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Re: [tor-bugs] #19025 [Core Tor/Tor]: Exit relays always return DNS TTL 60 to tor clients
#19025: Exit relays always return DNS TTL 60 to tor clients
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Reporter: phw | Owner:
Type: defect | Status: new
Priority: Medium | Milestone:
Component: Core Tor/Tor | Version: Tor: 0.2.8.2-alpha
Severity: Normal | Resolution:
Keywords: dns | Actual Points:
Parent ID: | Points:
Reviewer: | Sponsor:
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Comment (by phw):
This bug also affects an exit relay's DNS cache. Exits cache DNS responses
for the duration of their TTL (see `make_pending_resolve_cached`), but
since they are always set to 0, we end up with MIN_DNS_TTL (see
`dns_get_expiry_ttl`), which is 60. So each domain, regardless of its TTL,
is cached for only 60 seconds, resulting in more DNS requests than
necessary.
I have a patch in the branch `bug-19025` in the following repository:
https://github.com/NullHypothesis/tor
I briefly tested it on my exit relay, and it seems to work. The following
log is the result of requesting the domain cartography.nymity.ch three
times. The exit's cache was cold.
{{{
Jul 27 18:17:14.000 [notice] Added domain cartography.nymity.ch with
expiry=1800, ttlv4=10800, ttlv6=0, ttlhost=0 to cache.
Jul 27 18:17:22.000 [notice] Address cartography.nymity.ch was already in
cache, expire=1792.
Jul 27 18:23:59.000 [notice] Address cartography.nymity.ch was already in
cache, expire=1395.
}}}
My Tor client also received the correct TTL from the exit.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/19025#comment:1>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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