[NETFILTER]: Add nf_conntrack subsystem.

The existing connection tracking subsystem in netfilter can only
handle ipv4.  There were basically two choices present to add
connection tracking support for ipv6.  We could either duplicate all
of the ipv4 connection tracking code into an ipv6 counterpart, or (the
choice taken by these patches) we could design a generic layer that
could handle both ipv4 and ipv6 and thus requiring only one sub-protocol
(TCP, UDP, etc.) connection tracking helper module to be written.

In fact nf_conntrack is capable of working with any layer 3
protocol.

The existing ipv4 specific conntrack code could also not deal
with the pecularities of doing connection tracking on ipv6,
which is also cured here.  For example, these issues include:

1) ICMPv6 handling, which is used for neighbour discovery in
   ipv6 thus some messages such as these should not participate
   in connection tracking since effectively they are like ARP
   messages

2) fragmentation must be handled differently in ipv6, because
   the simplistic "defrag, connection track and NAT, refrag"
   (which the existing ipv4 connection tracking does) approach simply
   isn't feasible in ipv6

3) ipv6 extension header parsing must occur at the correct spots
   before and after connection tracking decisions, and there were
   no provisions for this in the existing connection tracking
   design

4) ipv6 has no need for stateful NAT

The ipv4 specific conntrack layer is kept around, until all of
the ipv4 specific conntrack helpers are ported over to nf_conntrack
and it is feature complete.  Once that occurs, the old conntrack
stuff will get placed into the feature-removal-schedule and we will
fully kill it off 6 months later.

