commit 492c512af4a4f9ee143b945296fd1c61fc68dba1 Author: teor teor@riseup.net Date: Thu May 7 22:06:13 2020 +1000

relay: Improve docs on inform_testing_reachability()

Document race conditions that we'll resolve in 34067 and 34137.

Part of 33222. --- src/feature/relay/selftest.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/src/feature/relay/selftest.c b/src/feature/relay/selftest.c index 3035c252d..e311c08ec 100644 --- a/src/feature/relay/selftest.c +++ b/src/feature/relay/selftest.c @@ -269,9 +269,12 @@ router_do_reachability_checks(int test_or, int test_dir) } }

-/** We've decided to start our reachability testing. If all - * is set, log this to the user. Return 1 if we did, or 0 if - * we chose not to log anything. */ +/** If reachability testing is in progress, let the user know that it's + * happening. + * + * If all is set, log a notice-level message. Return 1 if we did, or 0 if + * we chose not to log anything, because we were unable to test reachability. + */ int inform_testing_reachability(void) { @@ -279,6 +282,20 @@ inform_testing_reachability(void) char ipv6_or_buf[TOR_ADDRPORT_BUF_LEN]; char ipv4_dir_buf[TOR_ADDRPORT_BUF_LEN];

+ /* There's a race condition here, between: + * - tor launching reachability tests, + * - any circuits actually completing, + * - routerinfo updates, and + * - these log messages. + * In rare cases, we might log the wrong ports, log when we didn't actually + * start reachability tests, or fail to log after we actually started + * reachability tests. + * + * After we separate the IPv4 and IPv6 reachability flags in #34067, tor + * will test any IPv6 address that it discovers after launching reachability + * checks. We'll deal with late disabled IPv6 ORPorts and IPv4 DirPorts, and + * extra or skipped log messages in #34137. + */ const routerinfo_t *me = router_get_my_routerinfo(); if (!me) return 0;