patch-2.3.99-pre2 linux/net/ipv4/netfilter/ip_tables.c

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diff -u --recursive --new-file v2.3.99-pre1/linux/net/ipv4/netfilter/ip_tables.c linux/net/ipv4/netfilter/ip_tables.c
@@ -0,0 +1,1664 @@
+/*
+ * Packet matching code.
+ *
+ * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
+ */
+#include <linux/config.h>
+#include <linux/skbuff.h>
+#include <linux/kmod.h>
+#include <linux/vmalloc.h>
+#include <linux/netdevice.h>
+#include <linux/module.h>
+#include <linux/tcp.h>
+#include <linux/udp.h>
+#include <linux/icmp.h>
+#include <asm/uaccess.h>
+#include <asm/semaphore.h>
+
+#include <linux/netfilter_ipv4/ip_tables.h>
+
+#ifndef IP_OFFSET
+#define IP_OFFSET 0x1FFF
+#endif
+
+/*#define DEBUG_IP_FIREWALL*/
+/*#define DEBUG_ALLOW_ALL*/ /* Useful for remote debugging */
+/*#define DEBUG_IP_FIREWALL_USER*/
+
+#ifdef DEBUG_IP_FIREWALL
+#define dprintf(format, args...)  printk(format , ## args)
+#else
+#define dprintf(format, args...)
+#endif
+
+#ifdef DEBUG_IP_FIREWALL_USER
+#define duprintf(format, args...) printk(format , ## args)
+#else
+#define duprintf(format, args...)
+#endif
+
+#ifdef CONFIG_NETFILTER_DEBUG
+#define IP_NF_ASSERT(x)						\
+do {								\
+	if (!(x))						\
+		printk("IPT_ASSERT: %s:%s:%u\n",		\
+		       __FUNCTION__, __FILE__, __LINE__);	\
+} while(0)
+#else
+#define IP_NF_ASSERT(x)
+#endif
+#define SMP_ALIGN(x) (((x) + SMP_CACHE_BYTES-1) & ~(SMP_CACHE_BYTES-1))
+
+/* Mutex protects lists (only traversed in user context). */
+static DECLARE_MUTEX(ipt_mutex);
+
+/* Must have mutex */
+#define ASSERT_READ_LOCK(x) IP_NF_ASSERT(down_trylock(&ipt_mutex) != 0)
+#define ASSERT_WRITE_LOCK(x) IP_NF_ASSERT(down_trylock(&ipt_mutex) != 0)
+#include <linux/netfilter_ipv4/lockhelp.h>
+#include <linux/netfilter_ipv4/listhelp.h>
+
+#if 0
+/* All the better to debug you with... */
+#define static
+#define inline
+#endif
+
+/* Locking is simple: we assume at worst case there will be one packet
+   in user context and one from bottom halves (or soft irq if Alexey's
+   softnet patch was applied).
+
+   We keep a set of rules for each CPU, so we can avoid write-locking
+   them; doing a readlock_bh() stops packets coming through if we're
+   in user context.
+
+   To be cache friendly on SMP, we arrange them like so:
+   [ n-entries ]
+   ... cache-align padding ...
+   [ n-entries ]
+
+   Hence the start of any table is given by get_table() below.  */
+
+/* The table itself */
+struct ipt_table_info
+{
+	/* Size per table */
+	unsigned int size;
+	/* Number of entries: FIXME. --RR */
+	unsigned int number;
+
+	/* Entry points and underflows */
+	unsigned int hook_entry[NF_IP_NUMHOOKS];
+	unsigned int underflow[NF_IP_NUMHOOKS];
+
+	char padding[SMP_ALIGN((NF_IP_NUMHOOKS*2+2)*sizeof(unsigned int))];
+
+	/* ipt_entry tables: one per CPU */
+	char entries[0];
+};
+
+static LIST_HEAD(ipt_target);
+static LIST_HEAD(ipt_match);
+static LIST_HEAD(ipt_tables);
+#define ADD_COUNTER(c,b,p) do { (c).bcnt += (b); (c).pcnt += (p); } while(0)
+
+#ifdef CONFIG_SMP
+#define TABLE_OFFSET(t,p) (SMP_ALIGN((t)->size)*cpu_number_map(p))
+#else
+#define TABLE_OFFSET(t,p) 0
+#endif
+
+#if 0
+#define down(x) do { printk("DOWN:%u:" #x "\n", __LINE__); down(x); } while(0)
+#define down_interruptible(x) ({ int __r; printk("DOWNi:%u:" #x "\n", __LINE__); __r = down_interruptible(x); if (__r != 0) printk("ABORT-DOWNi:%u\n", __LINE__); __r; })
+#define up(x) do { printk("UP:%u:" #x "\n", __LINE__); up(x); } while(0)
+#endif
+
+/* Returns whether matches rule or not. */
+static inline int
+ip_packet_match(const struct iphdr *ip,
+		const char *indev,
+		const char *outdev,
+		const struct ipt_ip *ipinfo,
+		int isfrag)
+{
+	size_t i;
+	unsigned long ret;
+
+#define FWINV(bool,invflg) ((bool) ^ !!(ipinfo->invflags & invflg))
+
+	if (FWINV((ip->saddr&ipinfo->smsk.s_addr) != ipinfo->src.s_addr,
+		  IPT_INV_SRCIP)
+	    || FWINV((ip->daddr&ipinfo->dmsk.s_addr) != ipinfo->dst.s_addr,
+		     IPT_INV_DSTIP)) {
+		dprintf("Source or dest mismatch.\n");
+
+		dprintf("SRC: %u.%u.%u.%u. Mask: %u.%u.%u.%u. Target: %u.%u.%u.%u.%s\n",
+			NIPQUAD(ip->saddr),
+			NIPQUAD(ipinfo->smsk.s_addr),
+			NIPQUAD(ipinfo->src.s_addr),
+			ipinfo->invflags & IPT_INV_SRCIP ? " (INV)" : "");
+		dprintf("DST: %u.%u.%u.%u Mask: %u.%u.%u.%u Target: %u.%u.%u.%u.%s\n",
+			NIPQUAD(ip->daddr),
+			NIPQUAD(ipinfo->dmsk.s_addr),
+			NIPQUAD(ipinfo->dst.s_addr),
+			ipinfo->invflags & IPT_INV_DSTIP ? " (INV)" : "");
+		return 0;
+	}
+
+	/* Look for ifname matches; this should unroll nicely. */
+	for (i = 0, ret = 0; i < IFNAMSIZ/sizeof(unsigned long); i++) {
+		ret |= (((const unsigned long *)indev)[i]
+			^ ((const unsigned long *)ipinfo->iniface)[i])
+			& ((const unsigned long *)ipinfo->iniface_mask)[i];
+	}
+
+	if (FWINV(ret != 0, IPT_INV_VIA_IN)) {
+		dprintf("VIA in mismatch (%s vs %s).%s\n",
+			indev, ipinfo->iniface,
+			ipinfo->invflags&IPT_INV_VIA_IN ?" (INV)":"");
+		return 0;
+	}
+
+	for (i = 0, ret = 0; i < IFNAMSIZ/sizeof(unsigned long); i++) {
+		ret |= (((const unsigned long *)outdev)[i]
