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tncattach
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tncattach/tncattach.c

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#include <stdlib.h>
#include <stdbool.h>
#include <signal.h>
#include <poll.h>
#include <argp.h>
#include <syslog.h>
#include <sys/stat.h>
#include <time.h>
#include "Constants.h"
#include "Serial.h"
#include "KISS.h"
#include "TAP.h"
#define BAUDRATE_DEFAULT 0
#define SERIAL_BUFFER_SIZE 512
#define IF_FD_INDEX 0
#define TNC_FD_INDEX 1
#define N_FDS 2
struct pollfd fds[N_FDS];
int attached_tnc;
int attached_if;
char if_name[IFNAMSIZ];
uint8_t serial_buffer[MTU_MAX];
uint8_t if_buffer[MTU_MAX];
bool verbose = false;
bool noipv6 = false;
bool noup = false;
bool daemonize = false;
bool set_ipv4 = false;
bool set_netmask = false;
char* ipv4_addr;
char* netmask;
int mtu;
int device_type = IF_TUN;
char* id;
int id_interval = -1;
time_t last_id = 0;
void cleanup(void) {
close_port(attached_tnc);
close_tap(attached_if);
}
void signal_handler(int signal) {
if (daemonize) {
cleanup();
syslog(LOG_NOTICE, "tncattach daemon exiting");
exit(0);
} else {
cleanup();
exit(0);
}
}
bool is_ipv6(uint8_t* frame) {
if (device_type == IF_TAP) {
if (frame[12] == 0x86 && frame[13] == 0xdd) {
return true;
} else {
return false;
}
} else if (device_type == IF_TUN) {
if (frame[2] == 0x86 && frame[3] == 0xdd) {
return true;
} else {
return false;
}
} else {
printf("Error: Unsupported interface type\r\n");
cleanup();
exit(1);
}
}
void read_loop(void) {
bool should_continue = true;
int min_frame_size;
if (device_type == IF_TAP) {
min_frame_size = ETHERNET_MIN_FRAME_SIZE;
} else if (device_type == IF_TUN) {
min_frame_size = TUN_MIN_FRAME_SIZE;
} else {
if (daemonize) {
syslog(LOG_ERR, "Unsupported interface type");
} else {
printf("Error: Unsupported interface type\r\n");
}
cleanup();
exit(1);
}
while (should_continue) {
int poll_result = poll(fds, 2, -1);
if (poll_result != -1) {
for (int fdi = 0; fdi < N_FDS; fdi++) {
if (fds[fdi].revents != 0) {
// Check for hangup event
if (fds[fdi].revents & POLLHUP) {
if (fdi == IF_FD_INDEX) {
if (daemonize) {
syslog(LOG_ERR, "Received hangup from interface");
} else {
printf("Received hangup from interface\r\n");
}
cleanup();
exit(1);
}
if (fdi == TNC_FD_INDEX) {
if (daemonize) {
syslog(LOG_ERR, "Received hangup from TNC");
} else {
printf("Received hangup from TNC\r\n");
}
cleanup();
exit(1);
}
}
// Check for error event
if (fds[fdi].revents & POLLERR) {
if (fdi == IF_FD_INDEX) {
if (daemonize) {
syslog(LOG_ERR, "Received error event from interface");
} else {
perror("Received error event from interface\r\n");
}
cleanup();
exit(1);
}
if (fdi == TNC_FD_INDEX) {
if (daemonize) {
syslog(LOG_ERR, "Received error event from TNC");
} else {
perror("Received error event from TNC\r\n");
}
cleanup();
exit(1);
}
}
// If data is ready, read it
if (fds[fdi].revents & POLLIN) {
if (fdi == IF_FD_INDEX) {
int if_len = read(attached_if, if_buffer, sizeof(if_buffer));
if (if_len > 0) {
if (if_len >= min_frame_size) {
if (!noipv6 || (noipv6 && !is_ipv6(if_buffer))) {
if (id_interval != -1) {
time_t now = time(NULL);
if (now == -1) {
if (daemonize) {
syslog(LOG_ERR, "Could not get system time, exiting now");
} else {
printf("Error: Could not get system time, exiting now\r\n");
}
cleanup();
exit(1);
} else {
if (now > last_id + id_interval) {
int id_len = strlen(id);
if (verbose) {
if (!daemonize) {
printf("Transmitting %d bytes of identification data on %s: %s\r\n", id_len, if_name, id);
}
}
uint8_t* id_frame = malloc(strlen(id));
memcpy(id_frame, id, id_len);
kiss_write_frame(attached_tnc, id_frame, id_len);
last_id = now;
}
}
}
kiss_write_frame(attached_tnc, if_buffer, if_len);
}
}
} else {
if (daemonize) {
