static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
					 netdev_features_t features)
{
	struct sk_buff *segs = ERR_PTR(-EINVAL);
	unsigned int mss;
	unsigned int unfrag_ip6hlen, unfrag_len;
	struct frag_hdr *fptr;
	u8 *packet_start, *prevhdr;
	u8 nexthdr;
	u8 frag_hdr_sz = sizeof(struct frag_hdr);
	__wsum csum;
	int tnl_hlen;

	mss = skb_shinfo(skb)->gso_size;
	if (unlikely(skb->len <= mss))
		goto out;

	if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
		/* Packet is from an untrusted source, reset gso_segs. */

		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);

		/* Set the IPv6 fragment id if not set yet */
		if (!skb_shinfo(skb)->ip6_frag_id)
			ipv6_proxy_select_ident(dev_net(skb->dev), skb);

		segs = NULL;
		goto out;
	}

	if (skb->encapsulation && skb_shinfo(skb)->gso_type &
	    (SKB_GSO_UDP_TUNNEL|SKB_GSO_UDP_TUNNEL_CSUM))
		segs = skb_udp_tunnel_segment(skb, features, true);
	else {
		const struct ipv6hdr *ipv6h;
		struct udphdr *uh;

		if (!pskb_may_pull(skb, sizeof(struct udphdr)))
			goto out;

		/* Do software UFO. Complete and fill in the UDP checksum as HW cannot
		 * do checksum of UDP packets sent as multiple IP fragments.
		 */

		uh = udp_hdr(skb);
		ipv6h = ipv6_hdr(skb);

		uh->check = 0;
		csum = skb_checksum(skb, 0, skb->len, 0);
		uh->check = udp_v6_check(skb->len, &ipv6h->saddr,
					  &ipv6h->daddr, csum);
		if (uh->check == 0)
			uh->check = CSUM_MANGLED_0;

		skb->ip_summed = CHECKSUM_NONE;

		/* If there is no outer header we can fake a checksum offload
		 * due to the fact that we have already done the checksum in
		 * software prior to segmenting the frame.
		 */
		if (!skb->encap_hdr_csum)
			features |= NETIF_F_HW_CSUM;

		/* Check if there is enough headroom to insert fragment header. */
		tnl_hlen = skb_tnl_header_len(skb);
		if (skb->mac_header < (tnl_hlen + frag_hdr_sz)) {
			if (gso_pskb_expand_head(skb, tnl_hlen + frag_hdr_sz))
				goto out;
		}

		/* Find the unfragmentable header and shift it left by frag_hdr_sz
		 * bytes to insert fragment header.
		 */
		unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
		nexthdr = *prevhdr;
		*prevhdr = NEXTHDR_FRAGMENT;
		unfrag_len = (skb_network_header(skb) - skb_mac_header(skb)) +
			     unfrag_ip6hlen + tnl_hlen;
		packet_start = (u8 *) skb->head + SKB_GSO_CB(skb)->mac_offset;
		memmove(packet_start-frag_hdr_sz, packet_start, unfrag_len);

		SKB_GSO_CB(skb)->mac_offset -= frag_hdr_sz;
		skb->mac_header -= frag_hdr_sz;
		skb->network_header -= frag_hdr_sz;

		fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
		fptr->nexthdr = nexthdr;
		fptr->reserved = 0;
		if (!skb_shinfo(skb)->ip6_frag_id)
			ipv6_proxy_select_ident(dev_net(skb->dev), skb);
		fptr->identification = skb_shinfo(skb)->ip6_frag_id;

		/* Fragment the skb. ipv6 header and the remaining fields of the
		 * fragment header are updated in ipv6_gso_segment()
		 */
		segs = skb_segment(skb, features);
	}

out:
	return segs;
}
static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
					 netdev_features_t features)
{
	struct sk_buff *segs = ERR_PTR(-EINVAL);
	unsigned int mss;
	unsigned int unfrag_ip6hlen, unfrag_len;
	struct frag_hdr *fptr;
	u8 *packet_start, *prevhdr;
	u8 nexthdr;
	u8 frag_hdr_sz = sizeof(struct frag_hdr);
	__wsum csum;
	int tnl_hlen;

	mss = skb_shinfo(skb)->gso_size;
	if (unlikely(skb->len <= mss))
		goto out;

	if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
		 

		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);

		 
		if (!skb_shinfo(skb)->ip6_frag_id)
			ipv6_proxy_select_ident(dev_net(skb->dev), skb);

		segs = NULL;
		goto out;
	}

	if (skb->encapsulation && skb_shinfo(skb)->gso_type &
	    (SKB_GSO_UDP_TUNNEL|SKB_GSO_UDP_TUNNEL_CSUM))
		segs = skb_udp_tunnel_segment(skb, features, true);
	else {
		const struct ipv6hdr *ipv6h;
		struct udphdr *uh;

		if (!pskb_may_pull(skb, sizeof(struct udphdr)))
			goto out;

		 

		uh = udp_hdr(skb);
		ipv6h = ipv6_hdr(skb);

		uh->check = 0;
		csum = skb_checksum(skb, 0, skb->len, 0);
		uh->check = udp_v6_check(skb->len, &ipv6h->saddr,
					  &ipv6h->daddr, csum);
		if (uh->check == 0)
			uh->check = CSUM_MANGLED_0;

		skb->ip_summed = CHECKSUM_NONE;

		 
		if (!skb->encap_hdr_csum)
			features |= NETIF_F_HW_CSUM;

		 
		tnl_hlen = skb_tnl_header_len(skb);
		if (skb->mac_header < (tnl_hlen + frag_hdr_sz)) {
			if (gso_pskb_expand_head(skb, tnl_hlen + frag_hdr_sz))
				goto out;
		}

		 
		unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
		nexthdr = *prevhdr;
		*prevhdr = NEXTHDR_FRAGMENT;
		unfrag_len = (skb_network_header(skb) - skb_mac_header(skb)) +
			     unfrag_ip6hlen + tnl_hlen;
		packet_start = (u8 *) skb->head + SKB_GSO_CB(skb)->mac_offset;
		memmove(packet_start-frag_hdr_sz, packet_start, unfrag_len);

		SKB_GSO_CB(skb)->mac_offset -= frag_hdr_sz;
		skb->mac_header -= frag_hdr_sz;
		skb->network_header -= frag_hdr_sz;

		fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
		fptr->nexthdr = nexthdr;
		fptr->reserved = 0;
		if (!skb_shinfo(skb)->ip6_frag_id)
			ipv6_proxy_select_ident(dev_net(skb->dev), skb);
		fptr->identification = skb_shinfo(skb)->ip6_frag_id;

		 
		segs = skb_segment(skb, features);
	}

out:
	return segs;
}