+			^ ((const unsigned long *)ipinfo->outiface)[i])
+			& ((const unsigned long *)ipinfo->outiface_mask)[i];
+	}
+
+	if (FWINV(ret != 0, IPT_INV_VIA_OUT)) {
+		dprintf("VIA out mismatch (%s vs %s).%s\n",
+			outdev, ipinfo->outiface,
+			ipinfo->invflags&IPT_INV_VIA_OUT ?" (INV)":"");
+		return 0;
+	}
+
+	/* Check specific protocol */
+	if (ipinfo->proto
+	    && FWINV(ip->protocol != ipinfo->proto, IPT_INV_PROTO)) {
+		dprintf("Packet protocol %hi does not match %hi.%s\n",
+			ip->protocol, ipinfo->proto,
+			ipinfo->invflags&IPT_INV_PROTO ? " (INV)":"");
+		return 0;
+	}
+
+	/* If we have a fragment rule but the packet is not a fragment
+	 * then we return zero */
+	if (FWINV((ipinfo->flags&IPT_F_FRAG) && !isfrag, IPT_INV_FRAG)) {
+		dprintf("Fragment rule but not fragment.%s\n",
+			ipinfo->invflags & IPT_INV_FRAG ? " (INV)" : "");
+		return 0;
+	}
+
+	return 1;
+}
+
+static inline int
+ip_checkentry(const struct ipt_ip *ip)
+{
+	if (ip->flags & ~IPT_F_MASK) {
+		duprintf("Unknown flag bits set: %08X\n",
+			 ip->flags & ~IPT_F_MASK);
+		return 0;
+	}
+	if (ip->invflags & ~IPT_INV_MASK) {
+		duprintf("Unknown invflag bits set: %08X\n",
+			 ip->invflags & ~IPT_INV_MASK);
+		return 0;
+	}
+	return 1;
+}
+
+static unsigned int
+ipt_error(struct sk_buff **pskb,
+	  unsigned int hooknum,
+	  const struct net_device *in,
+	  const struct net_device *out,
+	  const void *targinfo,
+	  void *userinfo)
+{
+	if (net_ratelimit())
+		printk("ip_tables: error: `%s'\n", (char *)targinfo);
+
+	return NF_DROP;
+}
+
+static inline
+int do_match(struct ipt_entry_match *m,
+	     const struct sk_buff *skb,
+	     const struct net_device *in,
+	     const struct net_device *out,
+	     int offset,
+	     const void *hdr,
+	     u_int16_t datalen,
+	     int *hotdrop)
+{
+	/* Stop iteration if it doesn't match */
+	if (!m->u.match->match(skb, in, out, m->data,
+			       offset, hdr, datalen, hotdrop))
+		return 1;
+	else
+		return 0;
+}
+
+static inline struct ipt_entry *
+get_entry(void *base, unsigned int offset)
+{
+	return (struct ipt_entry *)(base + offset);
+}
+
+/* Returns one of the generic firewall policies, like NF_ACCEPT. */
+unsigned int
+ipt_do_table(struct sk_buff **pskb,
+	     unsigned int hook,
+	     const struct net_device *in,
+	     const struct net_device *out,
+	     struct ipt_table *table,
+	     void *userdata)
+{
+	static const char nulldevname[IFNAMSIZ] = { 0 };
+	u_int16_t offset;
+	struct iphdr *ip;
+	void *protohdr;
+	u_int16_t datalen;
+	int hotdrop = 0;
+	/* Initializing verdict to NF_DROP keeps gcc happy. */
+	unsigned int verdict = NF_DROP;
+	const char *indev, *outdev;
+	void *table_base;
+	struct ipt_entry *e, *back;
+
+	/* Initialization */
+	ip = (*pskb)->nh.iph;
+	protohdr = (u_int32_t *)ip + ip->ihl;
+	datalen = (*pskb)->len - ip->ihl * 4;
+	indev = in ? in->name : nulldevname;
+	outdev = out ? out->name : nulldevname;
+	/* We handle fragments by dealing with the first fragment as
+	 * if it was a normal packet.  All other fragments are treated
+	 * normally, except that they will NEVER match rules that ask
+	 * things we don't know, ie. tcp syn flag or ports).  If the
+	 * rule is also a fragment-specific rule, non-fragments won't
+	 * match it. */
+	offset = ntohs(ip->frag_off) & IP_OFFSET;
+
+	read_lock_bh(&table->lock);
+	IP_NF_ASSERT(table->valid_hooks & (1 << hook));
+	table_base = (void *)table->private->entries
+		+ TABLE_OFFSET(table->private, smp_processor_id());
+	e = get_entry(table_base, table->private->hook_entry[hook]);
+
+	/* Check noone else using our table */
+	IP_NF_ASSERT(((struct ipt_entry *)table_base)->comefrom == 0xdead57ac);
+#ifdef CONFIG_NETFILTER_DEBUG
+	((struct ipt_entry *)table_base)->comefrom = 0x57acc001;
+#endif
+
+	/* For return from builtin chain */
+	back = get_entry(table_base, table->private->underflow[hook]);
+
+	do {
+		IP_NF_ASSERT(e);
+		IP_NF_ASSERT(back);
+		(*pskb)->nfcache |= e->nfcache;
+		if (ip_packet_match(ip, indev, outdev, &e->ip, offset)) {
+			struct ipt_entry_target *t;
+
+			if (IPT_MATCH_ITERATE(e, do_match,
+					      *pskb, in, out,
+					      offset, protohdr,
+					      datalen, &hotdrop) != 0)
+				goto no_match;
+
+			ADD_COUNTER(e->counters, ntohs(ip->tot_len), 1);
+
+			t = ipt_get_target(e);
+			IP_NF_ASSERT(t->u.target);
+			/* Standard target? */
+			if (!t->u.target->target) {
+				int v;
+
+				v = ((struct ipt_standard_target *)t)->verdict;
+				if (v < 0) {
+					/* Pop from stack? */
+					if (v != IPT_RETURN) {
+						verdict = (unsigned)(-v) - 1;
+						break;
+					}
+					e = back;
+					back = get_entry(table_base,
+							 back->comefrom);
+					continue;
+				}
+				if (table_base + v
+				    != (void *)e + e->next_offset) {
+					/* Save old back ptr in next entry */
+					struct ipt_entry *next
+						= (void *)e + e->next_offset;
+					next->comefrom
+						= (void *)back - table_base;
+					/* set back pointer to next entry */
+					back = next;
+				}
+
+				e = get_entry(table_base, v);
+			} else {
+				verdict = t->u.target->target(pskb, hook,
+							      in, out,
+							      t->data,
+							      userdata);
