net/ipv4/udp_offload.c - kernel/msm-5.4 - Gitiles

 /*
  *	IPV4 GSO/GRO offload support
  *	Linux INET implementation
  *
  *	This program is free software; you can redistribute it and/or
  *	modify it under the terms of the GNU General Public License
  *	as published by the Free Software Foundation; either version
  *	2 of the License, or (at your option) any later version.
  *
  *	UDPv4 GSO support
  */

 #include <linux/skbuff.h>
 #include <net/udp.h>
 #include <net/protocol.h>

 static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
 	netdev_features_t features,
 	struct sk_buff *(*gso_inner_segment)(struct sk_buff *skb,
 					     netdev_features_t features),
 	__be16 new_protocol, bool is_ipv6)
 {
 	int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
 	bool remcsum, need_csum, offload_csum, gso_partial;
 	struct sk_buff *segs = ERR_PTR(-EINVAL);
 	struct udphdr *uh = udp_hdr(skb);
 	u16 mac_offset = skb->mac_header;
 	__be16 protocol = skb->protocol;
 	u16 mac_len = skb->mac_len;
 	int udp_offset, outer_hlen;
 	__wsum partial;
 	bool need_ipsec;

 	if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
 		goto out;

 	/* Adjust partial header checksum to negate old length.
 	 * We cannot rely on the value contained in uh->len as it is
 	 * possible that the actual value exceeds the boundaries of the
 	 * 16 bit length field due to the header being added outside of an
 	 * IP or IPv6 frame that was already limited to 64K - 1.
 	 */
 	if (skb_shinfo(skb)->gso_type & SKB_GSO_PARTIAL)
 		partial = (__force __wsum)uh->len;
 	else
 		partial = (__force __wsum)htonl(skb->len);
 	partial = csum_sub(csum_unfold(uh->check), partial);

 	/* setup inner skb. */
 	skb->encapsulation = 0;
 	SKB_GSO_CB(skb)->encap_level = 0;
 	__skb_pull(skb, tnl_hlen);
 	skb_reset_mac_header(skb);
 	skb_set_network_header(skb, skb_inner_network_offset(skb));
 	skb->mac_len = skb_inner_network_offset(skb);
 	skb->protocol = new_protocol;

 	need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL_CSUM);
 	skb->encap_hdr_csum = need_csum;

 	remcsum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_TUNNEL_REMCSUM);
 	skb->remcsum_offload = remcsum;

 	need_ipsec = skb_dst(skb) && dst_xfrm(skb_dst(skb));
 	/* Try to offload checksum if possible */
 	offload_csum = !!(need_csum &&
 			  !need_ipsec &&
 			  (skb->dev->features &
 			   (is_ipv6 ? (NETIF_F_HW_CSUM | NETIF_F_IPV6_CSUM) :
 				      (NETIF_F_HW_CSUM | NETIF_F_IP_CSUM))));

 	features &= skb->dev->hw_enc_features;

 	/* The only checksum offload we care about from here on out is the
 	 * outer one so strip the existing checksum feature flags and
 	 * instead set the flag based on our outer checksum offload value.
 	 */
 	if (remcsum) {
 		features &= ~NETIF_F_CSUM_MASK;
 		if (!need_csum || offload_csum)
 			features |= NETIF_F_HW_CSUM;
 	}

 	/* segment inner packet. */
 	segs = gso_inner_segment(skb, features);
 	if (IS_ERR_OR_NULL(segs)) {
 		skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset,
 				     mac_len);
 		goto out;
 	}

 	gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);

 	outer_hlen = skb_tnl_header_len(skb);
 	udp_offset = outer_hlen - tnl_hlen;
 	skb = segs;
 	do {
 		unsigned int len;

 		if (remcsum)
 			skb->ip_summed = CHECKSUM_NONE;

 		/* Set up inner headers if we are offloading inner checksum */
 		if (skb->ip_summed == CHECKSUM_PARTIAL) {
 			skb_reset_inner_headers(skb);
 			skb->encapsulation = 1;
 		}

 		skb->mac_len = mac_len;
 		skb->protocol = protocol;

 		__skb_push(skb, outer_hlen);
 		skb_reset_mac_header(skb);
 		skb_set_network_header(skb, mac_len);
 		skb_set_transport_header(skb, udp_offset);
 		len = skb->len - udp_offset;
 		uh = udp_hdr(skb);

