diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/cache.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/src/cache.c b/src/cache.c index 80cde01..b92957a 100644 --- a/src/cache.c +++ b/src/cache.c @@ -38,7 +38,14 @@ static u_int32_t hash(const void *data, struct hashtable *table) ((nfct_get_attr_u16(ct, ATTR_ORIG_PORT_SRC) << 16) | (nfct_get_attr_u16(ct, ATTR_ORIG_PORT_DST)))); - return jhash_2words(a, b, 0) % table->hashsize; + /* + * Instead of returning hash % table->hashsize (implying a divide) + * we return the high 32 bits of the (hash * table->hashsize) that will + * give results between [0 and hashsize-1] and same hash distribution, + * but using a multiply, less expensive than a divide. See: + * http://www.mail-archive.com/netdev@vger.kernel.org/msg56623.html + */ + return ((u_int64_t)jhash_2words(a, b, 0) * table->hashsize) >> 32; } static u_int32_t hash6(const void *data, struct hashtable *table) @@ -47,15 +54,15 @@ static u_int32_t hash6(const void *data, struct hashtable *table) const struct us_conntrack *u = data; struct nf_conntrack *ct = u->ct; - a = jhash(nfct_get_attr(ct, ATTR_ORIG_IPV6_SRC), sizeof(u_int32_t), + a = jhash(nfct_get_attr(ct, ATTR_ORIG_IPV6_SRC), sizeof(u_int32_t)*4, ((nfct_get_attr_u8(ct, ATTR_ORIG_L3PROTO) << 16) | (nfct_get_attr_u8(ct, ATTR_ORIG_L4PROTO)))); - b = jhash(nfct_get_attr(ct, ATTR_ORIG_IPV6_DST), sizeof(u_int32_t), + b = jhash(nfct_get_attr(ct, ATTR_ORIG_IPV6_DST), sizeof(u_int32_t)*4, ((nfct_get_attr_u16(ct, ATTR_ORIG_PORT_SRC) << 16) | (nfct_get_attr_u16(ct, ATTR_ORIG_PORT_DST)))); - return jhash_2words(a, b, 0) % table->hashsize; + return ((u_int64_t)jhash_2words(a, b, 0) * table->hashsize) >> 32; } static int __compare(const struct nf_conntrack *ct1, |