As per #738, there are usecases where the DNS TXT record strings should
not be concatenated like RFC 7208 indicates. We cannot break ABI with
those using the new API, so we need to support retrieving the
concatenated version as well as a new API to retrieve the individual
strings which will be used by `ares_parse_text_reply_ext()` to restore
the old behavior prior to c-ares 1.20.
Fixes Issue: #738
Fix By: Brad House (@bradh352)
**Summary**
This PR adds a server state callback that is invoked whenever a query to
a DNS server finishes.
The callback is invoked with the server details (as a string), a boolean
indicating whether the query succeeded or failed, flags describing the
query (currently just indicating whether TCP or UDP was used), and
custom userdata.
This can be used by user applications to gain observability into DNS
server health and usage. For example, alerts when a DNS server
fails/recovers or metrics to track how often a DNS server is used and
responds successfully.
**Testing**
Three new regression tests `MockChannelTest.ServStateCallback*` have
been added to test the new callback in different success/failure
scenarios.
Fix By: Oliver Welsh (@oliverwelsh)
c-ares has historically passed around raw dns packets in binary form.
Now that we have a new parser, and messages are already parsed
internally, lets pass around that parsed message rather than requiring
multiple parse attempts on the same message. Also add a new
`ares_send_dnsrec()` and `ares_query_dnsrec()` similar to
`ares_search_dnsrec()` added with PR #719 that can return the pointer to
the `ares_dns_record_t` to the caller enqueuing queries and rework
`ares_search_dnsrec()` to use `ares_send_dnsrec()` internally.
Fix By: Brad House (@bradh352)
This PR adds a new function `ares_search_dnsrec()` to search for records
using the new DNS record parser.
The function takes an arbitrary DNS record object to search (that must
represent a query for a single name). The function takes a new callback
type, `ares_callback_dnsrec`, that is invoked with a parsed DNS record
object rather than the raw buffer(+length).
The original motivation for this change is to provide support for
[draft-kaplan-enum-sip-routing-04](https://datatracker.ietf.org/doc/html/draft-kaplan-enum-sip-routing-04);
when routing phone calls using an ENUM server, it can be useful to
include identifying source information in an OPT RR options value, to
help select the appropriate route for the call. The new function allows
for more customisable searches like this.
**Summary of code changes**
A new function `ares_search_dnsrec()` has been added and exposed.
Moreover, the entire `ares_search_int()` internal code flow has been
refactored to use parsed DNS record objects and the new DNS record
parser. The DNS record object is passed through the `search_query`
structure by encoding/decoding to/from a buffer (if multiple search
domains are used). A helper function `ares_dns_write_query_altname()` is
used to re-write the DNS record object with a new query name (used to
append search domains).
`ares_search()` is now a wrapper around the new internal code, where the
DNS record object is created based on the name, class and type
parameters.
The new function uses a new callback type, `ares_callback_dnsrec`. This
is invoked with a parsed DNS record object. For now, we convert from
`ares_callback` to this new type using `ares__dnsrec_convert_cb()`.
Some functions that are common to both `ares_query()` and
`ares_search()` have been refactored using the new DNS record parser.
See `ares_dns_record_create_query()` and
`ares_dns_query_reply_tostatus()`.
**Testing**
A new FV has been added to test the new function, which searches for a
DNS record containing an OPT RR with custom options value.
As part of this, I needed to enhance the mock DNS server to expect
request text (and assert that it matches actual request text). This is
because the FV needs to check that the request contains the correct OPT
RR.
**Documentation**
The man page docs have been updated to describe the new feature.
**Futures**
In the future, a new variant of `ares_send()` could be introduced in the
same vein (`ares_send_dnsrec()`). This could be used by
`ares_search_dnsrec()`. Moreover, we could migrate internal code to use
`ares_callback_dnsrec` as the default callback.
This will help to make the new DNS record parser the norm in C-Ares.
---------
Co-authored-by: Oliver Welsh (@oliverwelsh)
Add a function to request the number of active queries from an ares
channel. This will return the number of inflight requests to dns
servers. Some functions like `ares_getaddrinfo()` when using `AF_UNSPEC`
may enqueue multiple queries which will be reflected in this count.
In the future, if we implement support for queuing (e.g. for throttling
purposes), and/or implement support for tracking user-requested queries
(e.g. for cancelation), we can provide additional functions for
inspecting those queues.
Fix By: Brad House (@bradh352)
It may be useful to wait for the queue to be empty under certain conditions (mainly test cases), expose a function to efficiently do this and rework test cases to use it.
Fix By: Brad House (@bradh352)
Some environments may send router advertisements on a link setting their link-local (fe80::/10) address as a valid DNS server to the remote system. This will cause a DNS entry to be created like `fe80::1%iface`, since all link-local network interfaces are technically part of the same /10 subnet, it must be told what interface to send packets through explicitly if there are multiple physical interfaces.
This PR adds support for the %iface modifier when setting DNS servers via `/etc/resolv.conf` as well as via `ares_set_servers_csv()`.
For MacOS and iOS it is assumed that libresolve will set the `sin6_scope_id` and should be supported, but my test systems don't seem to read the Router Advertisement for RDNSS link-local. Specifying the link-local dns server on MacOS via adig has been tested and confirmed working.
For Windows, this is similar to MacOS in that the system doesn't seem to honor the RDNSS RA, but specifying manually has been tested to work.
At this point, Android support does not exist.
Fixes Bug #462
Supersedes PR #463
Fix By: Brad House (@bradh352) and Serhii Purik (@sergvpurik)
This PR implements ares_reinit() to safely reload a channel's configuration even if there are existing queries. This function can be called when system configuration is detected to be changed, however since c-ares isn't thread aware, care must be taken to ensure no other c-ares calls are in progress at the time this function is called. Also, this function may update the open file descriptor list so care must also be taken to wake any event loops and reprocess the list of file descriptors.
Fixes Bug #301
Fix By: Brad House (@bradh352)
All files have their licence and copyright information clearly
identifiable. If not in the file header, they are set separately in
.reuse/dep5.
All used license texts are provided in LICENSES/
CAA (Certification Authority Authorization) was introduced in RFC 6844.
This has been obsoleted by RFC 8659. This commit added the possibility
to query CAA resource records with adig and adds a parser for CAA
records, that can be used in conjunction with ares_query(3).
Closes Bug: #292
Fix By: Daniela Sonnenschein (@lxdicted)
Originally started by Daniel Stenberg (@bagder) with #123, this patch reorganizes the c-ares source tree to have a more modern layout. It also fixes out of tree builds for autotools, and automatically builds the tests if tests are enabled. All tests are passing which tests each of the supported build systems (autotools, cmake, nmake, mingw gmake). There may be some edge cases that will have to be caught later on for things I'm not aware of.
Fix By: Brad House (@bradh352)
The rc4 function iterates over a buffer of size buffer_len who's maximum
value is INT_MAX with a counter of type short that is not guaranteed to
have maximum size INT_MAX.
In circumstances where short is narrower than int and where buffer_len
is larger than the maximum value of a short, it may be possible to loop
infinitely as counter will overflow and never be greater than or equal
to buffer_len.
The solution is to make the comparison be between types of equal width.
This commit defines counter as an int.
Fix By: Fionn Fitzmaurice (@fionn)
Brad House
Gregor Jasny
Oliver Welsh
Daniel Stenberg
Martin Holeš
Daniela Sonnenschein
Fionn Fitzmaurice