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
|
/* Shared library add-on to iptables to add source-NAT support. */
#include <stdio.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <getopt.h>
#include <iptables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ip_nat_rule.h>
/* Source NAT data consists of a multi-range, indicating where to map
to. */
struct ipt_natinfo
{
struct ipt_entry_target t;
struct ip_nat_multi_range mr;
};
/* Function which prints out usage message. */
static void
help(void)
{
printf(
"SNAT v%s options:\n"
" --to-source <ipaddr>[-<ipaddr>][:port-port]\n"
" Address to map source to.\n"
" (You can use this more than once)\n\n",
NETFILTER_VERSION);
}
static struct option opts[] = {
{ "to-source", 1, 0, '1' },
{ 0 }
};
/* Initialize the target. */
static void
init(struct ipt_entry_target *t, unsigned int *nfcache)
{
/* Can't cache this */
*nfcache |= NFC_UNKNOWN;
}
static struct ipt_natinfo *
append_range(struct ipt_natinfo *info, const struct ip_nat_range *range)
{
unsigned int size;
/* One rangesize already in struct ipt_natinfo */
size = IPT_ALIGN(sizeof(*info) + info->mr.rangesize * sizeof(*range));
info = realloc(info, size);
if (!info)
exit_error(OTHER_PROBLEM, "Out of memory\n");
info->t.target_size = size;
info->mr.range[info->mr.rangesize] = *range;
info->mr.rangesize++;
return info;
}
/* Ranges expected in network order. */
static struct ipt_entry_target *
parse_to(char *arg, int portok, struct ipt_natinfo *info)
{
struct ip_nat_range range;
char *colon, *dash;
struct in_addr *ip;
memset(&range, 0, sizeof(range));
colon = strchr(arg, ':');
if (colon) {
int port;
if (!portok)
exit_error(PARAMETER_PROBLEM,
"Need TCP or UDP with port specification");
range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
port = atoi(colon+1);
if (port == 0 || port > 65535)
exit_error(PARAMETER_PROBLEM,
"Port `%s' not valid\n", colon+1);
dash = strchr(colon, '-');
if (!dash) {
range.min.tcp.port
= range.max.tcp.port
= htons(port);
} else {
int maxport;
maxport = atoi(dash + 1);
if (maxport == 0 || maxport > 65535)
exit_error(PARAMETER_PROBLEM,
"Port `%s' not valid\n", dash+1);
if (maxport < port)
/* People are stupid. */
exit_error(PARAMETER_PROBLEM,
"Port range `%s' funky\n", colon+1);
range.min.tcp.port = htons(port);
range.max.tcp.port = htons(maxport);
}
/* Starts with a colon? No IP info...*/
if (colon == arg)
return &(append_range(info, &range)->t);
*colon = '\0';
}
range.flags |= IP_NAT_RANGE_MAP_IPS;
dash = strchr(arg, '-');
if (colon && dash && dash > colon)
dash = NULL;
if (dash)
*dash = '\0';
ip = dotted_to_addr(arg);
if (!ip)
exit_error(PARAMETER_PROBLEM, "Bad IP address `%s'\n",
arg);
range.min_ip = ip->s_addr;
if (dash) {
ip = dotted_to_addr(dash+1);
if (!ip)
exit_error(PARAMETER_PROBLEM, "Bad IP address `%s'\n",
dash+1);
range.max_ip = ip->s_addr;
} else
range.max_ip = range.min_ip;
return &(append_range(info, &range)->t);
}
/* Function which parses command options; returns true if it
ate an option */
static int
parse(int c, char **argv, int invert, unsigned int *flags,
const struct ipt_entry *entry,
struct ipt_entry_target **target)
{
struct ipt_natinfo *info = (void *)*target;
int portok;
if (entry->ip.proto == IPPROTO_TCP
|| entry->ip.proto == IPPROTO_UDP)
portok = 1;
else
portok = 0;
switch (c) {
case '1':
if (check_inverse(optarg, &invert))
exit_error(PARAMETER_PROBLEM,
"Unexpected `!' after --to-source");
*target = parse_to(optarg, portok, info);
*flags = 1;
return 1;
default:
return 0;
}
}
/* Final check; must have specfied --to-source. */
static void final_check(unsigned int flags)
{
if (!flags)
exit_error(PARAMETER_PROBLEM,
"You must specify --to-source");
}
static void print_range(const struct ip_nat_range *r)
{
if (r->flags & IP_NAT_RANGE_MAP_IPS) {
struct in_addr a;
a.s_addr = r->min_ip;
printf("%s", addr_to_dotted(&a));
if (r->max_ip != r->min_ip) {
a.s_addr = r->max_ip;
printf("-%s", addr_to_dotted(&a));
}
}
if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
printf(":");
printf("%hu", ntohs(r->min.tcp.port));
if (r->max.tcp.port != r->min.tcp.port)
printf("-%hu", ntohs(r->max.tcp.port));
}
}
/* Prints out the targinfo. */
static void
print(const struct ipt_ip *ip,
const struct ipt_entry_target *target,
int numeric)
{
struct ipt_natinfo *info = (void *)target;
unsigned int i = 0;
printf("to:");
for (i = 0; i < info->mr.rangesize; i++) {
print_range(&info->mr.range[i]);
printf(" ");
}
}
/* Saves the union ipt_targinfo in parsable form to stdout. */
static void
save(const struct ipt_ip *ip, const struct ipt_entry_target *target)
{
struct ipt_natinfo *info = (void *)target;
unsigned int i = 0;
for (i = 0; i < info->mr.rangesize; i++) {
printf("--to-source ");
print_range(&info->mr.range[i]);
printf(" ");
}
}
struct iptables_target snat
= { NULL,
"SNAT",
NETFILTER_VERSION,
sizeof(struct ip_nat_multi_range),
sizeof(struct ip_nat_multi_range),
&help,
&init,
&parse,
&final_check,
&print,
&save,
opts
};
void _init(void)
{
register_target(&snat);
}
|
