/*
   *	IPV6 GSO/GRO offload support
   *	Linux INET6 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.
   */
  
  #include <linux/kernel.h>
  #include <linux/socket.h>
  #include <linux/netdevice.h>
  #include <linux/skbuff.h>

  #include <linux/printk.h>

  
  #include <net/protocol.h>
  #include <net/ipv6.h>
  
  #include "ip6_offload.h"
  
  static int ipv6_gso_pull_exthdrs(struct sk_buff *skb, int proto)
  {
  	const struct net_offload *ops = NULL;
  
  	for (;;) {
  		struct ipv6_opt_hdr *opth;
  		int len;
  
  		if (proto != NEXTHDR_HOP) {
  			ops = rcu_dereference(inet6_offloads[proto]);
  
  			if (unlikely(!ops))
  				break;
  
  			if (!(ops->flags & INET6_PROTO_GSO_EXTHDR))
  				break;
  		}
  
  		if (unlikely(!pskb_may_pull(skb, 8)))
  			break;
  
  		opth = (void *)skb->data;
  		len = ipv6_optlen(opth);
  
  		if (unlikely(!pskb_may_pull(skb, len)))
  			break;
  
  		proto = opth->nexthdr;
  		__skb_pull(skb, len);
  	}
  
  	return proto;
  }
  
  static int ipv6_gso_send_check(struct sk_buff *skb)
  {
  	const struct ipv6hdr *ipv6h;
  	const struct net_offload *ops;
  	int err = -EINVAL;
  
  	if (unlikely(!pskb_may_pull(skb, sizeof(*ipv6h))))
  		goto out;
  
  	ipv6h = ipv6_hdr(skb);
  	__skb_pull(skb, sizeof(*ipv6h));
  	err = -EPROTONOSUPPORT;
  
  	rcu_read_lock();
  	ops = rcu_dereference(inet6_offloads[
  		ipv6_gso_pull_exthdrs(skb, ipv6h->nexthdr)]);

  	if (likely(ops && ops->callbacks.gso_send_check)) {

  		skb_reset_transport_header(skb);

  		err = ops->callbacks.gso_send_check(skb);

  	}
  	rcu_read_unlock();
  
  out:
  	return err;
  }
  
  static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
  	netdev_features_t features)
  {
  	struct sk_buff *segs = ERR_PTR(-EINVAL);
  	struct ipv6hdr *ipv6h;
  	const struct net_offload *ops;
  	int proto;
  	struct frag_hdr *fptr;
  	unsigned int unfrag_ip6hlen;
  	u8 *prevhdr;
  	int offset = 0;

  	if (unlikely(skb_shinfo(skb)->gso_type &
  		     ~(SKB_GSO_UDP |
  		       SKB_GSO_DODGY |
  		       SKB_GSO_TCP_ECN |

  		       SKB_GSO_GRE |

  		       SKB_GSO_UDP_TUNNEL |

  		       SKB_GSO_TCPV6 |
  		       0)))
  		goto out;
  
  	if (unlikely(!pskb_may_pull(skb, sizeof(*ipv6h))))
  		goto out;
  
  	ipv6h = ipv6_hdr(skb);
  	__skb_pull(skb, sizeof(*ipv6h));
  	segs = ERR_PTR(-EPROTONOSUPPORT);
  
  	proto = ipv6_gso_pull_exthdrs(skb, ipv6h->nexthdr);
  	rcu_read_lock();
  	ops = rcu_dereference(inet6_offloads[proto]);

  	if (likely(ops && ops->callbacks.gso_segment)) {

  		skb_reset_transport_header(skb);

  		segs = ops->callbacks.gso_segment(skb, features);

  	}
  	rcu_read_unlock();
  
  	if (IS_ERR(segs))
  		goto out;
  
  	for (skb = segs; skb; skb = skb->next) {
  		ipv6h = ipv6_hdr(skb);
  		ipv6h->payload_len = htons(skb->len - skb->mac_len -
  					   sizeof(*ipv6h));
  		if (proto == IPPROTO_UDP) {
  			unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
  			fptr = (struct frag_hdr *)(skb_network_header(skb) +
  				unfrag_ip6hlen);
  			fptr->frag_off = htons(offset);
  			if (skb->next != NULL)
  				fptr->frag_off |= htons(IP6_MF);
  			offset += (ntohs(ipv6h->payload_len) -
  				   sizeof(struct frag_hdr));
  		}
  	}
  
  out:
  	return segs;
  }
  
  static struct sk_buff **ipv6_gro_receive(struct sk_buff **head,
  					 struct sk_buff *skb)
  {
  	const struct net_offload *ops;
  	struct sk_buff **pp = NULL;
  	struct sk_buff *p;
  	struct ipv6hdr *iph;
  	unsigned int nlen;
  	unsigned int hlen;
  	unsigned int off;
  	int flush = 1;
  	int proto;
  	__wsum csum;
  
