search

openwrt / odhcpd

This repository is a mirror of https://git.openwrt.org/?p=project/odhcpd.git. Pull requests will be accepted which will be merged in odhcpd.git
GNU General Public License v2.0
160 stars 96 forks source link

mdhcp6 client not getting a stateful IP #121

Closed ThiefMaster closed 5 years ago

ThiefMaster commented 5 years ago

Since updating to the latest OpenWRT a few weeks ago, I noticed that my Axis IP cameras do not get a stateful IPv6 anymore, which worked fine before.

Since they receive NOTONLINK responses, I have the feeling that the issue got introduced with a2ffc5986cd35bea983b81b28b8a656e3b81fdf1. Might be a shitty dhcpv6 implementation on the camera, I don't know and I'm not familiar enough with DHCPv6 to see a bad implementation just from looking at the code.

The code of the "mdhcp6" client the camera uses is available in this git repo. Not sure if it's 100% up to date though, but I can reproduce the issue reliably.

Here's a pcap on my older router running LEDE 17.01.3: mdhcp6-lede-17.01.3.pcap.gz The advertise/request messages don't contain anything related to the configured IP (via the 'hostid' option), but the final reply contains the correct IP.

And here's a pcap on another router running the latest OpenWRT 18.06.1, coming from the exact same mdhcp6 client (just running on a different machine since they are different networks, hence the different DUID): mdhcp6-openwrt-18.06.1.pcap.gz

I'm not sure where the problem is - in the server or the client (more likely, since all other dhcpv6 clients work perfectly fine). But I'd appreciate some help - if it's a bug in the client (not sending any IA_NA requests in the solicit seems strange to me), I'd like to forward details to the camera vendor. They release firmware updates quite often so I think the chance that they actually fix their dhcpv6 client if it's broken is quite high.

dedeckeh commented 5 years ago

Closing; see https://bugs.openwrt.org/index.php?do=details&task_id=2060 for further details

ThiefMaster commented 5 years ago

Thanks a lot!

Copying your reply here just in case someone else has the issue and finds this issue on google:

The behavior by the mdhcp6 client implementation is quite odd as you would expect it to include an IA_NA option in the solicit message.

RFC3315 states in paragraph 17.1.1 :

The client MUST include a Client Identifier option to identify itself to the server. The client includes IA options for any IAs to which it wants the server to assign addresses. The client MAY include addresses in the IAs as a hint to the server about addresses for which the client has a preference. The client MUST NOT include any other options in the Solicit message, except as specifically allowed in the definition of individual options.

By doing so the DHCPv6 server can create a lease binding when receiving solicit message and include the binding in the advertise message.

Nevertheless RFC3315 does not seem to exclude sending solicit messages without IA_NA options as paragraph 17.2.2 states :

If the Solicit message from the client included one or more IA options, the server MUST include IA options in the Advertise message containing any addresses that would be assigned to IAs contained in the Solicit message from the client.

As a result I've changed the implementation it will not return a "not on link" status if no address or prefix is included in the request message (https://git.openwrt.org/?p=project/odhcpd.git;a=commit;h=1893905f6a9b699ae0f1813670e93bf4ec3402e9)