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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 sk_buff *skb, unsigned int addr_type)
21{
22 struct net *net = dev_net(skb_dst(skb)->dev);
23 const struct iphdr *iph = ip_hdr(skb);
24 struct rtable *rt;
25 struct flowi4 fl4 = {};
26 __be32 saddr = iph->saddr;
27 __u8 flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0;
28 unsigned int hh_len;
29
30 if (addr_type == RTN_UNSPEC)
31 addr_type = inet_addr_type(net, saddr);
32 if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST)
33 flags |= FLOWI_FLAG_ANYSRC;
34 else
35 saddr = 0;
36
37 /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
38 * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
39 */
40 fl4.daddr = iph->daddr;
41 fl4.saddr = saddr;
42 fl4.flowi4_tos = RT_TOS(iph->tos);
43 fl4.flowi4_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;
44 fl4.flowi4_mark = skb->mark;
45 fl4.flowi4_flags = flags;
46 rt = ip_route_output_key(net, &fl4);
47 if (IS_ERR(rt))
48 return PTR_ERR(rt);
49
50 /* Drop old route. */
51 skb_dst_drop(skb);
52 skb_dst_set(skb, &rt->dst);
53
54 if (skb_dst(skb)->error)
55 return skb_dst(skb)->error;
56
57#ifdef CONFIG_XFRM
58 if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
59 xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {
60 struct dst_entry *dst = skb_dst(skb);
61 skb_dst_set(skb, NULL);
62 dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), skb->sk, 0);
63 if (IS_ERR(dst))
64 return PTR_ERR(dst);
65 skb_dst_set(skb, dst);
66 }
67#endif
68
69 /* Change in oif may mean change in hh_len. */
70 hh_len = skb_dst(skb)->dev->hard_header_len;
71 if (skb_headroom(skb) < hh_len &&
72 pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
73 0, GFP_ATOMIC))
74 return -ENOMEM;
75
76 return 0;
77}
78EXPORT_SYMBOL(ip_route_me_harder);
79
80/*
81 * Extra routing may needed on local out, as the QUEUE target never
82 * returns control to the table.
83 */
84
85struct ip_rt_info {
86 __be32 daddr;
87 __be32 saddr;
88 u_int8_t tos;
89 u_int32_t mark;
90};
91
92static void nf_ip_saveroute(const struct sk_buff *skb,
93 struct nf_queue_entry *entry)
94{
95 struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
96
97 if (entry->hook == NF_INET_LOCAL_OUT) {
98 const struct iphdr *iph = ip_hdr(skb);
99
100 rt_info->tos = iph->tos;
101 rt_info->daddr = iph->daddr;
102 rt_info->saddr = iph->saddr;
103 rt_info->mark = skb->mark;
104 }
105}
106
107static int nf_ip_reroute(struct sk_buff *skb,
108 const struct nf_queue_entry *entry)
109{
110 const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
111
112 if (entry->hook == NF_INET_LOCAL_OUT) {
113 const struct iphdr *iph = ip_hdr(skb);
114
115 if (!(iph->tos == rt_info->tos &&
116 skb->mark == rt_info->mark &&
117 iph->daddr == rt_info->daddr &&
118 iph->saddr == rt_info->saddr))
119 return ip_route_me_harder(skb, RTN_UNSPEC);
120 }
121 return 0;
122}
123
124__sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
125 unsigned int dataoff, u_int8_t protocol)
126{
127 const struct iphdr *iph = ip_hdr(skb);
128 __sum16 csum = 0;
129
130 switch (skb->ip_summed) {
131 case CHECKSUM_COMPLETE:
132 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
133 break;
134 if ((protocol == 0 && !csum_fold(skb->csum)) ||
135 !csum_tcpudp_magic(iph->saddr, iph->daddr,
136 skb->len - dataoff, protocol,
137 skb->csum)) {
138 skb->ip_summed = CHECKSUM_UNNECESSARY;
139 break;
140 }