+
+				/* Target might have changed stuff. */
+				ip = (*pskb)->nh.iph;
+				protohdr = (u_int32_t *)ip + ip->ihl;
+				datalen = (*pskb)->len - ip->ihl * 4;
+
+				if (verdict == IPT_CONTINUE)
+					e = (void *)e + e->next_offset;
+				else
+					/* Verdict */
+					break;
+			}
+		} else {
+
+		no_match:
+			e = (void *)e + e->next_offset;
+		}
+	} while (!hotdrop);
+
+#ifdef CONFIG_NETFILTER_DEBUG
+	((struct ipt_entry *)table_base)->comefrom = 0xdead57ac;
+#endif
+	read_unlock_bh(&table->lock);
+
+#ifdef DEBUG_ALLOW_ALL
+	return NF_ACCEPT;
+#else
+	if (hotdrop)
+		return NF_DROP;
+	else return verdict;
+#endif
+}
+
+/* If it succeeds, returns element and locks mutex */
+static inline void *
+find_inlist_lock_noload(struct list_head *head,
+			const char *name,
+			int *error,
+			struct semaphore *mutex)
+{
+	void *ret;
+
+#if 0
+	duprintf("find_inlist: searching for `%s' in %s.\n",
+		 name, head == &ipt_target ? "ipt_target"
+		 : head == &ipt_match ? "ipt_match"
+		 : head == &ipt_tables ? "ipt_tables" : "UNKNOWN");
+#endif
+
+	*error = down_interruptible(mutex);
+	if (*error != 0)
+		return NULL;
+
+	ret = list_named_find(head, name);
+	if (!ret) {
+		*error = -ENOENT;
+		up(mutex);
+	}
+	return ret;
+}
+
+#ifndef CONFIG_KMOD
+#define find_inlist_lock(h,n,p,e,m) find_inlist_lock_noload((h),(n),(e),(m))
+#else
+static void *
+find_inlist_lock(struct list_head *head,
+		 const char *name,
+		 const char *prefix,
+		 int *error,
+		 struct semaphore *mutex)
+{
+	void *ret;
+
+	ret = find_inlist_lock_noload(head, name, error, mutex);
+	if (!ret) {
+		char modulename[IPT_FUNCTION_MAXNAMELEN + strlen(prefix) + 1];
+		strcpy(modulename, prefix);
+		strcat(modulename, name);
+		duprintf("find_inlist: loading `%s'.\n", modulename);
+		request_module(modulename);
+		ret = find_inlist_lock_noload(head, name, error, mutex);
+	}
+
+	return ret;
+}
+#endif
+
+static inline struct ipt_table *
+find_table_lock(const char *name, int *error, struct semaphore *mutex)
+{
+	return find_inlist_lock(&ipt_tables, name, "iptable_", error, mutex);
+}
+
+static inline struct ipt_match *
+find_match_lock(const char *name, int *error, struct semaphore *mutex)
+{
+	return find_inlist_lock(&ipt_match, name, "ipt_", error, mutex);
+}
+
+static inline struct ipt_target *
+find_target_lock(const char *name, int *error, struct semaphore *mutex)
+{
+	return find_inlist_lock(&ipt_target, name, "ipt_", error, mutex);
+}
+
+/* All zeroes == unconditional rule. */
+static inline int
+unconditional(const struct ipt_ip *ip)
+{
+	unsigned int i;
+
+	for (i = 0; i < sizeof(*ip)/sizeof(__u32); i++)
+		if (((__u32 *)ip)[i])
+			return 0;
+
+	return 1;
+}
+
+/* Figures out from what hook each rule can be called: returns 0 if
+   there are loops.  Puts hook bitmask in comefrom. */
+static int
+mark_source_chains(struct ipt_table_info *newinfo, unsigned int valid_hooks)
+{
+	unsigned int hook;
+
+	/* No recursion; use packet counter to save back ptrs (reset
+	   to 0 as we leave), and comefrom to save source hook bitmask */
+	for (hook = 0; hook < NF_IP_NUMHOOKS; hook++) {
+		unsigned int pos = newinfo->hook_entry[hook];
+		struct ipt_entry *e
+			= (struct ipt_entry *)(newinfo->entries + pos);
+
+		if (!(valid_hooks & (1 << hook)))
+			continue;
+
+		/* Set initial back pointer. */
+		e->counters.pcnt = pos;
+
+		for (;;) {
+			struct ipt_standard_target *t
+				= (void *)ipt_get_target(e);
+
+			if (e->comefrom & (1 << NF_IP_NUMHOOKS)) {
+				printk("iptables: loop hook %u pos %u %08X.\n",
+				       hook, pos, e->comefrom);
+				return 0;
+			}
+			e->comefrom
+				|= ((1 << hook) | (1 << NF_IP_NUMHOOKS));
+
+			/* Unconditional return/END. */
+			if (e->target_offset == sizeof(struct ipt_entry)
+			    && (strcmp(t->target.u.name, IPT_STANDARD_TARGET)
+				== 0)
+			    && t->verdict < 0
+			    && unconditional(&e->ip)) {
+				unsigned int oldpos, size;
+
+				/* Return: backtrack through the last
+				   big jump. */
+				do {
+					e->comefrom ^= (1<<NF_IP_NUMHOOKS);
+#ifdef DEBUG_IP_FIREWALL_USER
+					if (e->comefrom
+					    & (1 << NF_IP_NUMHOOKS)) {
+						duprintf("Back unset "
+							 "on hook %u "
+							 "rule %u\n",
+							 hook, pos);
+					}
+#endif
+					oldpos = pos;
+					pos = e->counters.pcnt;
+					e->counters.pcnt = 0;
+
+					/* We're at the start. */
+					if (pos == oldpos)
+						goto next;
+
+					e = (struct ipt_entry *)
+						(newinfo->entries + pos);
+				} while (oldpos == pos + e->next_offset);
+
+				/* Move along one */
+				size = e->next_offset;
+				e = (struct ipt_entry *)
+					(newinfo->entries + pos + size);
+				e->counters.pcnt = pos;
+				pos += size;
+			} else {
+				int newpos = t->verdict;
+
+				if (strcmp(t->target.u.name,
+					   IPT_STANDARD_TARGET) == 0
+				    && newpos >= 0) {
+					/* This a jump; chase it. */
+					duprintf("Jump rule %u -> %u\n",
+						 pos, newpos);
+				} else {
+					/* ... this is a fallthru */
+					newpos = pos + e->next_offset;
+				}
+				e = (struct ipt_entry *)
+					(newinfo->entries + newpos);
+				e->counters.pcnt = pos;
+				pos = newpos;
