- allow to specify when they are wanted on starting a resolve
- match dns cache entries accordingly. An entry which never
tried to get HTTPS-RRs is no answer for a resolve that wants
it.
- fix late arrivals of resolve answers to match the "async"
records that started them - if it still exists.
- provide for multiple "async" resolves in a transfer at the
same time. We may need to resolve an IP interface while the
main connection resolve has not finished yet.
- allow lookup of HTTPS-RR information as soon as it is
available, even if A/AAAA queries are still ongoing.
For this, the "async" infrastructure is changed:
- Defined bits for DNS queries `CURL_DNSQ_A`, `CURL_DNSQ_AAAA`
and `CURL_DNSQ_HTTPS`. These replace `ip_version` which says
nothing about HTTPS.
Use them in dns cache entries for matching.
- enhance the `async->id` to be a unique `uint32_t` for
resolves inside one multi. This is weak, as the id may
wrap around. However it is combined with the `mid` of
the easy handle, making collisions highly unlikely.
`data->state.async` is only accessed in few places where
the mid/async-id match is performed.
- vtls: for ECH supporting TLS backends (openssl, rustls, wolfssl),
retrieve the HTTPS-RR information from the dns connection filter.
Delay the connect if the HTTPS-RR is needed, but has not
been resolved yet.
The implementation of all this is complete for the threaded
resolver. c-ares resolver and DoH do not take advantage of
all new async features yet. To be done in separate PRs.
Details:
c-ares: cleanup settings and initialisation. Any ares channel
is only being created on starting a resolve and propagating
operations in setopt.c to the channel are not helpful.
Changed threaded+ares pollset handling so that they do not
overwrite each others `ASYNC_NAME` timeouts.
Add trace name 'threads' for tracing thread queue and
pool used by threaded resolver.
Closes#21175
New connection filter `cf-dns` that manages DNS queries. If hands
out addresses and HTTPS-RR records to anyone interested. Used by
HTTPS and IP happy eyeballing.
Information may become available *before* the libcurl "dns entry"
is complete, e.g. all queries have been answered. The cf-ip-happy
filter uses this information to start connection attempts as soon
as the first address is available.
The multi MSTATE_RESOLVING was removed. A new connection always
goes to MSTATE_CONNECTING. The connectdata bit `dns_resolved`
indicates when DNS information is complete. This is used for
error reporting and starting the progress meter.
Removed dns entries `data->state.dns[i]`, as the `cf-dns` filter
now keeps the reference now.
Many minor tweaks for making this work and pass address information
around safely.
Closes#21027
- Rename `Curl_resolv_unlink()` to `Curl_dns_entry_unlink()`.
- Change `Curl_dnscache_get()` to return CURLcode result. Returns
now `CURLE_COULDNT_RESOLVE_HOST` for "negative" cache entries.
- Add `Curl_dnscache_add_negative()` to put a "negative" entry
into the cache.
Closes#20864
