netfilter: arp_tables: unfold two critical loops in arp_packet_match()
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>
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@ -73,6 +73,36 @@ static inline int arp_devaddr_compare(const struct arpt_devaddr_info *ap,
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return (ret != 0);
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return (ret != 0);
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}
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}
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/*
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* Unfortunatly, _b and _mask are not aligned to an int (or long int)
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* Some arches dont care, unrolling the loop is a win on them.
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*/
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static unsigned long ifname_compare(const char *_a, const char *_b, const char *_mask)
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{
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#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
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const unsigned long *a = (const unsigned long *)_a;
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const unsigned long *b = (const unsigned long *)_b;
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const unsigned long *mask = (const unsigned long *)_mask;
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unsigned long ret;
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ret = (a[0] ^ b[0]) & mask[0];
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if (IFNAMSIZ > sizeof(unsigned long))
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ret |= (a[1] ^ b[1]) & mask[1];
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if (IFNAMSIZ > 2 * sizeof(unsigned long))
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ret |= (a[2] ^ b[2]) & mask[2];
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if (IFNAMSIZ > 3 * sizeof(unsigned long))
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ret |= (a[3] ^ b[3]) & mask[3];
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BUILD_BUG_ON(IFNAMSIZ > 4 * sizeof(unsigned long));
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#else
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unsigned long ret = 0;
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int i;
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for (i = 0; i < IFNAMSIZ; i++)
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ret |= (_a[i] ^ _b[i]) & _mask[i];
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#endif
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return ret;
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}
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/* Returns whether packet matches rule or not. */
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/* Returns whether packet matches rule or not. */
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static inline int arp_packet_match(const struct arphdr *arphdr,
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static inline int arp_packet_match(const struct arphdr *arphdr,
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struct net_device *dev,
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struct net_device *dev,
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@ -83,7 +113,7 @@ static inline int arp_packet_match(const struct arphdr *arphdr,
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const char *arpptr = (char *)(arphdr + 1);
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const char *arpptr = (char *)(arphdr + 1);
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const char *src_devaddr, *tgt_devaddr;
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const char *src_devaddr, *tgt_devaddr;
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__be32 src_ipaddr, tgt_ipaddr;
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__be32 src_ipaddr, tgt_ipaddr;
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int i, ret;
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long ret;
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#define FWINV(bool, invflg) ((bool) ^ !!(arpinfo->invflags & (invflg)))
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#define FWINV(bool, invflg) ((bool) ^ !!(arpinfo->invflags & (invflg)))
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@ -156,10 +186,7 @@ static inline int arp_packet_match(const struct arphdr *arphdr,
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}
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}
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/* Look for ifname matches. */
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/* Look for ifname matches. */
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for (i = 0, ret = 0; i < IFNAMSIZ; i++) {
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ret = ifname_compare(indev, arpinfo->iniface, arpinfo->iniface_mask);
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ret |= (indev[i] ^ arpinfo->iniface[i])
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& arpinfo->iniface_mask[i];
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}
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if (FWINV(ret != 0, ARPT_INV_VIA_IN)) {
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if (FWINV(ret != 0, ARPT_INV_VIA_IN)) {
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dprintf("VIA in mismatch (%s vs %s).%s\n",
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dprintf("VIA in mismatch (%s vs %s).%s\n",
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@ -168,10 +195,7 @@ static inline int arp_packet_match(const struct arphdr *arphdr,
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return 0;
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return 0;
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}
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}
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for (i = 0, ret = 0; i < IFNAMSIZ; i++) {
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ret = ifname_compare(outdev, arpinfo->outiface, arpinfo->outiface_mask);
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ret |= (outdev[i] ^ arpinfo->outiface[i])
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& arpinfo->outiface_mask[i];
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}
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if (FWINV(ret != 0, ARPT_INV_VIA_OUT)) {
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if (FWINV(ret != 0, ARPT_INV_VIA_OUT)) {
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dprintf("VIA out mismatch (%s vs %s).%s\n",
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dprintf("VIA out mismatch (%s vs %s).%s\n",
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@ -221,7 +245,7 @@ unsigned int arpt_do_table(struct sk_buff *skb,
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const struct net_device *out,
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const struct net_device *out,
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struct xt_table *table)
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struct xt_table *table)
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{
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{
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static const char nulldevname[IFNAMSIZ];
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static const char nulldevname[IFNAMSIZ] __attribute__((aligned(sizeof(long))));
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unsigned int verdict = NF_DROP;
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unsigned int verdict = NF_DROP;
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const struct arphdr *arp;
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const struct arphdr *arp;
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bool hotdrop = false;
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bool hotdrop = false;
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