llmnrd: don't exit on SO_BINDTODEVICE failure

The -i option requires running llmnrd as root for SO_BINDTODEVICE to
work. Packets are still filtered based on interface because only rtnl
messages for addresses of the specified interface are considered in
iface_nlmsg_change_addr. Instead log a warning only if SO_BINDTODEVICE
fails.

Signed-off-by: Jon Franklin <jvfranklin@gmail.com>
[tk: small adjustments to commit message, check return value of iface_init]
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

4 files changed, 17 insertions, 12 deletions

diff --git a/iface.c b/iface.c
index bcbca49..ab80063 100644
--- a/iface.c
+++ b/iface.c
@@ -319,18 +319,24 @@ static void iface_rtnl_enumerate(int sock, uint16_t type, unsigned char family)
 		log_err("Failed to enumerate rtnl interfaces: %s\n", strerror(errno));
 }
 
-void iface_init(int sock, const char *iface, bool ipv6,
+int iface_init(int sock, const char *iface, bool ipv6,
 		iface_event_handler_t event_handler)
 {
 	INIT_LIST_HEAD(&iface_list_head);
 	iface_event_handler = event_handler;
-	if (iface)
+	if (iface) {
 		iface_ifindex = if_nametoindex(iface);
+		if (!iface_ifindex) {
+			log_err("Interface %s not found: %s\n", iface, strerror(errno));
+			return -1;
+		}
+	}
 
 	/* send RTM_GETADDR request to initially populate the interface list */
 	iface_rtnl_enumerate(sock, RTM_GETADDR, AF_INET);
 	if (ipv6)
 		iface_rtnl_enumerate(sock, RTM_GETADDR, AF_INET6);
+	return 0;
 }
 
 int iface_recv(int sock)
diff --git a/iface.h b/iface.h
index a8eb92c..00a39ce 100644
--- a/iface.h
+++ b/iface.h
@@ -30,7 +30,7 @@ enum iface_event_type {
 typedef void (*iface_event_handler_t)(enum iface_event_type, unsigned char af,
 				      unsigned int ifindex);
 
-void iface_init(int sock, const char *iface, bool ipv6,
+int iface_init(int sock, const char *iface, bool ipv6,
 		iface_event_handler_t event_handler);
 int iface_recv(int sock);
 
diff --git a/llmnrd.c b/llmnrd.c
index d076484..ba5023c 100644
--- a/llmnrd.c
+++ b/llmnrd.c
@@ -236,7 +236,10 @@ int main(int argc, char **argv)
 		goto out;
 
 	llmnr_init(hostname, ipv6);
-	iface_init(llmnrd_sock_rtnl, iface, ipv6, &iface_event_handle);
+
+	ret = iface_init(llmnrd_sock_rtnl, iface, ipv6, &iface_event_handle);
+	if (ret < 0)
+		goto out;
 
 	nfds = max(llmnrd_sock_ipv4, llmnrd_sock_rtnl);
 	if (llmnrd_sock_ipv6 >= 0)
diff --git a/socket.c b/socket.c
index 73713eb..5f58e76 100644
--- a/socket.c
+++ b/socket.c
@@ -36,7 +36,7 @@
 static const int YES = 1;
 static const int TTL = 255;
 
-static int socket_bind_to_device(int sock, const char *iface) {
+static void socket_bind_to_device(int sock, const char *iface) {
 #ifdef SO_BINDTODEVICE
 	/* bind socket to specific interface */
 	if (iface) {
@@ -45,12 +45,10 @@ static int socket_bind_to_device(int sock, const char *iface) {
 		memset(&ifr, 0, sizeof(ifr));
 		strncpy(ifr.ifr_name, iface, sizeof(ifr.ifr_name) - 1);
 		if (setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, &ifr, sizeof(ifr)) < 0) {
-			log_err("Failed to bind socket to device %s: %s\n", iface, strerror(errno));
-			return -1;
+			log_warn("Failed to bind socket to device %s: %s\n", iface, strerror(errno));
 		}
 	}
 #endif
-	return 0;
 }
 
 int socket_open_ipv4(uint16_t port, const char *iface)
@@ -81,8 +79,7 @@ int socket_open_ipv4(uint16_t port, const char *iface)
 		goto err;
 	}
 
-	if (socket_bind_to_device(sock, iface) < 0)
-		goto err;
+	socket_bind_to_device(sock, iface);
 
 	/* bind the socket */
 	memset(&sa, 0, sizeof(sa));
@@ -140,8 +137,7 @@ int socket_open_ipv6(uint16_t port, const char *iface)
 		goto err;
 	}
 
-	if (socket_bind_to_device(sock, iface) < 0)
-		goto err;
+	socket_bind_to_device(sock, iface);
 
 	/* bind the socket */
 	memset(&sa, 0, sizeof(sa));