/* (C) 1999-2001 Paul `Rusty' Russell
   * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.

   */
  
  #include <linux/types.h>

  #include <linux/timer.h>
  #include <linux/module.h>

  #include <linux/udp.h>
  #include <linux/seq_file.h>
  #include <linux/skbuff.h>
  #include <linux/ipv6.h>
  #include <net/ip6_checksum.h>
  #include <net/checksum.h>

  #include <linux/netfilter.h>
  #include <linux/netfilter_ipv4.h>
  #include <linux/netfilter_ipv6.h>

  #include <net/netfilter/nf_conntrack_l4proto.h>

  #include <net/netfilter/nf_conntrack_ecache.h>

  #include <net/netfilter/nf_log.h>

  #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
  #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>

  static unsigned int nf_ct_udp_timeout __read_mostly = 30*HZ;
  static unsigned int nf_ct_udp_timeout_stream __read_mostly = 180*HZ;

  static bool udp_pkt_to_tuple(const struct sk_buff *skb,

  			     unsigned int dataoff,
  			     struct nf_conntrack_tuple *tuple)
  {

  	const struct udphdr *hp;
  	struct udphdr _hdr;

  
  	/* Actually only need first 8 bytes. */
  	hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  	if (hp == NULL)

  		return false;

  
  	tuple->src.u.udp.port = hp->source;
  	tuple->dst.u.udp.port = hp->dest;

  	return true;

  }

  static bool udp_invert_tuple(struct nf_conntrack_tuple *tuple,
  			     const struct nf_conntrack_tuple *orig)

  {
  	tuple->src.u.udp.port = orig->dst.u.udp.port;
  	tuple->dst.u.udp.port = orig->src.u.udp.port;

  	return true;

  }
  
  /* Print out the per-protocol part of the tuple. */
  static int udp_print_tuple(struct seq_file *s,
  			   const struct nf_conntrack_tuple *tuple)
  {
  	return seq_printf(s, "sport=%hu dport=%hu ",
  			  ntohs(tuple->src.u.udp.port),
  			  ntohs(tuple->dst.u.udp.port));
  }

  /* Returns verdict for packet, and may modify conntracktype */

  static int udp_packet(struct nf_conn *ct,

  		      const struct sk_buff *skb,
  		      unsigned int dataoff,
  		      enum ip_conntrack_info ctinfo,

  		      u_int8_t pf,

  		      unsigned int hooknum)
  {
  	/* If we've seen traffic both ways, this is some kind of UDP
  	   stream.  Extend timeout. */

  	if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
  		nf_ct_refresh_acct(ct, ctinfo, skb, nf_ct_udp_timeout_stream);

  		/* Also, more likely to be important, and not a probe */

  		if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))

  			nf_conntrack_event_cache(IPCT_ASSURED, ct);

  	} else

  		nf_ct_refresh_acct(ct, ctinfo, skb, nf_ct_udp_timeout);

  
  	return NF_ACCEPT;
  }
  
  /* Called when a new connection for this protocol found. */

  static bool udp_new(struct nf_conn *ct, const struct sk_buff *skb,
  		    unsigned int dataoff)

  {

  	return true;

  }

  static int udp_error(struct net *net, struct nf_conn *tmpl, struct sk_buff *skb,
  		     unsigned int dataoff, enum ip_conntrack_info *ctinfo,

  		     u_int8_t pf,

  		     unsigned int hooknum)

  {
  	unsigned int udplen = skb->len - dataoff;

  	const struct udphdr *hdr;
  	struct udphdr _hdr;

  
  	/* Header is too small? */
  	hdr = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  	if (hdr == NULL) {

  		if (LOG_INVALID(net, IPPROTO_UDP))

  			nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
  				      "nf_ct_udp: short packet ");
  		return -NF_ACCEPT;
  	}
  
  	/* Truncated/malformed packets */
  	if (ntohs(hdr->len) > udplen || ntohs(hdr->len) < sizeof(*hdr)) {

  		if (LOG_INVALID(net, IPPROTO_UDP))

  			nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
  				"nf_ct_udp: truncated/malformed packet ");
  		return -NF_ACCEPT;
  	}
  
  	/* Packet with no checksum */
  	if (!hdr->check)
  		return NF_ACCEPT;
  
  	/* Checksum invalid? Ignore.
  	 * We skip checking packets on the outgoing path

  	 * because the checksum is assumed to be correct.

