/* Kernel module to match one of a list of TCP/UDP ports: ports are in   the same place so we can treat them as equal. */#include <linux/module.h>#include <linux/types.h>#include <linux/udp.h>#include <linux/skbuff.h>#include <linux/netfilter_ipv4/ipt_multiport.h>#include <linux/netfilter_ipv4/ip_tables.h>#if 0#define duprintf(format, args...) printk(format , ## args)#else#define duprintf(format, args...)#endif/* Returns 1 if the port is matched by the test, 0 otherwise. */static inline intports_match(const u_int16_t *portlist, enum ipt_multiport_flags flags,	    u_int8_t count, u_int16_t src, u_int16_t dst){	unsigned int i;	for (i=0; i<count; i++) {		if (flags != IPT_MULTIPORT_DESTINATION		    && portlist[i] == src)			return 1;		if (flags != IPT_MULTIPORT_SOURCE		    && portlist[i] == dst)			return 1;	}	return 0;}static intmatch(const struct sk_buff *skb,      const struct net_device *in,      const struct net_device *out,      const void *matchinfo,      int offset,      const void *hdr,      u_int16_t datalen,      int *hotdrop){	const struct udphdr *udp = hdr;	const struct ipt_multiport *multiinfo = matchinfo;	/* Must be big enough to read ports. */	if (offset == 0 && datalen < sizeof(struct udphdr)) {		/* We've been asked to examine this packet, and we		   can't.  Hence, no choice but to drop. */			duprintf("ipt_multiport:"				 " Dropping evil offset=0 tinygram.\n");			*hotdrop = 1;			return 0;	}	/* Must not be a fragment. */	return !offset		&& ports_match(multiinfo->ports,			       multiinfo->flags, multiinfo->count,			       ntohs(udp->source), ntohs(udp->dest));}/* Called when user tries to insert an entry of this type. */static intcheckentry(const char *tablename,	   const struct ipt_ip *ip,	   void *matchinfo,	   unsigned int matchsize,	   unsigned int hook_mask){	const struct ipt_multiport *multiinfo = matchinfo;	if (matchsize != IPT_ALIGN(sizeof(struct ipt_multiport)))		return 0;	/* Must specify proto == TCP/UDP, no unknown flags or bad count */	return (ip->proto == IPPROTO_TCP || ip->proto == IPPROTO_UDP)		&& !(ip->flags & IPT_INV_PROTO)		&& matchsize == IPT_ALIGN(sizeof(struct ipt_multiport))		&& (multiinfo->flags == IPT_MULTIPORT_SOURCE		    || multiinfo->flags == IPT_MULTIPORT_DESTINATION		    || multiinfo->flags == IPT_MULTIPORT_EITHER)		&& multiinfo->count <= IPT_MULTI_PORTS;}static struct ipt_match multiport_match= { { NULL, NULL }, "multiport", &match, &checkentry, NULL, THIS_MODULE };static int __init init(void){	return ipt_register_match(&multiport_match);}static void __exit fini(void){	ipt_unregister_match(&multiport_match);}module_init(init);module_exit(fini);MODULE_LICENSE("GPL");