+			}
+		}
+		next:
+		duprintf("Finished chain %u\n", hook);
+	}
+	return 1;
+}
+
+static inline int
+cleanup_match(struct ipt_entry_match *m, unsigned int *i)
+{
+	if (i && (*i)-- == 0)
+		return 1;
+
+	if (m->u.match->me)
+		__MOD_DEC_USE_COUNT(m->u.match->me);
+
+	return 0;
+}
+
+static inline int
+standard_check(const struct ipt_entry_target *t,
+	       unsigned int max_offset)
+{
+	struct ipt_standard_target *targ = (void *)t;
+
+	/* Check standard info. */
+	if (t->target_size != sizeof(struct ipt_standard_target)) {
+		duprintf("standard_check: target size %u != %u\n",
+			 t->target_size, sizeof(struct ipt_standard_target));
+		return 0;
+	}
+
+	if (targ->verdict >= 0
+	    && targ->verdict > max_offset - sizeof(struct ipt_entry)) {
+		duprintf("ipt_standard_check: bad verdict (%i)\n",
+			 targ->verdict);
+		return 0;
+	}
+
+	if (targ->verdict < -NF_MAX_VERDICT - 1) {
+		duprintf("ipt_standard_check: bad negative verdict (%i)\n",
+			 targ->verdict);
+		return 0;
+	}
+	return 1;
+}
+
+static inline int
+check_match(struct ipt_entry_match *m,
+	    const char *name,
+	    const struct ipt_ip *ip,
+	    unsigned int hookmask,
+	    unsigned int *i)
+{
+	int ret;
+	struct ipt_match *match;
+
+	match = find_match_lock(m->u.name, &ret, &ipt_mutex);
+	if (!match) {
+		duprintf("check_match: `%s' not found\n", m->u.name);
+		return ret;
+	}
+	if (match->me)
+		__MOD_INC_USE_COUNT(match->me);
+	m->u.match = match;
+	up(&ipt_mutex);
+
+	if (m->u.match->checkentry
+	    && !m->u.match->checkentry(name, ip, m->data,
+				       m->match_size - sizeof(*m),
+				       hookmask)) {
+		if (m->u.match->me)
+			__MOD_DEC_USE_COUNT(m->u.match->me);
+		duprintf("ip_tables: check failed for `%s'.\n",
+			 m->u.match->name);
+		return -EINVAL;
+	}
+
+	(*i)++;
+	return 0;
+}
+
+static struct ipt_target ipt_standard_target;
+
+static inline int
+check_entry(struct ipt_entry *e, const char *name, unsigned int size,
+	    unsigned int *i)
+{
+	struct ipt_entry_target *t;
+	struct ipt_target *target;
+	int ret;
+	unsigned int j;
+
+	if (!ip_checkentry(&e->ip)) {
+		duprintf("ip_tables: ip check failed %p %s.\n", e, name);
+		return -EINVAL;
+	}
+
+	j = 0;
+	ret = IPT_MATCH_ITERATE(e, check_match, name, &e->ip, e->comefrom, &j);
+	if (ret != 0)
+		goto cleanup_matches;
+
+	t = ipt_get_target(e);
+	target = find_target_lock(t->u.name, &ret, &ipt_mutex);
+	if (!target) {
+		duprintf("check_entry: `%s' not found\n", t->u.name);
+		up(&ipt_mutex);
+		return ret;
+	}
+	if (target->me)
+		__MOD_INC_USE_COUNT(target->me);
+	t->u.target = target;
+	up(&ipt_mutex);
+
+	if (t->u.target == &ipt_standard_target) {
+		if (!standard_check(t, size)) {
+			ret = -EINVAL;
+			goto cleanup_matches;
+		}
+	} else if (t->u.target->checkentry
+		   && !t->u.target->checkentry(name, e, t->data,
+					       t->target_size - sizeof(*t),
+					       e->comefrom)) {
+		if (t->u.target->me)
+			__MOD_DEC_USE_COUNT(t->u.target->me);
+		duprintf("ip_tables: check failed for `%s'.\n",
+			 t->u.target->name);
+		ret = -EINVAL;
+		goto cleanup_matches;
+	}
+
+	(*i)++;
+	return 0;
+
+ cleanup_matches:
+	IPT_MATCH_ITERATE(e, cleanup_match, &j);
+	return ret;
+}
+
+static inline int
+check_entry_size_and_hooks(struct ipt_entry *e,
+			   struct ipt_table_info *newinfo,
+			   unsigned char *base,
+			   unsigned char *limit,
+			   const unsigned int *hook_entries,
+			   const unsigned int *underflows,
+			   unsigned int *i)
+{
+	unsigned int h;
+
+	if ((unsigned long)e % __alignof__(struct ipt_entry) != 0
+	    || (unsigned char *)e + sizeof(struct ipt_entry) >= limit) {
+		duprintf("Bad offset %p\n", e);
+		return -EINVAL;
+	}
+
+	if (e->next_offset
+	    < sizeof(struct ipt_entry) + sizeof(struct ipt_entry_target)) {
+		duprintf("checking: element %p size %u\n",
+			 e, e->next_offset);
+		return -EINVAL;
+	}
+
+	/* Check hooks & underflows */
+	for (h = 0; h < NF_IP_NUMHOOKS; h++) {
+		if ((unsigned char *)e - base == hook_entries[h])
+			newinfo->hook_entry[h] = hook_entries[h];
+		if ((unsigned char *)e - base == underflows[h])
+			newinfo->underflow[h] = underflows[h];
+	}
+
+	/* FIXME: underflows must be unconditional, standard verdicts
+           < 0 (not IPT_RETURN). --RR */
+
+	/* Clear counters and comefrom */
+	e->counters = ((struct ipt_counters) { 0, 0 });
+	e->comefrom = 0;
+
+	(*i)++;
+	return 0;
+}
+
+static inline int
+cleanup_entry(struct ipt_entry *e, unsigned int *i)
+{
+	struct ipt_entry_target *t;
+
+	if (i && (*i)-- == 0)
+		return 1;
+
+	/* Cleanup all matches */
+	IPT_MATCH_ITERATE(e, cleanup_match, NULL);
+	t = ipt_get_target(e);
+	if (t->u.target->me)
+		__MOD_DEC_USE_COUNT(t->u.target->me);
+
+	return 0;
+}
+
+/* Checks and translates the user-supplied table segment (held in
+   newinfo) */
+static int
+translate_table(const char *name,
+		unsigned int valid_hooks,
+		struct ipt_table_info *newinfo,
+		unsigned int size,
+		unsigned int number,
+		const unsigned int *hook_entries,
+		const unsigned int *underflows)
+{
+	unsigned int i;
+	int ret;
+
+	newinfo->size = size;
+	newinfo->number = number;
+