  	off = skb_gro_offset(skb);
  	hlen = off + sizeof(*iph);
  	iph = skb_gro_header_fast(skb, off);
  	if (skb_gro_header_hard(skb, hlen)) {
  		iph = skb_gro_header_slow(skb, hlen, off);
  		if (unlikely(!iph))
  			goto out;
  	}
  
  	skb_gro_pull(skb, sizeof(*iph));
  	skb_set_transport_header(skb, skb_gro_offset(skb));
  
  	flush += ntohs(iph->payload_len) != skb_gro_len(skb);
  
  	rcu_read_lock();
  	proto = iph->nexthdr;
  	ops = rcu_dereference(inet6_offloads[proto]);

  	if (!ops || !ops->callbacks.gro_receive) {

  		__pskb_pull(skb, skb_gro_offset(skb));
  		proto = ipv6_gso_pull_exthdrs(skb, proto);
  		skb_gro_pull(skb, -skb_transport_offset(skb));
  		skb_reset_transport_header(skb);
  		__skb_push(skb, skb_gro_offset(skb));
  
  		ops = rcu_dereference(inet6_offloads[proto]);

  		if (!ops || !ops->callbacks.gro_receive)

  			goto out_unlock;
  
  		iph = ipv6_hdr(skb);
  	}
  
  	NAPI_GRO_CB(skb)->proto = proto;
  
  	flush--;
  	nlen = skb_network_header_len(skb);
  
  	for (p = *head; p; p = p->next) {
  		const struct ipv6hdr *iph2;
  		__be32 first_word; /* <Version:4><Traffic_Class:8><Flow_Label:20> */
  
  		if (!NAPI_GRO_CB(p)->same_flow)
  			continue;
  
  		iph2 = ipv6_hdr(p);
  		first_word = *(__be32 *)iph ^ *(__be32 *)iph2 ;
  
  		/* All fields must match except length and Traffic Class. */
  		if (nlen != skb_network_header_len(p) ||
  		    (first_word & htonl(0xF00FFFFF)) ||
  		    memcmp(&iph->nexthdr, &iph2->nexthdr,
  			   nlen - offsetof(struct ipv6hdr, nexthdr))) {
  			NAPI_GRO_CB(p)->same_flow = 0;
  			continue;
  		}
  		/* flush if Traffic Class fields are different */
  		NAPI_GRO_CB(p)->flush |= !!(first_word & htonl(0x0FF00000));
  		NAPI_GRO_CB(p)->flush |= flush;
  	}
  
  	NAPI_GRO_CB(skb)->flush |= flush;
  
  	csum = skb->csum;
  	skb_postpull_rcsum(skb, iph, skb_network_header_len(skb));

  	pp = ops->callbacks.gro_receive(head, skb);

  
  	skb->csum = csum;
  
  out_unlock:
  	rcu_read_unlock();
  
  out:
  	NAPI_GRO_CB(skb)->flush |= flush;
  
  	return pp;
  }
  
  static int ipv6_gro_complete(struct sk_buff *skb)
  {
  	const struct net_offload *ops;
  	struct ipv6hdr *iph = ipv6_hdr(skb);
  	int err = -ENOSYS;
  
  	iph->payload_len = htons(skb->len - skb_network_offset(skb) -
  				 sizeof(*iph));
  
  	rcu_read_lock();
  	ops = rcu_dereference(inet6_offloads[NAPI_GRO_CB(skb)->proto]);

  	if (WARN_ON(!ops || !ops->callbacks.gro_complete))

  		goto out_unlock;

  	err = ops->callbacks.gro_complete(skb);

  
  out_unlock:
  	rcu_read_unlock();
  
  	return err;
  }
  
  static struct packet_offload ipv6_packet_offload __read_mostly = {
  	.type = cpu_to_be16(ETH_P_IPV6),

  	.callbacks = {
  		.gso_send_check = ipv6_gso_send_check,
  		.gso_segment = ipv6_gso_segment,
  		.gro_receive = ipv6_gro_receive,
  		.gro_complete = ipv6_gro_complete,
  	},

  };

  static int __init ipv6_offload_init(void)

  {

  
  	if (tcpv6_offload_init() < 0)
  		pr_crit("%s: Cannot add TCP protocol offload
  ", __func__);
  	if (udp_offload_init() < 0)
  		pr_crit("%s: Cannot add UDP protocol offload
  ", __func__);
  	if (ipv6_exthdrs_offload_init() < 0)
  		pr_crit("%s: Cannot add EXTHDRS protocol offload
  ", __func__);

  	dev_add_offload(&ipv6_packet_offload);

  	return 0;

  }

  fs_initcall(ipv6_offload_init);