Signed-off-by: Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>

1 files changed, 698 insertions, 0 deletions

diff --git a/net/netfilter/nf_conntrack_ftp.c b/net/netfilter/nf_conntrack_ftp.c
new file mode 100644
index 00000000000000..65080e269f2747
--- /dev/null
+++ b/net/netfilter/nf_conntrack_ftp.c
@@ -0,0 +1,698 @@
+/* FTP extension for connection tracking. */
+
+/* (C) 1999-2001 Paul `Rusty' Russell
+ * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
+ * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.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.
+ *
+ * 16 Dec 2003: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
+ *	- enable working with Layer 3 protocol independent connection tracking.
+ *	- track EPRT and EPSV commands with IPv6 address.
+ *
+ * Derived from net/ipv4/netfilter/ip_conntrack_ftp.c
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/netfilter.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/ctype.h>
+#include <net/checksum.h>
+#include <net/tcp.h>
+
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <linux/netfilter/nf_conntrack_ftp.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
+MODULE_DESCRIPTION("ftp connection tracking helper");
+
+/* This is slow, but it's simple. --RR */
+static char *ftp_buffer;
+
+static DEFINE_SPINLOCK(nf_ftp_lock);
+
+#define MAX_PORTS 8
+static u_int16_t ports[MAX_PORTS];
+static unsigned int ports_c;
+module_param_array(ports, ushort, &ports_c, 0400);
+
+static int loose;
+module_param(loose, int, 0600);
+
+unsigned int (*nf_nat_ftp_hook)(struct sk_buff **pskb,
+				enum ip_conntrack_info ctinfo,
+				enum ip_ct_ftp_type type,
+				unsigned int matchoff,
+				unsigned int matchlen,
+				struct nf_conntrack_expect *exp,
+				u32 *seq);
+EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
+
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(format, args...)
+#endif
+
+static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
+static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
+static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
+			     char);
+
+static struct ftp_search {
+	enum ip_conntrack_dir dir;
+	const char *pattern;
+	size_t plen;
+	char skip;
+	char term;
+	enum ip_ct_ftp_type ftptype;
+	int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
+} search[] = {
+	{
+		IP_CT_DIR_ORIGINAL,
+		"PORT", sizeof("PORT") - 1, ' ', '\r',
+		IP_CT_FTP_PORT,
+		try_rfc959,
+	},
+	{
+		IP_CT_DIR_REPLY,
+		"227 ", sizeof("227 ") - 1, '(', ')',
+		IP_CT_FTP_PASV,
+		try_rfc959,
+	},
+	{
+		IP_CT_DIR_ORIGINAL,
+		"EPRT", sizeof("EPRT") - 1, ' ', '\r',
+		IP_CT_FTP_EPRT,
+		try_eprt,
+	},
+	{
+		IP_CT_DIR_REPLY,
+		"229 ", sizeof("229 ") - 1, '(', ')',
+		IP_CT_FTP_EPSV,
+		try_epsv_response,
+	},
+};
+
+/* This code is based on inet_pton() in glibc-2.2.4 */
+static int
+get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
+{
+	static const char xdigits[] = "0123456789abcdef";
+	u_int8_t tmp[16], *tp, *endp, *colonp;
+	int ch, saw_xdigit;
+	u_int32_t val;
+	size_t clen = 0;
+
+	tp = memset(tmp, '\0', sizeof(tmp));
+	endp = tp + sizeof(tmp);
+	colonp = NULL;
+
+	/* Leading :: requires some special handling. */
+	if (*src == ':'){
+		if (*++src != ':') {
+			DEBUGP("invalid \":\" at the head of addr\n");
+			return 0;
+		}
+		clen++;
+	}
+
+	saw_xdigit = 0;
+	val = 0;
+	while ((clen < dlen) && (*src != term)) {
+		const char *pch;
+
+		ch = tolower(*src++);
+		clen++;
+
+                pch = strchr(xdigits, ch);
+                if (pch != NULL) {
+                        val <<= 4;
+                        val |= (pch - xdigits);
+                        if (val > 0xffff)
+                                return 0;
+
+			saw_xdigit = 1;
+                        continue;
+                }
+		if (ch != ':') {
+			DEBUGP("get_ipv6_addr: invalid char. \'%c\'\n", ch);
+			return 0;
+		}
+
+		if (!saw_xdigit) {
+			if (colonp) {
+				DEBUGP("invalid location of \"::\".\n");
+				return 0;
+			}
+			colonp = tp;
+			continue;
+		} else if (*src == term) {
+			DEBUGP("trancated IPv6 addr\n");
+			return 0;
+		}
+
+		if (tp + 2 > endp)
+			return 0;
+		*tp++ = (u_int8_t) (val >> 8) & 0xff;
+		*tp++ = (u_int8_t) val & 0xff;
+
+		saw_xdigit = 0;
+		val = 0;
+		continue;
+        }
+        if (saw_xdigit) {
+                if (tp + 2 > endp)
+                        return 0;
+                *tp++ = (u_int8_t) (val >> 8) & 0xff;
+                *tp++ = (u_int8_t) val & 0xff;
+        }
+        if (colonp != NULL) {
+                /*
+                 * Since some memmove()'s erroneously fail to handle
+                 * overlapping regions, we'll do the shift by hand.
+                 */
+                const int n = tp - colonp;
+                int i;
+
+                if (tp == endp)
+                        return 0;
+
+                for (i = 1; i <= n; i++) {
+                        endp[- i] = colonp[n - i];
+                        colonp[n - i] = 0;
+                }
+                tp = endp;
+        }
+        if (tp != endp || (*src != term))
+                return 0;
+
+        memcpy(dst->s6_addr, tmp, sizeof(dst->s6_addr));
+        return clen;
+}
+
+static int try_number(const char *data, size_t dlen, u_int32_t array[],
+                      int array_size, char sep, char term)
+{
+	u_int32_t i, len;
+
+	memset(array, 0, sizeof(array[0])*array_size);
+
+	/* Keep data pointing at next char. */
+	for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
+		if (*data >= '0' && *data <= '9') {
+			array[i] = array[i]*10 + *data - '0';
+		}
+		else if (*data == sep)
+			i++;
+		else {
+			/* Unexpected character; true if it's the
+			   terminator and we're finished. */
+			if (*data == term && i == array_size - 1)
+				return len;
+
+			DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
+			       len, i, *data);
+			return 0;
+		}
+	}
+	DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
+
+	return 0;
+}
+
+/* Returns 0, or length of numbers: 192,168,1,1,5,6 */
+static int try_rfc959(const char *data, size_t dlen,
+		      struct nf_conntrack_man *cmd, char term)
+{
+	int length;
+	u_int32_t array[6];
+
+	length = try_number(data, dlen, array, 6, ',', term);
+	if (length == 0)
+		return 0;
+
+	cmd->u3.ip =  htonl((array[0] << 24) | (array[1] << 16) |
+				    (array[2] << 8) | array[3]);
+	cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
+	return length;
+}
+
+/* Grab port: number up to delimiter */
+static int get_port(const char *data, int start, size_t dlen, char delim,
+		    u_int16_t *port)
+{
+	u_int16_t tmp_port = 0;
+	int i;
+
+	for (i = start; i < dlen; i++) {
+		/* Finished? */
+		if (data[i] == delim) {
+			if (tmp_port == 0)
+				break;
+			*port = htons(tmp_port);
+			DEBUGP("get_port: return %d\n", tmp_port);
+			return i + 1;
+		}
+		else if (data[i] >= '0' && data[i] <= '9')
+			tmp_port = tmp_port*10 + data[i] - '0';
+		else { /* Some other crap */
+			DEBUGP("get_port: invalid char.\n");
+			break;
+		}
+	}
+	return 0;
+}
+
+/* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
+static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
+		    char term)
+{
+	char delim;
+	int length;
+
+	/* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
+	   then delimiter again. */
+	if (dlen <= 3) {
+		DEBUGP("EPRT: too short\n");
+		return 0;
+	}
+	delim = data[0];
+	if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
+		DEBUGP("try_eprt: invalid delimitter.\n");
+		return 0;
+	}
+
+	if ((cmd->l3num == PF_INET && data[1] != '1') ||
+	    (cmd->l3num == PF_INET6 && data[1] != '2')) {
+		DEBUGP("EPRT: invalid protocol number.\n");
+		return 0;
+	}
+
+	DEBUGP("EPRT: Got %c%c%c\n", delim, data[1], delim);
+
+	if (data[1] == '1') {
+		u_int32_t array[4];
+
+		/* Now we have IP address. */
+		length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
+		if (length != 0)
+			cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
+					   | (array[2] << 8) | array[3]);
+	} else {
+		/* Now we have IPv6 address. */
+		length = get_ipv6_addr(data + 3, dlen - 3,
+				       (struct in6_addr *)cmd->u3.ip6, delim);
+	}
+
+	if (length == 0)
+		return 0;
+	DEBUGP("EPRT: Got IP address!\n");
+	/* Start offset includes initial "|1|", and trailing delimiter */
+	return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
+}
+
+/* Returns 0, or length of numbers: |||6446| */
+static int try_epsv_response(const char *data, size_t dlen,
+			     struct nf_conntrack_man *cmd, char term)
+{
+	char delim;
+
+	/* Three delimiters. */
+	if (dlen <= 3) return 0;
+	delim = data[0];
+	if (isdigit(delim) || delim < 33 || delim > 126
+	    || data[1] != delim || data[2] != delim)
+		return 0;
+
+	return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
+}
+
+/* Return 1 for match, 0 for accept, -1 for partial. */
+static int find_pattern(const char *data, size_t dlen,
+			const char *pattern, size_t plen,
+			char skip, char term,
+			unsigned int *numoff,
+			unsigned int *numlen,
+			struct nf_conntrack_man *cmd,
+			int (*getnum)(const char *, size_t,
+				      struct nf_conntrack_man *, char))
+{
+	size_t i;
+
+	DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
+	if (dlen == 0)
+		return 0;
+
+	if (dlen <= plen) {
+		/* Short packet: try for partial? */
+		if (strnicmp(data, pattern, dlen) == 0)
+			return -1;
+		else return 0;
+	}
+
+	if (strnicmp(data, pattern, plen) != 0) {
+#if 0
+		size_t i;
+
+		DEBUGP("ftp: string mismatch\n");
+		for (i = 0; i < plen; i++) {
+			DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
+				i, data[i], data[i],
+				pattern[i], pattern[i]);
+		}
+#endif
+		return 0;
+	}
+
+	DEBUGP("Pattern matches!\n");
+	/* Now we've found the constant string, try to skip
+	   to the 'skip' character */
+	for (i = plen; data[i] != skip; i++)
+		if (i == dlen - 1) return -1;
+
+	/* Skip over the last character */
+	i++;
+
+	DEBUGP("Skipped up to `%c'!\n", skip);
+
+	*numoff = i;
+	*numlen = getnum(data + i, dlen - i, cmd, term);
+	if (!*numlen)
+		return -1;
+
+	DEBUGP("Match succeeded!\n");
+	return 1;
+}
+
+/* Look up to see if we're just after a \n. */
+static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir)
+{
+	unsigned int i;
+
+	for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
+		if (info->seq_aft_nl[dir][i] == seq)
+			return 1;
+	return 0;
+}
+
+/* We don't update if it's older than what we have. */
+static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir,
+			  struct sk_buff *skb)
+{
+	unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
+
+	/* Look for oldest: if we find exact match, we're done. */
+	for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
+		if (info->seq_aft_nl[dir][i] == nl_seq)
+			return;
+
+		if (oldest == info->seq_aft_nl_num[dir]
+		    || before(info->seq_aft_nl[dir][i], oldest))
+			oldest = i;
+	}
+
+	if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
+		info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
+		nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
+	} else if (oldest != NUM_SEQ_TO_REMEMBER) {
+		info->seq_aft_nl[dir][oldest] = nl_seq;
+		nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
+	}
+}
+
+static int help(struct sk_buff **pskb,
+		unsigned int protoff,
+		struct nf_conn *ct,
+		enum ip_conntrack_info ctinfo)
+{
+	unsigned int dataoff, datalen;
+	struct tcphdr _tcph, *th;
+	char *fb_ptr;
+	int ret;
+	u32 seq;
+	int dir = CTINFO2DIR(ctinfo);
+	unsigned int matchlen, matchoff;
+	struct ip_ct_ftp_master *ct_ftp_info = &ct->help->ct_ftp_info;
+	struct nf_conntrack_expect *exp;
+	struct nf_conntrack_man cmd = {};
+
+	unsigned int i;
+	int found = 0, ends_in_nl;
+
+	/* Until there's been traffic both ways, don't look in packets. */
+	if (ctinfo != IP_CT_ESTABLISHED
+	    && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
+		DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);
+		return NF_ACCEPT;
+	}
+
+	th = skb_header_pointer(*pskb, protoff, sizeof(_tcph), &_tcph);
+	if (th == NULL)
+		return NF_ACCEPT;
+
+	dataoff = protoff + th->doff * 4;
+	/* No data? */
+	if (dataoff >= (*pskb)->len) {
+		DEBUGP("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
+			(*pskb)->len);
+		return NF_ACCEPT;
+	}
+	datalen = (*pskb)->len - dataoff;
+
+	spin_lock_bh(&nf_ftp_lock);
+	fb_ptr = skb_header_pointer(*pskb, dataoff, datalen, ftp_buffer);
+	BUG_ON(fb_ptr == NULL);
+
+	ends_in_nl = (fb_ptr[datalen - 1] == '\n');
+	seq = ntohl(th->seq) + datalen;
+
+	/* Look up to see if we're just after a \n. */
+	if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
+		/* Now if this ends in \n, update ftp info. */
+		DEBUGP("nf_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
+		       ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
+		       ct_ftp_info->seq_aft_nl[dir][0],
+		       ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
+		       ct_ftp_info->seq_aft_nl[dir][1]);
+		ret = NF_ACCEPT;
+		goto out_update_nl;
+	}
+
+        /* Initialize IP/IPv6 addr to expected address (it's not mentioned
+           in EPSV responses) */
+	cmd.l3num = ct->tuplehash[dir].tuple.src.l3num;
+	memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
+	       sizeof(cmd.u3.all));
+
+	for (i = 0; i < ARRAY_SIZE(search); i++) {
+		if (search[i].dir != dir) continue;
+
+		found = find_pattern(fb_ptr, datalen,
+				     search[i].pattern,
+				     search[i].plen,
+				     search[i].skip,
+				     search[i].term,
+				     &matchoff, &matchlen,
+				     &cmd,
+				     search[i].getnum);
+		if (found) break;
+	}
+	if (found == -1) {
+		/* We don't usually drop packets.  After all, this is
+		   connection tracking, not packet filtering.
+		   However, it is necessary for accurate tracking in
+		   this case. */
+		if (net_ratelimit())
+			printk("conntrack_ftp: partial %s %u+%u\n",
+			       search[i].pattern,
+			       ntohl(th->seq), datalen);
+		ret = NF_DROP;
+		goto out;
+	} else if (found == 0) { /* No match */
+		ret = NF_ACCEPT;
+		goto out_update_nl;
+	}
+
+	DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
+	       (int)matchlen, fb_ptr + matchoff,
+	       matchlen, ntohl(th->seq) + matchoff);
+
+	exp = nf_conntrack_expect_alloc(ct);
+	if (exp == NULL) {
+		ret = NF_DROP;
+		goto out;
+	}
+
+	/* We refer to the reverse direction ("!dir") tuples here,
+	 * because we're expecting something in the other direction.
+	 * Doesn't matter unless NAT is happening.  */
+	exp->tuple.dst.u3 = ct->tuplehash[!dir].tuple.dst.u3;
+
+	/* Update the ftp info */
+	if ((cmd.l3num == ct->tuplehash[dir].tuple.src.l3num) &&
+	    memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
+		     sizeof(cmd.u3.all))) {
+		/* Enrico Scholz's passive FTP to partially RNAT'd ftp
+                   server: it really wants us to connect to a
+                   different IP address.  Simply don't record it for
+                   NAT. */
+		if (cmd.l3num == PF_INET) {
+                	DEBUGP("conntrack_ftp: NOT RECORDING: %u,%u,%u,%u != %u.%u.%u.%u\n",
+			       NIPQUAD(cmd.u3.ip),
+			       NIPQUAD(ct->tuplehash[dir].tuple.src.u3.ip));
+		} else {
+			DEBUGP("conntrack_ftp: NOT RECORDING: %x:%x:%x:%x:%x:%x:%x:%x != %x:%x:%x:%x:%x:%x:%x:%x\n",
+			       NIP6(*((struct in6_addr *)cmd.u3.ip6)),
+			       NIP6(*((struct in6_addr *)ct->tuplehash[dir]
+							.tuple.src.u3.ip6)));
+		}
+
+		/* Thanks to Cristiano Lincoln Mattos
+		   <lincoln@cesar.org.br> for reporting this potential
+		   problem (DMZ machines opening holes to internal
+		   networks, or the packet filter itself). */
+		if (!loose) {
+			ret = NF_ACCEPT;
+			goto out_put_expect;
+		}
+		memcpy(&exp->tuple.dst.u3, &cmd.u3.all,
+		       sizeof(exp->tuple.dst.u3));
+	}
+
+	exp->tuple.src.u3 = ct->tuplehash[!dir].tuple.src.u3;
+	exp->tuple.src.l3num = cmd.l3num;
+	exp->tuple.src.u.tcp.port = 0;
+	exp->tuple.dst.u.tcp.port = cmd.u.tcp.port;
+	exp->tuple.dst.protonum = IPPROTO_TCP;
+
+	exp->mask = (struct nf_conntrack_tuple)
+		    { .src = { .l3num = 0xFFFF,
+			       .u = { .tcp = { 0 }},
+			     },
+		      .dst = { .protonum = 0xFF,
+			       .u = { .tcp = { 0xFFFF }},
+			     },
+		    };
+	if (cmd.l3num == PF_INET) {
+		exp->mask.src.u3.ip = 0xFFFFFFFF;
+		exp->mask.dst.u3.ip = 0xFFFFFFFF;
+	} else {
+		memset(exp->mask.src.u3.ip6, 0xFF,
+		       sizeof(exp->mask.src.u3.ip6));
+		memset(exp->mask.dst.u3.ip6, 0xFF,
+		       sizeof(exp->mask.src.u3.ip6));
+	}
+
+	exp->expectfn = NULL;
+	exp->flags = 0;
+
+	/* Now, NAT might want to mangle the packet, and register the
+	 * (possibly changed) expectation itself. */
+	if (nf_nat_ftp_hook)
+		ret = nf_nat_ftp_hook(pskb, ctinfo, search[i].ftptype,
+				      matchoff, matchlen, exp, &seq);
+	else {
+		/* Can't expect this?  Best to drop packet now. */
+		if (nf_conntrack_expect_related(exp) != 0)
+			ret = NF_DROP;
+		else
+			ret = NF_ACCEPT;
+	}
+
+out_put_expect:
+	nf_conntrack_expect_put(exp);
+
+out_update_nl:
+	/* Now if this ends in \n, update ftp info.  Seq may have been
+	 * adjusted by NAT code. */
+	if (ends_in_nl)
+		update_nl_seq(seq, ct_ftp_info, dir, *pskb);
+ out:
+	spin_unlock_bh(&nf_ftp_lock);
+	return ret;
+}
+
+static struct nf_conntrack_helper ftp[MAX_PORTS][2];
+static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")];
+
+/* don't make this __exit, since it's called from __init ! */
+static void fini(void)
+{
+	int i, j;
+	for (i = 0; i < ports_c; i++) {
+		for (j = 0; j < 2; j++) {
+			if (ftp[i][j].me == NULL)
+				continue;
+
+			DEBUGP("nf_ct_ftp: unregistering helper for pf: %d "
+			       "port: %d\n",
+				ftp[i][j].tuple.src.l3num, ports[i]);
+			nf_conntrack_helper_unregister(&ftp[i][j]);
+		}
+	}
+
+	kfree(ftp_buffer);
+}
+
+static int __init init(void)
+{
+	int i, j = -1, ret = 0;
+	char *tmpname;
+
+	ftp_buffer = kmalloc(65536, GFP_KERNEL);
+	if (!ftp_buffer)
+		return -ENOMEM;
+
+	if (ports_c == 0)
+		ports[ports_c++] = FTP_PORT;
+
+	/* FIXME should be configurable whether IPv4 and IPv6 FTP connections
+		 are tracked or not - YK */
+	for (i = 0; i < ports_c; i++) {
+		memset(&ftp[i], 0, sizeof(struct nf_conntrack_helper));
+
+		ftp[i][0].tuple.src.l3num = PF_INET;
+		ftp[i][1].tuple.src.l3num = PF_INET6;
+		for (j = 0; j < 2; j++) {
+			ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
+			ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
+			ftp[i][j].mask.src.u.tcp.port = 0xFFFF;
+			ftp[i][j].mask.dst.protonum = 0xFF;
+			ftp[i][j].max_expected = 1;
+			ftp[i][j].timeout = 5 * 60;	/* 5 Minutes */
+			ftp[i][j].me = THIS_MODULE;
+			ftp[i][j].help = help;
+			tmpname = &ftp_names[i][j][0];
+			if (ports[i] == FTP_PORT)
+				sprintf(tmpname, "ftp");
+			else
+				sprintf(tmpname, "ftp-%d", ports[i]);
+			ftp[i][j].name = tmpname;
+
+			DEBUGP("nf_ct_ftp: registering helper for pf: %d "
+			       "port: %d\n",
+				ftp[i][j].tuple.src.l3num, ports[i]);
+			ret = nf_conntrack_helper_register(&ftp[i][j]);
+			if (ret) {
+				printk("nf_ct_ftp: failed to register helper "
+				       " for pf: %d port: %d\n",
+					ftp[i][j].tuple.src.l3num, ports[i]);
+				fini();
+				return ret;
+			}
+		}
+	}
+
+	return 0;
+}
+
+module_init(init);
+module_exit(fini);