syslog(LOG_ERR, "Could not read from network interface, exiting now");
} else {
printf("Error: Could not read from network interface, exiting now\r\n");
}
cleanup();
exit(1);
}
}
if (fdi == TNC_FD_INDEX) {
int tnc_len = read(attached_tnc, serial_buffer, sizeof(serial_buffer));
if (tnc_len > 0) {
for (int i = 0; i < tnc_len; i++) {
kiss_serial_read(serial_buffer[i]);
}
} else {
if (daemonize) {
syslog(LOG_ERR, "Could not read from TNC, exiting now");
} else {
printf("Error: Could not read from TNC, exiting now\r\n");
}
cleanup();
exit(1);
}
}
}
}
}
} else {
should_continue = false;
}
}
cleanup();
exit(1);
}
const char *argp_program_version = "tncattach 0.1.3";
const char *argp_program_bug_address = "<mark@unsigned.io>";
static char doc[] = "\r\nAttach TNC devices as system network interfaces\vTo attach the TNC connected to /dev/ttyUSB0 as an ethernet device with an MTU of 512 bytes and assign an IPv4 address, while filtering IPv6 traffic, use:\r\n\r\n\ttncattach /dev/ttyUSB0 115200 -m 512 -e --noipv6 --ipv4 10.0.0.1/24\r\n\r\nStation identification can be performed automatically. Use the --id and --idinterval options. Identification beacons will be transmitted if the amount of time since the last identification is greater than the configured interval and there is any data to send. Channel capacity will therefore not be wasted on IDs for stations that are not actively transmitting.";
static char args_doc[] = "port baudrate";
static struct argp_option options[] = {
{ "mtu", 'm', "MTU", 0, "Specify interface MTU"},
{ "daemon", 'd', 0, 0, "Run tncattach as a daemon"},
{ "ethernet", 'e', 0, 0, "Create a full ethernet device"},
{ "ipv4", 'i', "IP_ADDRESS", 0, "Configure an IPv4 address on interface"},
{ "noipv6", 'n', 0, 0, "Filter IPv6 traffic from reaching TNC"},
{ "noup", 1, 0, 0, "Only create interface, don't bring it up"},
{ "interval", 't', "SECONDS", 0, "Maximum interval between station identifications"},
{ "id", 's', "CALLSIGN", 0, "Station identification data"},
{ "verbose", 'v', 0, 0, "Enable verbose output"},
{ 0 }
};
#define N_ARGS 2
struct arguments {
char *args[N_ARGS];
char *ipv4;
char *id;
bool valid_id;
int id_interval;
int baudrate;
int mtu;
bool tap;
bool daemon;
bool verbose;
bool set_ipv4;
bool set_netmask;
bool noipv6;
bool noup;
};
static error_t parse_opt(int key, char *arg, struct argp_state *state) {
struct arguments *arguments = state->input;
switch (key) {
case 'v':
arguments->verbose = true;
break;
case 'e':
arguments->tap = true;
break;
case 'm':
arguments->mtu = atoi(arg);
if (arguments->mtu < MTU_MIN || arguments->mtu > MTU_MAX) {
printf("Error: Invalid MTU specified\r\n\r\n");
argp_usage(state);
}
break;
case 't':
arguments->id_interval = atoi(arg);
if (arguments->id_interval < 0) {
printf("Error: Invalid identification interval specified\r\n\r\n");
argp_usage(state);
}
break;
case 's':
arguments->id = arg;
if (strlen(arg) < 1 || strlen(arg) > arguments->mtu) {
printf("Error: Invalid identification string specified\r\n\r\n");
argp_usage(state);
} else {
arguments->valid_id = true;
}
break;
case 'i':
arguments->ipv4 = arg;
arguments->set_ipv4 = true;
if (strchr(arg, '/')) {
char* net = strchr(arg, '/');
int pos = net-arg;
ipv4_addr = (char*)malloc(pos+1);
int mask = atoi(net+1);
strncpy(ipv4_addr, arg, pos);
switch (mask) {
case 0:
netmask = "0.0.0.0";
break;
case 1:
netmask = "128.0.0.0";
break;
case 2:
netmask = "192.0.0.0";
break;
case 3:
netmask = "224.0.0.0";
break;
case 4:
netmask = "240.0.0.0";
break;
case 5:
netmask = "248.0.0.0";
break;
case 6:
netmask = "252.0.0.0";
break;
case 7:
netmask = "254.0.0.0";
break;
case 8:
netmask = "255.0.0.0";
break;
case 9:
netmask = "255.128.0.0";
break;
case 10:
netmask = "255.192.0.0";
break;
case 11:
netmask = "255.224.0.0";
break;
case 12:
netmask = "255.240.0.0";
break;
case 13:
netmask = "255.248.0.0";
break;
case 14:
netmask = "255.252.0.0";
break;
case 15:
netmask = "255.254.0.0";
break;
case 16:
netmask = "255.255.0.0";
break;
case 17:
netmask = "255.255.128.0";
break;
case 18:
netmask = "255.255.192.0";
break;
case 19:
netmask = "255.255.224.0";
break;
case 20:
netmask = "255.255.240.0";
break;
case 21:
netmask = "255.255.248.0";
break;
case 22:
netmask = "255.255.252.0";
break;
case 23:
netmask = "255.255.254.0";
break;
case 24:
netmask = "255.255.255.0";
break;
case 25:
netmask = "255.255.255.128";
break;
case 26:
netmask = "255.255.255.192";
break;
case 27:
netmask = "255.255.255.224";
break;
case 28:
netmask = "255.255.255.240";
break;
case 29:
netmask = "255.255.255.248";
break;
case 30:
netmask = "255.255.255.252";
break;
case 31:
netmask = "255.255.255.254";
break;
case 32:
netmask = "255.255.255.255";
break;
default:
printf("Error: Invalid subnet mask specified\r\n");
cleanup();
exit(1);
}
arguments->set_netmask = true;
} else {
arguments->set_netmask = false;
ipv4_addr = (char*)malloc(strlen(arg)+1);
strcpy(ipv4_addr, arg);
}
break;
case 'n':
arguments->noipv6 = true;
break;
case 'd':
arguments->daemon = true;
arguments->verbose = false;
break;
case 1:
arguments->noup = true;
break;
case ARGP_KEY_ARG:
// Check if there's now too many text arguments
if (state->arg_num >= N_ARGS) argp_usage(state);
// If not add to args
arguments->args[state->arg_num] = arg;
break;
case ARGP_KEY_END:
// Check if there's too few text arguments
if (state->arg_num < N_ARGS) argp_usage(state);
break;
default:
return ARGP_ERR_UNKNOWN;
}
return 0;
}
static void become_daemon() {
pid_t pid;
pid = fork();
if (pid < 0) {
perror("Fork failed");
exit(EXIT_FAILURE);
}
if (pid > 0) {
exit(0);
}
if (setsid() < 0) exit(1);
signal(SIGCHLD, signal_handler);
signal(SIGHUP, signal_handler);
pid = fork();
if (pid < 0) exit(1);
if (pid > 0) exit(0);
umask(0);
chdir("/");
openlog("tncattach", LOG_PID, LOG_DAEMON);
}
static struct argp argp = {options, parse_opt, args_doc, doc};
int main(int argc, char **argv) {
struct arguments arguments;
signal(SIGINT, signal_handler);
arguments.baudrate = BAUDRATE_DEFAULT;
arguments.mtu = MTU_DEFAULT;
arguments.tap = false;
arguments.verbose = false;
arguments.set_ipv4 = false;
arguments.set_netmask = false;
arguments.noipv6 = false;
arguments.daemon = false;
arguments.noup = false;
arguments.id_interval = -1;
arguments.valid_id = false;
argp_parse(&argp, argc, argv, 0, 0, &arguments);
arguments.baudrate = atoi(arguments.args[1]);
if (arguments.daemon) daemonize = true;
if (arguments.verbose) verbose = true;
if (arguments.tap) device_type = IF_TAP;
if (arguments.noipv6) noipv6 = true;
if (arguments.set_ipv4) set_ipv4 = true;
if (arguments.set_netmask) set_netmask = true;
if (arguments.noup) noup = true;
mtu = arguments.mtu;
if (arguments.id_interval >= 0) {
if (!arguments.valid_id) {
printf("Error: Periodic identification requested, but no valid indentification data specified\r\n");
cleanup();
exit(1);
} else {
id_interval = arguments.id_interval;
id = malloc(strlen(arguments.id));
strcpy(id, arguments.id);
}
} else if (arguments.valid_id && arguments.id_interval == -1) {
printf("Error: Periodic identification requested, but no indentification interval specified\r\n");
cleanup();
exit(1);
}
attached_if = open_tap();
attached_tnc = open_port(arguments.args[0]);
if (setup_port(attached_tnc, arguments.baudrate)) {
printf("TNC interface configured as %s\r\n", if_name);
fds[IF_FD_INDEX].fd = attached_if;
fds[IF_FD_INDEX].events = POLLIN;
fds[TNC_FD_INDEX].fd = attached_tnc;
fds[TNC_FD_INDEX].events = POLLIN;
if (daemonize) {
become_daemon();
syslog(LOG_NOTICE, "tncattach daemon running");
}
read_loop();
}
return 0;
}
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