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1/*
2 * IPv4 specific functions of netfilter core
3 *
4 * Rusty Russell (C) 2000 -- This code is GPL.
5 * Patrick McHardy (C) 2006-2012
6 */
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/* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
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 /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
39 * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
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 /* Drop old route. */
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 /* Change in oif may mean change in hh_len. */
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
83int nf_ip_reroute(struct sk_buff *skb, const struct nf_queue_entry *entry)
84{
85 const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
86
87 if (entry->state.hook == NF_INET_LOCAL_OUT) {
88 const struct iphdr *iph = ip_hdr(skb);
89
90 if (!(iph->tos == rt_info->tos &&
91 skb->mark == rt_info->mark &&
92 iph->daddr == rt_info->daddr &&
93 iph->saddr == rt_info->saddr))
94 return ip_route_me_harder(entry->state.net, skb,
95 RTN_UNSPEC);
96 }
97 return 0;
98}
99EXPORT_SYMBOL_GPL(nf_ip_reroute);
100
101__sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
102 unsigned int dataoff, u_int8_t protocol)
103{
104 const struct iphdr *iph = ip_hdr(skb);
105 __sum16 csum = 0;
106
107 switch (skb->ip_summed) {
108 case CHECKSUM_COMPLETE:
109 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
110 break;
111 if ((protocol == 0 && !csum_fold(skb->csum)) ||
112 !csum_tcpudp_magic(iph->saddr, iph->daddr,
113 skb->len - dataoff, protocol,
114 skb->csum)) {
115 skb->ip_summed = CHECKSUM_UNNECESSARY;
116 break;
117 }
118 /* fall through */
119 case CHECKSUM_NONE:
120 if (protocol == 0)
121 skb->csum = 0;
122 else
123 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
124 skb->len - dataoff,
125 protocol, 0);
126 csum = __skb_checksum_complete(skb);
127 }
128 return csum;
129}
130EXPORT_SYMBOL(nf_ip_checksum);
131
132__sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook,
133 unsigned int dataoff, unsigned int len,
134 u_int8_t protocol)
135{
136 const struct iphdr *iph = ip_hdr(skb);
137 __sum16 csum = 0;
138
139 switch (skb->ip_summed) {
140 case CHECKSUM_COMPLETE:
141 if (len == skb->len - dataoff)
142 return nf_ip_checksum(skb, hook, dataoff, protocol);
143 /* fall through */
144 case CHECKSUM_NONE:
145 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol,
146 skb->len - dataoff, 0);
147 skb->ip_summed = CHECKSUM_NONE;
148 return __skb_checksum_complete_head(skb, dataoff + len);
149 }
150 return csum;
151}
152EXPORT_SYMBOL_GPL(nf_ip_checksum_partial);
153
154int nf_ip_route(struct net *net, struct dst_entry **dst, struct flowi *fl,
155 bool strict __always_unused)
156{
157 struct rtable *rt = ip_route_output_key(net, &fl->u.ip4);
158 if (IS_ERR(rt))
159 return PTR_ERR(rt);
160 *dst = &rt->dst;
161 return 0;
162}
163EXPORT_SYMBOL_GPL(nf_ip_route);
1/*
2 * IPv4 specific functions of netfilter core
3 *
4 * Rusty Russell (C) 2000 -- This code is GPL.
5 * Patrick McHardy (C) 2006-2012
6 */
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/* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
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 __u8 flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0;
27 unsigned int hh_len;
28
29 if (addr_type == RTN_UNSPEC)
30 addr_type = inet_addr_type(net, saddr);
31 if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST)
32 flags |= FLOWI_FLAG_ANYSRC;
33 else
34 saddr = 0;
35
36 /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
37 * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
38 */
39 fl4.daddr = iph->daddr;
40 fl4.saddr = saddr;
41 fl4.flowi4_tos = RT_TOS(iph->tos);
42 fl4.flowi4_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;
43 fl4.flowi4_mark = skb->mark;
44 fl4.flowi4_flags = flags;
45 rt = ip_route_output_key(net, &fl4);
46 if (IS_ERR(rt))
47 return PTR_ERR(rt);
48
49 /* Drop old route. */
50 skb_dst_drop(skb);
51 skb_dst_set(skb, &rt->dst);
52
53 if (skb_dst(skb)->error)
54 return skb_dst(skb)->error;
55
56#ifdef CONFIG_XFRM
57 if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
58 xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {
59 struct dst_entry *dst = skb_dst(skb);
60 skb_dst_set(skb, NULL);
61 dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), skb->sk, 0);
62 if (IS_ERR(dst))
63 return PTR_ERR(dst);
64 skb_dst_set(skb, dst);
65 }
66#endif
67
68 /* Change in oif may mean change in hh_len. */
69 hh_len = skb_dst(skb)->dev->hard_header_len;
70 if (skb_headroom(skb) < hh_len &&
71 pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
72 0, GFP_ATOMIC))
73 return -ENOMEM;
74
75 return 0;
76}
77EXPORT_SYMBOL(ip_route_me_harder);
78
79/*
80 * Extra routing may needed on local out, as the QUEUE target never
81 * returns control to the table.
