libiptc/libip6tc.c - platform/external/iptables - Gitiles

 /* Library which manipulates firewall rules.  Version 0.1. */

 /* Architecture of firewall rules is as follows:
  *
  * Chains go INPUT, FORWARD, OUTPUT then user chains.
  * Each user chain starts with an ERROR node.
  * Every chain ends with an unconditional jump: a RETURN for user chains,
  * and a POLICY for built-ins.
  */

 /* (C)1999 Paul ``Rusty'' Russell - Placed under the GNU GPL (See
    COPYING for details). */

 #include <assert.h>
 #include <string.h>
 #include <errno.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <arpa/inet.h>

 #ifdef DEBUG_CONNTRACK
 #define inline
 #endif

 #if !defined(__GLIBC__) || (__GLIBC__ < 2)
 typedef unsigned int socklen_t;
 #endif

 #include "libiptc/libip6tc.h"

 #define HOOK_PRE_ROUTING	NF_IP6_PRE_ROUTING
 #define HOOK_LOCAL_IN		NF_IP6_LOCAL_IN
 #define HOOK_FORWARD		NF_IP6_FORWARD
 #define HOOK_LOCAL_OUT		NF_IP6_LOCAL_OUT
 #define HOOK_POST_ROUTING	NF_IP6_POST_ROUTING

 #define STRUCT_ENTRY_TARGET	struct ip6t_entry_target
 #define STRUCT_ENTRY		struct ip6t_entry
 #define STRUCT_ENTRY_MATCH	struct ip6t_entry_match
 #define STRUCT_GETINFO		struct ip6t_getinfo
 #define STRUCT_GET_ENTRIES	struct ip6t_get_entries
 #define STRUCT_COUNTERS		struct ip6t_counters
 #define STRUCT_COUNTERS_INFO	struct ip6t_counters_info
 #define STRUCT_STANDARD_TARGET	struct ip6t_standard_target
 #define STRUCT_REPLACE		struct ip6t_replace

 #define STRUCT_TC_HANDLE	struct ip6tc_handle
 #define xtc_handle		ip6tc_handle

 #define ENTRY_ITERATE		IP6T_ENTRY_ITERATE
 #define TABLE_MAXNAMELEN	IP6T_TABLE_MAXNAMELEN
 #define FUNCTION_MAXNAMELEN	IP6T_FUNCTION_MAXNAMELEN

 #define GET_TARGET		ip6t_get_target

 #define ERROR_TARGET		IP6T_ERROR_TARGET
 #define NUMHOOKS		NF_IP6_NUMHOOKS

 #define IPT_CHAINLABEL		ip6t_chainlabel

 #define TC_DUMP_ENTRIES		dump_entries6
 #define TC_IS_CHAIN		ip6tc_is_chain
 #define TC_FIRST_CHAIN		ip6tc_first_chain
 #define TC_NEXT_CHAIN		ip6tc_next_chain
 #define TC_FIRST_RULE		ip6tc_first_rule
 #define TC_NEXT_RULE		ip6tc_next_rule
 #define TC_GET_TARGET		ip6tc_get_target
 #define TC_BUILTIN		ip6tc_builtin
 #define TC_GET_POLICY		ip6tc_get_policy
 #define TC_INSERT_ENTRY		ip6tc_insert_entry
 #define TC_REPLACE_ENTRY	ip6tc_replace_entry
 #define TC_APPEND_ENTRY		ip6tc_append_entry
 #define TC_DELETE_ENTRY		ip6tc_delete_entry
 #define TC_DELETE_NUM_ENTRY	ip6tc_delete_num_entry
 #define TC_FLUSH_ENTRIES	ip6tc_flush_entries
 #define TC_ZERO_ENTRIES		ip6tc_zero_entries
 #define TC_ZERO_COUNTER		ip6tc_zero_counter
 #define TC_READ_COUNTER		ip6tc_read_counter
 #define TC_SET_COUNTER		ip6tc_set_counter
 #define TC_CREATE_CHAIN		ip6tc_create_chain
 #define TC_GET_REFERENCES	ip6tc_get_references
 #define TC_DELETE_CHAIN		ip6tc_delete_chain
 #define TC_RENAME_CHAIN		ip6tc_rename_chain
 #define TC_SET_POLICY		ip6tc_set_policy
 #define TC_GET_RAW_SOCKET	ip6tc_get_raw_socket
 #define TC_INIT			ip6tc_init
 #define TC_FREE			ip6tc_free
 #define TC_COMMIT		ip6tc_commit
 #define TC_STRERROR		ip6tc_strerror
 #define TC_NUM_RULES		ip6tc_num_rules
 #define TC_GET_RULE		ip6tc_get_rule

