Re: [PATCH bpf-next v4 2/6] net: tun: enable transfer of XDP metadata to skb

[Martin KaFai Lau]

On 3/3/25 8:13 AM, Marcus Wichelmann wrote:
> Am 28.02.25 um 20:49 schrieb Martin KaFai Lau:
> > On 2/27/25 6:23 AM, Marcus Wichelmann wrote:
> > > When the XDP metadata area was used, it is expected that the same
> > > metadata can also be accessed from TC, as can be read in the description
> > > of the bpf_xdp_adjust_meta helper function. In the tun driver, this was
> > > not yet implemented.
> > >
> > > To make this work, the skb that is being built on XDP_PASS should know
> > > of the current size of the metadata area. This is ensured by adding
> > > calls to skb_metadata_set. For the tun_xdp_one code path, an additional
> > > check is necessary to handle the case where the externally initialized
> > > xdp_buff has no metadata support (xdp->data_meta == xdp->data + 1).
> > >
> > > More information about this feature can be found in the commit message
> > > of commit de8f3a83b0a0 ("bpf: add meta pointer for direct access").
> > > > Signed-off-by: Marcus Wichelmann <marcus.wichelmann@xxxxxxxxxxxxxxxx>
> > > Reviewed-by: Willem de Bruijn <willemb@xxxxxxxxxx>
> > > Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
> > > ---
> > >    drivers/net/tun.c | 25 ++++++++++++++++++++++---
> > >    1 file changed, 22 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> > > index 4ec8fbd93c8d..70208b3a2e93 100644
> > > --- a/drivers/net/tun.c
> > > +++ b/drivers/net/tun.c
> >
> > The changes have conflicts with the commit 2506251e81d1 ("tun: Decouple vnet handling").
> >
> > It is better to rebase the works onto the bpf-next/net,
> > i.e. the "net" branch instead of the "master" branch.
>
> Alright, will do that. Should I send it as a v5 and still with "PATCH bpf-next"
> in the header or something else?

That should do. The bpf CI should pick up the bpf-next/net if it fails to apply 
to the bpf-next/master because of the conflict mentioned above.

For patch 3, it should help to avoid the future merge conflict if the 
open_tuntap() is added a few lines above in the network_helpers.h. For patch 6, 
the "test_ns_" naming is not in bpf-next/net yet. Other tests in the same file 
is doing netns_new. May be just do the same and cleanup all at once of this file 
later.