/*
* (C) 2013-2024 by Christian Hesse <mail@eworm.de>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*
*/
#include "dyndhcpd.h"
const static char optstring[] = "c:hi:l:p:u:vVw:";
const static struct option options_long[] = {
/* name has_arg flag val */
{ "config", required_argument, NULL, 'c' },
{ "help", no_argument, NULL, 'h' },
{ "interface", required_argument, NULL, 'i' },
{ "leases", required_argument, NULL, 'l' },
{ "pidfile", required_argument, NULL, 'p' },
{ "user", required_argument, NULL, 'u' },
{ "verbose", no_argument, NULL, 'v' },
{ "version", no_argument, NULL, 'V' },
{ "write-config", required_argument, NULL, 'w' },
{ 0, 0, 0, 0 }
};
/*** replace ***/
int replace(char ** config, size_t *length, const char ** tmp,
const char * template, const char * value) {
size_t templatelength = strlen(template);
if (strncmp(template, *tmp, templatelength) == 0) {
*config = realloc(*config, *length + strlen(value) + 1);
*length += sprintf(*config + *length, "%s", value);
*tmp += templatelength;
return 1;
}
return 0;
}
/*** main ***/
int main(int argc, char ** argv) {
int i, rc = EXIT_FAILURE, verbose = 0;
const char * tmp;
struct ifaddrs *ifaddr = NULL, *ifa;
struct network network, dhcp, bootp;
char * interface = NULL;
char hostname[HOST_NAME_MAX];
char * domainname;
char * template = NULL;
FILE * templatefile;
const char * templatefilename = CONFIG_TEMPLATE;
char * config = NULL;
FILE * configfile;
char * configfilename = NULL;
size_t fsize, length = 0;
char * pidfile = NULL, * leasesfile = NULL, * username = NULL;
unsigned int version = 0, help = 0;
/* get command line options */
while ((i = getopt_long(argc, argv, optstring, options_long, NULL)) != -1)
switch (i) {
case 'c':
templatefilename = optarg;
if (strlen(templatefilename) == 0) {
fprintf(stderr, "Requested different config file, but no name given.\n");
return EXIT_FAILURE;
}
break;
case 'h':
help++;
break;
case 'i':
interface = optarg;
if (strlen(interface) == 0) {
fprintf(stderr, "No interface given!\n");
return EXIT_FAILURE;
}
break;
case 'l':
leasesfile = strdup(optarg);
break;
case 'p':
pidfile = strdup(optarg);
break;
case 'u':
username = optarg;
break;
case 'v':
verbose++;
break;
case 'V':
verbose++;
version++;
break;
case 'w':
configfilename = strdup(optarg);
break;
}
if (verbose > 0)
printf("%s: %s v%s (compiled: " __DATE__ ", " __TIME__ ")\n", argv[0], PROGNAME, VERSION);
if (help > 0)
fprintf(stderr, "usage: %s [-c config] [-h] -i INTERFACE [-v] [-V]\n", argv[0]);
if (version > 0 || help > 0)
return EXIT_SUCCESS;
/* bail if we are not root */
if (getuid() > 0) {
fprintf(stderr, "You need to be root!\n");
goto out;
}
/* check if dhcpd exists and is executable */
if (access(DHCPDFILE, X_OK) == -1) {
fprintf(stderr, "The dhcp daemon is not execatable!\n");
goto out;
}
/* get the hostname */
if (gethostname(hostname, HOST_NAME_MAX) == -1) {
fprintf(stderr, "Failed to get the hostname.\n");
goto out;
}
/* get the domainname and strip it from hostname */
if ((domainname = strchr(hostname, '.')) != NULL) {
*domainname = 0;
domainname++;
} else {
fprintf(stderr, "Could not get domainname, using '" FALLBACKDOMAIN "'\n");
domainname = FALLBACKDOMAIN;
}
/* give an error if we do not have an interface */
if (interface == NULL) {
fprintf(stderr, "No interface given!\n");
