[PATCH 04/10] tcp: Hash IPv4 and IPv4-mapped-IPv6 addresses the same

[David Gibson <david@gibson.dropbear.id.au>]

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@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);
 }
 
-- 
@@ -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