[net-next-2.6.git] / net / netfilter / xt_TCPMSS.c

/*
 * This is a module which is used for setting the MSS option in TCP packets.
 *
 * Copyright (C) 2000 Marc Boucher <marc@mbsi.ca>
 *
 * 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.
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/tcp.h>
#include <net/dst.h>
#include <net/flow.h>
#include <net/ipv6.h>
#include <net/route.h>
#include <net/tcp.h>

#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_tcpudp.h>
#include <linux/netfilter/xt_TCPMSS.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
MODULE_DESCRIPTION("Xtables: TCP Maximum Segment Size (MSS) adjustment");
MODULE_ALIAS("ipt_TCPMSS");
MODULE_ALIAS("ip6t_TCPMSS");

static inline unsigned int
optlen(const u_int8_t *opt, unsigned int offset)
{
	/* Beware zero-length options: make finite progress */
	if (opt[offset] <= TCPOPT_NOP || opt[offset+1] == 0)
		return 1;
	else
		return opt[offset+1];
}

static int
tcpmss_mangle_packet(struct sk_buff *skb,
		     const struct xt_tcpmss_info *info,
		     unsigned int in_mtu,
		     unsigned int tcphoff,
		     unsigned int minlen)
{
	struct tcphdr *tcph;
	unsigned int tcplen, i;
	__be16 oldval;
	u16 newmss;
	u8 *opt;

	if (!skb_make_writable(skb, skb->len))
		return -1;

	tcplen = skb->len - tcphoff;
	tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff);

	/* Since it passed flags test in tcp match, we know it is is
	   not a fragment, and has data >= tcp header length.  SYN
	   packets should not contain data: if they did, then we risk
	   running over MTU, sending Frag Needed and breaking things
	   badly. --RR */
	if (tcplen != tcph->doff*4) {
		if (net_ratelimit())
			printk(KERN_ERR "xt_TCPMSS: bad length (%u bytes)\n",
			       skb->len);
		return -1;
	}

	if (info->mss == XT_TCPMSS_CLAMP_PMTU) {
		if (dst_mtu(skb_dst(skb)) <= minlen) {
			if (net_ratelimit())
				printk(KERN_ERR "xt_TCPMSS: "
				       "unknown or invalid path-MTU (%u)\n",
				       dst_mtu(skb_dst(skb)));
			return -1;
		}
		if (in_mtu <= minlen) {
			if (net_ratelimit())
				printk(KERN_ERR "xt_TCPMSS: unknown or "
				       "invalid path-MTU (%u)\n", in_mtu);
			return -1;
		}
		newmss = min(dst_mtu(skb_dst(skb)), in_mtu) - minlen;
	} else
		newmss = info->mss;

	opt = (u_int8_t *)tcph;
	for (i = sizeof(struct tcphdr); i < tcph->doff*4; i += optlen(opt, i)) {
		if (opt[i] == TCPOPT_MSS && tcph->doff*4 - i >= TCPOLEN_MSS &&
		    opt[i+1] == TCPOLEN_MSS) {
			u_int16_t oldmss;

			oldmss = (opt[i+2] << 8) | opt[i+3];

			/* Never increase MSS, even when setting it, as
			 * doing so results in problems for hosts that rely
			 * on MSS being set correctly.
			 */
			if (oldmss <= newmss)
				return 0;

			opt[i+2] = (newmss & 0xff00) >> 8;
			opt[i+3] = newmss & 0x00ff;

			inet_proto_csum_replace2(&tcph->check, skb,
						 htons(oldmss), htons(newmss),
						 0);
			return 0;
		}
	}

