[PATCH net 2/2] gtp: fix fragmentation needed check with gso

[Pablo Neira Ayuso]

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 <pa...@netfilter.org>
---
 drivers/net/gtp.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index 144ec626230d..b22596b18ee8 100644
--- a/drivers/net/gtp.c
+++ b/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));
-- 
2.30.2