blob: f888041c0ffa1595b9dc37b50655d8968a1309b9 [file] [log] [blame]
/*
* Copyright 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* main.c - main function
*/
#include <arpa/inet.h>
#include <errno.h>
#include <netinet/in.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/personality.h>
#include <sys/utsname.h>
#include <unistd.h>
#include "clatd.h"
#include "common.h"
#include "config.h"
#include "logging.h"
#define DEVICEPREFIX "v4-"
/* function: stop_loop
* signal handler: stop the event loop
*/
static void stop_loop() { running = 0; };
/* function: print_help
* in case the user is running this on the command line
*/
void print_help() {
printf("android-clat arguments:\n");
printf("-i [uplink interface]\n");
printf("-p [plat prefix]\n");
printf("-4 [IPv4 address]\n");
printf("-6 [IPv6 address]\n");
printf("-t [tun file descriptor number]\n");
printf("-r [read socket descriptor number]\n");
printf("-w [write socket descriptor number]\n");
}
/* function: main
* allocate and setup the tun device, then run the event loop
*/
int main(int argc, char **argv) {
struct tun_data tunnel;
int opt;
char *uplink_interface = NULL, *plat_prefix = NULL;
char *v4_addr = NULL, *v6_addr = NULL, *tunfd_str = NULL, *read_sock_str = NULL,
*write_sock_str = NULL;
unsigned len;
while ((opt = getopt(argc, argv, "i:p:4:6:t:r:w:h")) != -1) {
switch (opt) {
case 'i':
uplink_interface = optarg;
break;
case 'p':
plat_prefix = optarg;
break;
case '4':
v4_addr = optarg;
break;
case '6':
v6_addr = optarg;
break;
case 't':
tunfd_str = optarg;
break;
case 'r':
read_sock_str = optarg;
break;
case 'w':
write_sock_str = optarg;
break;
case 'h':
print_help();
exit(0);
default:
logmsg(ANDROID_LOG_FATAL, "Unknown option -%c. Exiting.", (char)optopt);
exit(1);
}
}
if (uplink_interface == NULL) {
logmsg(ANDROID_LOG_FATAL, "clatd called without an interface");
exit(1);
}
if (tunfd_str != NULL && !parse_int(tunfd_str, &tunnel.fd4)) {
logmsg(ANDROID_LOG_FATAL, "invalid tunfd %s", tunfd_str);
exit(1);
}
if (!tunnel.fd4) {
logmsg(ANDROID_LOG_FATAL, "no tunfd specified on commandline.");
exit(1);
}
if (read_sock_str != NULL && !parse_int(read_sock_str, &tunnel.read_fd6)) {
logmsg(ANDROID_LOG_FATAL, "invalid read socket %s", read_sock_str);
exit(1);
}
if (!tunnel.read_fd6) {
logmsg(ANDROID_LOG_FATAL, "no read_fd6 specified on commandline.");
exit(1);
}
if (write_sock_str != NULL && !parse_int(write_sock_str, &tunnel.write_fd6)) {
logmsg(ANDROID_LOG_FATAL, "invalid write socket %s", write_sock_str);
exit(1);
}
if (!tunnel.write_fd6) {
logmsg(ANDROID_LOG_FATAL, "no write_fd6 specified on commandline.");
exit(1);
}
len = snprintf(tunnel.device4, sizeof(tunnel.device4), "%s%s", DEVICEPREFIX, uplink_interface);
if (len >= sizeof(tunnel.device4)) {
logmsg(ANDROID_LOG_FATAL, "interface name too long '%s'", tunnel.device4);
exit(1);
}
Global_Clatd_Config.native_ipv6_interface = uplink_interface;
if (!plat_prefix || inet_pton(AF_INET6, plat_prefix, &Global_Clatd_Config.plat_subnet) <= 0) {
logmsg(ANDROID_LOG_FATAL, "invalid IPv6 address specified for plat prefix: %s", plat_prefix);
exit(1);
}
if (!v4_addr || !inet_pton(AF_INET, v4_addr, &Global_Clatd_Config.ipv4_local_subnet.s_addr)) {
logmsg(ANDROID_LOG_FATAL, "Invalid IPv4 address %s", v4_addr);
exit(1);
}
if (!v6_addr || !inet_pton(AF_INET6, v6_addr, &Global_Clatd_Config.ipv6_local_subnet)) {
logmsg(ANDROID_LOG_FATAL, "Invalid source address %s", v6_addr);
exit(1);
}
logmsg(ANDROID_LOG_INFO, "Starting clat version %s on %s plat=%s v4=%s v6=%s", CLATD_VERSION,
uplink_interface, plat_prefix ? plat_prefix : "(none)", v4_addr ? v4_addr : "(none)",
v6_addr ? v6_addr : "(none)");
{
// Compile time detection of 32 vs 64-bit build. (note: C does not have 'constexpr')
// Avoid use of preprocessor macros to get compile time syntax checking even on 64-bit.
const int user_bits = sizeof(void*) * 8;
const bool user32 = (user_bits == 32);
// Note that on 64-bit all this personality related code simply compile optimizes out.
// 32-bit: fetch current personality (see 'man personality': 0xFFFFFFFF means retrieve only)
// On Linux fetching personality cannot fail.
const int prev_personality = user32 ? personality(0xFFFFFFFFuL) : PER_LINUX;
// 32-bit: attempt to get rid of kernel spoofing of 'uts.machine' architecture,
// In theory this cannot fail, as PER_LINUX should always be supported.
if (user32) (void)personality((prev_personality & ~PER_MASK) | PER_LINUX);
// 64-bit: this will compile time evaluate to false.
const bool was_linux32 = (prev_personality & PER_MASK) == PER_LINUX32;
struct utsname uts = {};
if (uname(&uts)) exit(1); // only possible error is EFAULT, but 'uts' is on stack
// sysname is likely 'Linux', release is 'kver', machine is kernel's *true* architecture
logmsg(ANDROID_LOG_INFO, "%d-bit userspace on %s kernel %s for %s%s.", user_bits,
uts.sysname, uts.release, uts.machine, was_linux32 ? " (was spoofed)" : "");
// 32-bit: try to return to the 'default' personality
// In theory this cannot fail, because it was already previously in use.
if (user32) (void)personality(prev_personality);
}
// Loop until someone sends us a signal or brings down the tun interface.
if (signal(SIGTERM, stop_loop) == SIG_ERR) {
logmsg(ANDROID_LOG_FATAL, "sigterm handler failed: %s", strerror(errno));
exit(1);
}
event_loop(&tunnel);
logmsg(ANDROID_LOG_INFO, "Shutting down clat on %s", uplink_interface);
if (running) {
logmsg(ANDROID_LOG_INFO, "Clatd on %s waiting for SIGTERM", uplink_interface);
// let's give higher level java code 15 seconds to kill us,
// but eventually terminate anyway, in case system server forgets about us...
// sleep() should be interrupted by SIGTERM, the handler should clear running
sleep(15);
logmsg(ANDROID_LOG_INFO, "Clatd on %s %s SIGTERM", uplink_interface,
running ? "timed out waiting for" : "received");
} else {
logmsg(ANDROID_LOG_INFO, "Clatd on %s already received SIGTERM", uplink_interface);
}
return 0;
}