llmnrd: Join IP multicast group on each new interface

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

5 files changed, 70 insertions, 27 deletions

diff --git a/iface.c b/iface.c
index 510a0c4..5d0117e 100644
--- a/iface.c
+++ b/iface.c
@@ -41,6 +41,7 @@
 
 static bool iface_running = true;
 static pthread_t iface_thread;
+static iface_event_handler_t iface_event_handler;
 
 struct iface_record {
 	struct list_head list;
@@ -198,7 +199,7 @@ static void iface_nlmsg_change_addr(const struct nlmsghdr *nlh)
 	rta = (const struct rtattr *)((const uint8_t *)nlh + NLMSG_SPACE(sizeof(*ifa)));
 	for ( ; RTA_OK(rta, rtalen); rta = RTA_NEXT(rta, rtalen)) {
 		char ifname[IF_NAMESIZE];
-		const char *action;
+		enum iface_event_type type;
 
 		switch (rta->rta_type) {
 		case IFA_ADDRESS:
@@ -207,17 +208,21 @@ static void iface_nlmsg_change_addr(const struct nlmsghdr *nlh)
 
 			if (nlh->nlmsg_type == RTM_NEWADDR) {
 				iface_addr_add(index, ifa->ifa_family, RTA_DATA(rta));
-				action = "Added";
+				type = IFACE_ADD;
 			} else if (nlh->nlmsg_type == RTM_DELADDR) {
 				iface_addr_del(index, ifa->ifa_family, RTA_DATA(rta));
-				action = "Deleted";
+				type = IFACE_DEL;
 			} else {
 				/* This case shouldn't occur */
 				continue;
 			}
 
+			if (iface_event_handler)
+				(*iface_event_handler)(type, ifa->ifa_family, ifa->ifa_index);
+
 			log_info("%s IPv%c address %s on interface %s\n",
-				 action, ifa->ifa_family == AF_INET ? '4' : '6', addr,
+				 type == IFACE_ADD ? "Added" : "Deleted",
+				 ifa->ifa_family == AF_INET ? '4' : '6', addr,
 				 if_indextoname(ifa->ifa_index, ifname));
 		}
 	}
@@ -290,6 +295,11 @@ static int iface_rtnl_enumerate(int sock, int type, int family)
 	return iface_nlmsg_process((const struct nlmsghdr *)pktbuf, recvlen);
 }
 
+void iface_register_event_handler(iface_event_handler_t event_handler)
+{
+	iface_event_handler = event_handler;
+}
+
 int iface_run(void)
 {
 	int ret = -1;
diff --git a/iface.h b/iface.h
index 952b58e..cdcf716 100644
--- a/iface.h
+++ b/iface.h
@@ -21,10 +21,18 @@
 
 #include <sys/socket.h>
 
-size_t iface_addr_lookup(unsigned int ifindex, unsigned char family, 
-			 struct sockaddr_storage *addrs, size_t addrs_size);
+enum iface_event_type {
+	IFACE_ADD,
+	IFACE_DEL,
+};
+
+typedef void (*iface_event_handler_t)(enum iface_event_type, int af, unsigned int ifindex);
 
+void iface_register_event_handler(iface_event_handler_t event_handler);
 int iface_start_thread(void);
 void iface_stop(void);
 
+size_t iface_addr_lookup(unsigned int ifindex, unsigned char family,
+			 struct sockaddr_storage *addrs, size_t addrs_size);
+
 #endif /* IFACE_H */
diff --git a/llmnr.c b/llmnr.c
index 92eb562..01f25d9 100644
--- a/llmnr.c
+++ b/llmnr.c
@@ -32,15 +32,49 @@
 #include "pkt.h"
 #include "socket.h"
 
+#include "iface.h"
 #include "llmnr-packet.h"
 #include "llmnr.h"
 
+static int llmnr_sock = -1;
+static int llmnr_sock_v6 = -1;
 static bool llmnr_running = true;
 /*
  * Host name in DNS name format (length octet + name + 0 byte)
  */
 static char llmnr_hostname[LLMNR_LABEL_MAX_SIZE + 2];
 
