--- zzzz-none-000/linux-4.9.279/net/ipv4/ip_tunnel.c	2021-08-08 06:38:54.000000000 +0000
+++ puma7-atom-6591-750/linux-4.9.279/net/ipv4/ip_tunnel.c	2023-02-08 11:43:43.000000000 +0000
@@ -745,7 +745,10 @@
 
 	df = tnl_params->frag_off;
 	if (skb->protocol == htons(ETH_P_IP) && !tunnel->ignore_df)
-		df |= (inner_iph->frag_off & htons(IP_DF));
+        /* change from '|' to '&' to support GREv4 outer packet ipv4
+         fragmentation based on the white paper recommendations
+         http://www.cisco.com/c/en/us/support/docs/ip/generic-routing-encapsulation-gre/25885-pmtud-ipfrag.html */
+		df &= (inner_iph->frag_off & htons(IP_DF));
 
 	if (tnl_update_pmtu(dev, skb, rt, df, inner_iph)) {
 		ip_rt_put(rt);