 #define TC_AF			AF_INET6
 #define TC_IPPROTO		IPPROTO_IPV6

 #define SO_SET_REPLACE		IP6T_SO_SET_REPLACE
 #define SO_SET_ADD_COUNTERS	IP6T_SO_SET_ADD_COUNTERS
 #define SO_GET_INFO		IP6T_SO_GET_INFO
 #define SO_GET_ENTRIES		IP6T_SO_GET_ENTRIES
 #define SO_GET_VERSION		IP6T_SO_GET_VERSION

 #define STANDARD_TARGET		IP6T_STANDARD_TARGET
 #define LABEL_RETURN		IP6TC_LABEL_RETURN
 #define LABEL_ACCEPT		IP6TC_LABEL_ACCEPT
 #define LABEL_DROP		IP6TC_LABEL_DROP
 #define LABEL_QUEUE		IP6TC_LABEL_QUEUE

 #define ALIGN			IP6T_ALIGN
 #define RETURN			IP6T_RETURN

 #include "libiptc.c"

 #define BIT6(a, l) \
  ((ntohl(a->s6_addr32[(l) / 32]) >> (31 - ((l) & 31))) & 1)

 int
 ipv6_prefix_length(const struct in6_addr *a)
 {
 	int l, i;
 	for (l = 0; l < 128; l++) {
 		if (BIT6(a, l) == 0)
 			break;
 	}
 	for (i = l + 1; i < 128; i++) {
 		if (BIT6(a, i) == 1)
 			return -1;
 	}
 	return l;
 }

 static int
 dump_entry(struct ip6t_entry *e, struct ip6tc_handle *const handle)
 {
 	size_t i;
 	char buf[40];
 	int len;
 	struct ip6t_entry_target *t;

 	printf("Entry %u (%lu):\n", iptcb_entry2index(handle, e),
 	       iptcb_entry2offset(handle, e));
 	puts("SRC IP: ");
 	inet_ntop(AF_INET6, &e->ipv6.src, buf, sizeof buf);
 	puts(buf);
 	putchar('/');
 	len = ipv6_prefix_length(&e->ipv6.smsk);
 	if (len != -1)
 		printf("%d", len);
 	else {
 		inet_ntop(AF_INET6, &e->ipv6.smsk, buf, sizeof buf);
 		puts(buf);
 	}
 	putchar('\n');

 	puts("DST IP: ");
 	inet_ntop(AF_INET6, &e->ipv6.dst, buf, sizeof buf);
 	puts(buf);
 	putchar('/');
 	len = ipv6_prefix_length(&e->ipv6.dmsk);
 	if (len != -1)
 		printf("%d", len);
 	else {
 		inet_ntop(AF_INET6, &e->ipv6.dmsk, buf, sizeof buf);
 		puts(buf);
 	}
 	putchar('\n');

 	printf("Interface: `%s'/", e->ipv6.iniface);
 	for (i = 0; i < IFNAMSIZ; i++)
 		printf("%c", e->ipv6.iniface_mask[i] ? 'X' : '.');
 	printf("to `%s'/", e->ipv6.outiface);
 	for (i = 0; i < IFNAMSIZ; i++)
 		printf("%c", e->ipv6.outiface_mask[i] ? 'X' : '.');
 	printf("\nProtocol: %u\n", e->ipv6.proto);
 	if (e->ipv6.flags & IP6T_F_TOS)
 		printf("TOS: %u\n", e->ipv6.tos);
 	printf("Flags: %02X\n", e->ipv6.flags);
 	printf("Invflags: %02X\n", e->ipv6.invflags);
 	printf("Counters: %llu packets, %llu bytes\n",
 	       (unsigned long long)e->counters.pcnt, (unsigned long long)e->counters.bcnt);
 	printf("Cache: %08X\n", e->nfcache);

 	IP6T_MATCH_ITERATE(e, print_match);

 	t = ip6t_get_target(e);
 	printf("Target name: `%s' [%u]\n", t->u.user.name, t->u.target_size);
 	if (strcmp(t->u.user.name, IP6T_STANDARD_TARGET) == 0) {
 		const unsigned char *data = t->data;
 		int pos = *(const int *)data;
 		if (pos < 0)
 			printf("verdict=%s\n",
 			       pos == -NF_ACCEPT-1 ? "NF_ACCEPT"
 			       : pos == -NF_DROP-1 ? "NF_DROP"
 			       : pos == IP6T_RETURN ? "RETURN"
 			       : "UNKNOWN");
 		else
 			printf("verdict=%u\n", pos);
 	} else if (strcmp(t->u.user.name, IP6T_ERROR_TARGET) == 0)
 		printf("error=`%s'\n", t->data);

 	printf("\n");
 	return 0;
 }

 static unsigned char *
 is_same(const STRUCT_ENTRY *a, const STRUCT_ENTRY *b,
 	unsigned char *matchmask)
 {
 	unsigned int i;
 	unsigned char *mptr;