 		/* If we are only performing partial GSO the inner header
 		 * will be using a length value equal to only one MSS sized
 		 * segment instead of the entire frame.
 		 */
 		if (gso_partial && skb_is_gso(skb)) {
 			uh->len = htons(skb_shinfo(skb)->gso_size +
 					SKB_GSO_CB(skb)->data_offset +
 					skb->head - (unsigned char *)uh);
 		} else {
 			uh->len = htons(len);
 		}

 		if (!need_csum)
 			continue;

 		uh->check = ~csum_fold(csum_add(partial,
 				       (__force __wsum)htonl(len)));

 		if (skb->encapsulation || !offload_csum) {
 			uh->check = gso_make_checksum(skb, ~uh->check);
 			if (uh->check == 0)
 				uh->check = CSUM_MANGLED_0;
 		} else {
 			skb->ip_summed = CHECKSUM_PARTIAL;
 			skb->csum_start = skb_transport_header(skb) - skb->head;
 			skb->csum_offset = offsetof(struct udphdr, check);
 		}
 	} while ((skb = skb->next));
 out:
 	return segs;
 }

 struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb,
 				       netdev_features_t features,
 				       bool is_ipv6)
 {
 	__be16 protocol = skb->protocol;
 	const struct net_offload **offloads;
 	const struct net_offload *ops;
 	struct sk_buff *segs = ERR_PTR(-EINVAL);
 	struct sk_buff *(*gso_inner_segment)(struct sk_buff *skb,
 					     netdev_features_t features);

 	rcu_read_lock();

 	switch (skb->inner_protocol_type) {
 	case ENCAP_TYPE_ETHER:
 		protocol = skb->inner_protocol;
 		gso_inner_segment = skb_mac_gso_segment;
 		break;
 	case ENCAP_TYPE_IPPROTO:
 		offloads = is_ipv6 ? inet6_offloads : inet_offloads;
 		ops = rcu_dereference(offloads[skb->inner_ipproto]);
 		if (!ops || !ops->callbacks.gso_segment)
 			goto out_unlock;
 		gso_inner_segment = ops->callbacks.gso_segment;
 		break;
 	default:
 		goto out_unlock;
 	}

 	segs = __skb_udp_tunnel_segment(skb, features, gso_inner_segment,
 					protocol, is_ipv6);

 out_unlock:
 	rcu_read_unlock();

 	return segs;
 }
 EXPORT_SYMBOL(skb_udp_tunnel_segment);

 static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
 					 netdev_features_t features)
 {
 	struct sk_buff *segs = ERR_PTR(-EINVAL);
 	unsigned int mss;
 	__wsum csum;
 	struct udphdr *uh;
 	struct iphdr *iph;

 	if (skb->encapsulation &&
 	    (skb_shinfo(skb)->gso_type &
 	     (SKB_GSO_UDP_TUNNEL|SKB_GSO_UDP_TUNNEL_CSUM))) {
 		segs = skb_udp_tunnel_segment(skb, features, false);
 		goto out;
 	}

 	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP))
 		goto out;

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

 	mss = skb_shinfo(skb)->gso_size;
 	if (unlikely(skb->len <= mss))
 		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);
 	iph = ip_hdr(skb);

 	uh->check = 0;
 	csum = skb_checksum(skb, 0, skb->len, 0);
 	uh->check = udp_v4_check(skb->len, iph->saddr, iph->daddr, csum);
 	if (uh->check == 0)
 		uh->check = CSUM_MANGLED_0;

 	skb->ip_summed = CHECKSUM_UNNECESSARY;

 	/* 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;

 	/* Fragment the skb. IP headers of the fragments are updated in
 	 * inet_gso_segment()
 	 */
 	segs = skb_segment(skb, features);
 out:
 	return segs;
 }

 struct sk_buff **udp_gro_receive(struct sk_buff **head, struct sk_buff *skb,
 				 struct udphdr *uh, udp_lookup_t lookup)
 {
 	struct sk_buff *p, **pp = NULL;
 	struct udphdr *uh2;
 	unsigned int off = skb_gro_offset(skb);
 	int flush = 1;
 	struct sock *sk;

 	if (NAPI_GRO_CB(skb)->encap_mark ||
 	    (skb->ip_summed != CHECKSUM_PARTIAL &&
 	     NAPI_GRO_CB(skb)->csum_cnt == 0 &&
 	     !NAPI_GRO_CB(skb)->csum_valid))
 		goto out;

