xfrm: interface: fix ipv4 pmtu check to honor ip header df

Frag needed should only be sent if the header enables DF.

This fix allows packets larger than MTU to pass the xfrm interface
and be fragmented after encapsulation, aligning behavior with
non-interface xfrm.

Fixes: f203b76d7809 ("xfrm: Add virtual xfrm interfaces")
Signed-off-by: Eyal Birger <eyal.birger@gmail.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

diff --git a/net/xfrm/xfrm_interface.c b/net/xfrm/xfrm_interface.c
index 495b1f5c979bc31bacdbca3aae4c50f4f7f21541..8831f5a9e99233c8b1b19bd20705c5174f88530b 100644 (file)
--- a/net/xfrm/xfrm_interface.c
+++ b/net/xfrm/xfrm_interface.c
@@ -306,6 +306,8 @@ xfrmi_xmit2(struct sk_buff *skb, struct net_device *dev, struct flowi *fl)
 
                        icmpv6_ndo_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
                } else {
+                       if (!(ip_hdr(skb)->frag_off & htons(IP_DF)))
+                               goto xmit;
                        icmp_ndo_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
                                      htonl(mtu));
                }
@@ -314,6 +316,7 @@ xfrmi_xmit2(struct sk_buff *skb, struct net_device *dev, struct flowi *fl)
                return -EMSGSIZE;
        }
 
+xmit:
        xfrmi_scrub_packet(skb, !net_eq(xi->net, dev_net(dev)));
        skb_dst_set(skb, dst);
        skb->dev = tdev;