1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
|
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/netfilter.h>
#include <linux/rhashtable.h>
#include <linux/ip.h>
#include <linux/netdevice.h>
#include <net/ip.h>
#include <net/neighbour.h>
#include <net/netfilter/nf_flow_table.h>
#include <net/netfilter/nf_tables.h>
/* For layer 4 checksum field offset. */
#include <linux/tcp.h>
#include <linux/udp.h>
static int nf_flow_nat_ip_tcp(struct sk_buff *skb, unsigned int thoff,
__be32 addr, __be32 new_addr)
{
struct tcphdr *tcph;
if (!pskb_may_pull(skb, thoff + sizeof(*tcph)) ||
skb_try_make_writable(skb, thoff + sizeof(*tcph)))
return -1;
tcph = (void *)(skb_network_header(skb) + thoff);
inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr, true);
return 0;
}
static int nf_flow_nat_ip_udp(struct sk_buff *skb, unsigned int thoff,
__be32 addr, __be32 new_addr)
{
struct udphdr *udph;
if (!pskb_may_pull(skb, thoff + sizeof(*udph)) ||
skb_try_make_writable(skb, thoff + sizeof(*udph)))
return -1;
udph = (void *)(skb_network_header(skb) + thoff);
if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
inet_proto_csum_replace4(&udph->check, skb, addr,
new_addr, true);
if (!udph->check)
udph->check = CSUM_MANGLED_0;
}
return 0;
}
static int nf_flow_nat_ip_l4proto(struct sk_buff *skb, struct iphdr *iph,
unsigned int thoff, __be32 addr,
__be32 new_addr)
{
switch (iph->protocol) {
case IPPROTO_TCP:
if (nf_flow_nat_ip_tcp(skb, thoff, addr, new_addr) < 0)
return NF_DROP;
break;
case IPPROTO_UDP:
if (nf_flow_nat_ip_udp(skb, thoff, addr, new_addr) < 0)
return NF_DROP;
break;
}
return 0;
}
static int nf_flow_snat_ip(const struct flow_offload *flow, struct sk_buff *skb,
struct iphdr *iph, unsigned int thoff,
enum flow_offload_tuple_dir dir)
{
__be32 addr, new_addr;
switch (dir) {
case FLOW_OFFLOAD_DIR_ORIGINAL:
addr = iph->saddr;
new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_v4.s_addr;
iph->saddr = new_addr;
break;
case FLOW_OFFLOAD_DIR_REPLY:
addr = iph->daddr;
new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.src_v4.s_addr;
iph->daddr = new_addr;
break;
default:
return -1;
}
csum_replace4(&iph->check, addr, new_addr);
return nf_flow_nat_ip_l4proto(skb, iph, thoff, addr, new_addr);
}
static int nf_flow_dnat_ip(const struct flow_offload *flow, struct sk_buff *skb,
struct iphdr *iph, unsigned int thoff,
enum flow_offload_tuple_dir dir)
{
__be32 addr, new_addr;
switch (dir) {
case FLOW_OFFLOAD_DIR_ORIGINAL:
addr = iph->daddr;
new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.src_v4.s_addr;
iph->daddr = new_addr;
break;
case FLOW_OFFLOAD_DIR_REPLY:
addr = iph->saddr;
new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.dst_v4.s_addr;
iph->saddr = new_addr;
break;
default:
return -1;
}
csum_replace4(&iph->check, addr, new_addr);
return nf_flow_nat_ip_l4proto(skb, iph, thoff, addr, new_addr);
}
static int nf_flow_nat_ip(const struct flow_offload *flow, struct sk_buff *skb,
enum flow_offload_tuple_dir dir)
{
struct iphdr *iph = ip_hdr(skb);
unsigned int thoff = iph->ihl * 4;
if (flow->flags & FLOW_OFFLOAD_SNAT &&
(nf_flow_snat_port(flow, skb, thoff, iph->protocol, dir) < 0 ||
nf_flow_snat_ip(flow, skb, iph, thoff, dir) < 0))
return -1;
if (flow->flags & FLOW_OFFLOAD_DNAT &&
(nf_flow_dnat_port(flow, skb, thoff, iph->protocol, dir) < 0 ||
nf_flow_dnat_ip(flow, skb, iph, thoff, dir) < 0))
