netfilter: xtables: use memcmp in unconditional check

Instead of inspecting each u32/char open-coded, clean up and make use
of memcmp. On some arches, memcmp is implemented as assembly or GCC's
__builtin_memcmp which can possibly take advantages of known
alignment.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 7505dff..b9f7243 100644 (file)
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -341,15 +341,11 @@ unsigned int arpt_do_table(struct sk_buff *skb,
 }
 
 /* All zeroes == unconditional rule. */
-static inline int unconditional(const struct arpt_arp *arp)
+static inline bool unconditional(const struct arpt_arp *arp)
 {
-       unsigned int i;
-
-       for (i = 0; i < sizeof(*arp)/sizeof(__u32); i++)
-               if (((__u32 *)arp)[i])
-                       return 0;
+       static const struct arpt_arp uncond;
 
-       return 1;
+       return memcmp(arp, &uncond, sizeof(uncond)) == 0;
 }
 
 /* Figures out from what hook each rule can be called: returns 0 if

diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 3856aa3..3431a77 100644 (file)
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -190,16 +190,11 @@ get_entry(void *base, unsigned int offset)
 
 /* All zeroes == unconditional rule. */
 /* Mildly perf critical (only if packet tracing is on) */
-static inline int
-unconditional(const struct ipt_ip *ip)
+static inline bool unconditional(const struct ipt_ip *ip)
 {
-       unsigned int i;
+       static const struct ipt_ip uncond;
 
-       for (i = 0; i < sizeof(*ip)/sizeof(__u32); i++)
-               if (((__u32 *)ip)[i])
-                       return 0;
-
-       return 1;
+       return memcmp(ip, &uncond, sizeof(uncond)) == 0;
 #undef FWINV
 }
 

diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index ced1f2c..1389ad9 100644 (file)
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -222,16 +222,11 @@ get_entry(void *base, unsigned int offset)
 
 /* All zeroes == unconditional rule. */
 /* Mildly perf critical (only if packet tracing is on) */
-static inline int
-unconditional(const struct ip6t_ip6 *ipv6)
+static inline bool unconditional(const struct ip6t_ip6 *ipv6)
 {
-       unsigned int i;
-
-       for (i = 0; i < sizeof(*ipv6); i++)
-               if (((char *)ipv6)[i])
-                       break;
+       static const struct ip6t_ip6 uncond;
 
-       return (i == sizeof(*ipv6));
+       return memcmp(ipv6, &uncond, sizeof(uncond)) == 0;
 }
 
 #if defined(CONFIG_NETFILTER_XT_TARGET_TRACE) || \