+	/* Init all hooks to impossible value. */
+	for (i = 0; i < NF_IP_NUMHOOKS; i++) {
+		newinfo->hook_entry[i] = 0xFFFFFFFF;
+		newinfo->underflow[i] = 0xFFFFFFFF;
+	}
+
+	duprintf("translate_table: size %u\n", newinfo->size);
+	i = 0;
+	/* Walk through entries, checking offsets. */
+	ret = IPT_ENTRY_ITERATE(newinfo->entries, newinfo->size,
+				check_entry_size_and_hooks,
+				newinfo,
+				newinfo->entries,
+				newinfo->entries + size,
+				hook_entries, underflows, &i);
+	if (ret != 0)
+		return ret;
+
+	if (i != number) {
+		duprintf("translate_table: %u not %u entries\n",
+			 i, number);
+		return -EINVAL;
+	}
+
+	/* Check hooks all assigned */
+	for (i = 0; i < NF_IP_NUMHOOKS; i++) {
+		/* Only hooks which are valid */
+		if (!(valid_hooks & (1 << i)))
+			continue;
+		if (newinfo->hook_entry[i] == 0xFFFFFFFF) {
+			duprintf("Invalid hook entry %u %u\n",
+				 i, hook_entries[i]);
+			return -EINVAL;
+		}
+		if (newinfo->underflow[i] == 0xFFFFFFFF) {
+			duprintf("Invalid underflow %u %u\n",
+				 i, underflows[i]);
+			return -EINVAL;
+		}
+	}
+
+	if (!mark_source_chains(newinfo, valid_hooks))
+		return -ELOOP;
+
+	/* Finally, each sanity check must pass */
+	i = 0;
+	ret = IPT_ENTRY_ITERATE(newinfo->entries, newinfo->size,
+				check_entry, name, size, &i);
+
+	if (ret != 0) {
+		IPT_ENTRY_ITERATE(newinfo->entries, newinfo->size,
+				  cleanup_entry, &i);
+		return ret;
+	}
+
+	/* And one copy for every other CPU */
+	for (i = 1; i < smp_num_cpus; i++) {
+		memcpy(newinfo->entries + SMP_ALIGN(newinfo->size*i),
+		       newinfo->entries,
+		       SMP_ALIGN(newinfo->size));
+	}
+
+	return ret;
+}
+
+static struct ipt_table_info *
+replace_table(struct ipt_table *table,
+	      unsigned int num_counters,
+	      struct ipt_table_info *newinfo,
+	      int *error)
+{
+	struct ipt_table_info *oldinfo;
+
+#ifdef CONFIG_NETFILTER_DEBUG
+	{
+		struct ipt_entry *table_base;
+		unsigned int i;
+
+		for (i = 0; i < smp_num_cpus; i++) {
+			table_base =
+				(void *)newinfo->entries
+				+ TABLE_OFFSET(newinfo, i);
+
+			table_base->comefrom = 0xdead57ac;
+		}
+	}
+#endif
+
+	/* Do the substitution. */
+	write_lock_bh(&table->lock);
+	/* Check inside lock: is the old number correct? */
+	if (num_counters != table->private->number) {
+		duprintf("num_counters != table->private->number (%u/%u)\n",
+			 num_counters, table->private->number);
+		write_unlock_bh(&table->lock);
+		*error = -EAGAIN;
+		return NULL;
+	}
+	oldinfo = table->private;
+	table->private = newinfo;
+	write_unlock_bh(&table->lock);
+
+	return oldinfo;
+}
+
+/* Gets counters. */
+static inline int
+add_entry_to_counter(const struct ipt_entry *e,
+		     struct ipt_counters total[],
+		     unsigned int *i)
+{
+	ADD_COUNTER(total[*i], e->counters.bcnt, e->counters.pcnt);
+
+	(*i)++;
+	return 0;
+}
+
+static void
+get_counters(const struct ipt_table_info *t,
+	     struct ipt_counters counters[])
+{
+	unsigned int cpu;
+	unsigned int i;
+
+	for (cpu = 0; cpu < smp_num_cpus; cpu++) {
+		i = 0;
+		IPT_ENTRY_ITERATE(t->entries + TABLE_OFFSET(t, cpu),
+				  t->size,
+				  add_entry_to_counter,
+				  counters,
+				  &i);
+	}
+}
+
+static int
+copy_entries_to_user(unsigned int total_size,
+		     struct ipt_table *table,
+		     void *userptr)
+{
+	unsigned int off, num, countersize;
+	struct ipt_entry *e;
+	struct ipt_counters *counters;
+	int ret = 0;
+
+	/* We need atomic snapshot of counters: rest doesn't change
+	   (other than comefrom, which userspace doesn't care
+	   about). */
+	countersize = sizeof(struct ipt_counters) * table->private->number;
+	counters = vmalloc(countersize);
+
+	if (counters == NULL)
+		return -ENOMEM;
+
+	/* First, sum counters... */
+	memset(counters, 0, countersize);
+	write_lock_bh(&table->lock);
+	get_counters(table->private, counters);
+	write_unlock_bh(&table->lock);
+
+	/* ... then copy entire thing from CPU 0... */
+	if (copy_to_user(userptr, table->private->entries, total_size) != 0) {
+		ret = -EFAULT;
+		goto free_counters;
+	}
+
+	/* FIXME: use iterator macros --RR */
+	/* ... then go back and fix counters and names */
+	for (off = 0, num = 0; off < total_size; off += e->next_offset, num++){
+		unsigned int i;
+		struct ipt_entry_match *m;
+		struct ipt_entry_target *t;
+
+		e = (struct ipt_entry *)(table->private->entries + off);
+		if (copy_to_user(userptr + off
+				 + offsetof(struct ipt_entry, counters),
+				 &counters[num],
+				 sizeof(counters[num])) != 0) {
+			ret = -EFAULT;
+			goto free_counters;
+		}
+
+		for (i = sizeof(struct ipt_entry);
+		     i < e->target_offset;
+		     i += m->match_size) {
+			m = (void *)e + i;
+
+			if (copy_to_user(userptr + off + i
+					 + offsetof(struct ipt_entry_match,
+						    u.name),
+					 m->u.match->name,
+					 strlen(m->u.match->name)+1) != 0) {
+				ret = -EFAULT;
+				goto free_counters;
+			}
+		}
+
+		t = ipt_get_target(e);
+		if (copy_to_user(userptr + off + e->target_offset
+				 + offsetof(struct ipt_entry_target,
+					    u.name),
+				 t->u.target->name,
+				 strlen(t->u.target->name)+1) != 0) {
+			ret = -EFAULT;
+			goto free_counters;
