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Diffstat (limited to 'dyndhcpd.c')
-rw-r--r--dyndhcpd.c35
1 files changed, 33 insertions, 2 deletions
diff --git a/dyndhcpd.c b/dyndhcpd.c
index e7b7bf9..20f043f 100644
--- a/dyndhcpd.c
+++ b/dyndhcpd.c
@@ -67,7 +67,9 @@ int main(int argc, char ** argv) {
struct sockaddr_in * s4;
struct in_addr * v_host, * v_mask;
struct in_addr s_broadcast, s_netaddress, s_minhost, s_maxhost;
- char c_address[INET_ADDRSTRLEN], c_netmask[INET_ADDRSTRLEN], c_netaddress[INET_ADDRSTRLEN], c_broadcast[INET_ADDRSTRLEN], c_minhost[INET_ADDRSTRLEN], c_maxhost[INET_ADDRSTRLEN];
+ char c_address[INET_ADDRSTRLEN], c_netmask[INET_ADDRSTRLEN],
+ c_netaddress[INET_ADDRSTRLEN], c_broadcast[INET_ADDRSTRLEN],
+ c_minhost[INET_ADDRSTRLEN], c_maxhost[INET_ADDRSTRLEN];
char * interface = NULL;
char hostname[254];
@@ -81,6 +83,7 @@ int main(int argc, char ** argv) {
printf("Starting dyndhcpd/" VERSION " (compiled: " __DATE__ ", " __TIME__ ")\n");
+ /* get command line options */
for (i = 1; i < argc; i++) {
switch ((int)argv[i][0]) {
case '-':
@@ -106,11 +109,13 @@ int main(int argc, char ** argv) {
}
}
+ /* bail if we are not root */
if (getuid() > 0) {
fprintf(stderr, "You need to be root!\n");
goto out;
}
+ /* get the domainname */
gethostname(hostname, 254);
hp = gethostbyname(hostname);
if ((domainname = strchr(hp->h_name, '.')) != NULL)
@@ -120,17 +125,21 @@ int main(int argc, char ** argv) {
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)
@@ -149,33 +158,42 @@ int main(int argc, char ** argv) {
if (!(ifa->ifa_flags & IFF_RUNNING))
fprintf(stderr, "Warning: Interface %s is not connected.\n", interface);
+ /* get variables in place for address */
s4 = (struct sockaddr_in *)ifa->ifa_addr;
v_host = &s4->sin_addr;
+ /* convert address from binary to text form */
if (!inet_ntop(ifa->ifa_addr->sa_family, v_host, c_address, INET_ADDRSTRLEN))
fprintf(stderr, "%s: inet_ntop failed!\n", ifa->ifa_name);
+ /* get variables in place for netmask */
s4 = (struct sockaddr_in *)ifa->ifa_netmask;
v_mask = &s4->sin_addr;
+ /* convert netmask from binary to text form */
if (!inet_ntop(ifa->ifa_netmask->sa_family, v_mask, c_netmask, INET_ADDRSTRLEN))
fprintf(stderr, "%s: inet_ntop failed!\n", ifa->ifa_name);
+ /* calculate broadcast and net address */
s_broadcast.s_addr = v_host->s_addr |~ v_mask->s_addr;
s_netaddress.s_addr = v_host->s_addr & v_mask->s_addr;
+ /* check if subnet has enough addresses */
if (ntohl(s_broadcast.s_addr) - ntohl(s_netaddress.s_addr) < 2) {
fprintf(stderr, "We do not have addresses to serve, need a netmask with 30 bit minimum.\n");
goto out;
}
+ /* calculate min and max host */
s_minhost.s_addr = htonl(ntohl(s_netaddress.s_addr) + 1);
s_maxhost.s_addr = htonl(ntohl(s_broadcast.s_addr) - 1);
+ /* convert missing addresses from binary to text form */
if (inet_ntop(AF_INET, &s_broadcast, c_broadcast, INET_ADDRSTRLEN) != NULL &&
inet_ntop(AF_INET, &s_netaddress, c_netaddress, INET_ADDRSTRLEN) != NULL &&
inet_ntop(AF_INET, &s_minhost, c_minhost, INET_ADDRSTRLEN) != NULL &&
inet_ntop(AF_INET, &s_maxhost, c_maxhost, INET_ADDRSTRLEN) != NULL) {
+ /* print information */
printf("Interface: %s\n"
"Domain: %s\n"
"Host Address: %s\n"
@@ -185,15 +203,18 @@ int main(int argc, char ** argv) {
"Hosts: %s - %s\n", interface, domainname, c_address, c_netaddress, c_broadcast, c_netmask, c_minhost, c_maxhost);
- /* read the template */
+ /* open the template for reading */
if ((configfile = fopen(CONFIG_TEMPLATE, "r")) == NULL) {
fprintf(stderr, "Failed opening config template for reading.\n");
goto out;
}
+
+ /* seek to the and so we know the file size */
fseek(configfile, 0, SEEK_END);
fsize = ftell(configfile);
fseek(configfile, 0, SEEK_SET);
+ /* allocate memory and read file */
config = malloc(fsize + 1);
if ((fread(config, fsize, 1, configfile)) != 1) {
fprintf(stderr, "Failed reading config template.\n");
@@ -202,6 +223,7 @@ int main(int argc, char ** argv) {
fclose(configfile);
config[fsize] = 0;
+ /* replace strings with real values */
if ((config = str_replace(config, "__INTERFACE__", interface)) == NULL)
goto out;
if ((config = str_replace(config, "__VERSION__", VERSION)) == NULL)
@@ -221,28 +243,37 @@ int main(int argc, char ** argv) {
if ((config = str_replace(config, "__MAXHOST__", c_maxhost)) == NULL)
goto out;
+ /* get new filename and open file for writing */
filename = malloc(strlen(CONFIG_OUTPUT) + strlen(interface) + 1);
sprintf(filename, CONFIG_OUTPUT, interface);
if ((configfile = fopen(filename, "w")) == NULL) {
fprintf(stderr, "Failed opening config file for writing.\n");
goto out;
}
+
+ /* actually write the final configuration to file and close it */
fputs(config, configfile);
fclose(configfile);
+ /* execute dhcp daemon, replace the current process
+ * dyndhcpd is cleared from memory here and code below is not execuded if
+ * everything goes well */
execlp("/usr/bin/dhcpd", "dhcpd", "-f", "-d", "-q", "-4", "-cf", filename, interface, NULL);
rc = EXIT_SUCCESS;
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 (filename != NULL)
free(filename);
if (config != NULL)
generated by cgit v1.2.3-70-g09d2 (git 2.47.0) at 2024-11-21 23:19:58 +0000