1 /*
2 * Copyright 2018 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 *
16 * main.c - main function
17 */
18
19 #include <errno.h>
20 #include <netinet/in.h>
21 #include <stdint.h>
22 #include <stdlib.h>
23 #include <string.h>
24 #include <sys/capability.h>
25 #include <unistd.h>
26
27 #include "resolv_netid.h"
28
29 #include "clatd.h"
30 #include "common.h"
31 #include "config.h"
32 #include "logging.h"
33 #include "setif.h"
34 #include "tun.h"
35
36 #define DEVICEPREFIX "v4-"
37
38 /* function: print_help
39 * in case the user is running this on the command line
40 */
print_help()41 void print_help() {
42 printf("android-clat arguments:\n");
43 printf("-i [uplink interface]\n");
44 printf("-p [plat prefix]\n");
45 printf("-4 [IPv4 address]\n");
46 printf("-6 [IPv6 address]\n");
47 printf("-n [NetId]\n");
48 printf("-m [socket mark]\n");
49 printf("-t [tun file descriptor number]\n");
50 }
51
52 /* function: main
53 * allocate and setup the tun device, then run the event loop
54 */
main(int argc,char ** argv)55 int main(int argc, char **argv) {
56 struct tun_data tunnel;
57 int opt;
58 char *uplink_interface = NULL, *plat_prefix = NULL, *net_id_str = NULL, *mark_str = NULL;
59 char *v4_addr = NULL, *v6_addr = NULL, *tunfd_str = NULL;
60 unsigned net_id = NETID_UNSET;
61 uint32_t mark = MARK_UNSET;
62 unsigned len;
63
64 while ((opt = getopt(argc, argv, "i:p:4:6:n:m:t:h")) != -1) {
65 switch (opt) {
66 case 'i':
67 uplink_interface = optarg;
68 break;
69 case 'p':
70 plat_prefix = optarg;
71 break;
72 case '4':
73 v4_addr = optarg;
74 break;
75 case '6':
76 v6_addr = optarg;
77 break;
78 case 'n':
79 net_id_str = optarg;
80 break;
81 case 'm':
82 mark_str = optarg;
83 break;
84 case 't':
85 tunfd_str = optarg;
86 break;
87 case 'h':
88 print_help();
89 exit(0);
90 default:
91 logmsg(ANDROID_LOG_FATAL, "Unknown option -%c. Exiting.", (char)optopt);
92 exit(1);
93 }
94 }
95
96 if (uplink_interface == NULL) {
97 logmsg(ANDROID_LOG_FATAL, "clatd called without an interface");
98 exit(1);
99 }
100
101 if (net_id_str != NULL && !parse_unsigned(net_id_str, &net_id)) {
102 logmsg(ANDROID_LOG_FATAL, "invalid NetID %s", net_id_str);
103 exit(1);
104 }
105
106 if (mark_str != NULL && !parse_unsigned(mark_str, &mark)) {
107 logmsg(ANDROID_LOG_FATAL, "invalid mark %s", mark_str);
108 exit(1);
109 }
110
111 if (tunfd_str != NULL && !parse_int(tunfd_str, &tunnel.fd4)) {
112 logmsg(ANDROID_LOG_FATAL, "invalid tunfd %s", tunfd_str);
113 exit(1);
114 }
115 if (!tunnel.fd4) {
116 logmsg(ANDROID_LOG_FATAL, "no tunfd specified on commandline.");
117 exit(1);
118 }
119
120 len = snprintf(tunnel.device4, sizeof(tunnel.device4), "%s%s", DEVICEPREFIX, uplink_interface);
121 if (len >= sizeof(tunnel.device4)) {
122 logmsg(ANDROID_LOG_FATAL, "interface name too long '%s'", tunnel.device4);
123 exit(1);
124 }
125
126 logmsg(ANDROID_LOG_INFO, "Starting clat version %s on %s netid=%s mark=%s plat=%s v4=%s v6=%s",
127 CLATD_VERSION, uplink_interface, net_id_str ? net_id_str : "(none)",
128 mark_str ? mark_str : "(none)", plat_prefix ? plat_prefix : "(none)",
129 v4_addr ? v4_addr : "(none)", v6_addr ? v6_addr : "(none)");
130
131 // run under a regular user but keep needed capabilities
132 drop_root_but_keep_caps();
133
134 // open our raw sockets before dropping privs
135 open_sockets(&tunnel, mark);
136
137 // keeps only admin capability
138 set_capability(1 << CAP_NET_ADMIN);
139
140 // When run from netd, the environment variable ANDROID_DNS_MODE is set to
141 // "local", but that only works for the netd process itself. Removing the
142 // following line causes XLAT failure in permissive mode.
143 unsetenv("ANDROID_DNS_MODE");
144
145 configure_interface(uplink_interface, plat_prefix, v4_addr, v6_addr, &tunnel, net_id);
146
147 // Drop all remaining capabilities.
148 set_capability(0);
149
150 // Loop until someone sends us a signal or brings down the tun interface.
151 if (signal(SIGTERM, stop_loop) == SIG_ERR) {
152 logmsg(ANDROID_LOG_FATAL, "sigterm handler failed: %s", strerror(errno));
153 exit(1);
154 }
155
156 event_loop(&tunnel);
157
158 logmsg(ANDROID_LOG_INFO, "Shutting down clat on %s", uplink_interface);
159 del_anycast_address(tunnel.write_fd6, &Global_Clatd_Config.ipv6_local_subnet);
160
161 return 0;
162 }
163