/*
   *	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 DEFINE_SPINLOCK(udp_offload_lock);
  static struct udp_offload_priv __rcu *udp_offload_base __read_mostly;
  
  #define udp_deref_protected(X) rcu_dereference_protected(X, lockdep_is_held(&udp_offload_lock))
  
  struct udp_offload_priv {
  	struct udp_offload	*offload;
  	struct rcu_head		rcu;
  	struct udp_offload_priv __rcu *next;
  };
  
  static int udp4_ufo_send_check(struct sk_buff *skb)
  {
  	if (!pskb_may_pull(skb, sizeof(struct udphdr)))
  		return -EINVAL;
  
  	if (likely(!skb->encapsulation)) {
  		const struct iphdr *iph;
  		struct udphdr *uh;
  
  		iph = ip_hdr(skb);
  		uh = udp_hdr(skb);
  
  		uh->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, skb->len,
  				IPPROTO_UDP, 0);
  		skb->csum_start = skb_transport_header(skb) - skb->head;
  		skb->csum_offset = offsetof(struct udphdr, check);
  		skb->ip_summed = CHECKSUM_PARTIAL;
  	}
  
  	return 0;
  }
  
  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;
  	int offset;
  	__wsum csum;
  
  	if (skb->encapsulation &&
  	    skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL) {
  		segs = skb_udp_tunnel_segment(skb, features);
  		goto out;
  	}
  
  	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. */
  		int type = skb_shinfo(skb)->gso_type;
  
  		if (unlikely(type & ~(SKB_GSO_UDP | SKB_GSO_DODGY |
  				      SKB_GSO_UDP_TUNNEL |
  				      SKB_GSO_IPIP |
  				      SKB_GSO_GRE | SKB_GSO_MPLS) ||
  			     !(type & (SKB_GSO_UDP))))
  			goto out;
  
  		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
  
  		segs = NULL;
  		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.
  	 */
  	offset = skb_checksum_start_offset(skb);
  	csum = skb_checksum(skb, offset, skb->len - offset, 0);
  	offset += skb->csum_offset;
  	*(__sum16 *)(skb->data + offset) = csum_fold(csum);
  	skb->ip_summed = CHECKSUM_NONE;
  
  	/* Fragment the skb. IP headers of the fragments are updated in
  	 * inet_gso_segment()
  	 */
  	segs = skb_segment(skb, features);
  out:
  	return segs;
  }
  
  int udp_add_offload(struct udp_offload *uo)
  {
  	struct udp_offload_priv *new_offload = kzalloc(sizeof(*new_offload), GFP_ATOMIC);
  
  	if (!new_offload)
  		return -ENOMEM;
  
  	new_offload->offload = uo;
  
  	spin_lock(&udp_offload_lock);
  	new_offload->next = udp_offload_base;
  	rcu_assign_pointer(udp_offload_base, new_offload);
  	spin_unlock(&udp_offload_lock);
  
  	return 0;
  }
  EXPORT_SYMBOL(udp_add_offload);
  
  static void udp_offload_free_routine(struct rcu_head *head)
  {
  	struct udp_offload_priv *ou_priv = container_of(head, struct udp_offload_priv, rcu);
  	kfree(ou_priv);
  }
  
  void udp_del_offload(struct udp_offload *uo)
  {
  	struct udp_offload_priv __rcu **head = &udp_offload_base;
  	struct udp_offload_priv *uo_priv;
  
  	spin_lock(&udp_offload_lock);
  
  	uo_priv = udp_deref_protected(*head);
  	for (; uo_priv != NULL;
  	     uo_priv = udp_deref_protected(*head)) {
  		if (uo_priv->offload == uo) {
  			rcu_assign_pointer(*head,
  					   udp_deref_protected(uo_priv->next));
  			goto unlock;
  		}
  		head = &uo_priv->next;
  	}
  	pr_warn("udp_del_offload: didn't find offload for port %d
  ", ntohs(uo->port));
  unlock:
  	spin_unlock(&udp_offload_lock);
  	if (uo_priv != NULL)
  		call_rcu(&uo_priv->rcu, udp_offload_free_routine);
  }
  EXPORT_SYMBOL(udp_del_offload);
  
  static struct sk_buff **udp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
  {
  	struct udp_offload_priv *uo_priv;
  	struct sk_buff *p, **pp = NULL;
  	struct udphdr *uh, *uh2;
  	unsigned int hlen, off;
  	int flush = 1;
  
  	if (NAPI_GRO_CB(skb)->udp_mark ||
  	    (!skb->encapsulation && skb->ip_summed != CHECKSUM_COMPLETE))
  		goto out;
  
  	/* mark that this skb passed once through the udp gro layer */
  	NAPI_GRO_CB(skb)->udp_mark = 1;
  
  	off  = skb_gro_offset(skb);
  	hlen = off + sizeof(*uh);
  	uh   = skb_gro_header_fast(skb, off);
  	if (skb_gro_header_hard(skb, hlen)) {
  		uh = skb_gro_header_slow(skb, hlen, off);
  		if (unlikely(!uh))
  			goto out;
  	}
  
  	rcu_read_lock();
  	uo_priv = rcu_dereference(udp_offload_base);
  	for (; uo_priv != NULL; uo_priv = rcu_dereference(uo_priv->next)) {
  		if (uo_priv->offload->port == uh->dest &&
  		    uo_priv->offload->callbacks.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);
  		if ((*(u32 *)&uh->source != *(u32 *)&uh2->source)) {
  			NAPI_GRO_CB(p)->same_flow = 0;
  			continue;
  		}
  	}
  
  	skb_gro_pull(skb, sizeof(struct udphdr)); /* pull encapsulating udp header */
  	pp = uo_priv->offload->callbacks.gro_receive(head, skb);
  
  out_unlock:
  	rcu_read_unlock();
  out:
  	NAPI_GRO_CB(skb)->flush |= flush;
  	return pp;
  }
  
  static int udp_gro_complete(struct sk_buff *skb, int nhoff)
  {
  	struct udp_offload_priv *uo_priv;
  	__be16 newlen = htons(skb->len - nhoff);
  	struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
  	int err = -ENOSYS;
  
  	uh->len = newlen;
  
  	rcu_read_lock();
  
  	uo_priv = rcu_dereference(udp_offload_base);
  	for (; uo_priv != NULL; uo_priv = rcu_dereference(uo_priv->next)) {
  		if (uo_priv->offload->port == uh->dest &&
  		    uo_priv->offload->callbacks.gro_complete)
  			break;
  	}
  
  	if (uo_priv != NULL)
  		err = uo_priv->offload->callbacks.gro_complete(skb, nhoff + sizeof(struct udphdr));
  
  	rcu_read_unlock();
  	return err;
  }
  
  static const struct net_offload udpv4_offload = {
  	.callbacks = {
  		.gso_send_check = udp4_ufo_send_check,
  		.gso_segment = udp4_ufo_fragment,
  		.gro_receive  =	udp_gro_receive,
  		.gro_complete =	udp_gro_complete,
  	},
  };
  
  int __init udpv4_offload_init(void)
  {
  	return inet_add_offload(&udpv4_offload, IPPROTO_UDP);
  }