 	/* mark that this skb passed once through the tunnel gro layer */
 	NAPI_GRO_CB(skb)->encap_mark = 1;

 	rcu_read_lock();
 	sk = (*lookup)(skb, uh->source, uh->dest);

 	if (sk && udp_sk(sk)->gro_receive)
 		goto unflush;
 	goto out_unlock;

 unflush:
 	flush = 0;

 	for (p = *head; p; p = p->next) {
 		if (!NAPI_GRO_CB(p)->same_flow)
 			continue;

 		uh2 = (struct udphdr   *)(p->data + off);

 		/* Match ports and either checksums are either both zero
 		 * or nonzero.
 		 */
 		if ((*(u32 *)&uh->source != *(u32 *)&uh2->source) ||
 		    (!uh->check ^ !uh2->check)) {
 			NAPI_GRO_CB(p)->same_flow = 0;
 			continue;
 		}
 	}

 	skb_gro_pull(skb, sizeof(struct udphdr)); /* pull encapsulating udp header */
 	skb_gro_postpull_rcsum(skb, uh, sizeof(struct udphdr));
 	pp = call_gro_receive_sk(udp_sk(sk)->gro_receive, sk, head, skb);

 out_unlock:
 	rcu_read_unlock();
 out:
 	NAPI_GRO_CB(skb)->flush |= flush;
 	return pp;
 }
 EXPORT_SYMBOL(udp_gro_receive);

 static struct sk_buff **udp4_gro_receive(struct sk_buff **head,
 					 struct sk_buff *skb)
 {
 	struct udphdr *uh = udp_gro_udphdr(skb);

 	if (unlikely(!uh))
 		goto flush;

 	/* Don't bother verifying checksum if we're going to flush anyway. */
 	if (NAPI_GRO_CB(skb)->flush)
 		goto skip;

 	if (skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
 						 inet_gro_compute_pseudo))
 		goto flush;
 	else if (uh->check)
 		skb_gro_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
 					     inet_gro_compute_pseudo);
 skip:
 	NAPI_GRO_CB(skb)->is_ipv6 = 0;
 	return udp_gro_receive(head, skb, uh, udp4_lib_lookup_skb);

 flush:
 	NAPI_GRO_CB(skb)->flush = 1;
 	return NULL;
 }

 int udp_gro_complete(struct sk_buff *skb, int nhoff,
 		     udp_lookup_t lookup)
 {
 	__be16 newlen = htons(skb->len - nhoff);
 	struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
 	int err = -ENOSYS;
 	struct sock *sk;

 	uh->len = newlen;

 	/* Set encapsulation before calling into inner gro_complete() functions
 	 * to make them set up the inner offsets.
 	 */
 	skb->encapsulation = 1;

 	rcu_read_lock();
 	sk = (*lookup)(skb, uh->source, uh->dest);
 	if (sk && udp_sk(sk)->gro_complete)
 		err = udp_sk(sk)->gro_complete(sk, skb,
 				nhoff + sizeof(struct udphdr));
 	rcu_read_unlock();

 	if (skb->remcsum_offload)
 		skb_shinfo(skb)->gso_type |= SKB_GSO_TUNNEL_REMCSUM;

 	return err;
 }
 EXPORT_SYMBOL(udp_gro_complete);

 static int udp4_gro_complete(struct sk_buff *skb, int nhoff)
 {
 	const struct iphdr *iph = ip_hdr(skb);
 	struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);

 	if (uh->check) {
 		skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL_CSUM;
 		uh->check = ~udp_v4_check(skb->len - nhoff, iph->saddr,
 					  iph->daddr, 0);
 	} else {
 		skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL;
 	}

 	return udp_gro_complete(skb, nhoff, udp4_lib_lookup_skb);
 }

 static const struct net_offload udpv4_offload = {
 	.callbacks = {
 		.gso_segment = udp4_ufo_fragment,
 		.gro_receive  =	udp4_gro_receive,
 		.gro_complete =	udp4_gro_complete,
 	},
 };

 int __init udpv4_offload_init(void)
 {
 	return inet_add_offload(&udpv4_offload, IPPROTO_UDP);
 }
	/*
	* IPV4 GSO/GRO offload support
	* Linux INET implementation
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* as published by the Free Software Foundation; either version
	* 2 of the License, or (at your option) any later version.
	*
	* UDPv4 GSO support
	*/

