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

  /*
   *	IPV4 GSO/GRO offload support
   *	Linux INET implementation
   *

   *	UDPv4 GSO support
   */
  
  #include <linux/skbuff.h>
  #include <net/udp.h>
  #include <net/protocol.h>

  #include <net/inet_common.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 *__udp_gso_segment_list(struct sk_buff *skb,
  					      netdev_features_t features)
  {
  	unsigned int mss = skb_shinfo(skb)->gso_size;
  
  	skb = skb_segment_list(skb, features, skb_mac_header_len(skb));
  	if (IS_ERR(skb))
  		return skb;
  
  	udp_hdr(skb)->len = htons(sizeof(struct udphdr) + mss);
  
  	return skb;
  }

  struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,

  				  netdev_features_t features)

  {

  	struct sock *sk = gso_skb->sk;
  	unsigned int sum_truesize = 0;

  	struct sk_buff *segs, *seg;

  	struct udphdr *uh;

  	unsigned int mss;

  	bool copy_dtor;

  	__sum16 check;
  	__be16 newlen;

  	if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST)
  		return __udp_gso_segment_list(gso_skb, features);

  	mss = skb_shinfo(gso_skb)->gso_size;

  	if (gso_skb->len <= sizeof(*uh) + mss)
  		return ERR_PTR(-EINVAL);

  	skb_pull(gso_skb, sizeof(*uh));

  	/* clear destructor to avoid skb_segment assigning it to tail */

  	copy_dtor = gso_skb->destructor == sock_wfree;
  	if (copy_dtor)
  		gso_skb->destructor = NULL;

  	segs = skb_segment(gso_skb, features);

  	if (IS_ERR_OR_NULL(segs)) {

  		if (copy_dtor)
  			gso_skb->destructor = sock_wfree;

  		return segs;

  	}

  	/* GSO partial and frag_list segmentation only requires splitting
  	 * the frame into an MSS multiple and possibly a remainder, both
  	 * cases return a GSO skb. So update the mss now.
  	 */
  	if (skb_is_gso(segs))
  		mss *= skb_shinfo(segs)->gso_segs;

  	seg = segs;
  	uh = udp_hdr(seg);

  	/* preserve TX timestamp flags and TS key for first segment */
  	skb_shinfo(seg)->tskey = skb_shinfo(gso_skb)->tskey;
  	skb_shinfo(seg)->tx_flags |=
  			(skb_shinfo(gso_skb)->tx_flags & SKBTX_ANY_TSTAMP);

  	/* compute checksum adjustment based on old length versus new */
  	newlen = htons(sizeof(*uh) + mss);
  	check = csum16_add(csum16_sub(uh->check, uh->len), newlen);

  	for (;;) {

  		if (copy_dtor) {
  			seg->destructor = sock_wfree;
  			seg->sk = sk;
  			sum_truesize += seg->truesize;
  		}

  		if (!seg->next)
  			break;

  
  		uh->len = newlen;
  		uh->check = check;

  		if (seg->ip_summed == CHECKSUM_PARTIAL)
  			gso_reset_checksum(seg, ~check);
  		else
  			uh->check = gso_make_checksum(seg, ~check) ? :
  				    CSUM_MANGLED_0;

  		seg = seg->next;
  		uh = udp_hdr(seg);

  	}

  	/* last packet can be partial gso_size, account for that in checksum */
  	newlen = htons(skb_tail_pointer(seg) - skb_transport_header(seg) +
  		       seg->data_len);
  	check = csum16_add(csum16_sub(uh->check, uh->len), newlen);
  
  	uh->len = newlen;
  	uh->check = check;

  	if (seg->ip_summed == CHECKSUM_PARTIAL)
  		gso_reset_checksum(seg, ~check);
  	else
  		uh->check = gso_make_checksum(seg, ~check) ? : CSUM_MANGLED_0;

  	/* update refcount for the packet */

  	if (copy_dtor) {
  		int delta = sum_truesize - gso_skb->truesize;
  
  		/* In some pathological cases, delta can be negative.
  		 * We need to either use refcount_add() or refcount_sub_and_test()
  		 */
  		if (likely(delta >= 0))
  			refcount_add(delta, &sk->sk_wmem_alloc);
  		else
  			WARN_ON_ONCE(refcount_sub_and_test(-delta, &sk->sk_wmem_alloc));
  	}

  	return segs;
  }
  EXPORT_SYMBOL_GPL(__udp_gso_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 | 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);

  	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;
  }

  #define UDP_GRO_CNT_MAX 64
  static struct sk_buff *udp_gro_receive_segment(struct list_head *head,
  					       struct sk_buff *skb)
  {

  	struct udphdr *uh = udp_gro_udphdr(skb);

  	struct sk_buff *pp = NULL;
  	struct udphdr *uh2;
  	struct sk_buff *p;

  	unsigned int ulen;

  	int ret = 0;

  
  	/* requires non zero csum, for symmetry with GSO */
  	if (!uh->check) {
  		NAPI_GRO_CB(skb)->flush = 1;
  		return NULL;
  	}

  	/* Do not deal with padded or malicious packets, sorry ! */
  	ulen = ntohs(uh->len);
  	if (ulen <= sizeof(*uh) || ulen != skb_gro_len(skb)) {
  		NAPI_GRO_CB(skb)->flush = 1;
  		return NULL;
  	}

  	/* pull encapsulating udp header */
  	skb_gro_pull(skb, sizeof(struct udphdr));

  
  	list_for_each_entry(p, head, list) {
  		if (!NAPI_GRO_CB(p)->same_flow)
  			continue;
  
  		uh2 = udp_hdr(p);
  
  		/* Match ports only, as csum is always non zero */
  		if ((*(u32 *)&uh->source != *(u32 *)&uh2->source)) {
  			NAPI_GRO_CB(p)->same_flow = 0;
  			continue;
  		}

  		if (NAPI_GRO_CB(skb)->is_flist != NAPI_GRO_CB(p)->is_flist) {
  			NAPI_GRO_CB(skb)->flush = 1;
  			return p;
  		}

  		/* Terminate the flow on len mismatch or if it grow "too much".
  		 * Under small packet flood GRO count could elsewhere grow a lot

  		 * leading to excessive truesize values.

