In the tcp_conn structure, we represent IPv4 connections with IPv4-mapped
IPv6 addresses in the single address field. However, we have different
paths which will calculate different hashes for IPv4 and equivalent
IPv4-mapped IPv6 addresses. This will cause problems for some future
changes.
Make the hash function work the same for these two cases, by always mapping
IPv4 addresses into IPv4-mapped addresses before hashing. This involves
some ugly temporaries, but later changes should improve this again.
Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
---
siphash.c | 1 +
tcp.c | 33 +++++++++++++++------------------
2 files changed, 16 insertions(+), 18 deletions(-)
diff --git a/siphash.c b/siphash.c
index 37a6d73..516a508 100644
--- a/siphash.c
+++ b/siphash.c
@@ -104,6 +104,7 @@
*
* Return: the 64-bit hash output
*/
+/* cppcheck-suppress unusedFunction */
uint64_t siphash_8b(const uint8_t *in, const uint64_t *k)
{
PREAMBLE(8);
diff --git a/tcp.c b/tcp.c
index 508d6e9..4645004 100644
--- a/tcp.c
+++ b/tcp.c
@@ -1315,30 +1315,27 @@ __attribute__((__noinline__)) /* See comment in Makefile */
static unsigned int tcp_hash(const struct ctx *c, int af, const void *addr,
in_port_t tap_port, in_port_t sock_port)
{
+ struct {
+ struct in6_addr addr;
+ in_port_t tap_port;
+ in_port_t sock_port;
+ } __attribute__((__packed__)) in = {
+ .tap_port = tap_port,
+ .sock_port = sock_port,
+ };
uint64_t b = 0;
if (af == AF_INET) {
- struct {
- struct in_addr addr;
- in_port_t tap_port;
- in_port_t sock_port;
- } __attribute__((__packed__)) in = {
- *(struct in_addr *)addr, tap_port, sock_port,
- };
-
- b = siphash_8b((uint8_t *)&in, c->tcp.hash_secret);
- } else if (af == AF_INET6) {
- struct {
- struct in6_addr addr;
- in_port_t tap_port;
- in_port_t sock_port;
- } __attribute__((__packed__)) in = {
- *(struct in6_addr *)addr, tap_port, sock_port,
- };
+ struct in6_addr v4mapped;
- b = siphash_20b((uint8_t *)&in, c->tcp.hash_secret);
+ encode_ip4mapped_ip6(&v4mapped, addr);
+ in.addr = v4mapped;
+ } else {
+ in.addr = *(struct in6_addr *)addr;
}
+ b = siphash_20b((uint8_t *)&in, c->tcp.hash_secret);
+
return (unsigned int)(b % TCP_HASH_TABLE_SIZE);
}
--
2.38.1