netfilter: xt_physdev: unfold two loops in physdev_mt()

xt_physdev netfilter module can use an ifname_compare() helper
so that two loops are unfolded.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 21 insertions, 11 deletions

diff --git a/net/netfilter/xt_physdev.c b/net/netfilter/xt_physdev.c
index 4b13ef7ce145..44a234ef4439 100644
--- a/net/netfilter/xt_physdev.c
+++ b/net/netfilter/xt_physdev.c
@@ -20,10 +20,27 @@ MODULE_DESCRIPTION("Xtables: Bridge physical device match");
 MODULE_ALIAS("ipt_physdev");
 MODULE_ALIAS("ip6t_physdev");
 
+static unsigned long ifname_compare(const char *_a, const char *_b, const char *_mask)
+{
+        const unsigned long *a = (const unsigned long *)_a;
+        const unsigned long *b = (const unsigned long *)_b;
+        const unsigned long *mask = (const unsigned long *)_mask;
+        unsigned long ret;
+
+        ret = (a[0] ^ b[0]) & mask[0];
+        if (IFNAMSIZ > sizeof(unsigned long))
+                ret |= (a[1] ^ b[1]) & mask[1];
+        if (IFNAMSIZ > 2 * sizeof(unsigned long))
+                ret |= (a[2] ^ b[2]) & mask[2];
+        if (IFNAMSIZ > 3 * sizeof(unsigned long))
+                ret |= (a[3] ^ b[3]) & mask[3];
+        BUILD_BUG_ON(IFNAMSIZ > 4 * sizeof(unsigned long));
+        return ret;
+}
+
 static bool
 physdev_mt(const struct sk_buff *skb, const struct xt_match_param *par)
 {
-        int i;
         static const char nulldevname[IFNAMSIZ] __attribute__((aligned(sizeof(long))));
         const struct xt_physdev_info *info = par->matchinfo;
         unsigned long ret;
@@ -68,11 +85,7 @@ physdev_mt(const struct sk_buff *skb, const struct xt_match_param *par)
         if (!(info->bitmask & XT_PHYSDEV_OP_IN))
                 goto match_outdev;
         indev = nf_bridge->physindev ? nf_bridge->physindev->name : nulldevname;
-        for (i = 0, ret = 0; i < IFNAMSIZ/sizeof(unsigned long); i++) {
-                ret |= (((const unsigned long *)indev)[i]
-                        ^ ((const unsigned long *)info->physindev)[i])
-                        & ((const unsigned long *)info->in_mask)[i];
-        }
+        ret = ifname_compare(indev, info->physindev, info->in_mask);
 
         if (!ret ^ !(info->invert & XT_PHYSDEV_OP_IN))
                 return false;
@@ -82,11 +95,8 @@ match_outdev:
                 return true;
         outdev = nf_bridge->physoutdev ?
                  nf_bridge->physoutdev->name : nulldevname;
-        for (i = 0, ret = 0; i < IFNAMSIZ/sizeof(unsigned long); i++) {
-                ret |= (((const unsigned long *)outdev)[i]
-                        ^ ((const unsigned long *)info->physoutdev)[i])
-                        & ((const unsigned long *)info->out_mask)[i];
-        }
+        ret = ifname_compare(outdev, info->physoutdev, info->out_mask);
+
         return (!!ret ^ !(info->invert & XT_PHYSDEV_OP_OUT));
 }