63221553d26b785f97d85ce0778cf82007643478
[linux-2.6.git] / net / ipv4 / netfilter.c
1 /* IPv4 specific functions of netfilter core */
2 #include <linux/kernel.h>
3 #include <linux/netfilter.h>
4 #include <linux/netfilter_ipv4.h>
5 #include <linux/ip.h>
6 #include <linux/skbuff.h>
7 #include <net/route.h>
8 #include <net/xfrm.h>
9 #include <net/ip.h>
10 #include <net/netfilter/nf_queue.h>
11
12 /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
13 int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
14 {
15         const struct iphdr *iph = ip_hdr(skb);
16         struct rtable *rt;
17         struct flowi fl = {};
18         struct dst_entry *odst;
19         unsigned int hh_len;
20         unsigned int type;
21
22         type = inet_addr_type(&init_net, iph->saddr);
23         if (addr_type == RTN_UNSPEC)
24                 addr_type = type;
25
26         /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
27          * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
28          */
29         if (addr_type == RTN_LOCAL) {
30                 fl.nl_u.ip4_u.daddr = iph->daddr;
31                 if (type == RTN_LOCAL)
32                         fl.nl_u.ip4_u.saddr = iph->saddr;
33                 fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
34                 fl.oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;
35                 fl.mark = skb->mark;
36                 if (ip_route_output_key(&rt, &fl) != 0)
37                         return -1;
38
39                 /* Drop old route. */
40                 dst_release(skb->dst);
41                 skb->dst = &rt->u.dst;
42         } else {
43                 /* non-local src, find valid iif to satisfy
44                  * rp-filter when calling ip_route_input. */
45                 fl.nl_u.ip4_u.daddr = iph->saddr;
46                 if (ip_route_output_key(&rt, &fl) != 0)
47                         return -1;
48
49                 odst = skb->dst;
50                 if (ip_route_input(skb, iph->daddr, iph->saddr,
51                                    RT_TOS(iph->tos), rt->u.dst.dev) != 0) {
52                         dst_release(&rt->u.dst);
53                         return -1;
54                 }
55                 dst_release(&rt->u.dst);
56                 dst_release(odst);
57         }
58
59         if (skb->dst->error)
60                 return -1;
61
62 #ifdef CONFIG_XFRM
63         if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
64             xfrm_decode_session(skb, &fl, AF_INET) == 0)
65                 if (xfrm_lookup(&skb->dst, &fl, skb->sk, 0))
66                         return -1;
67 #endif
68
69         /* Change in oif may mean change in hh_len. */
70         hh_len = skb->dst->dev->hard_header_len;
71         if (skb_headroom(skb) < hh_len &&
72             pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
73                 return -1;
74
75         return 0;
76 }
77 EXPORT_SYMBOL(ip_route_me_harder);
78
79 #ifdef CONFIG_XFRM
80 int ip_xfrm_me_harder(struct sk_buff *skb)
81 {
82         struct flowi fl;
83         unsigned int hh_len;
84         struct dst_entry *dst;
85
86         if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED)
87                 return 0;
88         if (xfrm_decode_session(skb, &fl, AF_INET) < 0)
89                 return -1;
90
91         dst = skb->dst;
92         if (dst->xfrm)
93                 dst = ((struct xfrm_dst *)dst)->route;
94         dst_hold(dst);
95
96         if (xfrm_lookup(&dst, &fl, skb->sk, 0) < 0)
97                 return -1;
98
99         dst_release(skb->dst);
100         skb->dst = dst;
101
102         /* Change in oif may mean change in hh_len. */
103         hh_len = skb->dst->dev->hard_header_len;
104         if (skb_headroom(skb) < hh_len &&
105             pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
106                 return -1;
107         return 0;
108 }
109 EXPORT_SYMBOL(ip_xfrm_me_harder);
110 #endif
111
112 void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *);
113 EXPORT_SYMBOL(ip_nat_decode_session);
114
115 /*
116  * Extra routing may needed on local out, as the QUEUE target never
117  * returns control to the table.
118  */
119
120 struct ip_rt_info {
121         __be32 daddr;
122         __be32 saddr;
123         u_int8_t tos;
124 };
125
126 static void nf_ip_saveroute(const struct sk_buff *skb,
127                             struct nf_queue_entry *entry)
128 {
129         struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
130
131         if (entry->hook == NF_INET_LOCAL_OUT) {
132                 const struct iphdr *iph = ip_hdr(skb);
133
134                 rt_info->tos = iph->tos;
135                 rt_info->daddr = iph->daddr;
136                 rt_info->saddr = iph->saddr;
137         }
138 }
139
140 static int nf_ip_reroute(struct sk_buff *skb,
141                          const struct nf_queue_entry *entry)
142 {
143         const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
144
145         if (entry->hook == NF_INET_LOCAL_OUT) {
146                 const struct iphdr *iph = ip_hdr(skb);
147
148                 if (!(iph->tos == rt_info->tos
149                       && iph->daddr == rt_info->daddr
150                       && iph->saddr == rt_info->saddr))
151                         return ip_route_me_harder(skb, RTN_UNSPEC);
152         }
153         return 0;
154 }
155
156 __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
157                             unsigned int dataoff, u_int8_t protocol)
158 {
159         const struct iphdr *iph = ip_hdr(skb);
160         __sum16 csum = 0;
161
162         switch (skb->ip_summed) {
163         case CHECKSUM_COMPLETE:
164                 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
165                         break;
166                 if ((protocol == 0 && !csum_fold(skb->csum)) ||
167                     !csum_tcpudp_magic(iph->saddr, iph->daddr,
168                                        skb->len - dataoff, protocol,
169                                        skb->csum)) {
170                         skb->ip_summed = CHECKSUM_UNNECESSARY;
171                         break;
172                 }
173                 /* fall through */
174         case CHECKSUM_NONE:
175                 if (protocol == 0)
176                         skb->csum = 0;
177                 else
178                         skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
179                                                        skb->len - dataoff,
180                                                        protocol, 0);
181                 csum = __skb_checksum_complete(skb);
182         }
183         return csum;
184 }
185
186 EXPORT_SYMBOL(nf_ip_checksum);
187
188 static int nf_ip_route(struct dst_entry **dst, struct flowi *fl)
189 {
190         return ip_route_output_key((struct rtable **)dst, fl);
191 }
192
193 static const struct nf_afinfo nf_ip_afinfo = {
194         .family         = AF_INET,
195         .checksum       = nf_ip_checksum,
196         .route          = nf_ip_route,
197         .saveroute      = nf_ip_saveroute,
198         .reroute        = nf_ip_reroute,
199         .route_key_size = sizeof(struct ip_rt_info),
200 };
201
202 static int ipv4_netfilter_init(void)
203 {
204         return nf_register_afinfo(&nf_ip_afinfo);
205 }
206
207 static void ipv4_netfilter_fini(void)
208 {
209         nf_unregister_afinfo(&nf_ip_afinfo);
210 }
211
212 module_init(ipv4_netfilter_init);
213 module_exit(ipv4_netfilter_fini);
214
215 #ifdef CONFIG_SYSCTL
216 struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = {
217         { .procname = "net", .ctl_name = CTL_NET, },
218         { .procname = "ipv4", .ctl_name = NET_IPV4, },
219         { .procname = "netfilter", .ctl_name = NET_IPV4_NETFILTER, },
220         { }
221 };
222 EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path);
223 #endif /* CONFIG_SYSCTL */