	#include <linux/skbuff.h>
	#include <net/udp.h>
	#include <net/protocol.h>

	static struct sk_buff __skb_udp_tunnel_segment(struct sk_buff skb,
	netdev_features_t features,
	struct sk_buff (gso_inner_segment)(struct sk_buff *skb,
	netdev_features_t features),
	__be16 new_protocol, bool is_ipv6)
	{
	int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
	bool remcsum, need_csum, offload_csum, gso_partial;
	struct sk_buff *segs = ERR_PTR(-EINVAL);
	struct udphdr *uh = udp_hdr(skb);
	u16 mac_offset = skb->mac_header;
	__be16 protocol = skb->protocol;
	u16 mac_len = skb->mac_len;
	int udp_offset, outer_hlen;
	__wsum partial;
	bool need_ipsec;

	if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
	goto out;

	/* Adjust partial header checksum to negate old length.
	* We cannot rely on the value contained in uh->len as it is
	* possible that the actual value exceeds the boundaries of the
	* 16 bit length field due to the header being added outside of an
	* IP or IPv6 frame that was already limited to 64K - 1.
	*/
	if (skb_shinfo(skb)->gso_type & SKB_GSO_PARTIAL)
	partial = (__force __wsum)uh->len;
	else
	partial = (__force __wsum)htonl(skb->len);
	partial = csum_sub(csum_unfold(uh->check), partial);

	/* setup inner skb. */
	skb->encapsulation = 0;
	SKB_GSO_CB(skb)->encap_level = 0;
	__skb_pull(skb, tnl_hlen);
	skb_reset_mac_header(skb);
	skb_set_network_header(skb, skb_inner_network_offset(skb));
	skb->mac_len = skb_inner_network_offset(skb);
	skb->protocol = new_protocol;

	need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL_CSUM);
	skb->encap_hdr_csum = need_csum;

	remcsum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_TUNNEL_REMCSUM);
	skb->remcsum_offload = remcsum;

	need_ipsec = skb_dst(skb) && dst_xfrm(skb_dst(skb));
	/* Try to offload checksum if possible */
	offload_csum = !!(need_csum &&
	!need_ipsec &&
	(skb->dev->features &
	(is_ipv6 ? (NETIF_F_HW_CSUM \| NETIF_F_IPV6_CSUM) :
	(NETIF_F_HW_CSUM \| NETIF_F_IP_CSUM))));

	features &= skb->dev->hw_enc_features;

	/* The only checksum offload we care about from here on out is the
	* outer one so strip the existing checksum feature flags and
	* instead set the flag based on our outer checksum offload value.
	*/
	if (remcsum) {
	features &= ~NETIF_F_CSUM_MASK;
	if (!need_csum \|\| offload_csum)
	features \|= NETIF_F_HW_CSUM;
	}

	/* segment inner packet. */
	segs = gso_inner_segment(skb, features);
	if (IS_ERR_OR_NULL(segs)) {
	skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset,
	mac_len);
	goto out;
	}

	gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);

	outer_hlen = skb_tnl_header_len(skb);
	udp_offset = outer_hlen - tnl_hlen;
	skb = segs;
	do {
	unsigned int len;

	if (remcsum)
	skb->ip_summed = CHECKSUM_NONE;

	/* Set up inner headers if we are offloading inner checksum */
	if (skb->ip_summed == CHECKSUM_PARTIAL) {
	skb_reset_inner_headers(skb);
	skb->encapsulation = 1;
	}

	skb->mac_len = mac_len;
	skb->protocol = protocol;

	__skb_push(skb, outer_hlen);
	skb_reset_mac_header(skb);
	skb_set_network_header(skb, mac_len);
	skb_set_transport_header(skb, udp_offset);
	len = skb->len - udp_offset;
	uh = udp_hdr(skb);

