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