82 */
83
84struct ip_rt_info {
85 __be32 daddr;
86 __be32 saddr;
87 u_int8_t tos;
88 u_int32_t mark;
89};
90
91static void nf_ip_saveroute(const struct sk_buff *skb,
92 struct nf_queue_entry *entry)
93{
94 struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
95
96 if (entry->state.hook == NF_INET_LOCAL_OUT) {
97 const struct iphdr *iph = ip_hdr(skb);
98
99 rt_info->tos = iph->tos;
100 rt_info->daddr = iph->daddr;
101 rt_info->saddr = iph->saddr;
102 rt_info->mark = skb->mark;
103 }
104}
105
106static int nf_ip_reroute(struct net *net, struct sk_buff *skb,
107 const struct nf_queue_entry *entry)
108{
109 const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
110
111 if (entry->state.hook == NF_INET_LOCAL_OUT) {
112 const struct iphdr *iph = ip_hdr(skb);
113
114 if (!(iph->tos == rt_info->tos &&
115 skb->mark == rt_info->mark &&
116 iph->daddr == rt_info->daddr &&
117 iph->saddr == rt_info->saddr))
118 return ip_route_me_harder(net, skb, RTN_UNSPEC);
119 }
120 return 0;
121}
122
123__sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
124 unsigned int dataoff, u_int8_t protocol)
125{
126 const struct iphdr *iph = ip_hdr(skb);
127 __sum16 csum = 0;
128
129 switch (skb->ip_summed) {
130 case CHECKSUM_COMPLETE:
131 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
132 break;
133 if ((protocol == 0 && !csum_fold(skb->csum)) ||
134 !csum_tcpudp_magic(iph->saddr, iph->daddr,
135 skb->len - dataoff, protocol,
136 skb->csum)) {
137 skb->ip_summed = CHECKSUM_UNNECESSARY;
138 break;
139 }
140 /* fall through */
141 case CHECKSUM_NONE:
142 if (protocol == 0)
143 skb->csum = 0;
144 else
145 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
146 skb->len - dataoff,
147 protocol, 0);
148 csum = __skb_checksum_complete(skb);
149 }
150 return csum;
151}
152EXPORT_SYMBOL(nf_ip_checksum);
153
154static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook,
155 unsigned int dataoff, unsigned int len,
156 u_int8_t protocol)
157{
158 const struct iphdr *iph = ip_hdr(skb);
159 __sum16 csum = 0;
160
161 switch (skb->ip_summed) {
162 case CHECKSUM_COMPLETE:
163 if (len == skb->len - dataoff)
164 return nf_ip_checksum(skb, hook, dataoff, protocol);
165 /* fall through */
166 case CHECKSUM_NONE:
167 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol,
168 skb->len - dataoff, 0);
169 skb->ip_summed = CHECKSUM_NONE;
170 return __skb_checksum_complete_head(skb, dataoff + len);
171 }
172 return csum;
173}
174
175static int nf_ip_route(struct net *net, struct dst_entry **dst,
176 struct flowi *fl, bool strict __always_unused)
177{
178 struct rtable *rt = ip_route_output_key(net, &fl->u.ip4);
179 if (IS_ERR(rt))
180 return PTR_ERR(rt);
181 *dst = &rt->dst;
182 return 0;
183}
184
185static const struct nf_afinfo nf_ip_afinfo = {
186 .family = AF_INET,
187 .checksum = nf_ip_checksum,
188 .checksum_partial = nf_ip_checksum_partial,
189 .route = nf_ip_route,
190 .saveroute = nf_ip_saveroute,
191 .reroute = nf_ip_reroute,
192 .route_key_size = sizeof(struct ip_rt_info),
193};
194
195static int __init ipv4_netfilter_init(void)
196{
197 return nf_register_afinfo(&nf_ip_afinfo);
198}
199subsys_initcall(ipv4_netfilter_init);