	/* If we are only performing partial GSO the inner header
	* will be using a length value equal to only one MSS sized
	* segment instead of the entire frame.
	*/
	if (gso_partial && skb_is_gso(skb)) {
	uh->len = htons(skb_shinfo(skb)->gso_size +
	SKB_GSO_CB(skb)->data_offset +
	skb->head - (unsigned char *)uh);
	} else {
	uh->len = htons(len);
	}

	if (!need_csum)
	continue;

	uh->check = ~csum_fold(csum_add(partial,
	(__force __wsum)htonl(len)));

	if (skb->encapsulation \|\| !offload_csum) {
	uh->check = gso_make_checksum(skb, ~uh->check);
	if (uh->check == 0)
	uh->check = CSUM_MANGLED_0;
	} else {
	skb->ip_summed = CHECKSUM_PARTIAL;
	skb->csum_start = skb_transport_header(skb) - skb->head;
	skb->csum_offset = offsetof(struct udphdr, check);
	}
	} while ((skb = skb->next));
	out:
	return segs;
	}

	struct sk_buff skb_udp_tunnel_segment(struct sk_buff skb,
	netdev_features_t features,
	bool is_ipv6)
	{
	__be16 protocol = skb->protocol;
	const struct net_offload **offloads;
	const struct net_offload *ops;
	struct sk_buff *segs = ERR_PTR(-EINVAL);
	struct sk_buff (gso_inner_segment)(struct sk_buff *skb,
	netdev_features_t features);

	rcu_read_lock();

	switch (skb->inner_protocol_type) {
	case ENCAP_TYPE_ETHER:
	protocol = skb->inner_protocol;
	gso_inner_segment = skb_mac_gso_segment;
	break;
	case ENCAP_TYPE_IPPROTO:
	offloads = is_ipv6 ? inet6_offloads : inet_offloads;
	ops = rcu_dereference(offloads[skb->inner_ipproto]);
	if (!ops \|\| !ops->callbacks.gso_segment)
	goto out_unlock;
	gso_inner_segment = ops->callbacks.gso_segment;
	break;
	default:
	goto out_unlock;
	}

	segs = __skb_udp_tunnel_segment(skb, features, gso_inner_segment,
	protocol, is_ipv6);

	out_unlock:
	rcu_read_unlock();

	return segs;
	}
	EXPORT_SYMBOL(skb_udp_tunnel_segment);

	static struct sk_buff udp4_ufo_fragment(struct sk_buff skb,
	netdev_features_t features)
	{
	struct sk_buff *segs = ERR_PTR(-EINVAL);
	unsigned int mss;
	__wsum csum;
	struct udphdr *uh;
	struct iphdr *iph;

	if (skb->encapsulation &&
	(skb_shinfo(skb)->gso_type &
	(SKB_GSO_UDP_TUNNEL\|SKB_GSO_UDP_TUNNEL_CSUM))) {
	segs = skb_udp_tunnel_segment(skb, features, false);
	goto out;
	}

	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP))
	goto out;

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

	mss = skb_shinfo(skb)->gso_size;
	if (unlikely(skb->len <= mss))
	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);
	iph = ip_hdr(skb);

	uh->check = 0;
	csum = skb_checksum(skb, 0, skb->len, 0);
	uh->check = udp_v4_check(skb->len, iph->saddr, iph->daddr, csum);
	if (uh->check == 0)
	uh->check = CSUM_MANGLED_0;

	skb->ip_summed = CHECKSUM_UNNECESSARY;

	/* 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;

	/* Fragment the skb. IP headers of the fragments are updated in
	* inet_gso_segment()
	*/
	segs = skb_segment(skb, features);
	out:
	return segs;
	}

	struct sk_buff udp_gro_receive(struct sk_buff head, struct sk_buff *skb,
	struct udphdr *uh, udp_lookup_t lookup)
	{
	struct sk_buff p, *pp = NULL;
	struct udphdr *uh2;
	unsigned int off = skb_gro_offset(skb);
	int flush = 1;
	struct sock *sk;

	if (NAPI_GRO_CB(skb)->encap_mark \|\|
	(skb->ip_summed != CHECKSUM_PARTIAL &&
	NAPI_GRO_CB(skb)->csum_cnt == 0 &&
	!NAPI_GRO_CB(skb)->csum_valid))
	goto out;