+		}
+	}
+
+ free_counters:
+	vfree(counters);
+	return ret;
+}
+
+static int
+get_entries(const struct ipt_get_entries *entries,
+	    struct ipt_get_entries *uptr)
+{
+	int ret;
+	struct ipt_table *t;
+
+	t = find_table_lock(entries->name, &ret, &ipt_mutex);
+	if (t) {
+		duprintf("t->private->number = %u\n",
+			 t->private->number);
+		if (entries->size == t->private->size)
+			ret = copy_entries_to_user(t->private->size,
+						   t, uptr->entries);
+		else {
+			duprintf("get_entries: I've got %u not %u!\n",
+				 t->private->size,
+				 entries->size);
+			ret = -EINVAL;
+		}
+		up(&ipt_mutex);
+	} else
+		duprintf("get_entries: Can't find %s!\n",
+			 entries->name);
+
+	return ret;
+}
+
+static int
+do_replace(void *user, unsigned int len)
+{
+	int ret;
+	struct ipt_replace tmp;
+	struct ipt_table *t;
+	struct ipt_table_info *newinfo, *oldinfo;
+	struct ipt_counters *counters;
+
+	if (copy_from_user(&tmp, user, sizeof(tmp)) != 0)
+		return -EFAULT;
+
+	newinfo = vmalloc(sizeof(struct ipt_table_info)
+			  + SMP_ALIGN(tmp.size) * smp_num_cpus);
+	if (!newinfo)
+		return -ENOMEM;
+
+	if (copy_from_user(newinfo->entries, user + sizeof(tmp),
+			   tmp.size) != 0) {
+		ret = -EFAULT;
+		goto free_newinfo;
+	}
+
+	counters = vmalloc(tmp.num_counters * sizeof(struct ipt_counters));
+	if (!counters) {
+		ret = -ENOMEM;
+		goto free_newinfo;
+	}
+	memset(counters, 0, tmp.num_counters * sizeof(struct ipt_counters));
+
+	ret = translate_table(tmp.name, tmp.valid_hooks,
+			      newinfo, tmp.size, tmp.num_entries,
+			      tmp.hook_entry, tmp.underflow);
+	if (ret != 0)
+		goto free_newinfo_counters;
+
+	duprintf("ip_tables: Translated table\n");
+
+	t = find_table_lock(tmp.name, &ret, &ipt_mutex);
+	if (!t)
+		goto free_newinfo_counters_untrans;
+
+	/* You lied! */
+	if (tmp.valid_hooks != t->valid_hooks) {
+		duprintf("Valid hook crap: %08X vs %08X\n",
+			 tmp.valid_hooks, t->valid_hooks);
+		ret = -EINVAL;
+		goto free_newinfo_counters_untrans_unlock;
+	}
+
+	oldinfo = replace_table(t, tmp.num_counters, newinfo, &ret);
+	if (!oldinfo)
+		goto free_newinfo_counters_untrans_unlock;
+
+	/* Get the old counters. */
+	get_counters(oldinfo, counters);
+	/* Decrease module usage counts and free resource */
+	IPT_ENTRY_ITERATE(oldinfo->entries, oldinfo->size, cleanup_entry,NULL);
+	vfree(oldinfo);
+	/* Silent error: too late now. */
+	copy_to_user(tmp.counters, counters,
+		     sizeof(struct ipt_counters) * tmp.num_counters);
+
+	up(&ipt_mutex);
+	return 0;
+
+ free_newinfo_counters_untrans_unlock:
+	up(&ipt_mutex);
+ free_newinfo_counters_untrans:
+	IPT_ENTRY_ITERATE(newinfo->entries, newinfo->size, cleanup_entry,NULL);
+ free_newinfo_counters:
+	vfree(counters);
+ free_newinfo:
+	vfree(newinfo);
+	return ret;
+}
+
+/* We're lazy, and add to the first CPU; overflow works its fey magic
+ * and everything is OK. */
+static inline int
+add_counter_to_entry(struct ipt_entry *e,
+		     const struct ipt_counters addme[],
+		     unsigned int *i)
+{
+#if 0
+	duprintf("add_counter: Entry %u %lu/%lu + %lu/%lu\n",
+		 *i,
+		 (long unsigned int)e->counters.pcnt,
+		 (long unsigned int)e->counters.bcnt,
+		 (long unsigned int)addme[*i].pcnt,
+		 (long unsigned int)addme[*i].bcnt);
+#endif
+
+	ADD_COUNTER(e->counters, addme[*i].bcnt, addme[*i].pcnt);
+
+	(*i)++;
+	return 0;
+}
+
+static int
+do_add_counters(void *user, unsigned int len)
+{
+	unsigned int i;
+	struct ipt_counters_info tmp, *paddc;
+	struct ipt_table *t;
+	int ret;
+
+	if (copy_from_user(&tmp, user, sizeof(tmp)) != 0)
+		return -EFAULT;
+
+	if (len != sizeof(tmp) + tmp.num_counters*sizeof(struct ipt_counters))
+		return -EINVAL;
+
+	paddc = vmalloc(len);
+	if (!paddc)
+		return -ENOMEM;
+
+	if (copy_from_user(paddc, user, len) != 0) {
+		ret = -EFAULT;
+		goto free;
+	}
+
+	t = find_table_lock(tmp.name, &ret, &ipt_mutex);
+	if (!t)
+		goto free;
+
+	write_lock_bh(&t->lock);
+	if (t->private->number != paddc->num_counters) {
+		ret = -EINVAL;
+		goto unlock_up_free;
+	}
+
+	i = 0;
+	IPT_ENTRY_ITERATE(t->private->entries,
+			  t->private->size,
+			  add_counter_to_entry,
+			  paddc->counters,
+			  &i);
+ unlock_up_free:
+	write_unlock_bh(&t->lock);
+	up(&ipt_mutex);
+ free:
+	vfree(paddc);
+
+	return ret;
+}
+
+static int
+do_ipt_set_ctl(struct sock *sk,	int cmd, void *user, unsigned int len)
+{
+	int ret;
+
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
+	switch (cmd) {
+	case IPT_SO_SET_REPLACE:
+		ret = do_replace(user, len);
+		break;
+
+	case IPT_SO_SET_ADD_COUNTERS:
+		ret = do_add_counters(user, len);
+		break;
+
+	default:
+		duprintf("do_ipt_set_ctl:  unknown request %i\n", cmd);
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+static int
+do_ipt_get_ctl(struct sock *sk, int cmd, void *user, int *len)
+{
+	int ret;
+
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
+	switch (cmd) {
+	case IPT_SO_GET_INFO: {
+		char name[IPT_TABLE_MAXNAMELEN];
+		struct ipt_table *t;
+
+		if (*len != sizeof(struct ipt_getinfo)) {
+			duprintf("length %u != %u\n", *len,
+				 sizeof(struct ipt_getinfo));
+			ret = -EINVAL;
+			break;
+		}
+
+		if (copy_from_user(name, user, sizeof(name)) != 0) {
+			ret = -EFAULT;
+			break;
+		}
+		t = find_table_lock(name, &ret, &ipt_mutex);
+		if (t) {
+			struct ipt_getinfo info;
+
+			info.valid_hooks = t->valid_hooks;
+			memcpy(info.hook_entry, t->private->hook_entry,
+			       sizeof(info.hook_entry));
+			memcpy(info.underflow, t->private->underflow,
+			       sizeof(info.underflow));
+			info.num_entries = t->private->number;
+			info.size = t->private->size;
+			strcpy(info.name, name);
+
+			if (copy_to_user(user, &info, *len) != 0)
+				ret = -EFAULT;
+			else
+				ret = 0;
+
+			up(&ipt_mutex);
+		}
+	}
+	break;
+
+	case IPT_SO_GET_ENTRIES: {
+		struct ipt_get_entries get;
+
+		if (*len < sizeof(get)) {
+			duprintf("get_entries: %u < %u\n", *len, sizeof(get));
+			ret = -EINVAL;
+		} else if (copy_from_user(&get, user, sizeof(get)) != 0) {
+			ret = -EFAULT;
+		} else if (*len != sizeof(struct ipt_get_entries) + get.size) {
+			duprintf("get_entries: %u != %u\n", *len,
+				 sizeof(struct ipt_get_entries) + get.size);
+			ret = -EINVAL;
+		} else
+			ret = get_entries(&get, user);
+		break;
+	}
+
+	default:
+		duprintf("do_ipt_get_ctl: unknown request %i\n", cmd);
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+/* Registration hooks for targets. */
+int
+ipt_register_target(struct ipt_target *target)
+{
+	int ret;
+
+	ret = down_interruptible(&ipt_mutex);
+	if (ret != 0)
+		return ret;
+
+	if (list_named_insert(&ipt_target, target)) {
+		MOD_INC_USE_COUNT;
+		ret = 0;
+	} else {
+		duprintf("ipt_register_target: `%s' already in list!\n",
+			 target->name);
+		ret = -EINVAL;
+	}
+	up(&ipt_mutex);
+	return ret;
+}
+
+void
+ipt_unregister_target(struct ipt_target *target)
+{
+	down(&ipt_mutex);
+	LIST_DELETE(&ipt_target, target);
+	up(&ipt_mutex);
+	MOD_DEC_USE_COUNT;
+}
+
+int
+ipt_register_match(struct ipt_match *match)
+{
+	int ret;
+
+	ret = down_interruptible(&ipt_mutex);
+	if (ret != 0)
+		return ret;
+
+	if (list_named_insert(&ipt_match, match)) {
+		MOD_INC_USE_COUNT;
+		ret = 0;
+	} else {
+		duprintf("ipt_register_match: `%s' already in list!\n",
+			 match->name);
+		ret = -EINVAL;
+	}
+	up(&ipt_mutex);
+
+	return ret;
+}
+
+void
+ipt_unregister_match(struct ipt_match *match)
+{
+	down(&ipt_mutex);
+	LIST_DELETE(&ipt_match, match);
+	up(&ipt_mutex);
+	MOD_DEC_USE_COUNT;
+}
+
+int ipt_register_table(struct ipt_table *table)
+{
+	int ret;
+	struct ipt_table_info *newinfo;
+	static struct ipt_table_info bootstrap
+		= { 0, 0, { 0 }, { 0 }, { }, { } };
+
+	newinfo = vmalloc(sizeof(struct ipt_table_info)
+			  + SMP_ALIGN(table->table->size) * smp_num_cpus);
+	if (!newinfo) {
+		ret = -ENOMEM;
+		return ret;
+	}
+	memcpy(newinfo->entries, table->table->entries, table->table->size);
+
+	ret = translate_table(table->name, table->valid_hooks,
+			      newinfo, table->table->size,
+			      table->table->num_entries,
+			      table->table->hook_entry,
+			      table->table->underflow);
+	if (ret != 0) {
+		vfree(newinfo);
+		return ret;
+	}
+
+	ret = down_interruptible(&ipt_mutex);
+	if (ret != 0) {
+		vfree(newinfo);
+		return ret;
+	}
+
+	/* Don't autoload: we'd eat our tail... */
+	if (list_named_find(&ipt_tables, table->name)) {
+		ret = -EEXIST;
+		goto free_unlock;
+	}
+
+	/* Simplifies replace_table code. */
+	table->private = &bootstrap;
+	if (!replace_table(table, 0, newinfo, &ret))
+		goto free_unlock;
+
+	duprintf("table->private->number = %u\n",
+		 table->private->number);
+
+	table->lock = RW_LOCK_UNLOCKED;
+	list_prepend(&ipt_tables, table);
+	MOD_INC_USE_COUNT;
+
+ unlock:
+	up(&ipt_mutex);
+	return ret;
+
+ free_unlock:
+	vfree(newinfo);
+	goto unlock;
+}
+
+void ipt_unregister_table(struct ipt_table *table)
+{
+	down(&ipt_mutex);
+	LIST_DELETE(&ipt_tables, table);
+	up(&ipt_mutex);
+
+	/* Decrease module usage counts and free resources */
+	IPT_ENTRY_ITERATE(table->private->entries, table->private->size,
+			  cleanup_entry, NULL);
+	vfree(table->private);
+	MOD_DEC_USE_COUNT;
+}
+
+/* Returns 1 if the port is matched by the range, 0 otherwise */
+static inline int
+port_match(u_int16_t min, u_int16_t max, u_int16_t port, int invert)
+{
+	int ret;
+
+	ret = (port >= min && port <= max) ^ invert;
+	return ret;
+}
+
+static int
+tcp_find_option(u_int8_t option,
+		const struct tcphdr *tcp,
+		u_int16_t datalen,
+		int invert,
+		int *hotdrop)
+{
+	unsigned int i = sizeof(struct tcphdr);
+	const u_int8_t *opt = (u_int8_t *)tcp;
+
+	duprintf("tcp_match: finding option\n");
+	/* If we don't have the whole header, drop packet. */
+	if (tcp->doff * 4 > datalen) {
+		*hotdrop = 1;
+		return 0;
+	}
+
+	while (i < tcp->doff * 4) {
+		if (opt[i] == option) return !invert;
+		if (opt[i] < 2) i++;
+		else i += opt[i+1]?:1;
+	}
+
+	return invert;
+}
+
+static int
+tcp_match(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 tcphdr *tcp = hdr;
+	const struct ipt_tcp *tcpinfo = matchinfo;
+
+	/* To quote Alan:
+
+	   Don't allow a fragment of TCP 8 bytes in. Nobody normal
+	   causes this. Its a cracker trying to break in by doing a
+	   flag overwrite to pass the direction checks.
