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
|
// SPDX-License-Identifier: GPL-2.0
/* Open a tun device.
*
* [modifications: use IFF_NAPI_FRAGS, add sk filter]
*
* Expects the device to have been configured previously, e.g.:
* sudo ip tuntap add name tap1 mode tap
* sudo ip link set tap1 up
* sudo ip link set dev tap1 addr 02:00:00:00:00:01
* sudo ip -6 addr add fdab::1 peer fdab::2 dev tap1 nodad
*
* And to avoid premature pskb_may_pull:
*
* sudo ethtool -K tap1 gro off
* sudo bash -c 'echo 0 > /proc/sys/net/ipv4/ip_early_demux'
*/
#define _GNU_SOURCE
#include <arpa/inet.h>
#include <errno.h>
#include <error.h>
#include <fcntl.h>
#include <getopt.h>
#include <linux/filter.h>
#include <linux/if.h>
#include <linux/if_packet.h>
#include <linux/if_tun.h>
#include <linux/ipv6.h>
#include <netinet/if_ether.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip6.h>
#include <netinet/udp.h>
#include <poll.h>
#include <signal.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/poll.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>
static bool cfg_do_filter;
static bool cfg_do_frags;
static int cfg_dst_port = 8000;
static char *cfg_ifname;
static int tun_open(const char *tun_name)
{
struct ifreq ifr = {0};
int fd, ret;
fd = open("/dev/net/tun", O_RDWR);
if (fd == -1)
error(1, errno, "open /dev/net/tun");
ifr.ifr_flags = IFF_TAP;
if (cfg_do_frags)
ifr.ifr_flags |= IFF_NAPI | IFF_NAPI_FRAGS;
strncpy(ifr.ifr_name, tun_name, IFNAMSIZ - 1);
ret = ioctl(fd, TUNSETIFF, &ifr);
if (ret)
error(1, ret, "ioctl TUNSETIFF");
return fd;
}
static void sk_set_filter(int fd)
{
const int offset_proto = offsetof(struct ip6_hdr, ip6_nxt);
const int offset_dport = sizeof(struct ip6_hdr) + offsetof(struct udphdr, dest);
/* Filter UDP packets with destination port cfg_dst_port */
struct sock_filter filter_code[] = {
BPF_STMT(BPF_LD + BPF_B + BPF_ABS, SKF_AD_OFF + SKF_AD_PKTTYPE),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, PACKET_HOST, 0, 4),
BPF_STMT(BPF_LD + BPF_B + BPF_ABS, SKF_NET_OFF + offset_proto),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 2),
BPF_STMT(BPF_LD + BPF_H + BPF_ABS, SKF_NET_OFF + offset_dport),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, cfg_dst_port, 1, 0),
BPF_STMT(BPF_RET + BPF_K, 0),
BPF_STMT(BPF_RET + BPF_K, 0xFFFF),
};
struct sock_fprog filter = {
sizeof(filter_code) / sizeof(filter_code[0]),
filter_code,
};
if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)))
error(1, errno, "setsockopt attach filter");
}
static int raw_open(void)
{
int fd;
fd = socket(PF_INET6, SOCK_RAW, IPPROTO_UDP);
if (fd == -1)
error(1, errno, "socket raw (udp)");
if (cfg_do_filter)
sk_set_filter(fd);
return fd;
}
static void tun_write(int fd)
{
const char eth_src[] = { 0x02, 0x00, 0x00, 0x00, 0x00, 0x02 };
const char eth_dst[] = { 0x02, 0x00, 0x00, 0x00, 0x00, 0x01 };
struct tun_pi pi = {0};
struct ipv6hdr ip6h = {0};
struct udphdr uh = {0};
struct ethhdr eth = {0};
uint32_t payload;
struct iovec iov[5];
int ret;
pi.proto = htons(ETH_P_IPV6);
memcpy(eth.h_source, eth_src, sizeof(eth_src));
memcpy(eth.h_dest, eth_dst, sizeof(eth_dst));
eth.h_proto = htons(ETH_P_IPV6);
ip6h.version = 6;
ip6h.payload_len = htons(sizeof(uh) + sizeof(uint32_t));
ip6h.nexthdr = IPPROTO_UDP;
ip6h.hop_limit = 8;
if (inet_pton(AF_INET6, "fdab::2", &ip6h.saddr) != 1)
error(1, errno, "inet_pton src");
if (inet_pton(AF_INET6, "fdab::1", &ip6h.daddr) != 1)
error(1, errno, "inet_pton src");
uh.source = htons(8000);
uh.dest = htons(cfg_dst_port);
uh.len = ip6h.payload_len;
uh.check = 0;
payload = htonl(0xABABABAB); /* Covered in IPv6 length */
iov[0].iov_base = π
iov[0].iov_len = sizeof(pi);
iov[1].iov_base = ð
iov[1].iov_len = sizeof(eth);
iov[2].iov_base = &ip6h;
iov[2].iov_len = sizeof(ip6h);
iov[3].iov_base = &uh;
iov[3].iov_len = sizeof(uh);
iov[4].iov_base = &payload;
iov[4].iov_len = sizeof(payload);
ret = writev(fd, iov, sizeof(iov) / sizeof(iov[0]));
if (ret <= 0)
error(1, errno, "writev");
}
static void raw_read(int fd)
{
struct timeval tv = { .tv_usec = 100 * 1000 };
struct msghdr msg = {0};
struct iovec iov[2];
struct udphdr uh;
uint32_t payload[2];
int ret;
if (setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)))
error(1, errno, "setsockopt rcvtimeo udp");
iov[0].iov_base = &uh;
iov[0].iov_len = sizeof(uh);
iov[1].iov_base = payload;
iov[1].iov_len = sizeof(payload);
msg.msg_iov = iov;
msg.msg_iovlen = sizeof(iov) / sizeof(iov[0]);
ret = recvmsg(fd, &msg, 0);
if (ret <= 0)
error(1, errno, "read raw");
if (ret != sizeof(uh) + sizeof(payload[0]))
error(1, errno, "read raw: len=%d\n", ret);
fprintf(stderr, "raw recv: 0x%x\n", payload[0]);
}
static void parse_opts(int argc, char **argv)
{
int c;
while ((c = getopt(argc, argv, "fFi:")) != -1) {
switch (c) {
case 'f':
cfg_do_filter = true;
printf("bpf filter enabled\n");
break;
case 'F':
cfg_do_frags = true;
printf("napi frags mode enabled\n");
break;
case 'i':
cfg_ifname = optarg;
break;
default:
error(1, 0, "unknown option %c", optopt);
break;
}
}
if (!cfg_ifname)
error(1, 0, "must specify tap interface name (-i)");
}
int main(int argc, char **argv)
{
int fdt, fdr;
parse_opts(argc, argv);
fdr = raw_open();
fdt = tun_open(cfg_ifname);
tun_write(fdt);
raw_read(fdr);
if (close(fdt))
error(1, errno, "close tun");
if (close(fdr))
error(1, errno, "close udp");
fprintf(stderr, "OK\n");
return 0;
}
|