+static void llmnr_iface_event_handle(enum iface_event_type type, int af, unsigned int ifindex)
+{
+	switch (af) {
+	case AF_INET:
+		socket_mcast_group_ipv4(llmnr_sock, ifindex, type == IFACE_ADD);
+		break;
+	case AF_INET6:
+		socket_mcast_group_ipv6(llmnr_sock_v6, ifindex, type == IFACE_ADD);
+		break;
+	default:
+		/* ignore */
+		break;
+	}
+}
+
+int llmnr_init(const char *hostname, uint16_t port)
+{
+	llmnr_hostname[0] = strlen(hostname);
+	strncpy(&llmnr_hostname[1], hostname, LLMNR_LABEL_MAX_SIZE);
+	llmnr_hostname[LLMNR_LABEL_MAX_SIZE + 1] = '\0';
+	log_info("Starting llmnrd on port %u, hostname %s\n", port, hostname);
+
+	llmnr_sock = socket_open_ipv4(port);
+	if (llmnr_sock < 0)
+		return -1;
+
+	iface_register_event_handler(&llmnr_iface_event_handle);
+
+	return 0;
+}
+
 static bool llmnr_name_matches(const uint8_t *query)
 {
 	uint8_t i, n = llmnr_hostname[0];
@@ -201,22 +235,9 @@ static void llmnr_packet_process(unsigned int ifindex, const uint8_t *pktbuf, si
 		llmnr_respond(ifindex, hdr, query, query_len, sock, sa);
 }
 
-int llmnr_run(const char *hostname, uint16_t port)
+int llmnr_run(void)
 {
 	int ret = -1;
-	int sock;
-
-	if (port == 0)
-		port = LLMNR_UDP_PORT;
-
-	llmnr_hostname[0] = strlen(hostname);
-	strncpy(&llmnr_hostname[1], hostname, LLMNR_LABEL_MAX_SIZE);
-	llmnr_hostname[LLMNR_LABEL_MAX_SIZE + 1] = '\0';
-	log_info("Listening on port %u, hostname %s\n", port, hostname);
-
-	sock = socket_open_v4(port);
-	if (sock < 0)
-		return -1;
 
 	while (llmnr_running) {
 		uint8_t pktbuf[2048], aux[128];
@@ -238,7 +259,7 @@ int llmnr_run(const char *hostname, uint16_t port)
 		msg.msg_control = aux;
 		msg.msg_controllen = sizeof(aux);
 
-		if ((recvlen = recvmsg(sock, &msg, 0)) < 0) {
+		if ((recvlen = recvmsg(llmnr_sock, &msg, 0)) < 0) {
 			if (errno != EINTR)
 				log_err("Failed to receive packet: %s\n", strerror(errno));
 			goto out;
@@ -251,12 +272,12 @@ int llmnr_run(const char *hostname, uint16_t port)
 			}
 		}
 
-		llmnr_packet_process(ifindex, pktbuf, recvlen, sock, (const struct sockaddr *)&saddr_r);
+		llmnr_packet_process(ifindex, pktbuf, recvlen, llmnr_sock, (const struct sockaddr *)&saddr_r);
 	}
 
 	ret = 0;
 out:
-	close(sock);
+	close(llmnr_sock);
 	return ret;
 }
 
diff --git a/llmnr.h b/llmnr.h
index 35050b2..cc515f1 100644
--- a/llmnr.h
+++ b/llmnr.h
@@ -21,7 +21,8 @@
 
 #include <stdint.h>
 
-int llmnr_run(const char *hostname, uint16_t port);
+int llmnr_init(const char *hostname, uint16_t port);
+int llmnr_run(void);
 void llmnr_stop(void);
 
 #endif /* LLMNR_H */
diff --git a/llmnrd.c b/llmnrd.c
index 5b1a4ea..4da5c4e 100644
--- a/llmnrd.c
+++ b/llmnrd.c
@@ -108,7 +108,7 @@ int main(int argc, char **argv)
 	int c, ret = EXIT_FAILURE;
 	long num_arg;
 	bool daemonize = false;
-	char *hostname = "";
+	char *hostname = NULL;
 	uint16_t port = LLMNR_UDP_PORT;
 
 	while ((c = getopt_long(argc, argv, short_opts, long_opts, NULL)) != -1) {
@@ -140,7 +140,7 @@ int main(int argc, char **argv)
 	register_signal(SIGTERM, signal_handler);
 	register_signal(SIGHUP, signal_handler);
 
-	if (hostname[0] == '\0') {
+	if (!hostname) {
 		/* TODO: Consider hostname changing at runtime */
 		hostname = xmalloc(255);
 		if (gethostname(hostname, 255) != 0) {
@@ -156,10 +156,13 @@ int main(int argc, char **argv)
 		}
 	}
 
+	if (llmnr_init(hostname, port) < 0)
+		goto out;
+
 	if (iface_start_thread() < 0)
 		goto out;
 
-	ret = llmnr_run(hostname, port);
+	ret = llmnr_run();
 out:
 	free(hostname);
 	return ret;