commit bcec1ec071400464f7cefa4f0d493964984905ce Author: teor teor@torproject.org Date: Wed Apr 29 21:37:31 2020 +1000
relay: Refactor choosing extend IPs
Flatten the logic in circuit_choose_ip_ap_for_extend().
Part of 33817. --- src/feature/relay/circuitbuild_relay.c | 45 +++++++++++++++++++--------------- 1 file changed, 25 insertions(+), 20 deletions(-)
diff --git a/src/feature/relay/circuitbuild_relay.c b/src/feature/relay/circuitbuild_relay.c index 2bf08547d..9420ea11a 100644 --- a/src/feature/relay/circuitbuild_relay.c +++ b/src/feature/relay/circuitbuild_relay.c @@ -250,8 +250,27 @@ STATIC const tor_addr_port_t * circuit_choose_ip_ap_for_extend(const tor_addr_port_t *ipv4_ap, const tor_addr_port_t *ipv6_ap) { - /* If we could make an IPv4 or an IPv6 connection, make an IPv6 connection - * at random, with probability 1 in N. + const bool ipv6_supported = router_has_advertised_ipv6_orport(get_options()); + + /* If IPv6 is not supported, we can't use the IPv6 address. */ + if (!ipv6_supported) { + ipv6_ap = NULL; + } + + /* If there is no IPv6 address, IPv4 is always supported. + * Until clients include IPv6 ORPorts, and most relays support IPv6, + * this is the most common case. */ + if (!ipv6_ap) { + return ipv4_ap; + } + + /* If there is no IPv4 address, return the (possibly NULL) IPv6 address. */ + if (!ipv4_ap) { + return ipv6_ap; + } + + /* Now we have an IPv4 and an IPv6 address, and IPv6 is supported. + * So make an IPv6 connection at random, with probability 1 in N. * 1 means "always IPv6 (and no IPv4)" * 2 means "equal probability of IPv4 or IPv6" * ... (and so on) ... @@ -260,26 +279,12 @@ circuit_choose_ip_ap_for_extend(const tor_addr_port_t *ipv4_ap, */ #define IPV6_CONNECTION_ONE_IN_N 2
- /* IPv4 is always supported */ - const bool ipv6_supported = router_has_advertised_ipv6_orport(get_options()); - - if (ipv4_ap && ipv6_ap && ipv6_supported) { - /* Choose between IPv4 and IPv6 at random */ - bool choose_ipv6 = crypto_fast_rng_one_in_n(get_thread_fast_rng(), - IPV6_CONNECTION_ONE_IN_N); - if (choose_ipv6) { - return ipv6_ap; - } else { - return ipv4_ap; - } - } else if (ipv6_ap && ipv6_supported) { - /* There's only one valid address: try to use it */ + bool choose_ipv6 = crypto_fast_rng_one_in_n(get_thread_fast_rng(), + IPV6_CONNECTION_ONE_IN_N); + if (choose_ipv6) { return ipv6_ap; - } else if (ipv4_ap) { - return ipv4_ap; } else { - /* IPv6-only extend, but IPv6 is not supported. */ - return NULL; + return ipv4_ap; } }