gtp: use icmp_ndo_send helper

Because gtp is calling icmp from network device context, it should use
the ndo helper so that the rate limiting applies correctly.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: Harald Welte <laforge@gnumonks.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/gtp.c

@@ -546,7 +546,7 @@ static int gtp_build_skb_ip4(struct sk_buff *skb, struct net_device *dev,
 	    mtu < ntohs(iph->tot_len)) {
 		netdev_dbg(dev, "packet too big, fragmentation needed\n");
 		memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
-		icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
+		icmp_ndo_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
 			      htonl(mtu));
 		goto err_rt;
 	}