d88a46c54fd1bbb62a6f9ed13570c518940666b5
[linux-3.10.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 <linux/gfp.h>
8 #include <net/route.h>
9 #include <net/xfrm.h>
10 #include <net/ip.h>
11 #include <net/netfilter/nf_queue.h>
12
13 /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
14 int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
15 {
16         struct net *net = dev_net(skb_dst(skb)->dev);
17         const struct iphdr *iph = ip_hdr(skb);
18         struct rtable *rt;
19         struct flowi fl = {};
20         unsigned long orefdst;
21         unsigned int hh_len;
22         unsigned int type;
23
24         type = inet_addr_type(net, iph->saddr);
25         if (skb->sk && inet_sk(skb->sk)->transparent)
26                 type = RTN_LOCAL;
27         if (addr_type == RTN_UNSPEC)
28                 addr_type = type;
29
30         /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
31          * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
32          */
33         if (addr_type == RTN_LOCAL) {
34                 fl.nl_u.ip4_u.daddr = iph->daddr;
35                 if (type == RTN_LOCAL)
36                         fl.nl_u.ip4_u.saddr = iph->saddr;
37                 fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
38                 fl.oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;
39                 fl.mark = skb->mark;
40                 fl.flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0;
41                 if (ip_route_output_key(net, &rt, &fl) != 0)
42                         return -1;
43
44                 /* Drop old route. */
45                 skb_dst_drop(skb);
46                 skb_dst_set(skb, &rt->dst);
47         } else {
48                 /* non-local src, find valid iif to satisfy
49                  * rp-filter when calling ip_route_input. */
50                 fl.nl_u.ip4_u.daddr = iph->saddr;
51                 if (ip_route_output_key(net, &rt, &fl) != 0)
52                         return -1;
53
54                 orefdst = skb->_skb_refdst;
55                 if (ip_route_input(skb, iph->daddr, iph->saddr,
56                                    RT_TOS(iph->tos), rt->dst.dev) != 0) {
57                         dst_release(&rt->dst);
58                         return -1;
59                 }
60                 dst_release(&rt->dst);
61                 refdst_drop(orefdst);
62         }
63
64         if (skb_dst(skb)->error)
65                 return -1;
66
67 #ifdef CONFIG_XFRM
68         if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
69             xfrm_decode_session(skb, &fl, AF_INET) == 0) {
70                 struct dst_entry *dst = skb_dst(skb);
71                 skb_dst_set(skb, NULL);
72                 if (xfrm_lookup(net, &dst, &fl, skb->sk, 0))
73                         return -1;
74                 skb_dst_set(skb, dst);
75         }
76 #endif
77
78         /* Change in oif may mean change in hh_len. */
79         hh_len = skb_dst(skb)->dev->hard_header_len;
80         if (skb_headroom(skb) < hh_len &&
81             pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
82                 return -1;
83
84         return 0;
85 }
86 EXPORT_SYMBOL(ip_route_me_harder);
87
88 #ifdef CONFIG_XFRM
89 int ip_xfrm_me_harder(struct sk_buff *skb)
90 {
91         struct flowi fl;
92         unsigned int hh_len;
93         struct dst_entry *dst;
94
95         if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED)
96                 return 0;
97         if (xfrm_decode_session(skb, &fl, AF_INET) < 0)
98                 return -1;
99
100         dst = skb_dst(skb);
101         if (dst->xfrm)
102                 dst = ((struct xfrm_dst *)dst)->route;
103         dst_hold(dst);
104
105         if (xfrm_lookup(dev_net(dst->dev), &dst, &fl, skb->sk, 0) < 0)
106                 return -1;
107
108         skb_dst_drop(skb);
109         skb_dst_set(skb, dst);
110
111         /* Change in oif may mean change in hh_len. */
112         hh_len = skb_dst(skb)->dev->hard_header_len;
113         if (skb_headroom(skb) < hh_len &&
114             pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
115                 return -1;
116         return 0;
117 }
118 EXPORT_SYMBOL(ip_xfrm_me_harder);
119 #endif
120
121 void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *);
122 EXPORT_SYMBOL(ip_nat_decode_session);
123
124 /*
125  * Extra routing may needed on local out, as the QUEUE target never
126  * returns control to the table.
