The retry timeout values were using a fixed calculation which could cause multiple simultaneous queries to timeout and retry at the exact same time. If a DNS server is throttling requests, this could cause the issue to never self-resolve due to all requests recurring at the same instance again.
This PR also creates a maximum timeout option to make sure the random value selected does not exceed this value.
Fix By: Ignat (@Kontakter)
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)
adig previously performed manual parsing of the DNS records. Now it can focus strictly on formatting of output data for printing. It simply iterates across the parsed DNS packet and queries for the RRs, parameters for each RR, and the datatypes for each parameter. adig will now automatically pick up new RRs from the c-ares library due to the dynamic nature.
The adig format also now more closely resembles that of BIND's `dig` output.
A few more helpers needed to be added to the c-ares library that were missing. There ware a couple of minor bugs and enhancements also needed.
Example:
```
./adig -t ANY www.google.com
; <<>> c-ares DiG 1.21.0 <<>> www.google.com
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: RCODE, id: 23913
;; flags: qr rd ra; QUERY: 1, ANSWER: 11, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags: 0; udp: 512
;; QUESTION SECTION:
;www.google.com. IN ANY
;; ANSWER SECTION:
www.google.com. 162 IN A 142.251.107.99
www.google.com. 162 IN A 142.251.107.105
www.google.com. 162 IN A 142.251.107.103
www.google.com. 162 IN A 142.251.107.147
www.google.com. 162 IN A 142.251.107.104
www.google.com. 162 IN A 142.251.107.106
www.google.com. 162 IN AAAA 2607:f8b0:400c:c32::93
www.google.com. 162 IN AAAA 2607:f8b0:400c:c32::69
www.google.com. 162 IN AAAA 2607:f8b0:400c:c32::68
www.google.com. 162 IN AAAA 2607:f8b0:400c:c32::6a
www.google.com. 21462 IN HTTPS 1 . alpn="h2,h3"
;; MSG SIZE rcvd: 276
```
Fix By: Brad House (@bradh352)
This PR makes the c-ares parser introduced in 1.21, and the new writer, along with associated helpers public. These helpers are contained in a new public header of `ares_dns_record.h` which should _**not**_ be included directly, instead simply including `ares.h` is sufficient. This will address #587, as well as #470.
A follow-up PR will be made which will transform `adig` to use the new parsers and helpers.
This PR does not currently add man pages for these public functions, that will be in a follow-up PR once the `adig` migration is done which may expose additional needed helpers.
The two aforementioned PRs will be done before the 1.22 release.
Fix By: Brad House (@bradh352)
The OPT RR record has some seldom used options with a 16bit key and a binary value. The current parser and writer was not supporting this. This PR adds support. The same format is also used for SVCB/HTTPS records, so getting this in there is necessary to support that RR type.
Also, we split the Binary record format into BIN and BINP, where BINP is an indicator that the binary data is _likely_ printable and will guarantee a NULL terminator. This is helpful for those attempting to print RRs.
Fix By: Brad House (@bradh352)
As per #470, c-ares is missing a parser for the TLSA record format (RFC 6698). This PR introduces that parser.
Once the new parser interface becomes public and this PR is merged, then #470 can be closed.
Fix By: Brad House (@bradh352)
The `ares_dns_record_t` data structure created in the prior release is capable of holding a complete parsed DNS message and also provides all helpers in order to fill in the data structure. This PR adds write capabilities for this data structure to form a complete message and supports features such as DNS name compression as defined in RFC1035. Though this message writing capability goes further than c-ares internally needs, external users may find it useful ... and we may find it useful for test validation as well.
This also replaces the existing message writing code in `ares_create_query()`, as well rewriting the request message without EDNS in ares_process.c's `process_answer()`.
Fix By: Brad House (@bradh352)
All DNS servers support EDNS, by using this by default, it will allow larger responses without the need to switch to TCP. If by chance a DNS server is hit that doesn't support EDNS, this is detected due to the lack of the OPT RR in the response and will be automatically retried without EDNS.
Fix By: Brad House (@bradh352)
`ares_channel` is defined as `typedef struct ares_channeldata *ares_channel;`. The problem with this, is it embeds the pointer into the typedef, which means an `ares_channel` can never be declared as `const` as if you write `const ares_channel channel`, that expands to `struct ares_channeldata * const ares_channel` and not `const struct ares_channeldata *channel`.
We will now typedef `ares_channel_t` as `typedef struct ares_channeldata ares_channel_t;`, so if you write `const ares_channel_t *channel`, it properly expands to `const struct ares_channeldata *channel`.
We are maintaining the old typedef for API compatibility with existing integrations, and due to typedef expansion this should not even cause any compiler warnings for existing code. There are no ABI implications with this change. I could be convinced to keep existing public functions as `ares_channel` if a sufficient argument exists, but internally we really need make this change for modern best practices.
This change will allow us to internally use `const ares_channel_t *` where appropriate. Whether or not we decide to change any public interfaces to use `const` may require further discussion on if there might be ABI implications (I don't think so, but I'm also not 100% sure what a compiler internally does with `const` when emitting machine code ... I think more likely ABI implications would occur going the opposite direction).
FYI, This PR was done via a combination of sed and clang-format, the only manual code change was the addition of the new typedef, and a couple doc fixes :)
Fix By: Brad House (@bradh352)
Brad House
Ignat