From 5d5bb8c1501e6ee02568d086e36081a756e45e51 Mon Sep 17 00:00:00 2001 From: David Gibson Date: Thu, 7 Dec 2023 16:53:53 +1100 Subject: tcp: Don't account for hash table size in tcp_hash() Currently tcp_hash() returns the hash bucket for a value, that is the hash modulo the size of the hash table. Usually it's a bit more flexible to have hash functions return a "raw" hash value and perform the modulus in the callers. That allows the same hash function to be used for multiple tables of different sizes, or to re-use the hash for other purposes. We don't do anything like that with tcp_hash() at present, but we have some plans to do so. Prepare for that by making tcp_hash() and tcp_conn_hash() return raw hash values. Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- tcp.c | 23 ++++++++++------------- 1 file changed, 10 insertions(+), 13 deletions(-) diff --git a/tcp.c b/tcp.c index cdaf2c2..53a699e 100644 --- a/tcp.c +++ b/tcp.c @@ -1160,18 +1160,15 @@ static int tcp_hash_match(const struct tcp_tap_conn *conn, * @eport: Guest side endpoint port * @fport: Guest side forwarding port * - * Return: hash value, already modulo size of the hash table + * Return: hash value, needs to be adjusted for table size */ -static unsigned int tcp_hash(const struct ctx *c, const union inany_addr *faddr, - in_port_t eport, in_port_t fport) +static uint64_t tcp_hash(const struct ctx *c, const union inany_addr *faddr, + in_port_t eport, in_port_t fport) { struct siphash_state state = SIPHASH_INIT(c->hash_secret); - uint64_t hash; inany_siphash_feed(&state, faddr); - hash = siphash_final(&state, 20, (uint64_t)eport << 16 | fport); - - return (unsigned int)(hash % TCP_HASH_TABLE_SIZE); + return siphash_final(&state, 20, (uint64_t)eport << 16 | fport); } /** @@ -1179,10 +1176,10 @@ static unsigned int tcp_hash(const struct ctx *c, const union inany_addr *faddr, * @c: Execution context * @conn: Connection * - * Return: hash value, already modulo size of the hash table + * Return: hash value, needs to be adjusted for table size */ -static unsigned int tcp_conn_hash(const struct ctx *c, - const struct tcp_tap_conn *conn) +static uint64_t tcp_conn_hash(const struct ctx *c, + const struct tcp_tap_conn *conn) { return tcp_hash(c, &conn->faddr, conn->eport, conn->fport); } @@ -1199,7 +1196,7 @@ static inline unsigned tcp_hash_probe(const struct ctx *c, const struct tcp_tap_conn *conn) { flow_sidx_t sidx = FLOW_SIDX(conn, TAPSIDE); - unsigned b = tcp_conn_hash(c, conn); + unsigned b = tcp_conn_hash(c, conn) % TCP_HASH_TABLE_SIZE; /* Linear probing */ while (!flow_sidx_eq(tc_hash[b], FLOW_SIDX_NONE) && @@ -1242,7 +1239,7 @@ static void tcp_hash_remove(const struct ctx *c, for (s = mod_sub(b, 1, TCP_HASH_TABLE_SIZE); (flow = flow_at_sidx(tc_hash[s])); s = mod_sub(s, 1, TCP_HASH_TABLE_SIZE)) { - unsigned h = tcp_conn_hash(c, &flow->tcp); + unsigned h = tcp_conn_hash(c, &flow->tcp) % TCP_HASH_TABLE_SIZE; if (!mod_between(h, s, b, TCP_HASH_TABLE_SIZE)) { /* tc_hash[s] can live in tc_hash[b]'s slot */ @@ -1298,7 +1295,7 @@ static struct tcp_tap_conn *tcp_hash_lookup(const struct ctx *c, inany_from_af(&aany, af, faddr); - b = tcp_hash(c, &aany, eport, fport); + b = tcp_hash(c, &aany, eport, fport) % TCP_HASH_TABLE_SIZE; while ((flow = flow_at_sidx(tc_hash[b])) && !tcp_hash_match(&flow->tcp, &aany, eport, fport)) b = mod_sub(b, 1, TCP_HASH_TABLE_SIZE); -- cgit v1.2.3