127  */
128
129 struct ip_rt_info {
130         __be32 daddr;
131         __be32 saddr;
132         u_int8_t tos;
133         u_int32_t mark;
134 };
135
136 static void nf_ip_saveroute(const struct sk_buff *skb,
137                             struct nf_queue_entry *entry)
138 {
139         struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
140
141         if (entry->hook == NF_INET_LOCAL_OUT) {
142                 const struct iphdr *iph = ip_hdr(skb);
143
144                 rt_info->tos = iph->tos;
145                 rt_info->daddr = iph->daddr;
146                 rt_info->saddr = iph->saddr;
147                 rt_info->mark = skb->mark;
148         }
149 }
150
151 static int nf_ip_reroute(struct sk_buff *skb,
152                          const struct nf_queue_entry *entry)
153 {
154         const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
155
156         if (entry->hook == NF_INET_LOCAL_OUT) {
157                 const struct iphdr *iph = ip_hdr(skb);
158
159                 if (!(iph->tos == rt_info->tos &&
160                       skb->mark == rt_info->mark &&
161                       iph->daddr == rt_info->daddr &&
162                       iph->saddr == rt_info->saddr))
163                         return ip_route_me_harder(skb, RTN_UNSPEC);
164         }
165         return 0;
166 }
167
168 __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
169                             unsigned int dataoff, u_int8_t protocol)
170 {
171         const struct iphdr *iph = ip_hdr(skb);
172         __sum16 csum = 0;
173
174         switch (skb->ip_summed) {
175         case CHECKSUM_COMPLETE:
176                 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
177                         break;
178                 if ((protocol == 0 && !csum_fold(skb->csum)) ||
179                     !csum_tcpudp_magic(iph->saddr, iph->daddr,
180                                        skb->len - dataoff, protocol,
181                                        skb->csum)) {
182                         skb->ip_summed = CHECKSUM_UNNECESSARY;
183                         break;
184                 }
185                 /* fall through */
186         case CHECKSUM_NONE:
187                 if (protocol == 0)
188                         skb->csum = 0;
189                 else
190                         skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
191                                                        skb->len - dataoff,
192                                                        protocol, 0);
193                 csum = __skb_checksum_complete(skb);
194         }
195         return csum;
196 }
197 EXPORT_SYMBOL(nf_ip_checksum);
198
199 static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook,
200                                       unsigned int dataoff, unsigned int len,
201                                       u_int8_t protocol)
202 {
203         const struct iphdr *iph = ip_hdr(skb);
204         __sum16 csum = 0;
205
206         switch (skb->ip_summed) {
207         case CHECKSUM_COMPLETE:
208                 if (len == skb->len - dataoff)
209                         return nf_ip_checksum(skb, hook, dataoff, protocol);
210                 /* fall through */
211         case CHECKSUM_NONE:
212                 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol,
213                                                skb->len - dataoff, 0);
214                 skb->ip_summed = CHECKSUM_NONE;
215                 return __skb_checksum_complete_head(skb, dataoff + len);
216         }
217         return csum;
218 }
219
220 static int nf_ip_route(struct dst_entry **dst, struct flowi *fl)
221 {
222         return ip_route_output_key(&init_net, (struct rtable **)dst, fl);
223 }
224
225 static const struct nf_afinfo nf_ip_afinfo = {
226         .family                 = AF_INET,
227         .checksum               = nf_ip_checksum,
228         .checksum_partial       = nf_ip_checksum_partial,
229         .route                  = nf_ip_route,
230         .saveroute              = nf_ip_saveroute,
231         .reroute                = nf_ip_reroute,
232         .route_key_size         = sizeof(struct ip_rt_info),
233 };
234
235 static int ipv4_netfilter_init(void)
236 {
237         return nf_register_afinfo(&nf_ip_afinfo);
238 }
239
240 static void ipv4_netfilter_fini(void)
241 {
242         nf_unregister_afinfo(&nf_ip_afinfo);
243 }
244
245 module_init(ipv4_netfilter_init);
246 module_exit(ipv4_netfilter_fini);
247
248 #ifdef CONFIG_SYSCTL
249 struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = {
250         { .procname = "net", },
251         { .procname = "ipv4", },
252         { .procname = "netfilter", },
253         { }
254 };
255 EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path);
256 #endif /* CONFIG_SYSCTL */