mtu = dst_mtu(dst);
if (skb->len > mtu) {
	skb_dst_update_pmtu(skb, mtu);
	if (skb->protocol == htons(ETH_P_IP))
		icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
	else
		icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, max(IPV6_MIN_MTU, mtu));
	dst_release(dst);
	goto tx_error;
}