net: Only do flow_dissector hash computation once per packet

Add sw_hash flag to skbuff to indicate that skb->hash was computed
from flow_dissector. This flag is checked in skb_get_hash to avoid
repeatedly trying to compute the hash (ie. in the case that no L4 hash
can be computed).

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index b297af7..890fb33 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -455,6 +455,7 @@ static inline u32 skb_mstamp_us_delta(const struct skb_mstamp *t1,
  *     @ooo_okay: allow the mapping of a socket to a queue to be changed
  *     @l4_hash: indicate hash is a canonical 4-tuple hash over transport
  *             ports.
+ *     @sw_hash: indicates hash was computed in software stack
  *     @wifi_acked_valid: wifi_acked was set
  *     @wifi_acked: whether frame was acked on wifi or not
  *     @no_fcs:  Request NIC to treat last 4 bytes as Ethernet FCS
@@ -562,6 +563,7 @@ struct sk_buff {
        __u8                    pfmemalloc:1;
        __u8                    ooo_okay:1;
        __u8                    l4_hash:1;
+       __u8                    sw_hash:1;
        __u8                    wifi_acked_valid:1;
        __u8                    wifi_acked:1;
        __u8                    no_fcs:1;
@@ -575,7 +577,7 @@ struct sk_buff {
        __u8                    encap_hdr_csum:1;
        __u8                    csum_valid:1;
        __u8                    csum_complete_sw:1;
-       /* 3/5 bit hole (depending on ndisc_nodetype presence) */
+       /* 2/4 bit hole (depending on ndisc_nodetype presence) */
        kmemcheck_bitfield_end(flags2);
 
 #if defined CONFIG_NET_DMA || defined CONFIG_NET_RX_BUSY_POLL
@@ -830,13 +832,14 @@ static inline void
 skb_set_hash(struct sk_buff *skb, __u32 hash, enum pkt_hash_types type)
 {
        skb->l4_hash = (type == PKT_HASH_TYPE_L4);
+       skb->sw_hash = 0;
        skb->hash = hash;
 }
 
 void __skb_get_hash(struct sk_buff *skb);
 static inline __u32 skb_get_hash(struct sk_buff *skb)
 {
-       if (!skb->l4_hash)
+       if (!skb->l4_hash && !skb->sw_hash)
                __skb_get_hash(skb);
 
        return skb->hash;
@@ -850,6 +853,7 @@ static inline __u32 skb_get_hash_raw(const struct sk_buff *skb)
 static inline void skb_clear_hash(struct sk_buff *skb)
 {
        skb->hash = 0;
+       skb->sw_hash = 0;
        skb->l4_hash = 0;
 }
 
@@ -862,6 +866,7 @@ static inline void skb_clear_hash_if_not_l4(struct sk_buff *skb)
 static inline void skb_copy_hash(struct sk_buff *to, const struct sk_buff *from)
 {
        to->hash = from->hash;
+       to->sw_hash = from->sw_hash;
        to->l4_hash = from->l4_hash;
 };
 

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index c5f3912..5f362c1 100644 (file)
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -256,6 +256,8 @@ void __skb_get_hash(struct sk_buff *skb)
        if (keys.ports)
                skb->l4_hash = 1;
 
+       skb->sw_hash = 1;
+
        skb->hash = __flow_hash_from_keys(&keys);
 }
 EXPORT_SYMBOL(__skb_get_hash);