can help spreading packets on several sockets with a fast
selection, after RPS dispatch to N cpus for example, or to catch a
percentage of flows in one queue.

tcpdump -s 500 "cpu = 1" :

[0] ld CPU
[1] jeq #1  jt 2  jf 3
[2] ret #500
[3] ret #0

# take 12.5 % of flows (average)
tcpdump -s 1000 "rxhash & 7 = 2" :

[0] ld RXHASH
[1] and #7
[2] jeq #2  jt 3  jf 4
[3] ret #1000
[4] ret #0

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Rui <wirelesser@gmail.com>
Acked-by: Changli Gao <xiaosuo@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 9 insertions, 1 deletions

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 447a775878fb..5334adaf4072 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -124,7 +124,9 @@ struct sock_fprog {	/* Required for SO_ATTACH_FILTER. */
 #define SKF_AD_MARK     20
 #define SKF_AD_QUEUE    24
 #define SKF_AD_HATYPE   28
-#define SKF_AD_MAX      32
+#define SKF_AD_RXHASH   32
+#define SKF_AD_CPU      36
+#define SKF_AD_MAX      40
 #define SKF_NET_OFF   (-0x100000)
 #define SKF_LL_OFF    (-0x200000)
 
diff --git a/net/core/filter.c b/net/core/filter.c
index a44d27f9f0f0..054e286861d2 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -375,6 +375,12 @@ load_b:
                                 return 0;
                         A = skb->dev->type;
                         continue;
+                case SKF_AD_RXHASH:
+                        A = skb->rxhash;
+                        continue;
+                case SKF_AD_CPU:
+                        A = raw_smp_processor_id();
+                        continue;
                 case SKF_AD_NLATTR: {
                         struct nlattr *nla;