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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;
bool tx_since_last_id = false;
void cleanup(void) {
close_port(attached_tnc);
close_tap(attached_if);
}
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);
}
}
time_t time_now(void) {
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 {
return now;
}
}
void transmit_id(void) {
time_t now = time(NULL);
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;
tx_since_last_id = false;
}
bool should_id(void) {
if (id_interval != -1) {
time_t now = time_now();
return now > last_id + id_interval;
} else {
return false;
}
}
void signal_handler(int signal) {
if (daemonize) syslog(LOG_NOTICE, "tncattach daemon exiting");
// Transmit final ID if necessary
if (id_interval != -1 && tx_since_last_id) transmit_id();
cleanup();
exit(0);
}
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);
}
int poll_timeout = 1000;
while (should_continue) {
int poll_result = poll(fds, 2, poll_timeout);
if (poll_result != -1) {
if (poll_result == 0) {
// No resources are ready for reading,
// run scheduled tasks instead.
if (id_interval != -1 && tx_since_last_id) {
time_t now = time_now();
if (now > last_id + id_interval) transmit_id();
}
} else {
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))) {
int tnc_written = kiss_write_frame(attached_tnc, if_buffer, if_len);
if (verbose && !daemonize) printf("Got %d bytes from interface, wrote %d bytes (KISS-framed and escaped) to TNC\r\n", if_len, tnc_written);
tx_since_last_id = true;
if (should_id()) transmit_id();
}
}
} 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 0.1.6";
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 to comply with Part 97 rules. See the README for a complete description. Use the --id and --interval options, which should commonly be set to your callsign, and 600 seconds.";
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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