4f47e064e262c2f24e7cb13eacfcebff0fad86a3
[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 <linux/gfp.h>
8 #include <linux/export.h>
9 #include <net/route.h>
10 #include <net/xfrm.h>
11 #include <net/ip.h>
12 #include <net/netfilter/nf_queue.h>
13
14 /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
15 int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
16 {
17         struct net *net = dev_net(skb_dst(skb)->dev);
18         const struct iphdr *iph = ip_hdr(skb);
19         struct rtable *rt;
20         struct flowi4 fl4 = {};
21         __be32 saddr = iph->saddr;
22         __u8 flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0;
23         unsigned int hh_len;
24
25         if (addr_type == RTN_UNSPEC)
26                 addr_type = inet_addr_type(net, saddr);
27         if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST)
28                 flags |= FLOWI_FLAG_ANYSRC;
29         else
30                 saddr = 0;
31
32         /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
33          * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
34          */
35         fl4.daddr = iph->daddr;
36         fl4.saddr = saddr;
37         fl4.flowi4_tos = RT_TOS(iph->tos);
38         fl4.flowi4_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;
39         fl4.flowi4_mark = skb->mark;
40         fl4.flowi4_flags = flags;
41         rt = ip_route_output_key(net, &fl4);
42         if (IS_ERR(rt))
43                 return -1;
44
45         /* Drop old route. */
46         skb_dst_drop(skb);
47         skb_dst_set(skb, &rt->dst);
48
49         if (skb_dst(skb)->error)
50                 return -1;
51
52 #ifdef CONFIG_XFRM
53         if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
54             xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {
55                 struct dst_entry *dst = skb_dst(skb);
56                 skb_dst_set(skb, NULL);
57                 dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), skb->sk, 0);
58                 if (IS_ERR(dst))
59                         return -1;
60                 skb_dst_set(skb, dst);
61         }
62 #endif
63
64         /* Change in oif may mean change in hh_len. */
65         hh_len = skb_dst(skb)->dev->hard_header_len;
66         if (skb_headroom(skb) < hh_len &&
67             pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
68                                 0, GFP_ATOMIC))
69                 return -1;
70
71         return 0;
72 }
73 EXPORT_SYMBOL(ip_route_me_harder);
74
75 #ifdef CONFIG_XFRM
76 int ip_xfrm_me_harder(struct sk_buff *skb)
77 {
78         struct flowi fl;
79         unsigned int hh_len;
80         struct dst_entry *dst;
81
82         if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED)
83                 return 0;
84         if (xfrm_decode_session(skb, &fl, AF_INET) < 0)
85                 return -1;
86
87         dst = skb_dst(skb);
88         if (dst->xfrm)
89                 dst = ((struct xfrm_dst *)dst)->route;
90         dst_hold(dst);
91
92         dst = xfrm_lookup(dev_net(dst->dev), dst, &fl, skb->sk, 0);
93         if (IS_ERR(dst))
94                 return -1;
95
96         skb_dst_drop(skb);
97         skb_dst_set(skb, dst);
98
99         /* Change in oif may mean change in hh_len. */
100         hh_len = skb_dst(skb)->dev->hard_header_len;
101         if (skb_headroom(skb) < hh_len &&
102             pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
103                 return -1;
104         return 0;
105 }
106 EXPORT_SYMBOL(ip_xfrm_me_harder);
107 #endif
108
109 void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *);
110 EXPORT_SYMBOL(ip_nat_decode_session);
111
112 /*
113  * Extra routing may needed on local out, as the QUEUE target never
114  * returns control to the table.
115  */
116
117 struct ip_rt_info {
118         __be32 daddr;
119         __be32 saddr;
120         u_int8_t tos;
121         u_int32_t mark;
122 };
123
124 static void nf_ip_saveroute(const struct sk_buff *skb,
125                             struct nf_queue_entry *entry)
126 {
127         struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
128
129         if (entry->hook == NF_INET_LOCAL_OUT) {
130                 const struct iphdr *iph = ip_hdr(skb);
131
132                 rt_info->tos = iph->tos;
133                 rt_info->daddr = iph->daddr;
134                 rt_info->saddr = iph->saddr;
135                 rt_info->mark = skb->mark;
136         }
137 }
138
139 static int nf_ip_reroute(struct sk_buff *skb,
140                          const struct nf_queue_entry *entry)
141 {
142         const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
143
144         if (entry->hook == NF_INET_LOCAL_OUT) {
145                 const struct iphdr *iph = ip_hdr(skb);
146
147                 if (!(iph->tos == rt_info->tos &&
148                       skb->mark == rt_info->mark &&
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 EXPORT_SYMBOL(nf_ip_checksum);
186
187 static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook,
188                                       unsigned int dataoff, unsigned int len,
189                                       u_int8_t protocol)
190 {
191         const struct iphdr *iph = ip_hdr(skb);
192         __sum16 csum = 0;
193
194         switch (skb->ip_summed) {
195         case CHECKSUM_COMPLETE:
196                 if (len == skb->len - dataoff)
197                         return nf_ip_checksum(skb, hook, dataoff, protocol);
198                 /* fall through */
199         case CHECKSUM_NONE:
200                 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol,
201                                                skb->len - dataoff, 0);
202                 skb->ip_summed = CHECKSUM_NONE;
203                 return __skb_checksum_complete_head(skb, dataoff + len);
204         }
205         return csum;
206 }
207
208 static int nf_ip_route(struct net *net, struct dst_entry **dst,
209                        struct flowi *fl, bool strict __always_unused)
210 {
211         struct rtable *rt = ip_route_output_key(net, &fl->u.ip4);
212         if (IS_ERR(rt))
213                 return PTR_ERR(rt);
214         *dst = &rt->dst;
215         return 0;
216 }
217
218 static const struct nf_afinfo nf_ip_afinfo = {
219         .family                 = AF_INET,
220         .checksum               = nf_ip_checksum,
221         .checksum_partial       = nf_ip_checksum_partial,
222         .route                  = nf_ip_route,
223         .saveroute              = nf_ip_saveroute,
224         .reroute                = nf_ip_reroute,
225         .route_key_size         = sizeof(struct ip_rt_info),
226 };
227
228 static int ipv4_netfilter_init(void)
229 {
230         return nf_register_afinfo(&nf_ip_afinfo);
231 }
232
233 static void ipv4_netfilter_fini(void)
234 {
235         nf_unregister_afinfo(&nf_ip_afinfo);
236 }
237
238 module_init(ipv4_netfilter_init);
239 module_exit(ipv4_netfilter_fini);
240
241 #ifdef CONFIG_SYSCTL
242 struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = {
243         { .procname = "net", },
244         { .procname = "ipv4", },
245         { .procname = "netfilter", },
246         { }
247 };
248 EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path);
249 #endif /* CONFIG_SYSCTL */