Re: [PATCH net-next v5 09/14] ip_tunnel: add drop reasons to the transmit path

[Ido Schimmel <idosch@nvidia.com>]

On Sun, Oct 04, 2026 at 07:08:20PM +0300, Ido Schimmel wrote:
> On Wed, Sep 30, 2026 at 09:39:05PM +0300, Anton Danilov wrote:
> > @@ -636,6 +641,12 @@ enum skb_drop_reason {
> >  	SKB_DROP_REASON_TUNNEL_OLD_SEQ,
> >  	/** @SKB_DROP_REASON_GRE_CSUM: GRE checksum error */
> >  	SKB_DROP_REASON_GRE_CSUM,
> > +	/**
> > +	 * @SKB_DROP_REASON_TUNNEL_ENCAP: failed to build the encapsulation
> > +	 * header of a tunnel, e.g. an unknown or unregistered encapsulation
> > +	 * type.
> > +	 */
> > +	SKB_DROP_REASON_TUNNEL_ENCAP,
> >  	/**
> >  	 * @SKB_DROP_REASON_MAX: the maximum of core drop reasons, which
> >  	 * shouldn't be used as a real 'reason' - only for tracing code gen
> 
> [...]
> 
> > @@ -620,8 +623,10 @@ void ip_md_tunnel_xmit(struct sk_buff *skb, struct net_device *dev,
> >  	if (!tunnel_hlen)
> >  		tunnel_hlen = ip_encap_hlen(&tun_info->encap);
> >  
> > -	if (ip_tunnel_encap(skb, &tun_info->encap, &proto, &fl4) < 0)
> > +	if (ip_tunnel_encap(skb, &tun_info->encap, &proto, &fl4) < 0) {
> > +		reason = SKB_DROP_REASON_TUNNEL_ENCAP;
> 
> This will also cover the -ENOMEM from the callbacks, where
> SKB_DROP_REASON_NOMEM is more appropriate. Better to change
> ip_tunnel_encap() to return the appropriate drop reason like you did
> with gre_parse_header().

And change ip6_tnl_encap() in a similar fashion.

> 
> >  		goto tx_error;
> > +	}
> >  
> >  	use_cache = ip_tunnel_dst_cache_usable(skb, tun_info);
> >  	if (use_cache)