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netfilter: arp_tables: unfold two critical loops in arp_packet_match()

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x86 and powerpc can perform long word accesses in an efficient maner.
We can use this to unroll two loops in arp_packet_match(), to
perform arithmetic on long words instead of bytes. This is a win
on x86_64 for example.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
This commit is contained in:
Eric Dumazet 2009-02-18 17:47:50 +01:00 committed by Patrick McHardy
parent 55df4ac0c9
commit ddc214c43a
1 changed files with 34 additions and 10 deletions
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44
net/ipv4/netfilter/arp_tables.c
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@ -73,6 +73,36 @@ static inline int arp_devaddr_compare(const struct arpt_devaddr_info *ap,
return (ret != 0);
}
/*
* Unfortunatly, _b and _mask are not aligned to an int (or long int)
* Some arches dont care, unrolling the loop is a win on them.
*/
static unsigned long ifname_compare(const char *_a, const char *_b, const char *_mask)
{
#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
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));
#else
unsigned long ret = 0;
int i;
for (i = 0; i < IFNAMSIZ; i++)
ret |= (_a[i] ^ _b[i]) & _mask[i];
#endif
return ret;
}
/* Returns whether packet matches rule or not. */
static inline int arp_packet_match(const struct arphdr *arphdr,
struct net_device *dev,
@ -83,7 +113,7 @@ static inline int arp_packet_match(const struct arphdr *arphdr,
const char *arpptr = (char *)(arphdr + 1);
const char *src_devaddr, *tgt_devaddr;
__be32 src_ipaddr, tgt_ipaddr;
int i, ret;
long ret;
#define FWINV(bool, invflg) ((bool) ^ !!(arpinfo->invflags & (invflg)))
@ -156,10 +186,7 @@ static inline int arp_packet_match(const struct arphdr *arphdr,
}
/* Look for ifname matches. */
for (i = 0, ret = 0; i < IFNAMSIZ; i++) {
ret |= (indev[i] ^ arpinfo->iniface[i])
& arpinfo->iniface_mask[i];
}
ret = ifname_compare(indev, arpinfo->iniface, arpinfo->iniface_mask);
if (FWINV(ret != 0, ARPT_INV_VIA_IN)) {
dprintf("VIA in mismatch (%s vs %s).%s\n",
@ -168,10 +195,7 @@ static inline int arp_packet_match(const struct arphdr *arphdr,
return 0;
}
for (i = 0, ret = 0; i < IFNAMSIZ; i++) {
ret |= (outdev[i] ^ arpinfo->outiface[i])
& arpinfo->outiface_mask[i];
}
ret = ifname_compare(outdev, arpinfo->outiface, arpinfo->outiface_mask);
if (FWINV(ret != 0, ARPT_INV_VIA_OUT)) {
dprintf("VIA out mismatch (%s vs %s).%s\n",
@ -221,7 +245,7 @@ unsigned int arpt_do_table(struct sk_buff *skb,
const struct net_device *out,
struct xt_table *table)
{
static const char nulldevname[IFNAMSIZ];
static const char nulldevname[IFNAMSIZ] __attribute__((aligned(sizeof(long))));
unsigned int verdict = NF_DROP;
const struct arphdr *arp;
bool hotdrop = false;