text: // SPDX-License-Identifier: GPL-2.0-only
  /* Kernel module to match one of a list of TCP/UDP(-Lite)/SCTP/DCCP ports:
     ports are in the same place so we can treat them as equal. */
  
  /* (C) 1999-2001 Paul `Rusty' Russell
   * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   */
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/udp.h>
  #include <linux/skbuff.h>
  #include <linux/in.h>
  
  #include <linux/netfilter/xt_multiport.h>
  #include <linux/netfilter/x_tables.h>
  #include <linux/netfilter_ipv4/ip_tables.h>
  #include <linux/netfilter_ipv6/ip6_tables.h>
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  MODULE_DESCRIPTION("Xtables: multiple port matching for TCP, UDP, UDP-Lite, SCTP and DCCP");
  MODULE_ALIAS("ipt_multiport");
  MODULE_ALIAS("ip6t_multiport");
  
  /* Returns 1 if the port is matched by the test, 0 otherwise. */
  static inline bool
  ports_match_v1(const struct xt_multiport_v1 *minfo,
  	       u_int16_t src, u_int16_t dst)
  {
  	unsigned int i;
  	u_int16_t s, e;
  
  	for (i = 0; i < minfo->count; i++) {
  		s = minfo->ports[i];
  
  		if (minfo->pflags[i]) {
  			/* range port matching */
  			e = minfo->ports[++i];
  			pr_debug("src or dst matches with %d-%d?\n", s, e);
  
  			switch (minfo->flags) {
  			case XT_MULTIPORT_SOURCE:
  				if (src >= s && src <= e)
  					return true ^ minfo->invert;
  				break;
  			case XT_MULTIPORT_DESTINATION:
  				if (dst >= s && dst <= e)
  					return true ^ minfo->invert;
  				break;
  			case XT_MULTIPORT_EITHER:
  				if ((dst >= s && dst <= e) ||
  				    (src >= s && src <= e))
  					return true ^ minfo->invert;
  				break;
  			default:
  				break;
  			}
  		} else {
  			/* exact port matching */
  			pr_debug("src or dst matches with %d?\n", s);
  
  			switch (minfo->flags) {
  			case XT_MULTIPORT_SOURCE:
  				if (src == s)
  					return true ^ minfo->invert;
  				break;
  			case XT_MULTIPORT_DESTINATION:
  				if (dst == s)
  					return true ^ minfo->invert;
  				break;
  			case XT_MULTIPORT_EITHER:
  				if (src == s || dst == s)
  					return true ^ minfo->invert;
  				break;
  			default:
  				break;
  			}
  		}
  	}
  
  	return minfo->invert;
  }
  
  static bool
  multiport_mt(const struct sk_buff *skb, struct xt_action_param *par)
  {
  	const __be16 *pptr;
  	__be16 _ports[2];
  	const struct xt_multiport_v1 *multiinfo = par->matchinfo;
  
  	if (par->fragoff != 0)
  		return false;
  
  	pptr = skb_header_pointer(skb, par->thoff, sizeof(_ports), _ports);
  	if (pptr == NULL) {
  		/* We've been asked to examine this packet, and we
  		 * can't.  Hence, no choice but to drop.
  		 */
  		pr_debug("Dropping evil offset=0 tinygram.\n");
  		par->hotdrop = true;
  		return false;
  	}
  
  	return ports_match_v1(multiinfo, ntohs(pptr[0]), ntohs(pptr[1]));
  }
  
  static inline bool
  check(u_int16_t proto,
        u_int8_t ip_invflags,
        u_int8_t match_flags,
        u_int8_t count)
  {
  	/* Must specify supported protocol, no unknown flags or bad count */
  	return (proto == IPPROTO_TCP || proto == IPPROTO_UDP
  		|| proto == IPPROTO_UDPLITE
  		|| proto == IPPROTO_SCTP || proto == IPPROTO_DCCP)
  		&& !(ip_invflags & XT_INV_PROTO)
  		&& (match_flags == XT_MULTIPORT_SOURCE
  		    || match_flags == XT_MULTIPORT_DESTINATION
  		    || match_flags == XT_MULTIPORT_EITHER)
  		&& count <= XT_MULTI_PORTS;
  }
  
  static int multiport_mt_check(const struct xt_mtchk_param *par)
  {
  	const struct ipt_ip *ip = par->entryinfo;
  	const struct xt_multiport_v1 *multiinfo = par->matchinfo;
  
  	return check(ip->proto, ip->invflags, multiinfo->flags,
  		     multiinfo->count) ? 0 : -EINVAL;
  }
  
  static int multiport_mt6_check(const struct xt_mtchk_param *par)
  {
  	const struct ip6t_ip6 *ip = par->entryinfo;
  	const struct xt_multiport_v1 *multiinfo = par->matchinfo;
  
  	return check(ip->proto, ip->invflags, multiinfo->flags,
  		     multiinfo->count) ? 0 : -EINVAL;
  }
  
  static struct xt_match multiport_mt_reg[] __read_mostly = {
  	{
  		.name		= "multiport",
  		.family		= NFPROTO_IPV4,
  		.revision	= 1,
  		.checkentry	= multiport_mt_check,
  		.match		= multiport_mt,
  		.matchsize	= sizeof(struct xt_multiport_v1),
  		.me		= THIS_MODULE,
  	},
  	{
  		.name		= "multiport",
  		.family		= NFPROTO_IPV6,
  		.revision	= 1,
  		.checkentry	= multiport_mt6_check,
  		.match		= multiport_mt,
  		.matchsize	= sizeof(struct xt_multiport_v1),
  		.me		= THIS_MODULE,
  	},
  };
  
  static int __init multiport_mt_init(void)
  {
  	return xt_register_matches(multiport_mt_reg,
  	       ARRAY_SIZE(multiport_mt_reg));
  }
  
  static void __exit multiport_mt_exit(void)
  {
  	xt_unregister_matches(multiport_mt_reg, ARRAY_SIZE(multiport_mt_reg));
  }
  
  module_init(multiport_mt_init);
  module_exit(multiport_mt_exit);
  