	/*
	 * MSS Option not found ?! add it..
	 */
	if (skb_tailroom(skb) < TCPOLEN_MSS) {
		if (pskb_expand_head(skb, 0,
				     TCPOLEN_MSS - skb_tailroom(skb),
				     GFP_ATOMIC))
			return -1;
		tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff);
	}

	skb_put(skb, TCPOLEN_MSS);

	opt = (u_int8_t *)tcph + sizeof(struct tcphdr);
	memmove(opt + TCPOLEN_MSS, opt, tcplen - sizeof(struct tcphdr));

	inet_proto_csum_replace2(&tcph->check, skb,
				 htons(tcplen), htons(tcplen + TCPOLEN_MSS), 1);
	opt[0] = TCPOPT_MSS;
	opt[1] = TCPOLEN_MSS;
	opt[2] = (newmss & 0xff00) >> 8;
	opt[3] = newmss & 0x00ff;

	inet_proto_csum_replace4(&tcph->check, skb, 0, *((__be32 *)opt), 0);

	oldval = ((__be16 *)tcph)[6];
	tcph->doff += TCPOLEN_MSS/4;
	inet_proto_csum_replace2(&tcph->check, skb,
				 oldval, ((__be16 *)tcph)[6], 0);
	return TCPOLEN_MSS;
}

static u_int32_t tcpmss_reverse_mtu(const struct sk_buff *skb,
				    unsigned int family)
{
	struct flowi fl = {};
	const struct nf_afinfo *ai;
	struct rtable *rt = NULL;
	u_int32_t mtu     = ~0U;

	if (family == PF_INET)
		fl.fl4_dst = ip_hdr(skb)->saddr;
	else
		fl.fl6_dst = ipv6_hdr(skb)->saddr;

	rcu_read_lock();
	ai = nf_get_afinfo(family);
	if (ai != NULL)
		ai->route((struct dst_entry **)&rt, &fl);
	rcu_read_unlock();

	if (rt != NULL) {
		mtu = dst_mtu(&rt->u.dst);
		dst_release(&rt->u.dst);
	}
	return mtu;
}

static unsigned int
tcpmss_tg4(struct sk_buff *skb, const struct xt_target_param *par)
{
	struct iphdr *iph = ip_hdr(skb);
	__be16 newlen;
	int ret;

	ret = tcpmss_mangle_packet(skb, par->targinfo,
				   tcpmss_reverse_mtu(skb, PF_INET),
				   iph->ihl * 4,
				   sizeof(*iph) + sizeof(struct tcphdr));
	if (ret < 0)
		return NF_DROP;
	if (ret > 0) {
		iph = ip_hdr(skb);
		newlen = htons(ntohs(iph->tot_len) + ret);
		csum_replace2(&iph->check, iph->tot_len, newlen);
		iph->tot_len = newlen;
	}
	return XT_CONTINUE;
}

#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
static unsigned int
tcpmss_tg6(struct sk_buff *skb, const struct xt_target_param *par)
{
	struct ipv6hdr *ipv6h = ipv6_hdr(skb);
	u8 nexthdr;
	int tcphoff;
	int ret;

	nexthdr = ipv6h->nexthdr;
	tcphoff = ipv6_skip_exthdr(skb, sizeof(*ipv6h), &nexthdr);
	if (tcphoff < 0)
		return NF_DROP;
	ret = tcpmss_mangle_packet(skb, par->targinfo,
				   tcpmss_reverse_mtu(skb, PF_INET6),
				   tcphoff,
				   sizeof(*ipv6h) + sizeof(struct tcphdr));
	if (ret < 0)
		return NF_DROP;
	if (ret > 0) {
		ipv6h = ipv6_hdr(skb);
		ipv6h->payload_len = htons(ntohs(ipv6h->payload_len) + ret);
	}
	return XT_CONTINUE;
}
#endif