	/* mark that this skb passed once through the tunnel gro layer */
	NAPI_GRO_CB(skb)->encap_mark = 1;

	rcu_read_lock();
	sk = (*lookup)(skb, uh->source, uh->dest);

	if (sk && udp_sk(sk)->gro_receive)
	goto unflush;
	goto out_unlock;

	unflush:
	flush = 0;

	for (p = *head; p; p = p->next) {
	if (!NAPI_GRO_CB(p)->same_flow)
	continue;

	uh2 = (struct udphdr *)(p->data + off);

	/* Match ports and either checksums are either both zero
	* or nonzero.
	*/
	if (((u32 )&uh->source != (u32 )&uh2->source) \|\|
	(!uh->check ^ !uh2->check)) {
	NAPI_GRO_CB(p)->same_flow = 0;
	continue;
	}
	}

	skb_gro_pull(skb, sizeof(struct udphdr)); /* pull encapsulating udp header */
	skb_gro_postpull_rcsum(skb, uh, sizeof(struct udphdr));
	pp = call_gro_receive_sk(udp_sk(sk)->gro_receive, sk, head, skb);

	out_unlock:
	rcu_read_unlock();
	out:
	NAPI_GRO_CB(skb)->flush \|= flush;
	return pp;
	}
	EXPORT_SYMBOL(udp_gro_receive);

	static struct sk_buff udp4_gro_receive(struct sk_buff head,
	struct sk_buff *skb)
	{
	struct udphdr *uh = udp_gro_udphdr(skb);

	if (unlikely(!uh))
	goto flush;

	/* Don't bother verifying checksum if we're going to flush anyway. */
	if (NAPI_GRO_CB(skb)->flush)
	goto skip;

	if (skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
	inet_gro_compute_pseudo))
	goto flush;
	else if (uh->check)
	skb_gro_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
	inet_gro_compute_pseudo);
	skip:
	NAPI_GRO_CB(skb)->is_ipv6 = 0;
	return udp_gro_receive(head, skb, uh, udp4_lib_lookup_skb);

	flush:
	NAPI_GRO_CB(skb)->flush = 1;
	return NULL;
	}

	int udp_gro_complete(struct sk_buff *skb, int nhoff,
	udp_lookup_t lookup)
	{
	__be16 newlen = htons(skb->len - nhoff);
	struct udphdr uh = (struct udphdr )(skb->data + nhoff);
	int err = -ENOSYS;
	struct sock *sk;

	uh->len = newlen;

	/* Set encapsulation before calling into inner gro_complete() functions
	* to make them set up the inner offsets.
	*/
	skb->encapsulation = 1;

	rcu_read_lock();
	sk = (*lookup)(skb, uh->source, uh->dest);
	if (sk && udp_sk(sk)->gro_complete)
	err = udp_sk(sk)->gro_complete(sk, skb,
	nhoff + sizeof(struct udphdr));
	rcu_read_unlock();

	if (skb->remcsum_offload)
	skb_shinfo(skb)->gso_type \|= SKB_GSO_TUNNEL_REMCSUM;

	return err;
	}
	EXPORT_SYMBOL(udp_gro_complete);

	static int udp4_gro_complete(struct sk_buff *skb, int nhoff)
	{
	const struct iphdr *iph = ip_hdr(skb);
	struct udphdr uh = (struct udphdr )(skb->data + nhoff);

	if (uh->check) {
	skb_shinfo(skb)->gso_type \|= SKB_GSO_UDP_TUNNEL_CSUM;
	uh->check = ~udp_v4_check(skb->len - nhoff, iph->saddr,
	iph->daddr, 0);
	} else {
	skb_shinfo(skb)->gso_type \|= SKB_GSO_UDP_TUNNEL;
	}

	return udp_gro_complete(skb, nhoff, udp4_lib_lookup_skb);
	}

	static const struct net_offload udpv4_offload = {
	.callbacks = {
	.gso_segment = udp4_ufo_fragment,
	.gro_receive = udp4_gro_receive,
	.gro_complete = udp4_gro_complete,
	},
	};

	int __init udpv4_offload_init(void)
	{
	return inet_add_offload(&udpv4_offload, IPPROTO_UDP);
	}