[ALSA] snd-bt87x: Improve support for different board types
[linux-2.6/verdex.git] / net / netfilter / xt_TCPMSS.c
blob07435a602b11fecb9be29e930d65462c46eff32b
1 /*
2 * This is a module which is used for setting the MSS option in TCP packets.
4 * Copyright (C) 2000 Marc Boucher <marc@mbsi.ca>
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 */
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>
16 #include <net/ipv6.h>
17 #include <net/tcp.h>
19 #include <linux/netfilter_ipv4/ip_tables.h>
20 #include <linux/netfilter_ipv6/ip6_tables.h>
21 #include <linux/netfilter/x_tables.h>
22 #include <linux/netfilter/xt_tcpudp.h>
23 #include <linux/netfilter/xt_TCPMSS.h>
25 MODULE_LICENSE("GPL");
26 MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
27 MODULE_DESCRIPTION("x_tables TCP MSS modification module");
28 MODULE_ALIAS("ipt_TCPMSS");
29 MODULE_ALIAS("ip6t_TCPMSS");
31 static inline unsigned int
32 optlen(const u_int8_t *opt, unsigned int offset)
34 /* Beware zero-length options: make finite progress */
35 if (opt[offset] <= TCPOPT_NOP || opt[offset+1] == 0)
36 return 1;
37 else
38 return opt[offset+1];
41 static int
42 tcpmss_mangle_packet(struct sk_buff *skb,
43 const struct xt_tcpmss_info *info,
44 unsigned int tcphoff,
45 unsigned int minlen)
47 struct tcphdr *tcph;
48 unsigned int tcplen, i;
49 __be16 oldval;
50 u16 newmss;
51 u8 *opt;
53 if (!skb_make_writable(skb, skb->len))
54 return -1;
56 tcplen = skb->len - tcphoff;
57 tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff);
59 /* Since it passed flags test in tcp match, we know it is is
60 not a fragment, and has data >= tcp header length. SYN
61 packets should not contain data: if they did, then we risk
62 running over MTU, sending Frag Needed and breaking things
63 badly. --RR */
64 if (tcplen != tcph->doff*4) {
65 if (net_ratelimit())
66 printk(KERN_ERR "xt_TCPMSS: bad length (%u bytes)\n",
67 skb->len);
68 return -1;
71 if (info->mss == XT_TCPMSS_CLAMP_PMTU) {
72 if (dst_mtu(skb->dst) <= minlen) {
73 if (net_ratelimit())
74 printk(KERN_ERR "xt_TCPMSS: "
75 "unknown or invalid path-MTU (%u)\n",
76 dst_mtu(skb->dst));
77 return -1;
79 newmss = dst_mtu(skb->dst) - minlen;
80 } else
81 newmss = info->mss;
83 opt = (u_int8_t *)tcph;
84 for (i = sizeof(struct tcphdr); i < tcph->doff*4; i += optlen(opt, i)) {
85 if (opt[i] == TCPOPT_MSS && tcph->doff*4 - i >= TCPOLEN_MSS &&
86 opt[i+1] == TCPOLEN_MSS) {
87 u_int16_t oldmss;
89 oldmss = (opt[i+2] << 8) | opt[i+3];
91 if (info->mss == XT_TCPMSS_CLAMP_PMTU &&
92 oldmss <= newmss)
93 return 0;
95 opt[i+2] = (newmss & 0xff00) >> 8;
96 opt[i+3] = newmss & 0x00ff;
98 nf_proto_csum_replace2(&tcph->check, skb,
99 htons(oldmss), htons(newmss), 0);
100 return 0;
105 * MSS Option not found ?! add it..
107 if (skb_tailroom(skb) < TCPOLEN_MSS) {
108 if (pskb_expand_head(skb, 0,
109 TCPOLEN_MSS - skb_tailroom(skb),
110 GFP_ATOMIC))
111 return -1;
112 tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff);
115 skb_put(skb, TCPOLEN_MSS);
117 opt = (u_int8_t *)tcph + sizeof(struct tcphdr);
118 memmove(opt + TCPOLEN_MSS, opt, tcplen - sizeof(struct tcphdr));
120 nf_proto_csum_replace2(&tcph->check, skb,
121 htons(tcplen), htons(tcplen + TCPOLEN_MSS), 1);
122 opt[0] = TCPOPT_MSS;
123 opt[1] = TCPOLEN_MSS;
124 opt[2] = (newmss & 0xff00) >> 8;
125 opt[3] = newmss & 0x00ff;
127 nf_proto_csum_replace4(&tcph->check, skb, 0, *((__be32 *)opt), 0);
129 oldval = ((__be16 *)tcph)[6];
130 tcph->doff += TCPOLEN_MSS/4;
131 nf_proto_csum_replace2(&tcph->check, skb,
132 oldval, ((__be16 *)tcph)[6], 0);
133 return TCPOLEN_MSS;
136 static unsigned int
137 xt_tcpmss_target4(struct sk_buff *skb,
138 const struct net_device *in,
139 const struct net_device *out,
140 unsigned int hooknum,
141 const struct xt_target *target,
142 const void *targinfo)
144 struct iphdr *iph = ip_hdr(skb);
