Merge branch 'gtp-tunnel-driver-fixes'

Pablo Neira Ayuso says:

====================
GTP tunnel driver fixes

The following patchset contains two fixes for the GTP tunnel driver:

1) Incorrect GTPA_MAX definition in UAPI headers. This is updating an
   existing UAPI definition but for a good reason, this is certainly
   broken. Similar fixes for incorrect _MAX definition in netlink
   headers were applied in the past too.

2) Fix GTP driver PMTU with GRO packets, add missing call to
   skb_gso_validate_network_len() to handle GRO packets.
====================

Link: https://lore.kernel.org/r/20231022202519.659526-1-pablo@netfilter.orgSigned-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/gtp.c

@@ -872,8 +872,9 @@ static int gtp_build_skb_ip4(struct sk_buff *skb, struct net_device *dev,
 
 	skb_dst_update_pmtu_no_confirm(skb, mtu);
 
-	if (!skb_is_gso(skb) && (iph->frag_off & htons(IP_DF)) &&
-	    mtu < ntohs(iph->tot_len)) {
+	if (iph->frag_off & htons(IP_DF) &&
+	    ((!skb_is_gso(skb) && skb->len > mtu) ||
+	     (skb_is_gso(skb) && !skb_gso_validate_network_len(skb, mtu)))) {
 		netdev_dbg(dev, "packet too big, fragmentation needed\n");
 		icmp_ndo_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
 			      htonl(mtu));

include/uapi/linux/gtp.h

@@ -33,6 +33,6 @@ enum gtp_attrs {
 	GTPA_PAD,
 	__GTPA_MAX,
 };
-#define GTPA_MAX (__GTPA_MAX + 1)
+#define GTPA_MAX (__GTPA_MAX - 1)
 
 #endif /* _UAPI_LINUX_GTP_H_ */