// SPDX-License-Identifier: GPL-2.0

  #include <net/ip.h>
  #include <net/udp.h>
  #include <net/udplite.h>
  #include <asm/checksum.h>
  
  #ifndef _HAVE_ARCH_IPV6_CSUM
  __sum16 csum_ipv6_magic(const struct in6_addr *saddr,
  			const struct in6_addr *daddr,

  			__u32 len, __u8 proto, __wsum csum)

  {
  
  	int carry;
  	__u32 ulen;
  	__u32 uproto;
  	__u32 sum = (__force u32)csum;
  
  	sum += (__force u32)saddr->s6_addr32[0];
  	carry = (sum < (__force u32)saddr->s6_addr32[0]);
  	sum += carry;
  
  	sum += (__force u32)saddr->s6_addr32[1];
  	carry = (sum < (__force u32)saddr->s6_addr32[1]);
  	sum += carry;
  
  	sum += (__force u32)saddr->s6_addr32[2];
  	carry = (sum < (__force u32)saddr->s6_addr32[2]);
  	sum += carry;
  
  	sum += (__force u32)saddr->s6_addr32[3];
  	carry = (sum < (__force u32)saddr->s6_addr32[3]);
  	sum += carry;
  
  	sum += (__force u32)daddr->s6_addr32[0];
  	carry = (sum < (__force u32)daddr->s6_addr32[0]);
  	sum += carry;
  
  	sum += (__force u32)daddr->s6_addr32[1];
  	carry = (sum < (__force u32)daddr->s6_addr32[1]);
  	sum += carry;
  
  	sum += (__force u32)daddr->s6_addr32[2];
  	carry = (sum < (__force u32)daddr->s6_addr32[2]);
  	sum += carry;
  
  	sum += (__force u32)daddr->s6_addr32[3];
  	carry = (sum < (__force u32)daddr->s6_addr32[3]);
  	sum += carry;
  
  	ulen = (__force u32)htonl((__u32) len);
  	sum += ulen;
  	carry = (sum < ulen);
  	sum += carry;
  
  	uproto = (__force u32)htonl(proto);
  	sum += uproto;
  	carry = (sum < uproto);
  	sum += carry;
  
  	return csum_fold((__force __wsum)sum);
  }
  EXPORT_SYMBOL(csum_ipv6_magic);
  #endif
  
  int udp6_csum_init(struct sk_buff *skb, struct udphdr *uh, int proto)
  {
  	int err;
  
  	UDP_SKB_CB(skb)->partial_cov = 0;
  	UDP_SKB_CB(skb)->cscov = skb->len;
  
  	if (proto == IPPROTO_UDPLITE) {
  		err = udplite_checksum_init(skb, uh);
  		if (err)
  			return err;

  
  		if (UDP_SKB_CB(skb)->partial_cov) {
  			skb->csum = ip6_compute_pseudo(skb, proto);
  			return 0;
  		}

  	}

  	/* To support RFC 6936 (allow zero checksum in UDP/IPV6 for tunnels)
  	 * we accept a checksum of zero here. When we find the socket
  	 * for the UDP packet we'll check if that socket allows zero checksum
  	 * for IPv6 (set by socket option).

  	 *
  	 * Note, we are only interested in != 0 or == 0, thus the
  	 * force to int.

  	 */

  	err = (__force int)skb_checksum_init_zero_check(skb, proto, uh->check,
  							ip6_compute_pseudo);
  	if (err)
  		return err;
  
  	if (skb->ip_summed == CHECKSUM_COMPLETE && !skb->csum_valid) {
  		/* If SW calculated the value, we know it's bad */
  		if (skb->csum_complete_sw)
  			return 1;
  
  		/* HW says the value is bad. Let's validate that.
  		 * skb->csum is no longer the full packet checksum,
  		 * so don't treat is as such.
  		 */
  		skb_checksum_complete_unset(skb);
  	}
  
  	return 0;

  }
  EXPORT_SYMBOL(udp6_csum_init);

  
  /* Function to set UDP checksum for an IPv6 UDP packet. This is intended
   * for the simple case like when setting the checksum for a UDP tunnel.
   */
  void udp6_set_csum(bool nocheck, struct sk_buff *skb,
  		   const struct in6_addr *saddr,
  		   const struct in6_addr *daddr, int len)
  {
  	struct udphdr *uh = udp_hdr(skb);
  
  	if (nocheck)
  		uh->check = 0;
  	else if (skb_is_gso(skb))
  		uh->check = ~udp_v6_check(len, saddr, daddr, 0);

  	else if (skb->ip_summed == CHECKSUM_PARTIAL) {
  		uh->check = 0;
  		uh->check = udp_v6_check(len, saddr, daddr, lco_csum(skb));
  		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);
  		uh->check = ~udp_v6_check(len, saddr, daddr, 0);

  	}
  }
  EXPORT_SYMBOL(udp6_set_csum);