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)
c-ares does not have any concept of thread-safety. It has always been 100% up to the implementor to ensure they never call c-ares from more than one thread at a time. This patch adds basic thread-safety support, which can be disabled at compile time if not desired. It uses a single recursive mutex per channel, which should be extremely quick when uncontested so overhead should be minimal.
Fixes Bug: #610
Also sets the stage to implement #611
Fix By: Brad House (@bradh352)
When building for UWP (WindowsStore), additional headers are needed and some functions are not available. This also adds AppVeyor CI/CD support to catch these issues in the future.
Fix By: Deal (@halx99) and Brad House (@bradh352)
AppVeyor was using Visual Studio 2015 along with old versions of MinGW. Update to the latest AppVeyor provides and also add an MSYS2 build test using MinGW which will use the bleeding edge version.
When researching #590 this also uncovered a bug in cmake not properly detecting if_indextoname() on windows. This has been corrected as well as the underlying issue reported in #590.
Fix By: Brad House (@bradh352) and Jonas Kvinge (@jonaski)
HOSTS FILE PROCESSING OVERVIEW
==============================
The hosts file on the system contains static entries to be processed locally
rather than querying the nameserver. Each row is an IP address followed by
a list of space delimited hostnames that match the ip address. This is used
for both forward and reverse lookups.
We are caching the entire parsed hosts file for performance reasons. Some
files may be quite sizable and as per Issue #458 can approach 1/2MB in size,
and the parse overhead on a rapid succession of queries can be quite large.
The entries are stored in forwards and backwards hashtables so we can get
O(1) performance on lookup. The file is cached until the file modification
timestamp changes (or 60s if there is no implemented stat() capability).
The hosts file processing is quite unique. It has to merge all related hosts
and ips into a single entry due to file formatting requirements. For
instance take the below:
```
127.0.0.1 localhost.localdomain localhost
::1 localhost.localdomain localhost
192.168.1.1 host.example.com host
192.168.1.5 host.example.com host
2620🔢:1 host.example.com host6.example.com host6 host
```
This will yield 2 entries.
1) ips: `127.0.0.1,::1`
hosts: `localhost.localdomain,localhost`
2) ips: `192.168.1.1,192.168.1.5,2620🔢:1`
hosts: `host.example.com,host,host6.example.com,host6`
It could be argued that if searching for `192.168.1.1` that the `host6`
hostnames should not be returned, but this implementation will return them
since they are related (both ips have the fqdn of host.example.com). It is
unlikely this will matter in the real world.
Fix By: Brad House (@bradh352)
c-ares was missing a couple of common compiler warnings during building that are widely recognized as a best practice. This PR makes no code changes, only build system changes to increase warning levels.
This PR does cause some new warnings to be emitted, a follow-up PR will address those.
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/
* segment random number generation into own file
* abstract random code to make it more modular so we can have multiple backends
* rand: add support for arc4random_buf() and also direct CARES_RANDOM_FILE reading
* autotools: fix detection of arc4random_buf
* rework initial rc4 seed for PRNG as last fallback
* rc4: more proper implementation, simplified for clarity
* clarifications
* CARES_RANDOM_FILE should always default to /dev/urandom
During cross-compilation, CARES_RANDOM_FILE may not be able to be appropriately
detected, therefore we should always set it to /dev/urandom and allow the
entity requesting compilation override the value. The code does appropriately
fall back if CARES_RANDOM_FILE cannot be opened.
* use set not option
There is no autoconf macro called STDC_HEADERS. AC_HEADER_STDC however does
exist and it defines the STDC_HEADERS macro for use.
Not clear that STDC_HEADERS from its use in the repo is needed but
would rather not meddle with it for now.
Fixes an annoying warning on `./configure`:
```
/var/tmp/portage/net-dns/c-ares-1.18.1/work/c-ares-1.18.1/configure: 24546: STDC_HEADERS: not found
```
Signed-off-by: Sam James <sam@gentoo.org>
RANDOM_FILE was never defined by cmake, causing RC4 key generation to use the less secure rand() method.
Also, due to clashes with chain-building from other projects (e.g. curl) that may define RANDOM_FILE, this was renamed to CARES_RANDOM_FILE.
This is the proposed change for #396
Fix By: Brad House (@bradh352)
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
Christian Clauss
Daniel Stenberg
Ben Noordhuis
Sam James
Felix Yan
dhrumilrana
Fionn Fitzmaurice