#define TH_SYN 0x02

/* Must specify -p tcp --syn */
static inline bool find_syn_match(const struct xt_entry_match *m)
{
	const struct xt_tcp *tcpinfo = (const struct xt_tcp *)m->data;

	if (strcmp(m->u.kernel.match->name, "tcp") == 0 &&
	    tcpinfo->flg_cmp & TH_SYN &&
	    !(tcpinfo->invflags & XT_TCP_INV_FLAGS))
		return true;

	return false;
}

static bool tcpmss_tg4_check(const struct xt_tgchk_param *par)
{
	const struct xt_tcpmss_info *info = par->targinfo;
	const struct ipt_entry *e = par->entryinfo;

	if (info->mss == XT_TCPMSS_CLAMP_PMTU &&
	    (par->hook_mask & ~((1 << NF_INET_FORWARD) |
			   (1 << NF_INET_LOCAL_OUT) |
			   (1 << NF_INET_POST_ROUTING))) != 0) {
		printk("xt_TCPMSS: path-MTU clamping only supported in "
		       "FORWARD, OUTPUT and POSTROUTING hooks\n");
		return false;
	}
	if (IPT_MATCH_ITERATE(e, find_syn_match))
		return true;
	printk("xt_TCPMSS: Only works on TCP SYN packets\n");
	return false;
}

#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
static bool tcpmss_tg6_check(const struct xt_tgchk_param *par)
{
	const struct xt_tcpmss_info *info = par->targinfo;
	const struct ip6t_entry *e = par->entryinfo;

	if (info->mss == XT_TCPMSS_CLAMP_PMTU &&
	    (par->hook_mask & ~((1 << NF_INET_FORWARD) |
			   (1 << NF_INET_LOCAL_OUT) |
			   (1 << NF_INET_POST_ROUTING))) != 0) {
		printk("xt_TCPMSS: path-MTU clamping only supported in "
		       "FORWARD, OUTPUT and POSTROUTING hooks\n");
		return false;
	}
	if (IP6T_MATCH_ITERATE(e, find_syn_match))
		return true;
	printk("xt_TCPMSS: Only works on TCP SYN packets\n");
	return false;
}
#endif

static struct xt_target tcpmss_tg_reg[] __read_mostly = {
	{
		.family		= NFPROTO_IPV4,
		.name		= "TCPMSS",
		.checkentry	= tcpmss_tg4_check,
		.target		= tcpmss_tg4,
		.targetsize	= sizeof(struct xt_tcpmss_info),
		.proto		= IPPROTO_TCP,
		.me		= THIS_MODULE,
	},
#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
	{
		.family		= NFPROTO_IPV6,
		.name		= "TCPMSS",
		.checkentry	= tcpmss_tg6_check,
		.target		= tcpmss_tg6,
		.targetsize	= sizeof(struct xt_tcpmss_info),
		.proto		= IPPROTO_TCP,
		.me		= THIS_MODULE,
	},
#endif
};

static int __init tcpmss_tg_init(void)
{
	return xt_register_targets(tcpmss_tg_reg, ARRAY_SIZE(tcpmss_tg_reg));
}

static void __exit tcpmss_tg_exit(void)
{
	xt_unregister_targets(tcpmss_tg_reg, ARRAY_SIZE(tcpmss_tg_reg));
}

module_init(tcpmss_tg_init);
module_exit(tcpmss_tg_exit);
Commit	Line	Data
cdd289a2 PM	1	/*
	2	* This is a module which is used for setting the MSS option in TCP packets.
	3	*
	4	* Copyright (C) 2000 Marc Boucher <marc@mbsi.ca>
	5	*
	6	* This program is free software; you can redistribute it and/or modify
	7	* it under the terms of the GNU General Public License version 2 as
	8	* published by the Free Software Foundation.
	9	*/
	10
	11	#include <linux/module.h>
	12	#include <linux/skbuff.h>
	13	#include <linux/ip.h>
	14	#include <linux/ipv6.h>
	15	#include <linux/tcp.h>
37c08387 JE	16	#include <net/dst.h>
37c08387 JE	17	#include <net/flow.h>
cdd289a2	18	#include <net/ipv6.h>
37c08387	19	#include <net/route.h>
cdd289a2 PM	20	#include <net/tcp.h>
	21
	22	#include <linux/netfilter_ipv4/ip_tables.h>
	23	#include <linux/netfilter_ipv6/ip6_tables.h>
	24	#include <linux/netfilter/x_tables.h>
	25	#include <linux/netfilter/xt_tcpudp.h>
	26	#include <linux/netfilter/xt_TCPMSS.h>
	27
	28	MODULE_LICENSE("GPL");
	29	MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
2ae15b64	30	MODULE_DESCRIPTION("Xtables: TCP Maximum Segment Size (MSS) adjustment");
cdd289a2 PM	31	MODULE_ALIAS("ipt_TCPMSS");
	32	MODULE_ALIAS("ip6t_TCPMSS");
	33
	34	static inline unsigned int
	35	optlen(const u_int8_t *opt, unsigned int offset)
	36	{
	37	/* Beware zero-length options: make finite progress */
	38	if (opt[offset] <= TCPOPT_NOP \|\| opt[offset+1] == 0)
	39	return 1;
	40	else
	41	return opt[offset+1];
	42	}
	43
	44	static int
3db05fea	45	tcpmss_mangle_packet(struct sk_buff *skb,
cdd289a2	46	const struct xt_tcpmss_info *info,
37c08387	47	unsigned int in_mtu,
cdd289a2 PM	48	unsigned int tcphoff,
	49	unsigned int minlen)
	50	{
	51	struct tcphdr *tcph;
	52	unsigned int tcplen, i;
	53	__be16 oldval;
	54	u16 newmss;
	55	u8 *opt;
	56
3db05fea	57	if (!skb_make_writable(skb, skb->len))
cdd289a2 PM	58	return -1;
cdd289a2 PM	59
3db05fea HX	60	tcplen = skb->len - tcphoff;
3db05fea HX	61	tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff);
cdd289a2 PM	62
	63	/* Since it passed flags test in tcp match, we know it is is
	64	not a fragment, and has data >= tcp header length. SYN
	65	packets should not contain data: if they did, then we risk
	66	running over MTU, sending Frag Needed and breaking things
	67	badly. --RR */
	68	if (tcplen != tcph->doff*4) {
	69	if (net_ratelimit())
	70	printk(KERN_ERR "xt_TCPMSS: bad length (%u bytes)\n",
3db05fea	71	skb->len);
cdd289a2 PM	72	return -1;
	73	}
	74
	75	if (info->mss == XT_TCPMSS_CLAMP_PMTU) {
adf30907	76	if (dst_mtu(skb_dst(skb)) <= minlen) {
cdd289a2 PM	77	if (net_ratelimit())
	78	printk(KERN_ERR "xt_TCPMSS: "
	79	"unknown or invalid path-MTU (%u)\n",
adf30907	80	dst_mtu(skb_dst(skb)));
cdd289a2 PM	81	return -1;
cdd289a2 PM	82	}
37c08387 JE	83	if (in_mtu <= minlen) {
	84	if (net_ratelimit())
	85	printk(KERN_ERR "xt_TCPMSS: unknown or "
	86	"invalid path-MTU (%u)\n", in_mtu);
	87	return -1;
	88	}
adf30907	89	newmss = min(dst_mtu(skb_dst(skb)), in_mtu) - minlen;
cdd289a2 PM	90	} else
	91	newmss = info->mss;
	92
	93	opt = (u_int8_t *)tcph;
	94	for (i = sizeof(struct tcphdr); i < tcph->doff*4; i += optlen(opt, i)) {
	95	if (opt[i] == TCPOPT_MSS && tcph->doff*4 - i >= TCPOLEN_MSS &&
	96	opt[i+1] == TCPOLEN_MSS) {
	97	u_int16_t oldmss;
	98
	99	oldmss = (opt[i+2] << 8) \| opt[i+3];
	100
17008064 BL	101	/* Never increase MSS, even when setting it, as
	102	* doing so results in problems for hosts that rely
	103	* on MSS being set correctly.
	104	*/
	105	if (oldmss <= newmss)
cdd289a2 PM	106	return 0;
	107
	108	opt[i+2] = (newmss & 0xff00) >> 8;
7c4e36bc	109	opt[i+3] = newmss & 0x00ff;
cdd289a2	110
be0ea7d5 PM	111	inet_proto_csum_replace2(&tcph->check, skb,
	112	htons(oldmss), htons(newmss),
	113	0);
cdd289a2 PM	114	return 0;
	115	}
	116	}
	117
	118	/*
	119	* MSS Option not found ?! add it..
	120	*/
3db05fea HX	121	if (skb_tailroom(skb) < TCPOLEN_MSS) {
	122	if (pskb_expand_head(skb, 0,
	123	TCPOLEN_MSS - skb_tailroom(skb),
2ca7b0ac	124	GFP_ATOMIC))
cdd289a2	125	return -1;
3db05fea	126	tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff);
cdd289a2 PM	127	}
cdd289a2 PM	128
3db05fea	129	skb_put(skb, TCPOLEN_MSS);
cdd289a2 PM	130
	131	opt = (u_int8_t *)tcph + sizeof(struct tcphdr);
	132	memmove(opt + TCPOLEN_MSS, opt, tcplen - sizeof(struct tcphdr));
	133
be0ea7d5 PM	134	inet_proto_csum_replace2(&tcph->check, skb,
be0ea7d5 PM	135	htons(tcplen), htons(tcplen + TCPOLEN_MSS), 1);
cdd289a2 PM	136	opt[0] = TCPOPT_MSS;
	137	opt[1] = TCPOLEN_MSS;
	138	opt[2] = (newmss & 0xff00) >> 8;
7c4e36bc	139	opt[3] = newmss & 0x00ff;
cdd289a2	140
be0ea7d5	141	inet_proto_csum_replace4(&tcph->check, skb, 0, ((__be32 )opt), 0);
cdd289a2 PM	142
	143	oldval = ((__be16 *)tcph)[6];
	144	tcph->doff += TCPOLEN_MSS/4;
be0ea7d5 PM	145	inet_proto_csum_replace2(&tcph->check, skb,
be0ea7d5 PM	146	oldval, ((__be16 *)tcph)[6], 0);
cdd289a2 PM	147	return TCPOLEN_MSS;
	148	}
	149
db1a75bd JE	150	static u_int32_t tcpmss_reverse_mtu(const struct sk_buff *skb,
db1a75bd JE	151	unsigned int family)
37c08387	152	{
db1a75bd	153	struct flowi fl = {};
37c08387 JE	154	const struct nf_afinfo *ai;
	155	struct rtable *rt = NULL;
	156	u_int32_t mtu = ~0U;
	157
db1a75bd JE	158	if (family == PF_INET)
	159	fl.fl4_dst = ip_hdr(skb)->saddr;
	160	else
	161	fl.fl6_dst = ipv6_hdr(skb)->saddr;
