When a request matching the clid or mac address is
recieved the server will iterate over all candidate
addresses until it find's one that is not already
leased to a different clid/iaid and advertise
this address.
Using multiple reservations for a single host makes it
possible to maintain a static leases only configuration
which support network booting systems with UEFI firmware
that request a new address (a new SOLICIT with a new IA_NA
option using a new IAID) for different boot modes, for
instance 'PXE over IPv6', and 'HTTP-Boot over IPv6'. Open
Virtual Machine Firmware (OVMF) and most UEFI firmware
build on the EDK2 code base exhibit this behaviour.
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.
In an era where everything has an MMU, this looks like
an anachronism, and it adds to (Ok, multiplies!) the
combinatorial explosion of compile-time options.
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.
Change anti cache-snooping behaviour with queries with the
recursion-desired bit unset. Instead to returning SERVFAIL, we
now always forward, and never answer from the cache. This
allows "dig +trace" command to work.
Dnsmasq does pass on the do-bit, and return DNSSEC RRs, irrespective
of of having DNSSEC validation compiled in or enabled.
The thing to understand here is that the cache does not store all the
DNSSEC RRs, and dnsmasq doesn't have the (very complex) logic required
to determine the set of DNSSEC RRs required in an answer. Therefore if
the client wants the DNSSEC RRs, the query can not be answered from
the cache. When DNSSEC validation is enabled, any query with the
do-bit set is never answered from the cache, unless the domain is
known not to be signed: the query is always forwarded. This ensures
that the DNSEC RRs are included.
The same thing should be true when DNSSEC validation is not enabled,
but there's a bug in the logic.
line 1666 of src/rfc1035.c looks like this
if ((crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG)) || !do_bit || !(crecp->flags & F_DNSSECOK))
{ ...answer from cache ... }
So local stuff (hosts, DHCP, ) get answered. If the do_bit is not set
then the query is answered, and if the domain is known not to be
signed, the query is answered.
Unfortunately, if DNSSEC validation is not turned on then the
F_DNSSECOK bit is not valid, and it's always zero, so the question
always gets answered from the cache, even when the do-bit is set.
This code should look like that at line 1468, dealing with PTR queries
if ((crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG)) ||
!do_bit ||
(option_bool(OPT_DNSSEC_VALID) && !(crecp->flags & F_DNSSECOK)))
where the F_DNSSECOK bit is only used when validation is enabled.
It's OK for NSEC records to be expanded from wildcards,
but in that case, the proof of non-existence is only valid
starting at the wildcard name, *.<domain> NOT the name expanded
from the wildcard. Without this check it's possible for an
attacker to craft an NSEC which wrongly proves non-existence
in a domain which includes a wildcard for NSEC.
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>
