Re: [PATCH v5 net-next 2/3] icmp: ICMPV6: Examine invoking packet for Segment Route Headers.

[Willem de Bruijn <willemb@google.com>]

On Mon, Jan 3, 2022 at 12:34 PM David Ahern <dsahern@gmail.com> wrote:
>
> On 1/3/22 10:11 AM, Andrew Lunn wrote:
> > RFC8754 says:
> >
> > ICMP error packets generated within the SR domain are sent to source
> > nodes within the SR domain.  The invoking packet in the ICMP error
> > message may contain an SRH.  Since the destination address of a packet
> > with an SRH changes as each segment is processed, it may not be the
> > destination used by the socket or application that generated the
> > invoking packet.
> >
> > For the source of an invoking packet to process the ICMP error
> > message, the ultimate destination address of the IPv6 header may be
> > required.  The following logic is used to determine the destination
> > address for use by protocol-error handlers.
> >
> > *  Walk all extension headers of the invoking IPv6 packet to the
> >    routing extension header preceding the upper-layer header.
> >
> >    -  If routing header is type 4 Segment Routing Header (SRH)
> >
> >       o  The SID at Segment List[0] may be used as the destination
> >          address of the invoking packet.
> >
> > Mangle the skb so the network header points to the invoking packet
> > inside the ICMP packet. The seg6 helpers can then be used on the skb
> > to find any segment routing headers. If found, mark this fact in the
> > IPv6 control block of the skb, and store the offset into the packet of
> > the SRH. Then restore the skb back to its old state.
> >
> > Signed-off-by: Andrew Lunn <andrew@lunn.ch>
> > ---
> >  include/linux/ipv6.h |  2 ++
> >  include/net/seg6.h   |  1 +
> >  net/ipv6/icmp.c      |  6 +++++-
> >  net/ipv6/seg6.c      | 30 ++++++++++++++++++++++++++++++
> >  4 files changed, 38 insertions(+), 1 deletion(-)
> >
>
> Reviewed-by: David Ahern <dsahern@kernel.org>
>
Reviewed-by: Willem de Bruijn <willemb@google.com>