// SPDX-License-Identifier: GPL-2.0-only

  #include <linux/module.h>
  #include <linux/errno.h>
  #include <linux/socket.h>
  #include <linux/udp.h>
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/in6.h>
  #include <net/udp.h>
  #include <net/udp_tunnel.h>
  #include <net/net_namespace.h>
  #include <net/netns/generic.h>
  #include <net/ip6_tunnel.h>
  #include <net/ip6_checksum.h>
  
  int udp_sock_create6(struct net *net, struct udp_port_cfg *cfg,
  		     struct socket **sockp)
  {

  	struct sockaddr_in6 udp6_addr = {};

  	int err;
  	struct socket *sock = NULL;

  	err = sock_create_kern(net, AF_INET6, SOCK_DGRAM, 0, &sock);

  	if (err < 0)
  		goto error;

  	if (cfg->ipv6_v6only) {

  		err = ip6_sock_set_v6only(sock->sk);

  		if (err < 0)
  			goto error;
  	}

  	if (cfg->bind_ifindex) {

  		err = sock_bindtoindex(sock->sk, cfg->bind_ifindex, true);

  		if (err < 0)
  			goto error;
  	}

  	udp6_addr.sin6_family = AF_INET6;
  	memcpy(&udp6_addr.sin6_addr, &cfg->local_ip6,
  	       sizeof(udp6_addr.sin6_addr));
  	udp6_addr.sin6_port = cfg->local_udp_port;
  	err = kernel_bind(sock, (struct sockaddr *)&udp6_addr,
  			  sizeof(udp6_addr));
  	if (err < 0)
  		goto error;
  
  	if (cfg->peer_udp_port) {

  		memset(&udp6_addr, 0, sizeof(udp6_addr));

  		udp6_addr.sin6_family = AF_INET6;
  		memcpy(&udp6_addr.sin6_addr, &cfg->peer_ip6,
  		       sizeof(udp6_addr.sin6_addr));
  		udp6_addr.sin6_port = cfg->peer_udp_port;
  		err = kernel_connect(sock,
  				     (struct sockaddr *)&udp6_addr,
  				     sizeof(udp6_addr), 0);
  	}
  	if (err < 0)
  		goto error;
  
  	udp_set_no_check6_tx(sock->sk, !cfg->use_udp6_tx_checksums);
  	udp_set_no_check6_rx(sock->sk, !cfg->use_udp6_rx_checksums);
  
  	*sockp = sock;
  	return 0;
  
  error:
  	if (sock) {
  		kernel_sock_shutdown(sock, SHUT_RDWR);

  		sock_release(sock);

  	}
  	*sockp = NULL;
  	return err;
  }
  EXPORT_SYMBOL_GPL(udp_sock_create6);

  int udp_tunnel6_xmit_skb(struct dst_entry *dst, struct sock *sk,
  			 struct sk_buff *skb,

  			 struct net_device *dev, struct in6_addr *saddr,
  			 struct in6_addr *daddr,

  			 __u8 prio, __u8 ttl, __be32 label,
  			 __be16 src_port, __be16 dst_port, bool nocheck)

  {
  	struct udphdr *uh;
  	struct ipv6hdr *ip6h;

  
  	__skb_push(skb, sizeof(*uh));
  	skb_reset_transport_header(skb);
  	uh = udp_hdr(skb);
  
  	uh->dest = dst_port;
  	uh->source = src_port;
  
  	uh->len = htons(skb->len);

  	skb_dst_set(skb, dst);

  	udp6_set_csum(nocheck, skb, saddr, daddr, skb->len);

  
  	__skb_push(skb, sizeof(*ip6h));
  	skb_reset_network_header(skb);
  	ip6h		  = ipv6_hdr(skb);

  	ip6_flow_hdr(ip6h, prio, label);

  	ip6h->payload_len = htons(skb->len);
  	ip6h->nexthdr     = IPPROTO_UDP;
  	ip6h->hop_limit   = ttl;
  	ip6h->daddr	  = *daddr;
  	ip6h->saddr	  = *saddr;

  	ip6tunnel_xmit(sk, skb, dev);

  	return 0;
  }
  EXPORT_SYMBOL_GPL(udp_tunnel6_xmit_skb);

  
  MODULE_LICENSE("GPL");