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