There was discussion in the past regarding DHCPv6 NTP server option
which needs special subclassing per RFC5908.
Patch adds support for unicast, multicast IPv6 address and for FQDN string,
preserving possibly used (as suggested earlier) hex value.
Unfortunately it's still not fully free from limitations - only address list or
only fqdn value list is possible, not mixed due current
state option parsing & flagging.
rfc3315.c:1711:28: warning: use of logical '&&' with constant operand [-Wconstant-logical-operand]
if (!(addr_list->flags && ADDRLIST_DECLINED) ||
^ ~~~~~~~~~~~~~~~~~
It's a flag bit so should be bitwise '&' operator
Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
When dhcp-host options can have many IPv6 addresses, we need
to deal with one of them being declined by a client. The other
addresses are still valid.
It seems that this logic never worked, even with only one address, since
the DECLINED flag was never tested.
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.
Fix information leak in DHCPv6. A crafted DHCPv6 packet can
cause dnsmasq to forward memory from outside the packet
buffer to a DHCPv6 server when acting as a relay.
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.
While testing https://github.com/sbyx/odhcp6c client I have noticed it
permanently crashes after startup.
The reason was it (odhcp6c) doesn't expect empty IA options in ADVERTISE
message without any suboptions.
Despite this validation bug of odhcp6c, dnsmasq should not generate
ADVERTISE messages with IA if there's nothing to advert per RFC 3315
17.2.2:
If the server will not assign any addresses to any IAs in a
subsequent Request from the client, the server MUST send an Advertise
message to the client that includes only a Status Code option with
code NoAddrsAvail and a status message for the user, a Server
Identifier option with the server's DUID, and a Client Identifier
option with the client's DUID.
Meanwhile it's need to add status code for every IA in REPLY message per
RFC3315 18.2.1:
If the server cannot assign any addresses to an IA in the message
from the client, the server MUST include the IA in the Reply message
with no addresses in the IA and a Status Code option in the IA
containing status code NoAddrsAvail.
So, I've changed the logic to skip IA completely from ADVERTISE messages and
to add NoAddrsAvail subcode into IA of REPLY messages.
As for overhead, yes, I believe it's ok to return NoAddrsAvail twice in IA
and in global section for compatibility with all old and new clients.
Vladislav Grishenko