The idea of this option was already discussed years ago on the mailing
list:
https://dnsmasq-discuss.thekelleys.org.narkive.com/ZoFQNaGo/always-ignore-client-identifier#post4
In our production environnement, we discovered that some devices are
using 'client identifier' not unique at all, resulting on IP addresses
conflicts between several devices (we saw up to four devices using same
IP address).
The root cause is probably a buggy operating system/configuration of
decices, but this patch add a configuration workaround on server side
when fixing clients is impossible.
Signed-off-by: Charles Daymand <charles.daymand@wifirst.fr>
Signed-off-by: Florent Fourcot <florent.fourcot@wifirst.fr>
In a reply proving that a DS doesn't exist, it doesn't matter if RRs
in the auth section _other_ than NSEC/NSEC3 are not signed. We can't
set the AD flag when returning the query, but it still proves
that the DS doesn't exist for internal use.
As one of the RRs which may not be signed is the SOA record, use the
TTL of the NSEC record to cache the negative result, not one
derived from the SOA.
Thanks to Tore Anderson for spotting and diagnosing the bug.
- aligned the handling of UBus connections with the DBus code as it
makes it a bit easier to comprehend;
- added logging to the various UBus calls to aid debugging from an
enduser point of view, but be careful to not flood the logs;
- show the (lack of) support for UBus in the configuration string.
Dear Simon,
the attached patch removes three redundant prototypes from dnsmasq.h. There is no functional change.
Best regards,
Dominik
From c0b2ccfd20c4eec9d09468fdfe9b4ca8a8f8591e Mon Sep 17 00:00:00 2001
From: DL6ER <dl6er@dl6er.de>
Date: Sun, 10 Mar 2019 19:34:07 +0100
Subject: [PATCH] Remove redundant prototypes from dnsmasq.h
Signed-off-by: DL6ER <dl6er@dl6er.de>
It is possible for a config entry to have one address family specified by a
dhcp-host directive and the other added from /etc/hosts. This is especially
common on OpenWrt because it uses odhcpd for DHCPv6 and IPv6 leases are
imported into dnsmasq via a hosts file.
To handle this case there need to be separate *_HOSTS flags for IPv4 and IPv6.
Otherwise when the hosts file is reloaded it will clear the CONFIG_ADDR(6) flag
which was set by the dhcp-host directive.
This moves the class argument to cache-insert into an argument,
rather then overloading a union in the address argument. Note that
tha class is NOT stored in the cache other than for DS/DNSKEY entries,
so must always be C_IN except for these. The data-extraction code
ensures this as it only attempts to cache C_IN class records.
Make options bits derived from size and count. Use size of option bits
and last supported bit in computation. No new change would be required
when new options are added. Just change OPT_LAST constant.
This was the source of a large number of #ifdefs, originally
included for use with old embedded libc versions. I'm
sure no-one wants or needs IPv6-free code these days, so this
is a move towards more maintainable code.
For ease of implementaion, dnsmasq has always forked a new process to
handle each incoming TCP connection. A side-effect of this is that any
DNS queries answered from TCP connections are not cached: when TCP
connections were rare, this was not a problem. With the coming of
DNSSEC, it's now the case that some DNSSEC queries have answers which
spill to TCP, and if, for instance, this applies to the keys for the
root then those never get cached, and performance is very bad. This
fix passes cache entries back from the TCP child process to the main
server process, and fixes the problem.
These normally have enough space for a name of up to SMALLDNAME characters.
When used to hold /etc/hosts entries, they are allocated with just enough
bytes for the name held. When used to hold other configured stuff, (CNAMES
DS records. DHCP names etc), the name is replaced by a pointer to a string
held elsewhere, and F_NAMEP set. Hence only enough space to hold a char *
is needed, rather than SMALLDNAME bytes.
When a record is defined locally, eg an A record for one.two.example then
we already know that if we forward, eg an AAAA query for one.two.example,
and get back NXDOMAIN, then we need to alter that to NODATA. This is handled
by check_for_local_domain(). But, if we forward two.example, because
one.two.example exists, then the answer to two.example should also be
a NODATA.
For most local records this is easy, just to substring matching.
for A, AAAA and CNAME records that are in the cache, it's more difficult.
The cache has no efficient way to find such records. The fix is to
insert empty (none of F_IPV4, F_IPV6 F_CNAME set) records for each
non-terminal.
The same considerations apply in auth mode, and the same basic mechanism
is used there too.
If we're talking to upstream servers from a fixed port, specified by query-port
we create the fds to do this once, before dropping root, so that ports <1024 can be used.
But we call check_servers() before reading /etc/resolv.conf, so if the only servers
are in resolv.conf, at that point there will be no servers, and the fds get garbage
collected away, only to be recreated (but without root) after we read /etc/resolv.conf
Make pre-allocated server fds immortal, to avoid this problem.
The current logic is naive in the case that there is more than
one RRset in an answer (Typically, when a non-CNAME query is answered
by one or more CNAME RRs, and then then an answer RRset.)
If all the RRsets validate, then they are cached and marked as validated,
but if any RRset doesn't validate, then the AD flag is not set (good) and
ALL the RRsets are cached marked as not validated.
This breaks when, eg, the answer contains a validated CNAME, pointing
to a non-validated answer. A subsequent query for the CNAME without do
will get an answer with the AD flag wrongly reset, and worse, the same
query with do will get a cached answer without RRSIGS, rather than
being forwarded.
The code now records the validation of individual RRsets and that
is used to correctly set the "validated" bits in the cache entries.
dnsmasq allows to specify a interface for each name server passed with
the -S option or pushed through D-Bus; when an interface is set,
queries to the server will be forced via that interface.
Currently dnsmasq uses SO_BINDTODEVICE to enforce that traffic goes
through the given interface; SO_BINDTODEVICE also guarantees that any
response coming from other interfaces is ignored.
This can cause problems in some scenarios: consider the case where
eth0 and eth1 are in the same subnet and eth0 has a name server ns0
associated. There is no guarantee that the response to a query sent
via eth0 to ns0 will be received on eth0 because the local router may
have in the ARP table the MAC address of eth1 for the IP of eth0. This
can happen because Linux sends ARP responses for all the IPs of the
machine through all interfaces. The response packet on the wrong
interface will be dropped because of SO_BINDTODEVICE and the
resolution will fail.
To avoid this situation, dnsmasq should only restrict queries, but not
responses, to the given interface. A way to do this on Linux is with
the IP_UNICAST_IF and IPV6_UNICAST_IF socket options which were added
in kernel 3.4 and, respectively, glibc versions 2.16 and 2.26.
Reported-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Beniamino Galvani <bgalvani@redhat.com>
Fix heap overflow in DNS code. This is a potentially serious
security hole. It allows an attacker who can make DNS
requests to dnsmasq, and who controls the contents of
a domain, which is thereby queried, to overflow
(by 2 bytes) a heap buffer and either crash, or
even take control of, dnsmasq.
