net: Dont use ifindices in hash fns
Eric noticed, that when there will be devices with equal indices, some
hash functions that use them will become less effective as they could.
Fix this in advance by mixing the net_device address into the hash value
instead of the device index.
This is true for arp and ndisc hash fns. The netlabel, can and llc ones
are also ifindex-based, but that three are init_net-only, thus will not
be affected.
Many thanks to David and Eric for the hash32_ptr implementation!
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/hash.h b/include/linux/hash.h
index b80506b..24df9e7 100644
--- a/include/linux/hash.h
+++ b/include/linux/hash.h
@@ -67,4 +67,14 @@
{
return hash_long((unsigned long)ptr, bits);
}
+
+static inline u32 hash32_ptr(const void *ptr)
+{
+ unsigned long val = (unsigned long)ptr;
+
+#if BITS_PER_LONG == 64
+ val ^= (val >> 32);
+#endif
+ return (u32)val;
+}
#endif /* _LINUX_HASH_H */