 	/* Always compare head structures: ignore mask here. */
 	if (memcmp(&a->ipv6.src, &b->ipv6.src, sizeof(struct in6_addr))
 	    || memcmp(&a->ipv6.dst, &b->ipv6.dst, sizeof(struct in6_addr))
 	    || memcmp(&a->ipv6.smsk, &b->ipv6.smsk, sizeof(struct in6_addr))
 	    || memcmp(&a->ipv6.dmsk, &b->ipv6.dmsk, sizeof(struct in6_addr))
 	    || a->ipv6.proto != b->ipv6.proto
 	    || a->ipv6.tos != b->ipv6.tos
 	    || a->ipv6.flags != b->ipv6.flags
 	    || a->ipv6.invflags != b->ipv6.invflags)
 		return NULL;

 	for (i = 0; i < IFNAMSIZ; i++) {
 		if (a->ipv6.iniface_mask[i] != b->ipv6.iniface_mask[i])
 			return NULL;
 		if ((a->ipv6.iniface[i] & a->ipv6.iniface_mask[i])
 		    != (b->ipv6.iniface[i] & b->ipv6.iniface_mask[i]))
 			return NULL;
 		if (a->ipv6.outiface_mask[i] != b->ipv6.outiface_mask[i])
 			return NULL;
 		if ((a->ipv6.outiface[i] & a->ipv6.outiface_mask[i])
 		    != (b->ipv6.outiface[i] & b->ipv6.outiface_mask[i]))
 			return NULL;
 	}

 	if (a->target_offset != b->target_offset
 	    || a->next_offset != b->next_offset)
 		return NULL;

 	mptr = matchmask + sizeof(STRUCT_ENTRY);
 	if (IP6T_MATCH_ITERATE(a, match_different, a->elems, b->elems, &mptr))
 		return NULL;
 	mptr += IP6T_ALIGN(sizeof(struct ip6t_entry_target));

 	return mptr;
 }

 /* All zeroes == unconditional rule. */
 static inline int
 unconditional(const struct ip6t_ip6 *ipv6)
 {
 	unsigned int i;

 	for (i = 0; i < sizeof(*ipv6); i++)
 		if (((char *)ipv6)[i])
 			break;

 	return (i == sizeof(*ipv6));
 }

 #ifdef IPTC_DEBUG
 /* Do every conceivable sanity check on the handle */
 static void
 do_check(struct xtc_handle *h, unsigned int line)
 {
 	unsigned int i, n;
 	unsigned int user_offset; /* Offset of first user chain */
 	int was_return;

 	assert(h->changed == 0 || h->changed == 1);
 	if (strcmp(h->info.name, "filter") == 0) {
 		assert(h->info.valid_hooks
 		       == (1 << NF_IP6_LOCAL_IN
 			   | 1 << NF_IP6_FORWARD
 			   | 1 << NF_IP6_LOCAL_OUT));

 		/* Hooks should be first three */
 		assert(h->info.hook_entry[NF_IP6_LOCAL_IN] == 0);

 		n = get_chain_end(h, 0);
 		n += get_entry(h, n)->next_offset;
 		assert(h->info.hook_entry[NF_IP6_FORWARD] == n);

 		n = get_chain_end(h, n);
 		n += get_entry(h, n)->next_offset;
 		assert(h->info.hook_entry[NF_IP6_LOCAL_OUT] == n);

 		user_offset = h->info.hook_entry[NF_IP6_LOCAL_OUT];
 	} else if (strcmp(h->info.name, "nat") == 0) {
 		assert((h->info.valid_hooks
 			== (1 << NF_IP6_PRE_ROUTING
 			    | 1 << NF_IP6_LOCAL_OUT
 			    | 1 << NF_IP6_POST_ROUTING)) ||
 		       (h->info.valid_hooks
 			== (1 << NF_IP6_PRE_ROUTING
 			    | 1 << NF_IP6_LOCAL_IN
 			    | 1 << NF_IP6_LOCAL_OUT
 			    | 1 << NF_IP6_POST_ROUTING)));

 		assert(h->info.hook_entry[NF_IP6_PRE_ROUTING] == 0);

 		n = get_chain_end(h, 0);

 		n += get_entry(h, n)->next_offset;
 		assert(h->info.hook_entry[NF_IP6_POST_ROUTING] == n);
 		n = get_chain_end(h, n);

 		n += get_entry(h, n)->next_offset;
 		assert(h->info.hook_entry[NF_IP6_LOCAL_OUT] == n);
 		user_offset = h->info.hook_entry[NF_IP6_LOCAL_OUT];

 		if (h->info.valid_hooks & (1 << NF_IP6_LOCAL_IN)) {
 			n = get_chain_end(h, n);
 			n += get_entry(h, n)->next_offset;
 			assert(h->info.hook_entry[NF_IP6_LOCAL_IN] == n);
 			user_offset = h->info.hook_entry[NF_IP6_LOCAL_IN];
 		}

