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ircd::net::dns: Strip the cached-error SRV target of its prefix; minor fixes.

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This commit is contained in:
Jason Volk 2018-04-28 17:39:08 -07:00
parent 405fcdef23
commit 3f2320c49e
2 changed files with 24 additions and 3 deletions
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1
include/ircd/net/dns.h
View file

@ -42,6 +42,7 @@ struct ircd::net::dns
// (internal) generate strings for rfc1035 questions or dns::cache keys.
static string_view make_SRV_key(const mutable_buffer &out, const hostport &, const opts &);
static string_view unmake_SRV_key(const string_view &);
public:
// Cache warming

26
ircd/net.cc
View file

@ -2419,16 +2419,17 @@ ircd::net::dns::operator()(const hostport &hp,
return calluser(std::move(eptr), 0, 0);
if(record.port != 0)
port(hp) = record.port;
hp.port = record.port;
// The host reference in hp has become invalid by the time of this cb.
assert(!record.tgt.empty());
host(hp) = record.tgt;
hp.host = record.tgt;
// Have to kill the service name to not run another SRV query now, and
// these are also invalid references too.
hp.service = {};
opts.srv = {};
opts.proto = {};
this->operator()(hp, opts, [hp, calluser(std::move(calluser))]
(std::exception_ptr eptr, const rfc1035::record::A &record)
@ -2510,6 +2511,25 @@ ircd::net::dns::operator()(const hostport &hostport,
(*resolver)(hostport, opts, std::move(cb));
}
/// Really assumptional and hacky right now. We're just assuming the SRV
/// key is the first two elements of a dot-delimited string which start
/// with underscores. If that isn't good enough in the future this will rot
/// and become a regression hazard.
ircd::string_view
ircd::net::dns::unmake_SRV_key(const string_view &key)
{
if(token_count(key, '.') < 3)
return key;
if(!startswith(token(key, '.', 0), '_'))
return key;
if(!startswith(token(key, '.', 1), '_'))
return key;
return tokens_after(key, '.', 1);
}
ircd::string_view
ircd::net::dns::make_SRV_key(const mutable_buffer &out,
const hostport &hp,
@ -2582,7 +2602,7 @@ ircd::net::dns::cache::put_error(const rfc1035::question &question,
rfc1035::record::SRV record;
record.ttl = ircd::time() + seconds(cache::clear_nxdomain).count(); //TODO: code
it = map.emplace_hint(it, host, record);
it->second.tgt = it->first;
it->second.tgt = unmake_SRV_key(it->first);
return &it->second;
}
}