141 /* fall through */
142 case CHECKSUM_NONE:
143 if (protocol == 0)
144 skb->csum = 0;
145 else
146 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
147 skb->len - dataoff,
148 protocol, 0);
149 csum = __skb_checksum_complete(skb);
150 }
151 return csum;
152}
153EXPORT_SYMBOL(nf_ip_checksum);
154
155static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook,
156 unsigned int dataoff, unsigned int len,
157 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 (len == skb->len - dataoff)
165 return nf_ip_checksum(skb, hook, dataoff, protocol);
166 /* fall through */
167 case CHECKSUM_NONE:
168 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol,
169 skb->len - dataoff, 0);
170 skb->ip_summed = CHECKSUM_NONE;
171 return __skb_checksum_complete_head(skb, dataoff + len);
172 }
173 return csum;
174}
175
176static int nf_ip_route(struct net *net, struct dst_entry **dst,
177 struct flowi *fl, bool strict __always_unused)
178{
179 struct rtable *rt = ip_route_output_key(net, &fl->u.ip4);
180 if (IS_ERR(rt))
181 return PTR_ERR(rt);
182 *dst = &rt->dst;
183 return 0;
184}
185
186static const struct nf_afinfo nf_ip_afinfo = {
187 .family = AF_INET,
188 .checksum = nf_ip_checksum,
189 .checksum_partial = nf_ip_checksum_partial,
190 .route = nf_ip_route,
191 .saveroute = nf_ip_saveroute,
192 .reroute = nf_ip_reroute,
193 .route_key_size = sizeof(struct ip_rt_info),
194};
195
196static int __init ipv4_netfilter_init(void)
197{
198 return nf_register_afinfo(&nf_ip_afinfo);
199}
200
201static void __exit ipv4_netfilter_fini(void)
202{
203 nf_unregister_afinfo(&nf_ip_afinfo);
204}
205
206module_init(ipv4_netfilter_init);
207module_exit(ipv4_netfilter_fini);
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 struct net_device *dev = skb_dst(skb)->dev;
28 unsigned int hh_len;
29
30 if (addr_type == RTN_UNSPEC)
31 addr_type = inet_addr_type_dev_table(net, dev, saddr);
32 if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST)
33 flags |= FLOWI_FLAG_ANYSRC;
34 else
35 saddr = 0;
36
37 /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
38 * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
39 */
40 fl4.daddr = iph->daddr;
41 fl4.saddr = saddr;
42 fl4.flowi4_tos = RT_TOS(iph->tos);
43 fl4.flowi4_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;
44 if (!fl4.flowi4_oif)
45 fl4.flowi4_oif = l3mdev_master_ifindex(dev);
46 fl4.flowi4_mark = skb->mark;
47 fl4.flowi4_flags = flags;
48 rt = ip_route_output_key(net, &fl4);
49 if (IS_ERR(rt))
50 return PTR_ERR(rt);
51
52 /* Drop old route. */
53 skb_dst_drop(skb);
54 skb_dst_set(skb, &rt->dst);
55
56 if (skb_dst(skb)->error)
57 return skb_dst(skb)->error;
58
59#ifdef CONFIG_XFRM
60 if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
61 xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {
62 struct dst_entry *dst = skb_dst(skb);
63 skb_dst_set(skb, NULL);
64 dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), skb->sk, 0);
65 if (IS_ERR(dst))
66 return PTR_ERR(dst);
67 skb_dst_set(skb, dst);
68 }
69#endif
70
71 /* Change in oif may mean change in hh_len. */
72 hh_len = skb_dst(skb)->dev->hard_header_len;
73 if (skb_headroom(skb) < hh_len &&
74 pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
75 0, GFP_ATOMIC))
76 return -ENOMEM;
77
78 return 0;
79}
80EXPORT_SYMBOL(ip_route_me_harder);
81
82/*
83 * Extra routing may needed on local out, as the QUEUE target never
84 * returns control to the table.
