Re: [PATCH net-next 2/5] seg6: handle a consumed SRH in SRv6 End with the PSP flavor

[Hangbin Liu <hangbin.liu@linux.dev>]

On Mon, Oct 12, 2026 at 11:40:39PM +0200, Andrea Mayer wrote:
> On Mon, 12 Oct 2026 17:28:06 +0800
> Hangbin Liu <hangbin.liu@linux.dev> wrote:
> 
> > [snip]
> > >  
> > > +/* look up the SRH to be processed by the RFC8986 flavors. As End does, a
> > > + * routing header with SL = 0 is skipped (e.g. an SRH already consumed).
> > > + * This function returns NULL when no valid SRH is found.
> > > + */
> > > +static struct ipv6_sr_hdr *seg6_flv8986_get_srh(struct sk_buff *skb)
> > > +{
> > > +	struct ipv6_sr_hdr *srh;
> > > +
> > > +	srh = seg6_get_srh(skb, IP6_FH_F_SKIP_RH);
> > > +	if (srh)
> > > +		return srh;
> > > +
> > > +	/* we take the first routing header without skipping it. In this way,
> > > +	 * seg6_get_srh_pktinfo() reports SL = 0 and not a missing SRH.
> > > +	 */
> > > +	return seg6_get_srh(skb, 0);
> > > +}
> > > +
> > >  /* process the packet on the basis of the RFC8986 flavors set for the given
> > >   * SRv6 End behavior instance.
> > >   */
> > > @@ -837,7 +858,7 @@ static int end_flv8986_core(struct sk_buff *skb, struct seg6_local_lwt *slwt)
> > >  	__u32 flvmask;
> > >  	int srhoff;
> > >  
> > > -	srh = seg6_get_srh(skb, 0);
> > > +	srh = seg6_flv8986_get_srh(skb);
> > 
> > Hmm, here we always try skip the SL = 0 SRH when multi SRH exists. What if
> > we want to add USP flavor support in future? Then we will not able to remove
> > the first SRH which SL = 0, right? e.g.
> > 
> >    +------+----------------------+----------------------+---------+
> >    | IPv6 | SRH, Segments Left 0 | SRH, Segments Left 2 | payload |
> >    +------+----------------------+----------------------+---------+
> > 
> > Thanks
> > Hangbin
> > 
> 
> Hi Hangbin,
> thanks for the review and for testing the series.
> 
> As it is now, seg6_flv8986_get_srh() skips that SRH, while with USP it
> should be removed. USP is not supported today, and for PSP without USP,
> skipping that SRH is correct.
> 
> When USP is implemented, that SRH can still be removed, for example by
> extending seg6_flv8986_get_srh() to take the flavors into account. Its
> comment would then be updated as well.
> 
> Does that sound reasonable to you?

Yes, this looks good to me. Thanks for the explanation. With this extendable
interface:

Reviewed-by: Hangbin Liu <liuhangbin@kylinos.cn>