gtp: fix fragmentation needed check with gso

[ Upstream commit 4530e5b8e2dad63dcad2206232dd86e4b1489b6c ]

Call skb_gso_validate_network_len() to check if packet is over PMTU.

Fixes: 459aa660eb1d ("gtp: add initial driver for datapath of GPRS Tunneling Protocol (GTP-U)")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index acb20ad..477b4d4 100644 (file)
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -871,8 +871,9 @@ 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));