85 */
86
87struct ip_rt_info {
88 __be32 daddr;
89 __be32 saddr;
90 u_int8_t tos;
91 u_int32_t mark;
92};
93
94static void nf_ip_saveroute(const struct sk_buff *skb,
95 struct nf_queue_entry *entry)
96{
97 struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
98
99 if (entry->state.hook == NF_INET_LOCAL_OUT) {
100 const struct iphdr *iph = ip_hdr(skb);
101
102 rt_info->tos = iph->tos;
103 rt_info->daddr = iph->daddr;
104 rt_info->saddr = iph->saddr;
105 rt_info->mark = skb->mark;
106 }
107}
108
109static int nf_ip_reroute(struct net *net, struct sk_buff *skb,
110 const struct nf_queue_entry *entry)
111{
112 const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
113
114 if (entry->state.hook == NF_INET_LOCAL_OUT) {
115 const struct iphdr *iph = ip_hdr(skb);
116
117 if (!(iph->tos == rt_info->tos &&
118 skb->mark == rt_info->mark &&
119 iph->daddr == rt_info->daddr &&
120 iph->saddr == rt_info->saddr))
121 return ip_route_me_harder(net, skb, RTN_UNSPEC);
122 }
123 return 0;
124}
125
126__sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
127 unsigned int dataoff, u_int8_t protocol)
128{
129 const struct iphdr *iph = ip_hdr(skb);
130 __sum16 csum = 0;
131
132 switch (skb->ip_summed) {
133 case CHECKSUM_COMPLETE:
134 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
135 break;
136 if ((protocol == 0 && !csum_fold(skb->csum)) ||
137 !csum_tcpudp_magic(iph->saddr, iph->daddr,
138 skb->len - dataoff, protocol,
139 skb->csum)) {
140 skb->ip_summed = CHECKSUM_UNNECESSARY;
141 break;
142 }
143 /* fall through */
144 case CHECKSUM_NONE:
145 if (protocol == 0)
146 skb->csum = 0;
147 else
148 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
149 skb->len - dataoff,
150 protocol, 0);
151 csum = __skb_checksum_complete(skb);
152 }
153 return csum;
154}
155EXPORT_SYMBOL(nf_ip_checksum);
156
157static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook,
158 unsigned int dataoff, unsigned int len,
159 u_int8_t protocol)
160{
161 const struct iphdr *iph = ip_hdr(skb);
162 __sum16 csum = 0;
163
164 switch (skb->ip_summed) {
165 case CHECKSUM_COMPLETE:
166 if (len == skb->len - dataoff)
167 return nf_ip_checksum(skb, hook, dataoff, protocol);
168 /* fall through */
169 case CHECKSUM_NONE:
170 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol,
171 skb->len - dataoff, 0);
172 skb->ip_summed = CHECKSUM_NONE;
173 return __skb_checksum_complete_head(skb, dataoff + len);
174 }
175 return csum;
176}
177
178static int nf_ip_route(struct net *net, struct dst_entry **dst,
179 struct flowi *fl, bool strict __always_unused)
180{
181 struct rtable *rt = ip_route_output_key(net, &fl->u.ip4);
182 if (IS_ERR(rt))
183 return PTR_ERR(rt);
184 *dst = &rt->dst;
185 return 0;
186}
187
188static const struct nf_afinfo nf_ip_afinfo = {
189 .family = AF_INET,
190 .checksum = nf_ip_checksum,
191 .checksum_partial = nf_ip_checksum_partial,
192 .route = nf_ip_route,
193 .saveroute = nf_ip_saveroute,
194 .reroute = nf_ip_reroute,
195 .route_key_size = sizeof(struct ip_rt_info),
196};
197
198static int __init ipv4_netfilter_init(void)
199{
200 return nf_register_afinfo(&nf_ip_afinfo);
201}
202subsys_initcall(ipv4_netfilter_init);