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relay: Refactor choosing extend IPs

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Flatten the logic in circuit_choose_ip_ap_for_extend().

Part of 33817.
This commit is contained in:
teor 2020-04-29 21:37:31 +10:00
parent df5ea29775
commit bcec1ec071
1 changed files with 25 additions and 20 deletions
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45
src/feature/relay/circuitbuild_relay.c
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@ -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;
}
}