return -1;
return 0;
}
static bool ip_has_options(unsigned int thoff)
{
return thoff != sizeof(struct iphdr);
}
static int nf_flow_tuple_ip(struct sk_buff *skb, const struct net_device *dev,
struct flow_offload_tuple *tuple)
{
struct flow_ports *ports;
unsigned int thoff;
struct iphdr *iph;
if (!pskb_may_pull(skb, sizeof(*iph)))
return -1;
iph = ip_hdr(skb);
thoff = iph->ihl * 4;
if (ip_is_fragment(iph) ||
unlikely(ip_has_options(thoff)))
return -1;
if (iph->protocol != IPPROTO_TCP &&
iph->protocol != IPPROTO_UDP)
return -1;
thoff = iph->ihl * 4;
if (!pskb_may_pull(skb, thoff + sizeof(*ports)))
return -1;
ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
tuple->src_v4.s_addr = iph->saddr;
tuple->dst_v4.s_addr = iph->daddr;
tuple->src_port = ports->source;
tuple->dst_port = ports->dest;
tuple->l3proto = AF_INET;
tuple->l4proto = iph->protocol;
tuple->iifidx = dev->ifindex;
return 0;
}
/* Based on ip_exceeds_mtu(). */
static bool __nf_flow_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
{
if (skb->len <= mtu)
return false;
if ((ip_hdr(skb)->frag_off & htons(IP_DF)) == 0)
return false;
if (skb_is_gso(skb) && skb_gso_validate_network_len(skb, mtu))
return false;
return true;
}
static bool nf_flow_exceeds_mtu(struct sk_buff *skb, const struct rtable *rt)
{
u32 mtu;
mtu = ip_dst_mtu_maybe_forward(&rt->dst, true);
if (__nf_flow_exceeds_mtu(skb, mtu))
return true;
return false;
}
unsigned int
nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state)
{
struct flow_offload_tuple_rhash *tuplehash;
struct nf_flowtable *flow_table = priv;
struct flow_offload_tuple tuple = {};
enum flow_offload_tuple_dir dir;
struct flow_offload *flow;
struct net_device *outdev;
const struct rtable *rt;
struct iphdr *iph;
__be32 nexthop;
if (skb->protocol != htons(ETH_P_IP))
return NF_ACCEPT;
if (nf_flow_tuple_ip(skb, state->in, &tuple) < 0)
return NF_ACCEPT;
tuplehash = flow_offload_lookup(flow_table, &tuple);
if (tuplehash == NULL)
return NF_ACCEPT;
outdev = dev_get_by_index_rcu(state->net, tuplehash->tuple.oifidx);
if (!outdev)
return NF_ACCEPT;
dir = tuplehash->tuple.dir;
flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
rt = (const struct rtable *)flow->tuplehash[dir].tuple.dst_cache;
if (unlikely(nf_flow_exceeds_mtu(skb, rt)))
return NF_ACCEPT;
if (skb_try_make_writable(skb, sizeof(*iph)))
return NF_DROP;
if (flow->flags & (FLOW_OFFLOAD_SNAT | FLOW_OFFLOAD_DNAT) &&
nf_flow_nat_ip(flow, skb, dir) < 0)
return NF_DROP;
flow->timeout = (u32)jiffies + NF_FLOW_TIMEOUT;
iph = ip_hdr(skb);
ip_decrease_ttl(iph);
skb->dev = outdev;
nexthop = rt_nexthop(rt, flow->tuplehash[!dir].tuple.src_v4.s_addr);
neigh_xmit(NEIGH_ARP_TABLE, outdev, &nexthop, skb);
return NF_STOLEN;
}
EXPORT_SYMBOL_GPL(nf_flow_offload_ip_hook);
static struct nf_flowtable_type flowtable_ipv4 = {
.family = NFPROTO_IPV4,
.params = &nf_flow_offload_rhash_params,
.gc = nf_flow_offload_work_gc,
.free = nf_flow_table_free,
.hook = nf_flow_offload_ip_hook,
.owner = THIS_MODULE,
};
static int __init nf_flow_ipv4_module_init(void)
{
nft_register_flowtable_type(&flowtable_ipv4);
return 0;
}
static void __exit nf_flow_ipv4_module_exit(void)
{
nft_unregister_flowtable_type(&flowtable_ipv4);
}
module_init(nf_flow_ipv4_module_init);
module_exit(nf_flow_ipv4_module_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
MODULE_ALIAS_NF_FLOWTABLE(AF_INET);
|
