diff options
| -rw-r--r-- | changes/ipv6_automap | 7 | ||||
| -rw-r--r-- | src/or/addressmap.c | 10 |
2 files changed, 14 insertions, 3 deletions
diff --git a/changes/ipv6_automap b/changes/ipv6_automap index 150349c382..1b44585277 100644 --- a/changes/ipv6_automap +++ b/changes/ipv6_automap @@ -10,3 +10,10 @@ - AutomapHostsOnResolve responses are now randomized, to avoid annoying situations where Tor is restarted and applications connect to the wrong addresses. + + - We never try more than 1000 times to pick a virtual address + when AutomapHostsOnResolve is set. That's good enough so long + as we aren't close to handing out our entire virtual address + space; if you're getting there, it's best to switch to IPv6 + virtual addresses anyway. + diff --git a/src/or/addressmap.c b/src/or/addressmap.c index e1efbf4bfd..f4c31295a8 100644 --- a/src/or/addressmap.c +++ b/src/or/addressmap.c @@ -863,9 +863,13 @@ addressmap_get_virtual_address(int type) const virtual_addr_conf_t *conf = ipv6 ? &virtaddr_conf_ipv6 : &virtaddr_conf_ipv4; - // This is an imperfect estimate of how many addresses are available, but - // that's ok. We also don't try every one. - uint32_t attempts = ipv6 ? UINT32_MAX : (1u << (32- conf->bits)); + /* Don't try more than 1000 times. This gives us P < 1e-9 for + * failing to get a good address so long as the address space is + * less than ~97.95% full. That's always going to be true under + * sensible circumstances for an IPv6 /10, and it's going to be + * true for an IPv4 /10 as long as we've handed out less than + * 4.08 million addresses. */ + uint32_t attempts = 1000; tor_addr_t addr; |