return EXIT_FAILURE;
}
/* initialize ifaddr */
if (getifaddrs(&ifaddr) == -1) {
fprintf(stderr, "getifaddrs() failed.\n");
return EXIT_FAILURE;
}
/* to find the correct interface */
for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
/* next iteration if requirements do not match */
if (strcmp(interface, ifa->ifa_name) != 0)
continue;
if (ifa->ifa_addr == NULL)
continue;
if (ifa->ifa_addr->sa_family != AF_INET)
continue;
/* check if the device is up */
if (!(ifa->ifa_flags & IFF_UP)) {
fprintf(stderr, "Interface %s is down.\n", interface);
goto out;
}
/* check if the device is connected / cable is plugged in
* do warn here, but do not fail */
if (!(ifa->ifa_flags & IFF_RUNNING))
fprintf(stderr, "Warning: Interface %s is not connected.\n", interface);
/* get variables in place for address and netmask */
memcpy(&network.address.i, &((struct sockaddr_in *)ifa->ifa_addr)->sin_addr, sizeof(struct in_addr));
memcpy(&network.netmask.i, &((struct sockaddr_in *)ifa->ifa_netmask)->sin_addr, sizeof(struct in_addr));
/* check if subnet has enough addresses */
if ((network.netmask.i.s_addr & 0x0f000000) > 0) {
fprintf(stderr, "We do not have addresses to serve, need a netmask with 28 bit minimum.\n");
goto out;
}
/* calculate broadcast and netaddress */
network.broadcast.i.s_addr = network.address.i.s_addr | ~network.netmask.i.s_addr;
network.netaddress.i.s_addr = network.address.i.s_addr & network.netmask.i.s_addr;
/* calculate for dhcp subnet */
dhcp.netmask.i.s_addr = htonl(ntohl(network.netmask.i.s_addr) >> 1 | (1 << 31));
dhcp.address.i.s_addr = network.address.i.s_addr ^ (dhcp.netmask.i.s_addr ^ network.netmask.i.s_addr);
dhcp.broadcast.i.s_addr = dhcp.address.i.s_addr | ~dhcp.netmask.i.s_addr;
dhcp.netaddress.i.s_addr = dhcp.address.i.s_addr & dhcp.netmask.i.s_addr;
dhcp.minhost.i.s_addr = htonl(ntohl(dhcp.netaddress.i.s_addr) + 1);
dhcp.maxhost.i.s_addr = htonl(ntohl(dhcp.broadcast.i.s_addr) - 1);
/* calculate for pxe subnet */
bootp.netmask.i.s_addr = htonl(ntohl(dhcp.netmask.i.s_addr) >> 1 | (1 << 31));
bootp.address.i.s_addr = network.address.i.s_addr ^ (bootp.netmask.i.s_addr ^ dhcp.netmask.i.s_addr);
bootp.broadcast.i.s_addr = bootp.address.i.s_addr | ~bootp.netmask.i.s_addr;
bootp.netaddress.i.s_addr = bootp.address.i.s_addr & bootp.netmask.i.s_addr;
bootp.minhost.i.s_addr = htonl(ntohl(bootp.netaddress.i.s_addr) + 1);
bootp.maxhost.i.s_addr = htonl(ntohl(bootp.broadcast.i.s_addr) - 1);
/* convert addresses from binary to text form */
if (inet_ntop(AF_INET, &network.address.i, network.address.c, INET_ADDRSTRLEN) != NULL &&
inet_ntop(AF_INET, &network.netmask.i, network.netmask.c, INET_ADDRSTRLEN) != NULL &&
inet_ntop(AF_INET, &network.broadcast.i, network.broadcast.c, INET_ADDRSTRLEN) != NULL &&
inet_ntop(AF_INET, &network.netaddress.i, network.netaddress.c, INET_ADDRSTRLEN) != NULL &&
inet_ntop(AF_INET, &dhcp.minhost.i, dhcp.minhost.c, INET_ADDRSTRLEN) != NULL &&
inet_ntop(AF_INET, &dhcp.maxhost.i, dhcp.maxhost.c, INET_ADDRSTRLEN) != NULL &&
inet_ntop(AF_INET, &bootp.minhost.i, bootp.minhost.c, INET_ADDRSTRLEN) != NULL &&
inet_ntop(AF_INET, &bootp.maxhost.i, bootp.maxhost.c, INET_ADDRSTRLEN) != NULL) {
/* print information */
if (verbose) {
int pad = strlen(dhcp.minhost.c) > strlen(bootp.minhost.c) ?