	162
37c08387	163	rcu_read_lock();
db1a75bd	164	ai = nf_get_afinfo(family);
37c08387 JE	165	if (ai != NULL)
	166	ai->route((struct dst_entry **)&rt, &fl);
	167	rcu_read_unlock();
	168
	169	if (rt != NULL) {
	170	mtu = dst_mtu(&rt->u.dst);
	171	dst_release(&rt->u.dst);
	172	}
	173	return mtu;
	174	}
	175
cdd289a2	176	static unsigned int
7eb35586	177	tcpmss_tg4(struct sk_buff skb, const struct xt_target_param par)
cdd289a2	178	{
3db05fea	179	struct iphdr *iph = ip_hdr(skb);
cdd289a2 PM	180	__be16 newlen;
	181	int ret;
	182
7eb35586	183	ret = tcpmss_mangle_packet(skb, par->targinfo,
db1a75bd	184	tcpmss_reverse_mtu(skb, PF_INET),
37c08387	185	iph->ihl * 4,
cdd289a2 PM	186	sizeof(*iph) + sizeof(struct tcphdr));
	187	if (ret < 0)
	188	return NF_DROP;
	189	if (ret > 0) {
3db05fea	190	iph = ip_hdr(skb);
cdd289a2	191	newlen = htons(ntohs(iph->tot_len) + ret);
be0ea7d5	192	csum_replace2(&iph->check, iph->tot_len, newlen);
cdd289a2 PM	193	iph->tot_len = newlen;
	194	}
	195	return XT_CONTINUE;
	196	}
	197
	198	#if defined(CONFIG_IP6_NF_IPTABLES) \|\| defined(CONFIG_IP6_NF_IPTABLES_MODULE)
	199	static unsigned int
7eb35586	200	tcpmss_tg6(struct sk_buff skb, const struct xt_target_param par)
cdd289a2	201	{
3db05fea	202	struct ipv6hdr *ipv6h = ipv6_hdr(skb);
cdd289a2 PM	203	u8 nexthdr;
	204	int tcphoff;
	205	int ret;
	206
	207	nexthdr = ipv6h->nexthdr;
3db05fea	208	tcphoff = ipv6_skip_exthdr(skb, sizeof(*ipv6h), &nexthdr);
9dc0564e	209	if (tcphoff < 0)
cdd289a2	210	return NF_DROP;
7eb35586	211	ret = tcpmss_mangle_packet(skb, par->targinfo,
db1a75bd	212	tcpmss_reverse_mtu(skb, PF_INET6),
37c08387	213	tcphoff,
cdd289a2 PM	214	sizeof(*ipv6h) + sizeof(struct tcphdr));
	215	if (ret < 0)
	216	return NF_DROP;
	217	if (ret > 0) {
3db05fea	218	ipv6h = ipv6_hdr(skb);
cdd289a2 PM	219	ipv6h->payload_len = htons(ntohs(ipv6h->payload_len) + ret);
	220	}
	221	return XT_CONTINUE;
	222	}
	223	#endif
	224
	225	#define TH_SYN 0x02
	226
	227	/* Must specify -p tcp --syn */
e1931b78	228	static inline bool find_syn_match(const struct xt_entry_match *m)
cdd289a2 PM	229	{
	230	const struct xt_tcp tcpinfo = (const struct xt_tcp )m->data;
	231
	232	if (strcmp(m->u.kernel.match->name, "tcp") == 0 &&
	233	tcpinfo->flg_cmp & TH_SYN &&
	234	!(tcpinfo->invflags & XT_TCP_INV_FLAGS))
e1931b78	235	return true;
cdd289a2	236
e1931b78	237	return false;
cdd289a2 PM	238	}
cdd289a2 PM	239
af5d6dc2	240	static bool tcpmss_tg4_check(const struct xt_tgchk_param *par)
cdd289a2	241	{
af5d6dc2 JE	242	const struct xt_tcpmss_info *info = par->targinfo;
af5d6dc2 JE	243	const struct ipt_entry *e = par->entryinfo;
cdd289a2 PM	244
cdd289a2 PM	245	if (info->mss == XT_TCPMSS_CLAMP_PMTU &&