+	*/
+
+	if (offset == 1) {
+		duprintf("Dropping evil TCP offset=1 frag.\n");
+		*hotdrop = 1;
+		return 0;
+	} else if (offset == 0 && datalen < sizeof(struct tcphdr)) {
+		/* We've been asked to examine this packet, and we
+		   can't.  Hence, no choice but to drop. */
+		duprintf("Dropping evil TCP offset=0 tinygram.\n");
+		*hotdrop = 1;
+		return 0;
+	}
+
+	/* FIXME: Try tcp doff >> packet len against various stacks --RR */
+
+#define FWINVTCP(bool,invflg) ((bool) ^ !!(tcpinfo->invflags & invflg))
+
+	/* Must not be a fragment. */
+	return !offset
+		&& port_match(tcpinfo->spts[0], tcpinfo->spts[1],
+			      ntohs(tcp->source),
+			      !!(tcpinfo->invflags & IPT_TCP_INV_SRCPT))
+		&& port_match(tcpinfo->dpts[0], tcpinfo->dpts[1],
+			      ntohs(tcp->dest),
+			      !!(tcpinfo->invflags & IPT_TCP_INV_DSTPT))
+		&& FWINVTCP((((unsigned char *)tcp)[13]
+			     & tcpinfo->flg_mask)
+			    == tcpinfo->flg_cmp,
+			    IPT_TCP_INV_FLAGS)
+		&& (!tcpinfo->option
+		    || tcp_find_option(tcpinfo->option, tcp, datalen,
+				       tcpinfo->invflags
+				       & IPT_TCP_INV_OPTION,
+				       hotdrop));
+}
+
+/* Called when user tries to insert an entry of this type. */
+static int
+tcp_checkentry(const char *tablename,
+	       const struct ipt_ip *ip,
+	       void *matchinfo,
+	       unsigned int matchsize,
+	       unsigned int hook_mask)
+{
+	const struct ipt_tcp *tcpinfo = matchinfo;
+
+	/* Must specify proto == TCP, and no unknown invflags */
+	return ip->proto == IPPROTO_TCP
+		&& !(ip->invflags & IPT_INV_PROTO)
+		&& matchsize == IPT_ALIGN(sizeof(struct ipt_tcp))
+		&& !(tcpinfo->invflags & ~IPT_TCP_INV_MASK);
+}
+
+static int
+udp_match(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_udp *udpinfo = matchinfo;
+
+	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("Dropping evil UDP tinygram.\n");
+		*hotdrop = 1;
+		return 0;
+	}
+
+	/* Must not be a fragment. */
+	return !offset
+		&& port_match(udpinfo->spts[0], udpinfo->spts[1],
+			      ntohs(udp->source),
+			      !!(udpinfo->invflags & IPT_UDP_INV_SRCPT))
+		&& port_match(udpinfo->dpts[0], udpinfo->dpts[1],
+			      ntohs(udp->dest),
+			      !!(udpinfo->invflags & IPT_UDP_INV_DSTPT));
+}
+
+/* Called when user tries to insert an entry of this type. */
+static int
+udp_checkentry(const char *tablename,
+	       const struct ipt_ip *ip,
+	       void *matchinfo,
+	       unsigned int matchinfosize,
+	       unsigned int hook_mask)
+{
+	const struct ipt_udp *udpinfo = matchinfo;
+
+	/* Must specify proto == UDP, and no unknown invflags */
+	if (ip->proto != IPPROTO_UDP || (ip->invflags & IPT_INV_PROTO)) {
+		duprintf("ipt_udp: Protocol %u != %u\n", ip->proto,
+			 IPPROTO_UDP);
+		return 0;
+	}
+	if (matchinfosize != IPT_ALIGN(sizeof(struct ipt_udp))) {
+		duprintf("ipt_udp: matchsize %u != %u\n",
+			 matchinfosize, IPT_ALIGN(sizeof(struct ipt_udp)));
+		return 0;
+	}
+	if (udpinfo->invflags & ~IPT_UDP_INV_MASK) {
+		duprintf("ipt_udp: unknown flags %X\n",
+			 udpinfo->invflags);
+		return 0;
+	}
+
+	return 1;
+}
+
+/* Returns 1 if the type and code is matched by the range, 0 otherwise */
+static inline int
+icmp_type_code_match(u_int8_t test_type, u_int8_t min_code, u_int8_t max_code,
+		     u_int8_t type, u_int8_t code,
+		     int invert)
+{
+	return (type == test_type && code >= min_code && code <= max_code)
+		^ invert;
+}
+
+static int
+icmp_match(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 icmphdr *icmp = hdr;
+	const struct ipt_icmp *icmpinfo = matchinfo;
+
+	if (offset == 0 && datalen < 2) {
+		/* We've been asked to examine this packet, and we
+		   can't.  Hence, no choice but to drop. */
+		duprintf("Dropping evil ICMP tinygram.\n");
+		*hotdrop = 1;
+		return 0;
+	}
+
+	/* Must not be a fragment. */
+	return !offset
+		&& icmp_type_code_match(icmpinfo->type,
+					icmpinfo->code[0],
+					icmpinfo->code[1],
+					icmp->type, icmp->code,
+					!!(icmpinfo->invflags&IPT_ICMP_INV));
+}
+
+/* Called when user tries to insert an entry of this type. */
+static int
+icmp_checkentry(const char *tablename,
+	   const struct ipt_ip *ip,
+	   void *matchinfo,
+	   unsigned int matchsize,
+	   unsigned int hook_mask)
+{
+	const struct ipt_icmp *icmpinfo = matchinfo;
+
+	/* Must specify proto == ICMP, and no unknown invflags */
+	return ip->proto == IPPROTO_ICMP
+		&& !(ip->invflags & IPT_INV_PROTO)
+		&& matchsize == IPT_ALIGN(sizeof(struct ipt_icmp))
+		&& !(icmpinfo->invflags & ~IPT_ICMP_INV);
+}
+
+/* The built-in targets: standard (NULL) and error. */
+static struct ipt_target ipt_standard_target
+= { { NULL, NULL }, IPT_STANDARD_TARGET, NULL, NULL, NULL };
+static struct ipt_target ipt_error_target
+= { { NULL, NULL }, IPT_ERROR_TARGET, ipt_error, NULL, NULL };
+
+static struct nf_sockopt_ops ipt_sockopts
+= { { NULL, NULL }, PF_INET, IPT_BASE_CTL, IPT_SO_SET_MAX+1, do_ipt_set_ctl,
+    IPT_BASE_CTL, IPT_SO_GET_MAX+1, do_ipt_get_ctl, 0, NULL  };
+
+static struct ipt_match tcp_matchstruct
+= { { NULL, NULL }, "tcp", &tcp_match, &tcp_checkentry, NULL };
+static struct ipt_match udp_matchstruct
+= { { NULL, NULL }, "udp", &udp_match, &udp_checkentry, NULL };
+static struct ipt_match icmp_matchstruct
+= { { NULL, NULL }, "icmp", &icmp_match, &icmp_checkentry, NULL };
+
+static int __init init(void)
+{
+	int ret;
+
+	/* Noone else will be downing sem now, so we won't sleep */
+	down(&ipt_mutex);
+	list_append(&ipt_target, &ipt_standard_target);
+	list_append(&ipt_target, &ipt_error_target);
+	list_append(&ipt_match, &tcp_matchstruct);
+	list_append(&ipt_match, &udp_matchstruct);
+	list_append(&ipt_match, &icmp_matchstruct);
+	up(&ipt_mutex);
+
+	/* Register setsockopt */
+	ret = nf_register_sockopt(&ipt_sockopts);
+	if (ret < 0) {
+		duprintf("Unable to register sockopts.\n");
+		return ret;
+	}
+
+	printk("iptables: (c)2000 Netfilter core team\n");
+	return 0;
+}
+
+static void __exit fini(void)
+{
+	nf_unregister_sockopt(&ipt_sockopts);
+}
+
+module_init(init);
+module_exit(fini);
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TCL-scripts by Sam Shen (who was at: slshen@lbl.gov)