Handling events on file descriptors can result in new file
descriptors being created or old ones being deleted. As such
the results of the last call to poll() become invalid in subtle
ways.
After handling each file descriptor in check_dns_listeners()
return, to go around the poll() loop again and get valid data
for the new situation.
Thanks to Dominik Derigs for his indefatigable sleuthing of this one.
I have no memory for why this was ever there. It breaks DNSSEC
validation of large RRsets.
I can't see any DoS potential that is exposed by removing it.
Print a specific INFO message instead of a generic WARNING message,
so users aren't inconvenienced and maintainers know what to do.
Debian currently runs this service as part of NetworkManager,
in a systemd service without CAP_CHOWN. Other distributions may
have the same problem, or might add the issue in future.
This fix should communicate the issue clearly to them.
I misread the man page for socket(7) and TCP timeouts.
A timeout generates a -1 return and EAGAIN errno, NOT a short read.
Short reads are legit, and aborting when they are seen creates
hard-to-reproduce errors.
If dnsmasq is configured to add an EDNS client subnet to a query,
it is careful to suppress use of the cache, since a cached answer may
not be valid for a query with a different client subnet.
Extend this behaviour to queries which arrive a dnsmasq
already carrying an EDNS client subnet.
This change is rather more involved than may seem necessary at first sight,
since the existing code relies on all queries being decorated by dnsmasq
and therefore not cached, so there is no chance that an incoming query
might hit the cache and cache lookup don't need to be suppressed, just
cache insertion. When downstream queries may be a mix of client-subnet
bearing and plain vanilla, it can't be assumed that the answers are never
in the cache, and queries with subnets must not do lookups.
I am attaching an incremental git-am ready patch to go on top your Git HEAD,
to fix all sorts of issues and make this conforming C99 with default
options set,
and fix another load of warnings you receive when setting the compiler
to pick the nits,
-pedantic-errors -std=c99 (or c11, c18, c2x).
It changes many void * to uint8_t * to make the "increment by bytes"
explicit.
You can't do:
void *foo;
// ...
foo += 2.
The make target 'install-common' expects results from the target 'all'.
A 'make -j install' may fail because both targets are brought
up-to-todate in parallel. As a result the final binary will not exist at
the time 'install-common' runs, because 'all' is not yet done.
Adjust the dependencies to update 'all' before processing 'install-common'.
Signed-off-by: Olaf Hering <olaf@aepfle.de>
Not doing so can result in a use after free since the name for DHCP
derived DNS records is represented as a pointer into the DHCP lease
table. Update will only happen when necessary since lease_update_dns
tests internally on dns_dirty and the force argument is zero.
Signed-off-by: Erik Karlsson <erik.karlsson@iopsys.eu>
We can't answer and shouldn't forward non-QUERY DNS requests.
This patch fixes handling such requests from TCP connections; before
the connection would be closed without reply.
It also changes the RCODE in the answer from REFUSED to NOTIMP and
provides clearer logging.
When DNSEC validation is enabled, but a query is not validated
because it gets forwarded to a non-DNSEC-capable upstream
server, the rr_status array is not correctly cleared, with
the effect that the answer may be maked as DNSSEC validated
if the immediately preceding query was DNS signed and validated.
When using PXE proxy-DHCP, dnsmasq supplies PXE information to
the client, which also talks to another "normal" DHCP server
for address allocation and similar. The normal DHCP server may
be on the local network, but it may also be remote, and accessed via
a DHCP relay. This change allows dnsmasq to act as both a
PXE proxy-DHCP server AND a DHCP relay for the same network.
This acts almost exactly like --dhcp-option except that the defined option
is only sent when replying to PXE clients. More importantly, these
options are sent in reply PXE clients when dnsmasq in acting in PXE
proxy mode. In PXE proxy mode, the set of options sent is defined by
the PXE standard and the normal set of options is not sent. This config
allows arbitrary options in PXE-proxy replies. A typical use-case is
to send option 175 to iPXE. Thanks to Jason Berry for finding the
requirement for this.
A bug in gentoo linux https://bugs.gentoo.org/945183 reported that dnsmasq 2.90 fails to compile with GCC 15.
The issue is that while previous versions of GCC defaulted to the C17 standard and C23 could be selected with
"-std=c23" or "-std=gnu23", GCC 15 defaults to C23. In C23 incompatible pointer types are an error instead of
a warning, so the "int (*callback)()" incomplete prototypes cause errors.
For example, compiling dnsmasq 2.90 with gcc 14.2.1 and "-std=gnu23" fails with errors such as:
lease.c: In function `lease_find_interfaces':
lease.c:467:34: warning: passing argument 3 of `iface_enumerate' from incompatible pointer type [-Wincompatible-pointer-types[https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wincompatible-pointer-types]]
467 | iface_enumerate(AF_INET, &now, find_interface_v4);
| ^~~~~~~~~~~~~~~~~
| |
| int (*)(struct in_addr, int, char *, struct in_addr, struct in_addr, void *)
In file included from lease.c:17:
dnsmasq.h:1662:50: note: expected `int (*)(void)' but argument is of type `int (*)(struct in_addr, int, char *, struct in_addr, struct in_addr, void *)'
1662 | int iface_enumerate(int family, void *parm, int (callback)());
| ~~~~~^~~~~~~~~~~
This patch uses a typedef'ed union of pointer types to get type checking of the pointers. If that's too complicated,
another way might be to use (void *) casts to disable type checking.
Also, some of the IPv6 callbacks had "int preferred, int valid" and some had
"unsigned int preferred, unsigned int valid". This patch changes them all to "unsigned int"
so they're the same and to avoid casting "u32" to "int", eg:
u32 preferred = 0xffffffff;
callback(..., (int)preferred, ...)
Even if those cast values aren't used in the callback, casting u32 to "int" feels bad, especially if "int" is 32 bits.
When deriving a domain name from an IPv6 address, an address
such as 1234:: would become 1234--.example.com, which is
not legal in IDNA2008. Stop using the :: compression method,
so 1234:: becomes
1234-0000-0000-0000-0000-0000-0000-0000.example.com
Timeouts for TCP connections to non-responive servers are very long.
This in not appropriate for DNS connections.
Set timeouts for connection setup, sending data and recieving data.
The timeouts for connection setup and sending data are set at 5 seconds.
For recieving the reply this is doubled, to take into account the
time for usptream to actually get the answer.
Thanks to Petr Menšík for pointing out this problem, and finding a better
and more portable solution than the one in place heretofore.
In the post 2020 flag-day world, we limit UDP packets to 1232 bytes
which can go anywhere, so the dodgy code to try and determine the
functional maxmimum packet size on the path from upstream servers
is obsolete.
