From: wenxu <[email protected]> In case almost or all available ports are taken, clash resolution can take a very long time, resulting in soft lockup.
This can happen when many to-be-natted hosts connect to same destination:port (e.g. a proxy) and all connections pass the same SNAT. Pick a random offset in the acceptable range, then try ever smaller number of adjacent port numbers, until either the limit is reached or a useable port was found. This results in at most 248 attempts (128 + 64 + 32 + 16 + 8, i.e. 4 restarts with new search offset) instead of 64000+. Signed-off-by: wenxu <[email protected]> --- lib/conntrack.c | 35 +++++++++++++++++++++++++++++++---- 1 file changed, 31 insertions(+), 4 deletions(-) diff --git a/lib/conntrack.c b/lib/conntrack.c index 2d14205..bc7de17 100644 --- a/lib/conntrack.c +++ b/lib/conntrack.c @@ -2414,6 +2414,10 @@ nat_get_unique_tuple(struct conntrack *ct, const struct conn *conn, conn->key.nw_proto == IPPROTO_UDP; uint16_t min_dport, max_dport, curr_dport, orig_dport; uint16_t min_sport, max_sport, curr_sport, orig_sport; + static const unsigned int max_attempts = 128; + uint16_t range_src, range_dst, range_max; + unsigned int attempts; + unsigned int i; min_addr = conn->nat_info->min_addr; max_addr = conn->nat_info->max_addr; @@ -2430,6 +2434,10 @@ nat_get_unique_tuple(struct conntrack *ct, const struct conn *conn, set_dport_range(conn->nat_info, &conn->key, hash, &orig_dport, &min_dport, &max_dport); + range_src = max_sport - min_sport + 1; + range_dst = max_dport - min_dport + 1; + range_max = range_src > range_dst ? range_src : range_dst; + another_round: store_addr_to_key(&curr_addr, &nat_conn->rev_key, conn->nat_info->nat_action); @@ -2446,17 +2454,36 @@ another_round: curr_sport = orig_sport; curr_dport = orig_dport; + attempts = range_max; + if (attempts > max_attempts) { + attempts = max_attempts; + } + +another_port_round: + i = 0; FOR_EACH_PORT_IN_RANGE(curr_dport, min_dport, max_dport) { nat_conn->rev_key.src.port = htons(curr_dport); FOR_EACH_PORT_IN_RANGE(curr_sport, min_sport, max_sport) { - nat_conn->rev_key.dst.port = htons(curr_sport); - if (!conn_lookup(ct, &nat_conn->rev_key, - time_msec(), NULL, NULL)) { - return true; + if (i++ < attempts) { + nat_conn->rev_key.dst.port = htons(curr_sport); + if (!conn_lookup(ct, &nat_conn->rev_key, + time_msec(), NULL, NULL)) { + return true; + } } } } + if (attempts >= range_max || attempts < 16) { + goto next_addr; + } + + attempts /= 2; + curr_dport = random_uint32() % range_dst; + curr_sport = random_uint32() % range_src; + + goto another_port_round; + /* Check if next IP is in range and respin. Otherwise, notify * exhaustion to the caller. */ next_addr: -- 1.8.3.1 _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
