llmnrd: Don't enumerate and store IPv6 addresses if IPv6 is disabled

Currently IPv6 addresses are always enumerated via RTNL socket and then
stored internally, even if llmnrd was started without the IPv6 command
line option '-6'. Even though no queries on AF_INET6 sockets will be
answered, this behavior might be confusing. Especially due to messages
like:

  Added IPv6 address fe80::f0eb:aaff:feb3:ae58 on interface tap0

being logged.

Explicitely disable IPv6 address enumeration on the RTNL socket to fix
this behavior.

Closes #8

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

5 files changed, 21 insertions, 13 deletions

diff --git a/iface.c b/iface.c
index 9664a0c..8cb88fc 100644
--- a/iface.c
+++ b/iface.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2015 Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2015-2016 Tobias Klauser <tklauser@distanz.ch>
  *
  * This file is part of llmnrd.
  *
@@ -41,6 +41,7 @@
 #include "iface.h"
 
 static bool iface_running = true;
+static bool iface_ipv6 = false;
 static pthread_t iface_thread;
 static iface_event_handler_t iface_event_handler;
 
@@ -349,15 +350,17 @@ int iface_run(void)
 		return -1;
 	}
 
-	sock = socket_open_rtnl();
+	sock = socket_open_rtnl(iface_ipv6);
 	if (sock < 0)
 		return -1;
 
 	/* send RTM_GETADDR request to initially populate the interface list */
 	if (iface_rtnl_enumerate(sock, RTM_GETADDR, AF_INET) < 0)
 		goto out;
-	if (iface_rtnl_enumerate(sock, RTM_GETADDR, AF_INET6) < 0)
-		goto out;
+	if (iface_ipv6) {
+		if (iface_rtnl_enumerate(sock, RTM_GETADDR, AF_INET6) < 0)
+			goto out;
+	}
 
 	while (iface_running) {
 		ssize_t recvlen;
@@ -385,8 +388,10 @@ static void* iface_run_wrapper(void *data __unused)
 	return ERR_PTR(iface_run());
 }
 
-int iface_start_thread(void)
+int iface_start_thread(bool ipv6)
 {
+	iface_ipv6 = ipv6;
+
 	if (pthread_create(&iface_thread, NULL, iface_run_wrapper, NULL) < 0) {
 		log_err("Failed to start interface monitoring thread\n");
 		return -1;
diff --git a/iface.h b/iface.h
index 47321d5..5032d87 100644
--- a/iface.h
+++ b/iface.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2015 Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2015-2016 Tobias Klauser <tklauser@distanz.ch>
  *
  * This file is part of llmnrd.
  *
@@ -19,6 +19,7 @@
 #ifndef IFACE_H
 #define IFACE_H
 
+#include <stdbool.h>
 #include <sys/socket.h>
 
 enum iface_event_type {
@@ -30,7 +31,7 @@ typedef void (*iface_event_handler_t)(enum iface_event_type, unsigned char af,
 				      unsigned int ifindex);
 
 void iface_register_event_handler(iface_event_handler_t event_handler);
-int iface_start_thread(void);
+int iface_start_thread(bool ipv6);
 void iface_stop(void);
 
 size_t iface_addr_lookup(unsigned int ifindex, unsigned char family,
diff --git a/llmnrd.c b/llmnrd.c
index 48e4030..866e919 100644
--- a/llmnrd.c
+++ b/llmnrd.c
@@ -167,7 +167,7 @@ int main(int argc, char **argv)
 	if (llmnr_init(hostname, port, ipv6) < 0)
 		goto out;
 
-	if (iface_start_thread() < 0)
+	if (iface_start_thread(ipv6) < 0)
 		goto out;
 
 	ret = llmnr_run();
diff --git a/socket.c b/socket.c
index 872796d..21e715a 100644
--- a/socket.c
+++ b/socket.c
@@ -136,7 +136,7 @@ err:
 	return -1;
 }
 
-int socket_open_rtnl(void)
+int socket_open_rtnl(bool ipv6)
 {
 	int sock;
 	struct sockaddr_nl sa;
@@ -153,9 +153,11 @@ int socket_open_rtnl(void)
 	 * listen for following events:
 	 * - network interface create/delete/up/down
 	 * - IPv4 address add/delete
-	 * - IPv6 address add/delete
+	 * - IPv6 address add/delete (if enabled)
 	 */
-	sa.nl_groups = RTMGRP_LINK | RTMGRP_IPV4_IFADDR | RTMGRP_IPV6_IFADDR;
+	sa.nl_groups = RTMGRP_LINK | RTMGRP_IPV4_IFADDR;
+	if (ipv6)
+		sa.nl_groups |= RTMGRP_IPV6_IFADDR;
 
 	if (bind(sock, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
 		log_err("Failed to bind() netlink socket: %s\n", strerror(errno));
diff --git a/socket.h b/socket.h
index bb555c8..93c41a0 100644
--- a/socket.h
+++ b/socket.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2014-2015 Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2014-2016 Tobias Klauser <tklauser@distanz.ch>
  *
  * This file is part of llmnrd.
  *
@@ -24,7 +24,7 @@
 
 int socket_open_ipv4(uint16_t port);
 int socket_open_ipv6(uint16_t port);
-int socket_open_rtnl(void);
+int socket_open_rtnl(bool ipv6);
 
 int socket_mcast_group_ipv4(int sock, unsigned int ifindex, bool join);
 int socket_mcast_group_ipv6(int sock, unsigned int ifindex, bool join);