Similar to local-service, but more strict. Listen only on localhost
unless other interface is specified. Has no effect when interface is
provided explicitly. I had multiple bugs fillen on Fedora, because I have
changed default configuration to:
interface=lo
bind-interfaces
People just adding configuration parts to /etc/dnsmasq.d or appending to
existing configuration often fail to see some defaults are already there.
Give them auto-ignored configuration as smart default.
Signed-off-by: Petr Menšík <pemensik@redhat.com>
Do not add a new parameter on command line. Instead add just parameter
for behaviour modification of existing local-service option. Now it
accepts two optional values:
- net: exactly the same as before
- host: bind only to lo interface, do not listen on any other addresses
than loopback.
By design, dnsmasq forwards queries for RR-types it has no data
on, even if it has data for the same domain and other RR-types.
This can lead to an inconsitent view of the DNS when an upstream
server returns NXDOMAIN for an RR-type and domain but the same domain
but a different RR-type gets an answer from dnsmasq. To avoid this,
dnsmasq converts NXDOMAIN answer from upstream to NODATA answers if
it would answer a query for the domain and a different RR-type.
An oversight missed out --synth-domain from the code to do this, so
--synth-domain=thekelleys.org.uk,192.168.0.0/24
would result in the correct answer to an A query for
192-168.0.1.thekelleys.org.uk and an AAAA query for the same domain
would be forwarded upstream and the resulting NXDOMAIN reply
returned.
After the fix, the reply gets converted to NODATA.
Thanks to Matt Wong for spotting the bug.
At startup, the leases file is read by lease_init(), and
in lease_init() undecorated hostnames are expanded into
FQDNs by adding the domain associated with the address
of the lease.
lease_init() happens relavtively early in the startup, party because
if it calls the dhcp-lease helper script, we don't want that to inherit
a load of sensitive file descriptors. This has implications if domains
are defined using the --domain=example.com,eth0 format since it's long
before we call enumerate_interfaces(), so get_domain fails for such domains.
The patch just moves the hostname expansion function to a seperate
subroutine that gets called later, after enumerate_interfaces().
Add the relevant information to the metrics and to the output of
dump_cache() (which is called when dnsmasq receives SIGUSR1).
Hence, users not collecting metrics will still be able to
troubleshoot with SIGUSR1. In addition to the current usage,
dump_cache() contains the information on the highest usage
since it was last called.
In bind-dynamic mode, its OK to fail to bind a socket to an address
given by --listen-address if no interface with that address exists
for the time being. Dnsmasq will attempt to create the socket again
when the host's network configuration changes.
The code used to ignore pretty much any error from bind(), which is
incorrect and can lead to confusing behaviour. This change make ONLY
a return of EADDRNOTAVAIL from bind() a non-error: anything else will be
fatal during startup phase, or logged after startup phase.
Thanks to Petr Menšík for the problem report and first-pass patch.
Bug report here:
https://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2023q4/017332.html
This error probably has no practical effect since even if the hash
is wrong, it's only compared internally to other hashes computed using
the same code.
Understanding the error:
hash-questions.c:168:21: runtime error: left shift of 128 by 24 places
cannot be represented in type 'int'
requires a certain amount of c-lawyerliness. I think the problem is that
m[i] = data[j] << 24
promotes the unsigned char data array value to int before doing the shift and
then promotes the result to unsigned char to match the type of m[i].
What needs to happen is to cast the unsigned char to unsigned int
BEFORE the shift.
This patch does that with explicit casts.
If the cache insertion process fails for any reason, any
blockdata storage allocated needs to be freed.
Thanks to Damian Sawicki for spotting the problem and
supplying patches against earlier releases. This patch by SRK,
and any bugs are his.
answer_request() builds answers in the same packet buffer
as the request. This means that any EDNS0 header from the
original request is overwritten. If the answer is in cache, that's
fine: dnsmasq adds its own EDNS0 header, but if the cache lookup fails
partially and the request needs to be sent upstream, it's a problem.
This was fixed a long, long time ago by running the cache
lookup twice if the request included an EDNS0 header. The first time,
nothing would be written to the answer packet, nad if the cache
lookup failed, the untouched question packet was still available
to forward upstream. If cache lookup succeeded, the whole thing
was done again, this time writing the data into the reply packet.
In a world where EDNS0 was rare and so was memory, this was a
reasonable solution. Today EDNS0 is ubiquitous so basically
every query is being looked up twice in the cache. There's also
the problem that any code change which makes successive cache lookups
for a query possibly return different answers adds a subtle hidden
bug, because this hack depends on absence of that behaviour.
This commit removes the lookup-twice hack entirely. answer_request()
can now return zero and overwrite the question packet. The code which
was previously added to support stale caching by saving a copy of the
query in the block-storage system is extended to always be active.
This handles the case where answer_request() returns no answer OR
a stale answer and a copy of the original query is needed to forward
upstream.
Caching an answer which has more that one RR, with at least
one answer being <=13 bytes and at least one being >13 bytes
can screw up the F_KEYTAG flag bit, resulting in the wrong
type of the address union being used and either a bad value
return or a crash in the block code.
Thanks to Dominik Derigs and the Pi-hole project for finding
and characterising this.
By default TCP connect takes minutes to fail when trying to
connect a server which is not responding and for which the
network layer doesn't generate HOSTUNREACH errors.
This is doubled because having failed to connect in FASTOPEN
mode, the code then tries again with a call to connect().
We set TCP_SYNCNT to 2, which make the timeout about 10 seconds.
This in an unportable Linux feature, so it doesn't work on other
platforms.
No longer try connect() if sendmsg in fastopen mode fails with
ETIMEDOUT or EHOSTUNREACH since the story will just be the same.
On 15/5/2023 8.8.8.8 was returning SERVFAIL for a query on ec.europa.eu
ec.europa.eu is not a domain cut, that happens at jrc.ec.europa.eu. which
does return a signed proof of non-existance for a DS record.
Abandoning the search for a DS or proof of non existence at ec.europa.eu
renders everything within that domain BOGUS, since nothing is signed.
This code changes behaviour on a SERVFAIL to continue looking
deeper for a DS or proof of its nonexistence.
After replying with stale data, dnsmasq sends the query upstream to
refresh the cache asynchronously and sometimes sends the wrong packet:
packet length can be wrong, and if an EDE marking stale data is added
to the answer that can end up in the query also. This bug only seems
to cause problems when the usptream server is a DOH/DOT proxy. Thanks
to Justin He for the bug report.
If I configure dnsmasq to use dbus and then restart dbus.service with watchers present,
it crashes dnsmasq. The reason is simple, it uses loop to walk over watchers to call
dbus handling code. But from that code the same list can be modified and watchers removed.
But the list iteration continues anyway.
Restart the loop if list were modified.
A NXDOMAIN answer recieved over TCP by a child process would
be correctly sent back to the master process which would then
fail to insert it into the cache.
the compiler padding it with an extra 8 bytes.
Use the F_KEYTAG flag in a a cache record to discriminate between
an arbitrary RR stored entirely in the addr union and one
which has a point to block storage.