 	} else if (strcmp(h->info.name, "mangle") == 0) {
 		/* This code is getting ugly because linux < 2.4.18-pre6 had
 		 * two mangle hooks, linux >= 2.4.18-pre6 has five mangle hooks
 		 * */
 		assert((h->info.valid_hooks
 			== (1 << NF_IP6_PRE_ROUTING
 			    | 1 << NF_IP6_LOCAL_OUT)) ||
 		       (h->info.valid_hooks
 			== (1 << NF_IP6_PRE_ROUTING
 			    | 1 << NF_IP6_LOCAL_IN
 			    | 1 << NF_IP6_FORWARD
 			    | 1 << NF_IP6_LOCAL_OUT
 			    | 1 << NF_IP6_POST_ROUTING)));

 		/* Hooks should be first five */
 		assert(h->info.hook_entry[NF_IP6_PRE_ROUTING] == 0);

 		n = get_chain_end(h, 0);

 		if (h->info.valid_hooks & (1 << NF_IP6_LOCAL_IN)) {
 			n += get_entry(h, n)->next_offset;
 			assert(h->info.hook_entry[NF_IP6_LOCAL_IN] == n);
 			n = get_chain_end(h, n);
 		}

 		if (h->info.valid_hooks & (1 << NF_IP6_FORWARD)) {
 			n += get_entry(h, n)->next_offset;
 			assert(h->info.hook_entry[NF_IP6_FORWARD] == n);
 			n = get_chain_end(h, n);
 		}

 		n += get_entry(h, n)->next_offset;
 		assert(h->info.hook_entry[NF_IP6_LOCAL_OUT] == n);
 		user_offset = h->info.hook_entry[NF_IP6_LOCAL_OUT];

 		if (h->info.valid_hooks & (1 << NF_IP6_POST_ROUTING)) {
 			n = get_chain_end(h, n);
 			n += get_entry(h, n)->next_offset;
 			assert(h->info.hook_entry[NF_IP6_POST_ROUTING] == n);
 			user_offset = h->info.hook_entry[NF_IP6_POST_ROUTING];
 		}
 	} else if (strcmp(h->info.name, "raw") == 0) {
 		assert(h->info.valid_hooks
 		       == (1 << NF_IP6_PRE_ROUTING
 			   | 1 << NF_IP6_LOCAL_OUT));

 		/* Hooks should be first three */
 		assert(h->info.hook_entry[NF_IP6_PRE_ROUTING] == 0);

 		n = get_chain_end(h, n);
 		n += get_entry(h, n)->next_offset;
 		assert(h->info.hook_entry[NF_IP6_LOCAL_OUT] == n);

 		user_offset = h->info.hook_entry[NF_IP6_LOCAL_OUT];
 	} else {
                 fprintf(stderr, "Unknown table `%s'\n", h->info.name);
 		abort();
 	}

 	/* User chain == end of last builtin + policy entry */
 	user_offset = get_chain_end(h, user_offset);
 	user_offset += get_entry(h, user_offset)->next_offset;

 	/* Overflows should be end of entry chains, and unconditional
            policy nodes. */
 	for (i = 0; i < NUMHOOKS; i++) {
 		STRUCT_ENTRY *e;
 		STRUCT_STANDARD_TARGET *t;

 		if (!(h->info.valid_hooks & (1 << i)))
 			continue;
 		assert(h->info.underflow[i]
 		       == get_chain_end(h, h->info.hook_entry[i]));

 		e = get_entry(h, get_chain_end(h, h->info.hook_entry[i]));
 		assert(unconditional(&e->ipv6));
 		assert(e->target_offset == sizeof(*e));
 		t = (STRUCT_STANDARD_TARGET *)GET_TARGET(e);
 		printf("target_size=%u, align=%u\n",
 			t->target.u.target_size, ALIGN(sizeof(*t)));
 		assert(t->target.u.target_size == ALIGN(sizeof(*t)));
 		assert(e->next_offset == sizeof(*e) + ALIGN(sizeof(*t)));

 		assert(strcmp(t->target.u.user.name, STANDARD_TARGET)==0);
 		assert(t->verdict == -NF_DROP-1 || t->verdict == -NF_ACCEPT-1);

 		/* Hooks and underflows must be valid entries */
 		iptcb_entry2index(h, get_entry(h, h->info.hook_entry[i]));
 		iptcb_entry2index(h, get_entry(h, h->info.underflow[i]));
 	}

 	assert(h->info.size
 	       >= h->info.num_entries * (sizeof(STRUCT_ENTRY)
 					 +sizeof(STRUCT_STANDARD_TARGET)));

 	assert(h->entries.size
 	       >= (h->new_number
 		   * (sizeof(STRUCT_ENTRY)
 		      + sizeof(STRUCT_STANDARD_TARGET))));
 	assert(strcmp(h->info.name, h->entries.name) == 0);

 	i = 0; n = 0;
 	was_return = 0;

 #if 0
 	/* Check all the entries. */
 	ENTRY_ITERATE(h->entries.entrytable, h->entries.size,
 		      check_entry, &i, &n, user_offset, &was_return, h);

 	assert(i == h->new_number);
 	assert(n == h->entries.size);

