commit ec57cbf179257bc56b6649e30855a550eb110cd4 Author: David Goulet dgoulet@torproject.org Date: Tue Jun 30 09:32:21 2020 -0400

addr: Document better is_local_addr_to_resolve_addr()

This function is about learning if a given address is local to us as in the resolved address as a relay.

Closes #40009

Signed-off-by: David Goulet dgoulet@torproject.org --- src/app/config/resolve_addr.c | 26 ++++++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/src/app/config/resolve_addr.c b/src/app/config/resolve_addr.c index c8b44de84..8224e8868 100644 --- a/src/app/config/resolve_addr.c +++ b/src/app/config/resolve_addr.c @@ -568,8 +568,26 @@ find_my_address(const or_options_t *options, int family, int warn_severity, return true; }

-/** Return true iff <b>addr</b> is judged to be on the same network as us, or - * on a private network. +/** @brief: Return true iff the given addr is judged to be local to our + * resolved address. + * + * This function is used to tell whether another address is 'remote' enough + * that we can trust it when it tells us that we are reachable, or that we + * have a certain address." + * + * The criterion to learn if the address is local are the following: + * + * 1. Internal address. + * 2. If EnforceDistinctSubnets is set then it is never local. + * 3. Network mask is compared. IPv4: /24 and IPv6 /48. This is different + * from the path selection that looks at /16 and /32 because we only + * want to learn here if the address is considered to come from the + * Internet basically. + * + * @param addr The address to test if local and also test against our resovled + * address. + * + * @return True iff address is considered local or else False. */ MOCK_IMPL(bool, is_local_to_resolve_addr, (const tor_addr_t *addr)) @@ -589,10 +607,6 @@ is_local_to_resolve_addr, (const tor_addr_t *addr))

switch (family) { case AF_INET: - /* XXX: Why is this /24 and not /16 which the rest of tor does? Unknown - * reasons at the moment highlighted in ticket #40009. Because of that, we - * can't use addrs_in_same_network_family(). */ - /* It's possible that this next check will hit before the first time * find_my_address actually succeeds. For clients, it is likely that * find_my_address will never be called at all. In those cases,