af5d6dc2	246	(par->hook_mask & ~((1 << NF_INET_FORWARD) \|
6e23ae2a PM	247	(1 << NF_INET_LOCAL_OUT) \|
6e23ae2a PM	248	(1 << NF_INET_POST_ROUTING))) != 0) {
cdd289a2 PM	249	printk("xt_TCPMSS: path-MTU clamping only supported in "
cdd289a2 PM	250	"FORWARD, OUTPUT and POSTROUTING hooks\n");
e1931b78	251	return false;
cdd289a2 PM	252	}
cdd289a2 PM	253	if (IPT_MATCH_ITERATE(e, find_syn_match))
e1931b78	254	return true;
cdd289a2	255	printk("xt_TCPMSS: Only works on TCP SYN packets\n");
e1931b78	256	return false;
cdd289a2 PM	257	}
	258
	259	#if defined(CONFIG_IP6_NF_IPTABLES) \|\| defined(CONFIG_IP6_NF_IPTABLES_MODULE)
af5d6dc2	260	static bool tcpmss_tg6_check(const struct xt_tgchk_param *par)
cdd289a2	261	{
af5d6dc2 JE	262	const struct xt_tcpmss_info *info = par->targinfo;
af5d6dc2 JE	263	const struct ip6t_entry *e = par->entryinfo;
cdd289a2 PM	264
cdd289a2 PM	265	if (info->mss == XT_TCPMSS_CLAMP_PMTU &&
af5d6dc2	266	(par->hook_mask & ~((1 << NF_INET_FORWARD) \|
6e23ae2a PM	267	(1 << NF_INET_LOCAL_OUT) \|
6e23ae2a PM	268	(1 << NF_INET_POST_ROUTING))) != 0) {
cdd289a2 PM	269	printk("xt_TCPMSS: path-MTU clamping only supported in "
cdd289a2 PM	270	"FORWARD, OUTPUT and POSTROUTING hooks\n");
e1931b78	271	return false;
cdd289a2 PM	272	}
cdd289a2 PM	273	if (IP6T_MATCH_ITERATE(e, find_syn_match))
e1931b78	274	return true;
cdd289a2	275	printk("xt_TCPMSS: Only works on TCP SYN packets\n");
e1931b78	276	return false;
cdd289a2 PM	277	}
	278	#endif
	279
d3c5ee6d	280	static struct xt_target tcpmss_tg_reg[] __read_mostly = {
cdd289a2	281	{
ee999d8b	282	.family = NFPROTO_IPV4,
cdd289a2	283	.name = "TCPMSS",
d3c5ee6d JE	284	.checkentry = tcpmss_tg4_check,
d3c5ee6d JE	285	.target = tcpmss_tg4,
cdd289a2 PM	286	.targetsize = sizeof(struct xt_tcpmss_info),
	287	.proto = IPPROTO_TCP,
	288	.me = THIS_MODULE,
	289	},
	290	#if defined(CONFIG_IP6_NF_IPTABLES) \|\| defined(CONFIG_IP6_NF_IPTABLES_MODULE)
	291	{
ee999d8b	292	.family = NFPROTO_IPV6,
cdd289a2	293	.name = "TCPMSS",
d3c5ee6d JE	294	.checkentry = tcpmss_tg6_check,
d3c5ee6d JE	295	.target = tcpmss_tg6,
cdd289a2 PM	296	.targetsize = sizeof(struct xt_tcpmss_info),
	297	.proto = IPPROTO_TCP,
	298	.me = THIS_MODULE,
	299	},
	300	#endif
	301	};
	302
d3c5ee6d	303	static int __init tcpmss_tg_init(void)
cdd289a2	304	{
d3c5ee6d	305	return xt_register_targets(tcpmss_tg_reg, ARRAY_SIZE(tcpmss_tg_reg));
cdd289a2 PM	306	}
cdd289a2 PM	307
d3c5ee6d	308	static void __exit tcpmss_tg_exit(void)
cdd289a2	309	{
d3c5ee6d	310	xt_unregister_targets(tcpmss_tg_reg, ARRAY_SIZE(tcpmss_tg_reg));
cdd289a2 PM	311	}
cdd289a2 PM	312
d3c5ee6d JE	313	module_init(tcpmss_tg_init);
d3c5ee6d JE	314	module_exit(tcpmss_tg_exit);