 	/* Final entry must be error node */
 	assert(strcmp(GET_TARGET(index2entry(h, h->new_number-1))
 		      ->u.user.name,
 		      ERROR_TARGET) == 0);
 #endif
 }
 #endif /*IPTC_DEBUG*/
	/* Library which manipulates firewall rules. Version 0.1. */

	/* Architecture of firewall rules is as follows:
	*
	* Chains go INPUT, FORWARD, OUTPUT then user chains.
	* Each user chain starts with an ERROR node.
	* Every chain ends with an unconditional jump: a RETURN for user chains,
	* and a POLICY for built-ins.
	*/

	/* (C)1999 Paul ``Rusty'' Russell - Placed under the GNU GPL (See
	COPYING for details). */

	#include <assert.h>
	#include <string.h>
	#include <errno.h>
	#include <stdlib.h>
	#include <stdio.h>
	#include <unistd.h>
	#include <arpa/inet.h>

	#ifdef DEBUG_CONNTRACK
	#define inline
	#endif

	#if !defined(__GLIBC__) \|\| (__GLIBC__ < 2)
	typedef unsigned int socklen_t;
	#endif

	#include "libiptc/libip6tc.h"

	#define HOOK_PRE_ROUTING NF_IP6_PRE_ROUTING
	#define HOOK_LOCAL_IN NF_IP6_LOCAL_IN
	#define HOOK_FORWARD NF_IP6_FORWARD
	#define HOOK_LOCAL_OUT NF_IP6_LOCAL_OUT
	#define HOOK_POST_ROUTING NF_IP6_POST_ROUTING

	#define STRUCT_ENTRY_TARGET struct ip6t_entry_target
	#define STRUCT_ENTRY struct ip6t_entry
	#define STRUCT_ENTRY_MATCH struct ip6t_entry_match
	#define STRUCT_GETINFO struct ip6t_getinfo
	#define STRUCT_GET_ENTRIES struct ip6t_get_entries
	#define STRUCT_COUNTERS struct ip6t_counters
	#define STRUCT_COUNTERS_INFO struct ip6t_counters_info
	#define STRUCT_STANDARD_TARGET struct ip6t_standard_target
	#define STRUCT_REPLACE struct ip6t_replace

	#define STRUCT_TC_HANDLE struct ip6tc_handle
	#define xtc_handle ip6tc_handle

	#define ENTRY_ITERATE IP6T_ENTRY_ITERATE
	#define TABLE_MAXNAMELEN IP6T_TABLE_MAXNAMELEN
	#define FUNCTION_MAXNAMELEN IP6T_FUNCTION_MAXNAMELEN

	#define GET_TARGET ip6t_get_target

	#define ERROR_TARGET IP6T_ERROR_TARGET
	#define NUMHOOKS NF_IP6_NUMHOOKS

	#define IPT_CHAINLABEL ip6t_chainlabel

	#define TC_DUMP_ENTRIES dump_entries6
	#define TC_IS_CHAIN ip6tc_is_chain
	#define TC_FIRST_CHAIN ip6tc_first_chain
	#define TC_NEXT_CHAIN ip6tc_next_chain
	#define TC_FIRST_RULE ip6tc_first_rule
	#define TC_NEXT_RULE ip6tc_next_rule
	#define TC_GET_TARGET ip6tc_get_target
	#define TC_BUILTIN ip6tc_builtin
	#define TC_GET_POLICY ip6tc_get_policy
	#define TC_INSERT_ENTRY ip6tc_insert_entry
	#define TC_REPLACE_ENTRY ip6tc_replace_entry
	#define TC_APPEND_ENTRY ip6tc_append_entry
	#define TC_DELETE_ENTRY ip6tc_delete_entry
	#define TC_DELETE_NUM_ENTRY ip6tc_delete_num_entry
	#define TC_FLUSH_ENTRIES ip6tc_flush_entries
	#define TC_ZERO_ENTRIES ip6tc_zero_entries
	#define TC_ZERO_COUNTER ip6tc_zero_counter
	#define TC_READ_COUNTER ip6tc_read_counter
	#define TC_SET_COUNTER ip6tc_set_counter
	#define TC_CREATE_CHAIN ip6tc_create_chain
	#define TC_GET_REFERENCES ip6tc_get_references
	#define TC_DELETE_CHAIN ip6tc_delete_chain
	#define TC_RENAME_CHAIN ip6tc_rename_chain
	#define TC_SET_POLICY ip6tc_set_policy
	#define TC_GET_RAW_SOCKET ip6tc_get_raw_socket
	#define TC_INIT ip6tc_init
	#define TC_FREE ip6tc_free
	#define TC_COMMIT ip6tc_commit
	#define TC_STRERROR ip6tc_strerror
	#define TC_NUM_RULES ip6tc_num_rules
	#define TC_GET_RULE ip6tc_get_rule

