content-type: text/plain; charset="utf-8"
X-RT-Original-Encoding: utf-8
Content-Length: 2023

On Tue, Jul 17, 2018 at 11:40 AM, DHCP Bugs via RT
<dhcp-confidential@isc.org> wrote:
> Greetings,
>
> This message was automatically generated to acknowledge receipt of
> your recent email
>  "dhcpv6 may ignore requests when there are interface aliases",
> and to let you know that we have opened a ticket for your request
> (a summary of which appears below.)
>
> We do not need a further response from you at this time, but if you
> do respond, please include in the Subject of your reply the ID
>    '[ISC-Bugs #47957]'
> so that we can match up your reply with the ticket in our system.
>
>
> Hi,
>
> I run a dhcpv6 server (package dhcp-server-4.3.6-20.fc28.x86_64 from
> fedora, kernel 4.17.*) for the purpose of delegating prefixes to my
> wifi network (Google wifi).  This worked fine until I added an
> interface alias on the server in order to add an additional ipv4
> address; the server then failed to respond to SOLICIT packets.
>
> As the alias has no ipv6 address (for v6, the kernel keeps all the
> details with the parent interface and ignores aliases), the dhcp
> server ignores incoming requests if they are thought to have come in
> on the alias.  Unfortunately, the pktinfo data attached to the packets
> identifies the alias as the incoming interface.
>
> See attached patch for a suggested fix that was verified to work on my
> network.  If the interface identified by the pktinfo data is an alias,
> find the parent interface and use that instead.
>
> Note that independently of this workaround, it is possibly something
> that should be fixed in the kernel, as it doesn't seem right to
> identify an interface that doesn't have an ipv6 interface as the
> source of packets.
>
> Thanks,
> Marc
>
>

Having looked into it a bit further, this is really a dhcpd issue.

I noticed that there is code to map alias names to the parent name,
but it's inside a section that is only compiled for Solaris afaict.

See attached patch for an alternate fix; not sure if this could have
other side effects.

Marc