  		 * On len mismatch merge the first packet shorter than gso_size,
  		 * otherwise complete the GRO packet.

  		 */

  		if (ulen > ntohs(uh2->len)) {
  			pp = p;
  		} else {
  			if (NAPI_GRO_CB(skb)->is_flist) {
  				if (!pskb_may_pull(skb, skb_gro_offset(skb))) {
  					NAPI_GRO_CB(skb)->flush = 1;
  					return NULL;
  				}
  				if ((skb->ip_summed != p->ip_summed) ||
  				    (skb->csum_level != p->csum_level)) {
  					NAPI_GRO_CB(skb)->flush = 1;
  					return NULL;
  				}
  				ret = skb_gro_receive_list(p, skb);
  			} else {
  				skb_gro_postpull_rcsum(skb, uh,
  						       sizeof(struct udphdr));
  
  				ret = skb_gro_receive(p, skb);
  			}
  		}
  
  		if (ret || ulen != ntohs(uh2->len) ||

  		    NAPI_GRO_CB(p)->count >= UDP_GRO_CNT_MAX)
  			pp = p;

  
  		return pp;
  	}
  
  	/* mismatch, but we never need to flush */
  	return NULL;
  }

  struct sk_buff *udp_gro_receive(struct list_head *head, struct sk_buff *skb,

  				struct udphdr *uh, struct sock *sk)

  {

  	struct sk_buff *pp = NULL;
  	struct sk_buff *p;

  	struct udphdr *uh2;
  	unsigned int off = skb_gro_offset(skb);

  	int flush = 1;

  	NAPI_GRO_CB(skb)->is_flist = 0;

  	if (skb->dev->features & NETIF_F_GRO_FRAGLIST)
  		NAPI_GRO_CB(skb)->is_flist = sk ? !udp_sk(sk)->gro_enabled: 1;

  	if ((sk && udp_sk(sk)->gro_enabled) || NAPI_GRO_CB(skb)->is_flist) {

  		pp = call_gro_receive(udp_gro_receive_segment, head, skb);

  		return pp;
  	}

  	if (!sk || NAPI_GRO_CB(skb)->encap_mark ||

  	    (skb->ip_summed != CHECKSUM_PARTIAL &&
  	     NAPI_GRO_CB(skb)->csum_cnt == 0 &&

  	     !NAPI_GRO_CB(skb)->csum_valid) ||
  	    !udp_sk(sk)->gro_receive)

  		goto out;

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

  	flush = 0;

  	list_for_each_entry(p, head, list) {

  		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:

  	skb_gro_flush_final(skb, pp, flush);

  	return pp;
  }

  EXPORT_SYMBOL(udp_gro_receive);

  static struct sock *udp4_gro_lookup_skb(struct sk_buff *skb, __be16 sport,
  					__be16 dport)
  {
  	const struct iphdr *iph = skb_gro_network_header(skb);
  
  	return __udp4_lib_lookup(dev_net(skb->dev), iph->saddr, sport,
  				 iph->daddr, dport, inet_iif(skb),
  				 inet_sdif(skb), &udp_table, NULL);
  }

  INDIRECT_CALLABLE_SCOPE
  struct sk_buff *udp4_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,
  						 inet_gro_compute_pseudo))
  		goto flush;
  	else if (uh->check)

  		skb_gro_checksum_try_convert(skb, IPPROTO_UDP,

  					     inet_gro_compute_pseudo);
  skip:

  	NAPI_GRO_CB(skb)->is_ipv6 = 0;

  	rcu_read_lock();

  
  	if (static_branch_unlikely(&udp_encap_needed_key))
  		sk = udp4_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;

  }

  static int udp_gro_complete_segment(struct sk_buff *skb)
  {
  	struct udphdr *uh = udp_hdr(skb);
  
  	skb->csum_start = (unsigned char *)uh - skb->head;
  	skb->csum_offset = offsetof(struct udphdr, check);
  	skb->ip_summed = CHECKSUM_PARTIAL;
  
  	skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
  	skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_L4;
  	return 0;
  }

  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;
  
  	rcu_read_lock();

  	sk = INDIRECT_CALL_INET(lookup, udp6_lib_lookup_skb,
  				udp4_lib_lookup_skb, skb, uh->source, uh->dest);

  	if (sk && udp_sk(sk)->gro_complete) {

  		skb_shinfo(skb)->gso_type = uh->check ? SKB_GSO_UDP_TUNNEL_CSUM
  					: SKB_GSO_UDP_TUNNEL;
  
  		/* Set encapsulation before calling into inner gro_complete()
  		 * functions to make them set up the inner offsets.
  		 */
  		skb->encapsulation = 1;

  		err = udp_sk(sk)->gro_complete(sk, skb,
  				nhoff + sizeof(struct udphdr));

  	} else {
  		err = udp_gro_complete_segment(skb);

  	}

  	rcu_read_unlock();

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

  	return err;
  }

  EXPORT_SYMBOL(udp_gro_complete);

  INDIRECT_CALLABLE_SCOPE 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 (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_v4_check(skb->len - nhoff, iph->saddr,
  					  iph->daddr, 0);

  	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);
  }