text: /*
   *	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:
  	skb_gro_flush_final(skb, pp, 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);
  }
  