// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   *	IPV6 GSO/GRO offload support
   *	Linux INET6 implementation
   *

   *      UDPv6 GSO support
   */
  #include <linux/skbuff.h>

  #include <linux/netdevice.h>

  #include <linux/indirect_call_wrapper.h>

  #include <net/protocol.h>
  #include <net/ipv6.h>
  #include <net/udp.h>

  #include <net/ip6_checksum.h>

  #include "ip6_offload.h"

  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;
  	int err;
  
  	mss = skb_shinfo(skb)->gso_size;
  	if (unlikely(skb->len <= mss))
  		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 (!(skb_shinfo(skb)->gso_type & (SKB_GSO_UDP | SKB_GSO_UDP_L4)))

  			goto out;

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

  		if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)

  			return __udp_gso_segment(skb, features);

  		/* 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_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;
  
  		/* 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.
  		 */
  		err = ip6_find_1stfragopt(skb, &prevhdr);
  		if (err < 0)
  			return ERR_PTR(err);
  		unfrag_ip6hlen = err;
  		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;
  		fptr->identification = ipv6_proxy_select_ident(dev_net(skb->dev), skb);
  
  		/* 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 sock *udp6_gro_lookup_skb(struct sk_buff *skb, __be16 sport,
  					__be16 dport)
  {
  	const struct ipv6hdr *iph = skb_gro_network_header(skb);
  
  	return __udp6_lib_lookup(dev_net(skb->dev), &iph->saddr, sport,
  				 &iph->daddr, dport, inet6_iif(skb),
  				 inet6_sdif(skb), &udp_table, NULL);
  }

  INDIRECT_CALLABLE_SCOPE
  struct sk_buff *udp6_gro_receive(struct list_head *head, struct sk_buff *skb)

  {
  	struct udphdr *uh = udp_gro_udphdr(skb);

  	struct sock *sk = NULL;

  	struct sk_buff *pp;

  	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,
  						 ip6_gro_compute_pseudo))
  		goto flush;
  	else if (uh->check)

  		skb_gro_checksum_try_convert(skb, IPPROTO_UDP,

  					     ip6_gro_compute_pseudo);
  
  skip:

  	NAPI_GRO_CB(skb)->is_ipv6 = 1;

  	rcu_read_lock();

  
  	if (static_branch_unlikely(&udpv6_encap_needed_key))
  		sk = udp6_gro_lookup_skb(skb, uh->source, uh->dest);

  	pp = udp_gro_receive(head, skb, uh, sk);
  	rcu_read_unlock();
  	return pp;

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

  }

  INDIRECT_CALLABLE_SCOPE int udp6_gro_complete(struct sk_buff *skb, int nhoff)

  {
  	const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
  	struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);

  	if (NAPI_GRO_CB(skb)->is_flist) {
  		uh->len = htons(skb->len - nhoff);
  
  		skb_shinfo(skb)->gso_type |= (SKB_GSO_FRAGLIST|SKB_GSO_UDP_L4);
  		skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
  
  		if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
  			if (skb->csum_level < SKB_MAX_CSUM_LEVEL)
  				skb->csum_level++;
  		} else {
  			skb->ip_summed = CHECKSUM_UNNECESSARY;
  			skb->csum_level = 0;
  		}
  
  		return 0;
  	}

  	if (uh->check)

  		uh->check = ~udp_v6_check(skb->len - nhoff, &ipv6h->saddr,
  					  &ipv6h->daddr, 0);

  	return udp_gro_complete(skb, nhoff, udp6_lib_lookup_skb);

  }

  static const struct net_offload udpv6_offload = {

  	.callbacks = {

  		.gso_segment	=	udp6_ufo_fragment,

  		.gro_receive	=	udp6_gro_receive,
  		.gro_complete	=	udp6_gro_complete,

  	},

  };

  int udpv6_offload_init(void)

  {
  	return inet6_add_offload(&udpv6_offload, IPPROTO_UDP);
  }

  
  int udpv6_offload_exit(void)
  {
  	return inet6_del_offload(&udpv6_offload, IPPROTO_UDP);
  }