145 __be16 newlen;
146 int ret;
148 ret = tcpmss_mangle_packet(skb, targinfo, iph->ihl * 4,
149 sizeof(*iph) + sizeof(struct tcphdr));
150 if (ret < 0)
151 return NF_DROP;
152 if (ret > 0) {
153 iph = ip_hdr(skb);
154 newlen = htons(ntohs(iph->tot_len) + ret);
155 nf_csum_replace2(&iph->check, iph->tot_len, newlen);
156 iph->tot_len = newlen;
158 return XT_CONTINUE;
161 #if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
162 static unsigned int
163 xt_tcpmss_target6(struct sk_buff *skb,
164 const struct net_device *in,
165 const struct net_device *out,
166 unsigned int hooknum,
167 const struct xt_target *target,
168 const void *targinfo)
170 struct ipv6hdr *ipv6h = ipv6_hdr(skb);
171 u8 nexthdr;
172 int tcphoff;
173 int ret;
175 nexthdr = ipv6h->nexthdr;
176 tcphoff = ipv6_skip_exthdr(skb, sizeof(*ipv6h), &nexthdr);
177 if (tcphoff < 0) {
178 WARN_ON(1);
179 return NF_DROP;
181 ret = tcpmss_mangle_packet(skb, targinfo, tcphoff,
182 sizeof(*ipv6h) + sizeof(struct tcphdr));
183 if (ret < 0)
184 return NF_DROP;
185 if (ret > 0) {
186 ipv6h = ipv6_hdr(skb);
187 ipv6h->payload_len = htons(ntohs(ipv6h->payload_len) + ret);
189 return XT_CONTINUE;
191 #endif
193 #define TH_SYN 0x02
195 /* Must specify -p tcp --syn */
196 static inline bool find_syn_match(const struct xt_entry_match *m)
198 const struct xt_tcp *tcpinfo = (const struct xt_tcp *)m->data;
200 if (strcmp(m->u.kernel.match->name, "tcp") == 0 &&
201 tcpinfo->flg_cmp & TH_SYN &&
202 !(tcpinfo->invflags & XT_TCP_INV_FLAGS))
203 return true;
205 return false;
208 static bool
209 xt_tcpmss_checkentry4(const char *tablename,
210 const void *entry,
211 const struct xt_target *target,
212 void *targinfo,
213 unsigned int hook_mask)
215 const struct xt_tcpmss_info *info = targinfo;
216 const struct ipt_entry *e = entry;
218 if (info->mss == XT_TCPMSS_CLAMP_PMTU &&
219 (hook_mask & ~((1 << NF_IP_FORWARD) |
220 (1 << NF_IP_LOCAL_OUT) |
221 (1 << NF_IP_POST_ROUTING))) != 0) {
222 printk("xt_TCPMSS: path-MTU clamping only supported in "
223 "FORWARD, OUTPUT and POSTROUTING hooks\n");
224 return false;
226 if (IPT_MATCH_ITERATE(e, find_syn_match))
227 return true;
228 printk("xt_TCPMSS: Only works on TCP SYN packets\n");
229 return false;
232 #if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
233 static bool
234 xt_tcpmss_checkentry6(const char *tablename,
235 const void *entry,
236 const struct xt_target *target,
237 void *targinfo,
238 unsigned int hook_mask)
240 const struct xt_tcpmss_info *info = targinfo;
241 const struct ip6t_entry *e = entry;
243 if (info->mss == XT_TCPMSS_CLAMP_PMTU &&
244 (hook_mask & ~((1 << NF_IP6_FORWARD) |
245 (1 << NF_IP6_LOCAL_OUT) |
246 (1 << NF_IP6_POST_ROUTING))) != 0) {
247 printk("xt_TCPMSS: path-MTU clamping only supported in "
248 "FORWARD, OUTPUT and POSTROUTING hooks\n");
249 return false;
251 if (IP6T_MATCH_ITERATE(e, find_syn_match))
252 return true;
253 printk("xt_TCPMSS: Only works on TCP SYN packets\n");
254 return false;
256 #endif
258 static struct xt_target xt_tcpmss_reg[] __read_mostly = {
260 .family = AF_INET,
261 .name = "TCPMSS",
262 .checkentry = xt_tcpmss_checkentry4,
263 .target = xt_tcpmss_target4,
264 .targetsize = sizeof(struct xt_tcpmss_info),
265 .proto = IPPROTO_TCP,
266 .me = THIS_MODULE,
268 #if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
270 .family = AF_INET6,
271 .name = "TCPMSS",
272 .checkentry = xt_tcpmss_checkentry6,
273 .target = xt_tcpmss_target6,
274 .targetsize = sizeof(struct xt_tcpmss_info),
275 .proto = IPPROTO_TCP,
276 .me = THIS_MODULE,
278 #endif
281 static int __init xt_tcpmss_init(void)
283 return xt_register_targets(xt_tcpmss_reg, ARRAY_SIZE(xt_tcpmss_reg));
286 static void __exit xt_tcpmss_fini(void)
288 xt_unregister_targets(xt_tcpmss_reg, ARRAY_SIZE(xt_tcpmss_reg));
291 module_init(xt_tcpmss_init);
292 module_exit(xt_tcpmss_fini);