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

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:

quoted

@@ -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

[...]

quoted

@@ -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.

quoted

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