dhcpv6c: exportable DUID

src/dhcpv6.c

@@ -25,6 +25,7 @@
 #include <unistd.h>
 #include <syslog.h>
 #include <stdbool.h>
+#include <stdio.h>
 #include <ctype.h>
 #include <sys/time.h>
 #include <sys/ioctl.h>
@@ -194,7 +195,7 @@ static char *dhcpv6_status_code_to_str(uint16_t code)
 	return "Unknown";
 }
 
-int init_dhcpv6(const char *ifname, unsigned int options, int sol_timeout)
+int init_dhcpv6(const char *ifname, unsigned int options, int sol_timeout, const char *duid_path)
 {
 	client_options = options;
 	dhcpv6_retx[DHCPV6_MSG_SOLICIT].max_timeo = sol_timeout;
@@ -247,6 +248,29 @@ int init_dhcpv6(const char *ifname, unsigned int options, int sol_timeout)
 		odhcp6c_add_state(STATE_CLIENT_ID, duid, sizeof(duid));
 	}
 
+	// Write duid to path
+	if (duid_path) {
+		// read duid
+		size_t duid_len;
+		void *duid = odhcp6c_get_state(STATE_CLIENT_ID, &duid_len);
+		char duid_buf[duid_len * 2 + 1];
+		script_hexlify(duid_buf, &((uint8_t *) duid)[4], duid_len - 4);
+		duid_buf[duid_len * 2] = 0;
+
+		// generate path
+		char file_path[strlen(duid_path) + strlen(ifname) + 2];
+		sprintf(file_path, "%s.%s", duid_path, ifname);
+
+		// write to file
+		FILE *fp = fopen(file_path, "w");
+		if (fp) {
+			fprintf(fp, "%s\n", duid_buf);
+			fclose(fp);
+		} else {
+			syslog(LOG_ERR, "Failed to write DUID '%s' into file '%s'!", duid_buf, file_path);
+		};
+	}
+
 	// Create ORO
 	if (!(client_options & DHCPV6_STRICT_OPTIONS)) {
 		uint16_t oro[] = {

src/odhcp6c.c

@@ -169,6 +169,7 @@ int main(_unused int argc, char* const argv[])
 	// Allocate resources
 	const char *pidfile = NULL;
 	const char *script = "/usr/sbin/odhcp6c-update";
+	const char *duid_path = "/var/run/odhcp6c-duid";
 	ssize_t l;
 	uint8_t buf[134], *o_data;
 	char *optpos;
@@ -187,7 +188,7 @@ int main(_unused int argc, char* const argv[])
 	unsigned int ra_options = RA_RDNSS_DEFAULT_LIFETIME;
 	unsigned int ra_holdoff_interval = RA_MIN_ADV_INTERVAL;
 
-	while ((c = getopt(argc, argv, "S::DN:V:P:FB:c:i:r:Ru:Ux:s:kt:m:Lhedp:fav")) != -1) {
+	while ((c = getopt(argc, argv, "S::DN:V:P:FB:c:C:i:r:Ru:Ux:s:kt:m:Lhedp:fav")) != -1) {
 		switch (c) {
 		case 'S':
 			allow_slaac_only = (optarg) ? atoi(optarg) : -1;
@@ -284,6 +285,10 @@ int main(_unused int argc, char* const argv[])
 				help = true;
 			break;
 
+		case 'C':
+			duid_path = optarg;
+			break;
+
 		case 'i':
 			if (inet_pton(AF_INET6, optarg, &ifid) != 1)
 				help = true;
@@ -417,7 +422,7 @@ int main(_unused int argc, char* const argv[])
 	signal(SIGUSR2, sighandler);
 
 	if ((urandom_fd = open("/dev/urandom", O_CLOEXEC | O_RDONLY)) < 0 ||
-			init_dhcpv6(ifname, client_options, sol_timeout) ||
+			init_dhcpv6(ifname, client_options, sol_timeout, duid_path) ||
 			ra_init(ifname, &ifid, ra_options, ra_holdoff_interval) ||
 			script_init(script, ifname)) {
 		syslog(LOG_ERR, "failed to initialize: %s", strerror(errno));
@@ -620,6 +625,7 @@ static int usage(void)
 	"			-x 0x1f4:ABBA - option 500\n"
 	"			-x 202:'\"file\"' - option 202\n"
 	"	-c <clientid>	Override client-ID (base-16 encoded 16-bit type + value)\n"
+	"	-C <path>	Export used client-ID to specified path\n"
 	"	-i <iface-id>	Use a custom interface identifier for RA handling\n"
 	"	-r <options>	Options to be requested (comma-separated)\n"
 	"	-R		Do not request any options except those specified with -r\n"

src/odhcp6c.h

@@ -392,7 +392,7 @@ struct odhcp6c_opt {
 	const char *str;
 };
 
-int init_dhcpv6(const char *ifname, unsigned int client_options, int sol_timeout);
+int init_dhcpv6(const char *ifname, unsigned int client_options, int sol_timeout, const char *duid_path);
 int dhcpv6_set_ia_mode(enum odhcp6c_ia_mode na, enum odhcp6c_ia_mode pd, bool stateful_only);
 int dhcpv6_request(enum dhcpv6_msg type);
 int dhcpv6_poll_reconfigure(void);
@@ -408,6 +408,7 @@ int ra_get_reachable(void);
 int ra_get_retransmit(void);
 
 int script_init(const char *path, const char *ifname);
+void script_hexlify(char *dst, const uint8_t *src, size_t len);
 ssize_t script_unhexlify(uint8_t *dst, size_t len, const char *src);
 void script_call(const char *status, int delay, bool resume);
 

src/script.c

@@ -84,7 +84,7 @@ ssize_t script_unhexlify(uint8_t *dst, size_t len, const char *src)
 	return c;
 }
 
-static void script_hexlify(char *dst, const uint8_t *src, size_t len)
+void script_hexlify(char *dst, const uint8_t *src, size_t len)
 {
 	for (size_t i = 0; i < len; ++i) {
 		*dst++ = hexdigits[src[i] >> 4];