  	 * FIXME: Source route IP option packets --RR */

  	if (net->ct.sysctl_checksum && hooknum == NF_INET_PRE_ROUTING &&

  	    nf_checksum(skb, hooknum, dataoff, IPPROTO_UDP, pf)) {

  		if (LOG_INVALID(net, IPPROTO_UDP))

  			nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
  				"nf_ct_udp: bad UDP checksum ");
  		return -NF_ACCEPT;
  	}
  
  	return NF_ACCEPT;
  }

  #ifdef CONFIG_SYSCTL
  static unsigned int udp_sysctl_table_users;
  static struct ctl_table_header *udp_sysctl_header;
  static struct ctl_table udp_sysctl_table[] = {
  	{

  		.procname	= "nf_conntrack_udp_timeout",
  		.data		= &nf_ct_udp_timeout,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "nf_conntrack_udp_timeout_stream",
  		.data		= &nf_ct_udp_timeout_stream,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},

  	{ }

  };

  #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
  static struct ctl_table udp_compat_sysctl_table[] = {
  	{

  		.procname	= "ip_conntrack_udp_timeout",
  		.data		= &nf_ct_udp_timeout,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "ip_conntrack_udp_timeout_stream",
  		.data		= &nf_ct_udp_timeout_stream,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},

  	{ }

  };
  #endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */

  #endif /* CONFIG_SYSCTL */

  struct nf_conntrack_l4proto nf_conntrack_l4proto_udp4 __read_mostly =

  {
  	.l3proto		= PF_INET,

  	.l4proto		= IPPROTO_UDP,

  	.name			= "udp",
  	.pkt_to_tuple		= udp_pkt_to_tuple,
  	.invert_tuple		= udp_invert_tuple,
  	.print_tuple		= udp_print_tuple,

  	.packet			= udp_packet,
  	.new			= udp_new,

  	.error			= udp_error,

  #if IS_ENABLED(CONFIG_NF_CT_NETLINK)

  	.tuple_to_nlattr	= nf_ct_port_tuple_to_nlattr,
  	.nlattr_to_tuple	= nf_ct_port_nlattr_to_tuple,

  	.nlattr_tuple_size	= nf_ct_port_nlattr_tuple_size,

  	.nla_policy		= nf_ct_port_nla_policy,

  #endif

  #ifdef CONFIG_SYSCTL
  	.ctl_table_users	= &udp_sysctl_table_users,
  	.ctl_table_header	= &udp_sysctl_header,
  	.ctl_table		= udp_sysctl_table,

  #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
  	.ctl_compat_table	= udp_compat_sysctl_table,
  #endif

  #endif

  };

  EXPORT_SYMBOL_GPL(nf_conntrack_l4proto_udp4);

  struct nf_conntrack_l4proto nf_conntrack_l4proto_udp6 __read_mostly =

  {
  	.l3proto		= PF_INET6,

  	.l4proto		= IPPROTO_UDP,

  	.name			= "udp",
  	.pkt_to_tuple		= udp_pkt_to_tuple,
  	.invert_tuple		= udp_invert_tuple,
  	.print_tuple		= udp_print_tuple,

  	.packet			= udp_packet,
  	.new			= udp_new,

  	.error			= udp_error,

  #if IS_ENABLED(CONFIG_NF_CT_NETLINK)

  	.tuple_to_nlattr	= nf_ct_port_tuple_to_nlattr,
  	.nlattr_to_tuple	= nf_ct_port_nlattr_to_tuple,

  	.nlattr_tuple_size	= nf_ct_port_nlattr_tuple_size,

  	.nla_policy		= nf_ct_port_nla_policy,

  #endif

  #ifdef CONFIG_SYSCTL
  	.ctl_table_users	= &udp_sysctl_table_users,
  	.ctl_table_header	= &udp_sysctl_header,
  	.ctl_table		= udp_sysctl_table,
  #endif

  };

  EXPORT_SYMBOL_GPL(nf_conntrack_l4proto_udp6);