	#define TC_AF AF_INET6
	#define TC_IPPROTO IPPROTO_IPV6

	#define SO_SET_REPLACE IP6T_SO_SET_REPLACE
	#define SO_SET_ADD_COUNTERS IP6T_SO_SET_ADD_COUNTERS
	#define SO_GET_INFO IP6T_SO_GET_INFO
	#define SO_GET_ENTRIES IP6T_SO_GET_ENTRIES
	#define SO_GET_VERSION IP6T_SO_GET_VERSION

	#define STANDARD_TARGET IP6T_STANDARD_TARGET
	#define LABEL_RETURN IP6TC_LABEL_RETURN
	#define LABEL_ACCEPT IP6TC_LABEL_ACCEPT
	#define LABEL_DROP IP6TC_LABEL_DROP
	#define LABEL_QUEUE IP6TC_LABEL_QUEUE

	#define ALIGN IP6T_ALIGN
	#define RETURN IP6T_RETURN

	#include "libiptc.c"

	#define BIT6(a, l) \
	((ntohl(a->s6_addr32[(l) / 32]) >> (31 - ((l) & 31))) & 1)

	int
	ipv6_prefix_length(const struct in6_addr *a)
	{
	int l, i;
	for (l = 0; l < 128; l++) {
	if (BIT6(a, l) == 0)
	break;
	}
	for (i = l + 1; i < 128; i++) {
	if (BIT6(a, i) == 1)
	return -1;
	}
	return l;
	}

	static int
	dump_entry(struct ip6t_entry e, struct ip6tc_handle const handle)
	{
	size_t i;
	char buf[40];
	int len;
	struct ip6t_entry_target *t;

	printf("Entry %u (%lu):\n", iptcb_entry2index(handle, e),
	iptcb_entry2offset(handle, e));
	puts("SRC IP: ");
	inet_ntop(AF_INET6, &e->ipv6.src, buf, sizeof buf);
	puts(buf);
	putchar('/');
	len = ipv6_prefix_length(&e->ipv6.smsk);
	if (len != -1)
	printf("%d", len);
	else {
	inet_ntop(AF_INET6, &e->ipv6.smsk, buf, sizeof buf);
	puts(buf);
	}
	putchar('\n');

	puts("DST IP: ");
	inet_ntop(AF_INET6, &e->ipv6.dst, buf, sizeof buf);
	puts(buf);
	putchar('/');
	len = ipv6_prefix_length(&e->ipv6.dmsk);
	if (len != -1)
	printf("%d", len);
	else {
	inet_ntop(AF_INET6, &e->ipv6.dmsk, buf, sizeof buf);
	puts(buf);
	}
	putchar('\n');

	printf("Interface: `%s'/", e->ipv6.iniface);
	for (i = 0; i < IFNAMSIZ; i++)
	printf("%c", e->ipv6.iniface_mask[i] ? 'X' : '.');
	printf("to `%s'/", e->ipv6.outiface);
	for (i = 0; i < IFNAMSIZ; i++)
	printf("%c", e->ipv6.outiface_mask[i] ? 'X' : '.');
	printf("\nProtocol: %u\n", e->ipv6.proto);
	if (e->ipv6.flags & IP6T_F_TOS)
	printf("TOS: %u\n", e->ipv6.tos);
	printf("Flags: %02X\n", e->ipv6.flags);
	printf("Invflags: %02X\n", e->ipv6.invflags);
	printf("Counters: %llu packets, %llu bytes\n",
	(unsigned long long)e->counters.pcnt, (unsigned long long)e->counters.bcnt);
	printf("Cache: %08X\n", e->nfcache);

	IP6T_MATCH_ITERATE(e, print_match);

	t = ip6t_get_target(e);
	printf("Target name: `%s' [%u]\n", t->u.user.name, t->u.target_size);
	if (strcmp(t->u.user.name, IP6T_STANDARD_TARGET) == 0) {
	const unsigned char *data = t->data;
	int pos = (const int )data;
	if (pos < 0)
	printf("verdict=%s\n",
	pos == -NF_ACCEPT-1 ? "NF_ACCEPT"
	: pos == -NF_DROP-1 ? "NF_DROP"
	: pos == IP6T_RETURN ? "RETURN"
	: "UNKNOWN");
	else
	printf("verdict=%u\n", pos);
	} else if (strcmp(t->u.user.name, IP6T_ERROR_TARGET) == 0)
	printf("error=`%s'\n", t->data);

	printf("\n");
	return 0;
	}

	static unsigned char *
	is_same(const STRUCT_ENTRY a, const STRUCT_ENTRY b,
	unsigned char *matchmask)
	{
	unsigned int i;
	unsigned char *mptr;

	/* Always compare head structures: ignore mask here. */
	if (memcmp(&a->ipv6.src, &b->ipv6.src, sizeof(struct in6_addr))
	\|\| memcmp(&a->ipv6.dst, &b->ipv6.dst, sizeof(struct in6_addr))
	\|\| memcmp(&a->ipv6.smsk, &b->ipv6.smsk, sizeof(struct in6_addr))
	\|\| memcmp(&a->ipv6.dmsk, &b->ipv6.dmsk, sizeof(struct in6_addr))
	\|\| a->ipv6.proto != b->ipv6.proto
	\|\| a->ipv6.tos != b->ipv6.tos
	\|\| a->ipv6.flags != b->ipv6.flags
	\|\| a->ipv6.invflags != b->ipv6.invflags)
	return NULL;

	for (i = 0; i < IFNAMSIZ; i++) {
	if (a->ipv6.iniface_mask[i] != b->ipv6.iniface_mask[i])
	return NULL;
	if ((a->ipv6.iniface[i] & a->ipv6.iniface_mask[i])
	!= (b->ipv6.iniface[i] & b->ipv6.iniface_mask[i]))
	return NULL;
	if (a->ipv6.outiface_mask[i] != b->ipv6.outiface_mask[i])
	return NULL;
	if ((a->ipv6.outiface[i] & a->ipv6.outiface_mask[i])
	!= (b->ipv6.outiface[i] & b->ipv6.outiface_mask[i]))
	return NULL;
	}

	if (a->target_offset != b->target_offset
	\|\| a->next_offset != b->next_offset)
	return NULL;

	mptr = matchmask + sizeof(STRUCT_ENTRY);
	if (IP6T_MATCH_ITERATE(a, match_different, a->elems, b->elems, &mptr))
	return NULL;
	mptr += IP6T_ALIGN(sizeof(struct ip6t_entry_target));

	return mptr;
	}

	/* All zeroes == unconditional rule. */
	static inline int
	unconditional(const struct ip6t_ip6 *ipv6)
	{
	unsigned int i;

	for (i = 0; i < sizeof(*ipv6); i++)
	if (((char *)ipv6)[i])
	break;

	return (i == sizeof(*ipv6));
	}

	#ifdef IPTC_DEBUG
	/* Do every conceivable sanity check on the handle */
	static void
	do_check(struct xtc_handle *h, unsigned int line)
	{
	unsigned int i, n;
	unsigned int user_offset; /* Offset of first user chain */
	int was_return;

	assert(h->changed == 0 \|\| h->changed == 1);
	if (strcmp(h->info.name, "filter") == 0) {
	assert(h->info.valid_hooks
	== (1 << NF_IP6_LOCAL_IN
	\| 1 << NF_IP6_FORWARD
	\| 1 << NF_IP6_LOCAL_OUT));

	/* Hooks should be first three */
	assert(h->info.hook_entry[NF_IP6_LOCAL_IN] == 0);

	n = get_chain_end(h, 0);
	n += get_entry(h, n)->next_offset;
	assert(h->info.hook_entry[NF_IP6_FORWARD] == n);

	n = get_chain_end(h, n);
	n += get_entry(h, n)->next_offset;
	assert(h->info.hook_entry[NF_IP6_LOCAL_OUT] == n);

	user_offset = h->info.hook_entry[NF_IP6_LOCAL_OUT];
	} else if (strcmp(h->info.name, "nat") == 0) {
	assert((h->info.valid_hooks
	== (1 << NF_IP6_PRE_ROUTING
	\| 1 << NF_IP6_LOCAL_OUT
	\| 1 << NF_IP6_POST_ROUTING)) \|\|
	(h->info.valid_hooks
	== (1 << NF_IP6_PRE_ROUTING
	\| 1 << NF_IP6_LOCAL_IN
	\| 1 << NF_IP6_LOCAL_OUT
	\| 1 << NF_IP6_POST_ROUTING)));

	assert(h->info.hook_entry[NF_IP6_PRE_ROUTING] == 0);

	n = get_chain_end(h, 0);

	n += get_entry(h, n)->next_offset;
	assert(h->info.hook_entry[NF_IP6_POST_ROUTING] == n);
	n = get_chain_end(h, n);

	n += get_entry(h, n)->next_offset;
	assert(h->info.hook_entry[NF_IP6_LOCAL_OUT] == n);
	user_offset = h->info.hook_entry[NF_IP6_LOCAL_OUT];

	if (h->info.valid_hooks & (1 << NF_IP6_LOCAL_IN)) {
	n = get_chain_end(h, n);
	n += get_entry(h, n)->next_offset;
	assert(h->info.hook_entry[NF_IP6_LOCAL_IN] == n);
	user_offset = h->info.hook_entry[NF_IP6_LOCAL_IN];
	}

	} else if (strcmp(h->info.name, "mangle") == 0) {
	/* This code is getting ugly because linux < 2.4.18-pre6 had
	* two mangle hooks, linux >= 2.4.18-pre6 has five mangle hooks
	* */
	assert((h->info.valid_hooks
	== (1 << NF_IP6_PRE_ROUTING
	\| 1 << NF_IP6_LOCAL_OUT)) \|\|
	(h->info.valid_hooks
	== (1 << NF_IP6_PRE_ROUTING
	\| 1 << NF_IP6_LOCAL_IN
	\| 1 << NF_IP6_FORWARD
	\| 1 << NF_IP6_LOCAL_OUT
	\| 1 << NF_IP6_POST_ROUTING)));

	/* Hooks should be first five */
	assert(h->info.hook_entry[NF_IP6_PRE_ROUTING] == 0);

	n = get_chain_end(h, 0);

	if (h->info.valid_hooks & (1 << NF_IP6_LOCAL_IN)) {
	n += get_entry(h, n)->next_offset;
	assert(h->info.hook_entry[NF_IP6_LOCAL_IN] == n);
	n = get_chain_end(h, n);
	}

	if (h->info.valid_hooks & (1 << NF_IP6_FORWARD)) {
	n += get_entry(h, n)->next_offset;
	assert(h->info.hook_entry[NF_IP6_FORWARD] == n);
	n = get_chain_end(h, n);
	}

	n += get_entry(h, n)->next_offset;
	assert(h->info.hook_entry[NF_IP6_LOCAL_OUT] == n);
	user_offset = h->info.hook_entry[NF_IP6_LOCAL_OUT];

	if (h->info.valid_hooks & (1 << NF_IP6_POST_ROUTING)) {
	n = get_chain_end(h, n);
	n += get_entry(h, n)->next_offset;
	assert(h->info.hook_entry[NF_IP6_POST_ROUTING] == n);
	user_offset = h->info.hook_entry[NF_IP6_POST_ROUTING];
	}
	} else if (strcmp(h->info.name, "raw") == 0) {
	assert(h->info.valid_hooks
	== (1 << NF_IP6_PRE_ROUTING
	\| 1 << NF_IP6_LOCAL_OUT));

	/* Hooks should be first three */
	assert(h->info.hook_entry[NF_IP6_PRE_ROUTING] == 0);

	n = get_chain_end(h, n);
	n += get_entry(h, n)->next_offset;
	assert(h->info.hook_entry[NF_IP6_LOCAL_OUT] == n);

	user_offset = h->info.hook_entry[NF_IP6_LOCAL_OUT];
	} else {
	fprintf(stderr, "Unknown table `%s'\n", h->info.name);
	abort();
	}

	/* User chain == end of last builtin + policy entry */
	user_offset = get_chain_end(h, user_offset);
	user_offset += get_entry(h, user_offset)->next_offset;

	/* Overflows should be end of entry chains, and unconditional
	policy nodes. */
	for (i = 0; i < NUMHOOKS; i++) {
	STRUCT_ENTRY *e;
	STRUCT_STANDARD_TARGET *t;

	if (!(h->info.valid_hooks & (1 << i)))
	continue;
	assert(h->info.underflow[i]
	== get_chain_end(h, h->info.hook_entry[i]));

	e = get_entry(h, get_chain_end(h, h->info.hook_entry[i]));
	assert(unconditional(&e->ipv6));
	assert(e->target_offset == sizeof(*e));
	t = (STRUCT_STANDARD_TARGET *)GET_TARGET(e);
	printf("target_size=%u, align=%u\n",
	t->target.u.target_size, ALIGN(sizeof(*t)));
	assert(t->target.u.target_size == ALIGN(sizeof(*t)));
	assert(e->next_offset == sizeof(e) + ALIGN(sizeof(t)));

	assert(strcmp(t->target.u.user.name, STANDARD_TARGET)==0);
	assert(t->verdict == -NF_DROP-1 \|\| t->verdict == -NF_ACCEPT-1);

	/* Hooks and underflows must be valid entries */
	iptcb_entry2index(h, get_entry(h, h->info.hook_entry[i]));
	iptcb_entry2index(h, get_entry(h, h->info.underflow[i]));
	}

	assert(h->info.size
	>= h->info.num_entries * (sizeof(STRUCT_ENTRY)
	+sizeof(STRUCT_STANDARD_TARGET)));

	assert(h->entries.size
	>= (h->new_number
	* (sizeof(STRUCT_ENTRY)
	+ sizeof(STRUCT_STANDARD_TARGET))));
	assert(strcmp(h->info.name, h->entries.name) == 0);

	i = 0; n = 0;
	was_return = 0;

	#if 0
	/* Check all the entries. */
	ENTRY_ITERATE(h->entries.entrytable, h->entries.size,
	check_entry, &i, &n, user_offset, &was_return, h);

	assert(i == h->new_number);
	assert(n == h->entries.size);

	/* Final entry must be error node */
	assert(strcmp(GET_TARGET(index2entry(h, h->new_number-1))
	->u.user.name,
	ERROR_TARGET) == 0);
	#endif
	}
	#endif /IPTC_DEBUG/