siphash: Make siphash functions consistently return 64-bit results

Some of the siphas_*b() functions return 64-bit results, others 32-bit
results, with no obvious pattern.  siphash_32b() also appears to do this
incorrectly - taking the 64-bit hash value and simply returning it
truncated, rather than folding the two halves together.

Since SipHash proper is defined to give a 64-bit hash, make all of them
return 64-bit results.  In the one caller which needs a 32-bit value,
tcp_seq_init() do the fold down to 32-bits ourselves.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/tcp.c b/tcp.c
index 2933123..19baba5 100644
--- a/tcp.c
+++ b/tcp.c
@@ -1826,7 +1826,8 @@ static void tcp_seq_init(const struct ctx *c, struct tcp_tap_conn *conn,
 		.srcport = conn->fport,
 		.dstport = conn->eport,
 	};
-	uint32_t ns, seq = 0;
+	uint64_t hash;
+	uint32_t ns;
 
 	if (CONN_V4(conn))
 		inany_from_af(&aany, AF_INET, &c->ip4.addr);
@@ -1834,12 +1835,12 @@ static void tcp_seq_init(const struct ctx *c, struct tcp_tap_conn *conn,
 		inany_from_af(&aany, AF_INET6, &c->ip6.addr);
 	in.dst = aany;
 
-	seq = siphash_36b((uint8_t *)&in, c->tcp.hash_secret);
+	hash = siphash_36b((uint8_t *)&in, c->tcp.hash_secret);
 
 	/* 32ns ticks, overflows 32 bits every 137s */
 	ns = (now->tv_sec * 1000000000 + now->tv_nsec) >> 5;
 
-	conn->seq_to_tap = seq + ns;
+	conn->seq_to_tap = ((uint32_t)(hash >> 32) ^ (uint32_t)hash) + ns;
 }
 
 /**