src/patches/linux-3.2-codel/0008-flow_dissector-use-a-64bit-load-store.patch

   1 From: Eric Dumazet <eric.dumazet@gmail.com>
   2 Date: Mon, 28 Nov 2011 20:30:35 +0000
   3 Subject: [PATCH 2/3] flow_dissector: use a 64bit load/store
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   7
   8 commit 4d77d2b567ec66a443792d99e96ac760991d80d0 upstream.
   9
  10 Le lundi 28 novembre 2011 à 19:06 -0500, David Miller a écrit :
  11 > From: Dimitris Michailidis <dm@chelsio.com>
  12 > Date: Mon, 28 Nov 2011 08:25:39 -0800
  13 >
  14 > >> +bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys
  15 > >> *flow)
  16 > >> +{
  17 > >> +  int poff, nhoff = skb_network_offset(skb);
  18 > >> +  u8 ip_proto;
  19 > >> +  u16 proto = skb->protocol;
  20 > >
  21 > > __be16 instead of u16 for proto?
  22 >
  23 > I'll take care of this when I apply these patches.
  24
  25 ( CC trimmed )
  26
  27 Thanks David !
  28
  29 Here is a small patch to use one 64bit load/store on x86_64 instead of
  30 two 32bit load/stores.
  31
  32 [PATCH net-next] flow_dissector: use a 64bit load/store
  33
  34 gcc compiler is smart enough to use a single load/store if we
  35 memcpy(dptr, sptr, 8) on x86_64, regardless of
  36 CONFIG_CC_OPTIMIZE_FOR_SIZE
  37
  38 In IP header, daddr immediately follows saddr, this wont change in the
  39 future. We only need to make sure our flow_keys (src,dst) fields wont
  40 break the rule.
  41
  42 Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
  43 Signed-off-by: David S. Miller <davem@davemloft.net>
  44
  45 diff --git a/include/net/flow_keys.h b/include/net/flow_keys.h
  46 index e4cb285..80461c1 100644
  47 --- a/include/net/flow_keys.h
  48 +++ b/include/net/flow_keys.h
  49 @@ -2,6 +2,7 @@
  50  #define _NET_FLOW_KEYS_H
  51
  52  struct flow_keys {
  53 +       /* (src,dst) must be grouped, in the same way than in IP header */
  54         __be32 src;
  55         __be32 dst;
  56         union {
  57 diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
  58 index f0516d9..0985b9b 100644
  59 --- a/net/core/flow_dissector.c
  60 +++ b/net/core/flow_dissector.c
  61 @@ -8,6 +8,16 @@
  62  #include <linux/ppp_defs.h>
  63  #include <net/flow_keys.h>
  64
  65 +/* copy saddr & daddr, possibly using 64bit load/store
  66 + * Equivalent to :     flow->src = iph->saddr;
  67 + *                     flow->dst = iph->daddr;
  68 + */
  69 +static void iph_to_flow_copy_addrs(struct flow_keys *flow, const struct iphdr *iph)
  70 +{
  71 +       BUILD_BUG_ON(offsetof(typeof(*flow), dst) !=
  72 +                    offsetof(typeof(*flow), src) + sizeof(flow->src));
  73 +       memcpy(&flow->src, &iph->saddr, sizeof(flow->src) + sizeof(flow->dst));
  74 +}
  75
  76  bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow)
  77  {
  78 @@ -31,8 +41,7 @@ ip:
  79                         ip_proto = 0;
  80                 else
  81                         ip_proto = iph->protocol;
  82 -               flow->src = iph->saddr;
  83 -               flow->dst = iph->daddr;
  84 +               iph_to_flow_copy_addrs(flow, iph);
  85                 nhoff += iph->ihl * 4;
  86                 break;
  87         }
  88 --
  89 1.7.10
  90