BAREUDP_BASE_HLEN
if (iptunnel_pull_header(skb, BAREUDP_BASE_HLEN,
BAREUDP_BASE_HLEN + info->options_len + sizeof(struct iphdr);
BAREUDP_BASE_HLEN + info->options_len + sizeof(struct ipv6hdr);
dev->max_mtu = IP_MAX_MTU - BAREUDP_BASE_HLEN;
if (skb_copy_bits(skb, BAREUDP_BASE_HLEN, &ipversion,