strlen(dhcp.minhost.c) : strlen(bootp.minhost.c);
printf( "Interface: %s\n"
"Domain: %s\n"
"Host Address: %s\n"
"Network: %s\n"
"Broadcast: %s\n"
"Netmask: %s\n"
"Hosts DHCP: %-*s - %s\n"
"Hosts BOOTP: %-*s - %s\n",
interface, domainname,
network.address.c, network.netaddress.c,
network.broadcast.c, network.netmask.c,
pad, dhcp.minhost.c, dhcp.maxhost.c,
pad, bootp.minhost.c, bootp.maxhost.c);
}
/* open the template for reading */
if ((templatefile = fopen(templatefilename, "r")) != NULL) {
/* seek to the and so we know the file size */
fseek(templatefile, 0, SEEK_END);
fsize = ftell(templatefile);
fseek(templatefile, 0, SEEK_SET);
/* allocate memory and read file */
template = malloc(fsize + 1);
if ((fread(template, fsize, 1, templatefile)) != 1) {
fprintf(stderr, "Failed reading config template.\n");
goto out;
}
fclose(templatefile);
template[fsize] = 0;
} else {
fprintf(stderr, "Failed opening config template for reading.\n"
"Using fallback to built in defaults, functionality is limited.\n");
template = strdup(FALLBACKCONFIG);
}
/* replace strings with real values */
for (tmp = template; *tmp;) {
if (*tmp == '_') {
if (replace(&config, &length, &tmp, "__INTERFACE__", interface) ||
replace(&config, &length, &tmp, "__VERSION__", VERSION) ||
replace(&config, &length, &tmp, "__HOSTNAME__", hostname) ||
replace(&config, &length, &tmp, "__DOMAINNAME__", domainname) ||
replace(&config, &length, &tmp, "__ADDRESS__", network.address.c) ||
replace(&config, &length, &tmp, "__NETADDRESS__", network.netaddress.c) ||
replace(&config, &length, &tmp, "__BROADCAST__", network.broadcast.c) ||
replace(&config, &length, &tmp, "__NETMASK__", network.netmask.c) ||
replace(&config, &length, &tmp, "__MINDHCP__", dhcp.minhost.c) ||
replace(&config, &length, &tmp, "__MAXDHCP__", dhcp.maxhost.c) ||
replace(&config, &length, &tmp, "__MINBOOTP__", bootp.minhost.c) ||
replace(&config, &length, &tmp, "__MAXBOOTP__", bootp.maxhost.c)) {
/* do nothing, work has been done */
} else {
config = realloc(config, length + 1);
config[length++] = *tmp++;
}
} else {
config = realloc(config, length + 1);
config[length++] = *tmp++;
}
}
config = realloc(config, length + 1);
config[length++] = 0;
/* get new filename and open file for writing */
if (configfilename == NULL) {
configfilename = malloc(strlen(CONFIG_OUTPUT) + strlen(interface) + 1);
sprintf(configfilename, CONFIG_OUTPUT, interface);
}
/* try to open the config file for writing */
if ((configfile = fopen(configfilename, "w")) == NULL) {
fprintf(stderr, "Failed opening config file '%s' for writing.\n", configfilename);
goto out;
}
/* actually write the final configuration to file and close it */
fputs(config, configfile);
fclose(configfile);
/* get name for pidfile */
if (pidfile == NULL) {
pidfile = malloc(strlen(PIDFILE) + strlen(interface) + 1);
sprintf(pidfile, PIDFILE, interface);
}
/* get name for leases file */
if (leasesfile == NULL) {
leasesfile = malloc(strlen(LEASESFILE) + strlen(interface) + 1);
sprintf(leasesfile, LEASESFILE, interface);
}
/* check if leases file exists, create it if it does not */
if (access(leasesfile, R_OK) == -1) {
if (verbose)
printf("Creating leases file '%s'.\n", leasesfile);
fclose(fopen(leasesfile, "w"));
}
/* get use name */
if (username == NULL)
username = USER;
/* execute dhcp daemon, replace the current process
* dyndhcpd is cleared from memory here and code below is not execuded if
* everything goes well */
if (verbose > 1)
printf("Running: dhcpd -f -q -4 -user %s -pf %s -lf %s -cf %s %s\n",
username, pidfile, leasesfile, configfilename, interface);
rc = execlp(DHCPDFILE, "dhcpd", "-f", "-q", "-4", "-user", username,
"-pf", pidfile, "-lf", leasesfile, "-cf", configfilename, interface, NULL);
fprintf(stderr, "The dhcp daemon failed to execute.\n");
goto out;
} else {
/* failed to convert addresses from binary to string */
fprintf(stderr, "Failed converting number to string\n");
goto out;
}
}
/* we did not find an interface to work with */
fprintf(stderr, "Interface not found, link down or no address.\n");
out:
/* free memory */
if (leasesfile != NULL)
free(leasesfile);
if (pidfile != NULL)
free(pidfile);
if (configfilename != NULL)
free(configfilename);
if (config != NULL)
free(config);
if (template != NULL)
free(template);
if (ifaddr != NULL)
freeifaddrs(ifaddr);
return rc;
}
// vim: set syntax=c: