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Code Issues Releases Wiki Activity

ircd::net: Improve/comment on various sundry DNS cache related.

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This commit is contained in:
Jason Volk 2018-04-13 18:34:48 -07:00
parent 5b6ffdaed2
commit dc81d77c19
1 changed files with 18 additions and 8 deletions
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26
ircd/net.cc
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@ -2446,7 +2446,13 @@ ircd::net::dns::query_cache(const hostport &hp,
const opts &opts,
const callback &cb)
{
thread_local const rfc1035::record *record[resolver::MAX_COUNT];
// It's no use putting the result record array on the stack in case this
// function is either called from an ircd::ctx or calls back an ircd::ctx.
// If the ctx yields the records can still be evicted from the cache.
// It's better to just force the user to conform here rather than adding
// ref counting and other pornographic complications to this cache.
const ctx::critical_assertion ca;
thread_local std::array<const rfc1035::record *, resolver::MAX_COUNT> record;
std::exception_ptr eptr;
size_t count{0};
@ -2481,21 +2487,23 @@ ircd::net::dns::query_cache(const hostport &hp,
assert(!eptr);
if(!rr.tgt)
{
const auto rcode{3}; //NXDomain
//TODO: we don't cache what the error was, assuming it's
//TODO: NXDomain can be incorrect and in bad ways downstream...
static const auto rcode{3}; //NXDomain
eptr = std::make_exception_ptr(rfc1035::error
{
"protocol error #%u (cached) :%s", rcode, rfc1035::rcode.at(rcode)
});
}
record[count++] = &rr;
record.at(count++) = &rr;
++it;
}
}
else // Deduced A query (for now)
{
auto &map{cache.A};
const auto pit{map.equal_range(std::string{host(hp)})}; //TODO: XXX
const auto pit{map.equal_range(host(hp))};
if(pit.first == pit.second)
return false;
@ -2516,14 +2524,16 @@ ircd::net::dns::query_cache(const hostport &hp,
assert(!eptr);
if(!rr.ip4)
{
const auto rcode{3}; //NXDomain
//TODO: we don't cache what the error was, assuming it's
//TODO: NXDomain can be incorrect and in bad ways downstream...
static const auto rcode{3}; //NXDomain
eptr = std::make_exception_ptr(rfc1035::error
{
"protocol error #%u (cached) :%s", rcode, rfc1035::rcode.at(rcode)
});
}
record[count++] = &rr;
record.at(count++) = &rr;
++it;
}
}
@ -2532,7 +2542,7 @@ ircd::net::dns::query_cache(const hostport &hp,
assert(!eptr || count == 1); // if error, should only be one entry.
if(count)
cb(std::move(eptr), vector_view<const rfc1035::record *>(record, count));
cb(std::move(eptr), vector_view<const rfc1035::record *>(record.data(), count));
return count;
}
@ -2570,7 +2580,7 @@ decltype(ircd::net::dns::resolver::send_rate)
ircd::net::dns::resolver::send_rate
{
{ "name", "ircd.net.dns.resolver.send_rate" },
{ "default", 100L },
{ "default", 60L },
};
ircd::net::dns::resolver::resolver()