netdev - Re: IPv6 Destination Options question

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Message-ID: <CALx6S36PsbRW+Z0Eeh2Dtkb-hzXGekD-PLyML08g4xo5Vddvug@mail.gmail.com>
Date:   Sat, 14 Dec 2019 12:40:16 -0800
From:   Tom Herbert <tom@...bertland.com>
To:     Christoph Grenz <christophg+lkml@...nz-bonn.de>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: IPv6 Destination Options question

On Sat, Dec 14, 2019 at 8:19 AM Christoph Grenz
<christophg+lkml@...nz-bonn.de> wrote:
>
> Hello,
>
> I'm playing around with Mobile IPv6 and noticed a strange behaviour in the
> Linux network system when using IPv6 destination options:
>
> I'm able to send destination options on SOCK_DGRAM and SOCK_RAW sockets with
> sendmsg() and IPV6_DSTOPTS ancillary data. The sent packets also look correct
> in Wireshark.
>
> But I'm not able to receive packets with destination options on a socket with
> the IPV6_RECVDSTOPTS socket option enabled. Both a packet with a Home Address
> Option and a packet with an empty destination options header (only containing
> padding) won't be received on a socket for the payload protocol.

Christoph, Can you post your receive code?

Thanks

>
> Only a SOCK_RAW socket for IPPROTO_DSTOPTS receives the packet.
>
> I tested this on a vanilla 5.4.0 kernel and got the same behaviour. Activating
> dyndbg for everything in net/ipv6 didn't produce any relevant output in dmesg.
>
> Is this expected behaviour or a bug? Or do I maybe need some other socket
> option or a xfrm policy to receive packets with destination options?
>
> Best regards
> Christoph
>