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7#include <linux/kernel.h>
8#include <linux/netfilter.h>
9#include <linux/netfilter_ipv4.h>
10#include <linux/ip.h>
11#include <linux/skbuff.h>
12#include <linux/gfp.h>
13#include <linux/export.h>
14#include <net/route.h>
15#include <net/xfrm.h>
16#include <net/ip.h>
17#include <net/netfilter/nf_queue.h>
18
19
20int ip_route_me_harder(struct net *net, struct sk_buff *skb, unsigned int addr_type)
21{
22 const struct iphdr *iph = ip_hdr(skb);
23 struct rtable *rt;
24 struct flowi4 fl4 = {};
25 __be32 saddr = iph->saddr;
26 const struct sock *sk = skb_to_full_sk(skb);
27 __u8 flags = sk ? inet_sk_flowi_flags(sk) : 0;
28 struct net_device *dev = skb_dst(skb)->dev;
29 unsigned int hh_len;
30
31 if (addr_type == RTN_UNSPEC)
32 addr_type = inet_addr_type_dev_table(net, dev, saddr);
33 if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST)
34 flags |= FLOWI_FLAG_ANYSRC;
35 else
36 saddr = 0;
37
38
39
40
41 fl4.daddr = iph->daddr;
42 fl4.saddr = saddr;
43 fl4.flowi4_tos = RT_TOS(iph->tos);
44 fl4.flowi4_oif = sk ? sk->sk_bound_dev_if : 0;
45 if (!fl4.flowi4_oif)
46 fl4.flowi4_oif = l3mdev_master_ifindex(dev);
47 fl4.flowi4_mark = skb->mark;
48 fl4.flowi4_flags = flags;
49 rt = ip_route_output_key(net, &fl4);
50 if (IS_ERR(rt))
51 return PTR_ERR(rt);
52
53
54 skb_dst_drop(skb);
55 skb_dst_set(skb, &rt->dst);
56
57 if (skb_dst(skb)->error)
58 return skb_dst(skb)->error;
59
60#ifdef CONFIG_XFRM
61 if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
62 xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {
63 struct dst_entry *dst = skb_dst(skb);
64 skb_dst_set(skb, NULL);
65 dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), sk, 0);
66 if (IS_ERR(dst))
67 return PTR_ERR(dst);
68 skb_dst_set(skb, dst);
69 }
70#endif
71
72
73 hh_len = skb_dst(skb)->dev->hard_header_len;
74 if (skb_headroom(skb) < hh_len &&
75 pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
76 0, GFP_ATOMIC))
77 return -ENOMEM;
78
79 return 0;
80}
81EXPORT_SYMBOL(ip_route_me_harder);
82
83
84
85
86
87
88struct ip_rt_info {
89 __be32 daddr;
90 __be32 saddr;
91 u_int8_t tos;
92 u_int32_t mark;
93};
94
95static void nf_ip_saveroute(const struct sk_buff *skb,
96 struct nf_queue_entry *entry)
97{
98 struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
99
100 if (entry->state.hook == NF_INET_LOCAL_OUT) {
101 const struct iphdr *iph = ip_hdr(skb);
102
103 rt_info->tos = iph->tos;
104 rt_info->daddr = iph->daddr;
105 rt_info->saddr = iph->saddr;
106 rt_info->mark = skb->mark;
107 }
108}
109
110static int nf_ip_reroute(struct net *net, struct sk_buff *skb,
111 const struct nf_queue_entry *entry)
112{
113 const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
114
115 if (entry->state.hook == NF_INET_LOCAL_OUT) {
116 const struct iphdr *iph = ip_hdr(skb);
117
118 if (!(iph->tos == rt_info->tos &&
119 skb->mark == rt_info->mark &&
120 iph->daddr == rt_info->daddr &&
121 iph->saddr == rt_info->saddr))
122 return ip_route_me_harder(net, skb, RTN_UNSPEC);
123 }
124 return 0;
125}
126
127__sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
128 unsigned int dataoff, u_int8_t protocol)
129{
130 const struct iphdr *iph = ip_hdr(skb);
131 __sum16 csum = 0;
132
133 switch (skb->ip_summed) {
134 case CHECKSUM_COMPLETE:
135 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
136 break;
137 if ((protocol == 0 && !csum_fold(skb->csum)) ||
138 !csum_tcpudp_magic(iph->saddr, iph->daddr,
139 skb->len - dataoff, protocol,
140 skb->csum)) {
141 skb->ip_summed = CHECKSUM_UNNECESSARY;
142 break;
143 }
144
145 case CHECKSUM_NONE:
146 if (protocol == 0)
147 skb->csum = 0;
148 else
149 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
150 skb->len - dataoff,
151 protocol, 0);
152 csum = __skb_checksum_complete(skb);
153 }
154 return csum;
155}
156EXPORT_SYMBOL(nf_ip_checksum);
157
158static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook,
159 unsigned int dataoff, unsigned int len,
160 u_int8_t protocol)
161{
162 const struct iphdr *iph = ip_hdr(skb);
163 __sum16 csum = 0;
164
165 switch (skb->ip_summed) {
166 case CHECKSUM_COMPLETE:
167 if (len == skb->len - dataoff)
168 return nf_ip_checksum(skb, hook, dataoff, protocol);
169
170 case CHECKSUM_NONE:
171 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol,
172 skb->len - dataoff, 0);
173 skb->ip_summed = CHECKSUM_NONE;
174 return __skb_checksum_complete_head(skb, dataoff + len);
175 }
176 return csum;
177}
178
179static int nf_ip_route(struct net *net, struct dst_entry **dst,
180 struct flowi *fl, bool strict __always_unused)
181{
182 struct rtable *rt = ip_route_output_key(net, &fl->u.ip4);
183 if (IS_ERR(rt))
184 return PTR_ERR(rt);
185 *dst = &rt->dst;
186 return 0;
187}
188
189static const struct nf_afinfo nf_ip_afinfo = {
190 .family = AF_INET,
191 .checksum = nf_ip_checksum,
192 .checksum_partial = nf_ip_checksum_partial,
193 .route = nf_ip_route,
194 .saveroute = nf_ip_saveroute,
195 .reroute = nf_ip_reroute,
196 .route_key_size = sizeof(struct ip_rt_info),
197};
198
199static int __init ipv4_netfilter_init(void)
200{
201 return nf_register_afinfo(&nf_ip_afinfo);
202}
203subsys_initcall(ipv4_netfilter_init);
204