Automatic merge of /spare/repo/netdev-2.6 branch hdlc
[linux-2.6] / net / ipv4 / netfilter / ipt_ECN.c
1 /* iptables module for the IPv4 and TCP ECN bits, Version 1.5
2  *
3  * (C) 2002 by Harald Welte <laforge@netfilter.org>
4  * 
5  * This program is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License version 2 as 
7  * published by the Free Software Foundation.
8  *
9  * ipt_ECN.c,v 1.5 2002/08/18 19:36:51 laforge Exp
10 */
11
12 #include <linux/module.h>
13 #include <linux/skbuff.h>
14 #include <linux/ip.h>
15 #include <linux/tcp.h>
16 #include <net/checksum.h>
17
18 #include <linux/netfilter_ipv4/ip_tables.h>
19 #include <linux/netfilter_ipv4/ipt_ECN.h>
20
21 MODULE_LICENSE("GPL");
22 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
23 MODULE_DESCRIPTION("iptables ECN modification module");
24
25 /* set ECT codepoint from IP header.
26  *      return 0 if there was an error. */
27 static inline int
28 set_ect_ip(struct sk_buff **pskb, const struct ipt_ECN_info *einfo)
29 {
30         if (((*pskb)->nh.iph->tos & IPT_ECN_IP_MASK)
31             != (einfo->ip_ect & IPT_ECN_IP_MASK)) {
32                 u_int16_t diffs[2];
33
34                 if (!skb_ip_make_writable(pskb, sizeof(struct iphdr)))
35                         return 0;
36
37                 diffs[0] = htons((*pskb)->nh.iph->tos) ^ 0xFFFF;
38                 (*pskb)->nh.iph->tos &= ~IPT_ECN_IP_MASK;
39                 (*pskb)->nh.iph->tos |= (einfo->ip_ect & IPT_ECN_IP_MASK);
40                 diffs[1] = htons((*pskb)->nh.iph->tos);
41                 (*pskb)->nh.iph->check
42                         = csum_fold(csum_partial((char *)diffs,
43                                                  sizeof(diffs),
44                                                  (*pskb)->nh.iph->check
45                                                  ^0xFFFF));
46                 (*pskb)->nfcache |= NFC_ALTERED;
47         } 
48         return 1;
49 }
50
51 /* Return 0 if there was an error. */
52 static inline int
53 set_ect_tcp(struct sk_buff **pskb, const struct ipt_ECN_info *einfo, int inward)
54 {
55         struct tcphdr _tcph, *tcph;
56         u_int16_t diffs[2];
57
58         /* Not enought header? */
59         tcph = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4,
60                                   sizeof(_tcph), &_tcph);
61         if (!tcph)
62                 return 0;
63
64         if (!(einfo->operation & IPT_ECN_OP_SET_ECE
65               || tcph->ece == einfo->proto.tcp.ece)
66             && (!(einfo->operation & IPT_ECN_OP_SET_CWR
67                   || tcph->cwr == einfo->proto.tcp.cwr)))
68                 return 1;
69
70         if (!skb_ip_make_writable(pskb, (*pskb)->nh.iph->ihl*4+sizeof(*tcph)))
71                 return 0;
72         tcph = (void *)(*pskb)->nh.iph + (*pskb)->nh.iph->ihl*4;
73
74         diffs[0] = ((u_int16_t *)tcph)[6];
75         if (einfo->operation & IPT_ECN_OP_SET_ECE)
76                 tcph->ece = einfo->proto.tcp.ece;
77         if (einfo->operation & IPT_ECN_OP_SET_CWR)
78                 tcph->cwr = einfo->proto.tcp.cwr;
79         diffs[1] = ((u_int16_t *)tcph)[6];
80         diffs[0] = diffs[0] ^ 0xFFFF;
81
82         if ((*pskb)->ip_summed != CHECKSUM_HW)
83                 tcph->check = csum_fold(csum_partial((char *)diffs,
84                                                      sizeof(diffs),
85                                                      tcph->check^0xFFFF));
86         else
87                 if (skb_checksum_help(*pskb, inward))
88                         return 0;
89         (*pskb)->nfcache |= NFC_ALTERED;
90         return 1;
91 }
92
93 static unsigned int
94 target(struct sk_buff **pskb,
95        const struct net_device *in,
96        const struct net_device *out,
97        unsigned int hooknum,
98        const void *targinfo,
99        void *userinfo)
100 {
101         const struct ipt_ECN_info *einfo = targinfo;
102
103         if (einfo->operation & IPT_ECN_OP_SET_IP)
104                 if (!set_ect_ip(pskb, einfo))
105                         return NF_DROP;
106
107         if (einfo->operation & (IPT_ECN_OP_SET_ECE | IPT_ECN_OP_SET_CWR)
108             && (*pskb)->nh.iph->protocol == IPPROTO_TCP)
109                 if (!set_ect_tcp(pskb, einfo, (out == NULL)))
110                         return NF_DROP;
111
112         return IPT_CONTINUE;
113 }
114
115 static int
116 checkentry(const char *tablename,
117            const struct ipt_entry *e,
118            void *targinfo,
119            unsigned int targinfosize,
120            unsigned int hook_mask)
121 {
122         const struct ipt_ECN_info *einfo = (struct ipt_ECN_info *)targinfo;
123
124         if (targinfosize != IPT_ALIGN(sizeof(struct ipt_ECN_info))) {
125                 printk(KERN_WARNING "ECN: targinfosize %u != %Zu\n",
126                        targinfosize,
127                        IPT_ALIGN(sizeof(struct ipt_ECN_info)));
128                 return 0;
129         }
130
131         if (strcmp(tablename, "mangle") != 0) {
132                 printk(KERN_WARNING "ECN: can only be called from \"mangle\" table, not \"%s\"\n", tablename);
133                 return 0;
134         }
135
136         if (einfo->operation & IPT_ECN_OP_MASK) {
137                 printk(KERN_WARNING "ECN: unsupported ECN operation %x\n",
138                         einfo->operation);
139                 return 0;
140         }
141         if (einfo->ip_ect & ~IPT_ECN_IP_MASK) {
142                 printk(KERN_WARNING "ECN: new ECT codepoint %x out of mask\n",
143                         einfo->ip_ect);
144                 return 0;
145         }
146
147         if ((einfo->operation & (IPT_ECN_OP_SET_ECE|IPT_ECN_OP_SET_CWR))
148             && (e->ip.proto != IPPROTO_TCP || (e->ip.invflags & IPT_INV_PROTO))) {
149                 printk(KERN_WARNING "ECN: cannot use TCP operations on a "
150                        "non-tcp rule\n");
151                 return 0;
152         }
153
154         return 1;
155 }
156
157 static struct ipt_target ipt_ecn_reg = {
158         .name           = "ECN",
159         .target         = target,
160         .checkentry     = checkentry,
161         .me             = THIS_MODULE,
162 };
163
164 static int __init init(void)
165 {
166         return ipt_register_target(&ipt_ecn_reg);
167 }
168
169 static void __exit fini(void)
170 {
171         ipt_unregister_target(&ipt_ecn_reg);
172 }
173
174 module_init(init);
175 module_exit(fini);