From: John Crispin <blogic@openwrt.org>
Date: Tue, 27 May 2014 17:16:10 +0000 (+0100)
Subject: make the code work for bridge interfaces
X-Git-Url: https://git.archive.openwrt.org/?p=project%2Fmdnsd.git;a=commitdiff_plain;h=8381f595a6066f893cc24e8a161e27a10a140cf0

make the code work for bridge interfaces

Signed-off-by: John Crispin <blogic@openwrt.org>
---

diff --git a/dns.c b/dns.c
index 1d8a830..ecfaa63 100644
--- a/dns.c
+++ b/dns.c
@@ -67,12 +67,16 @@ dns_type_string(uint16_t type)
 void
 dns_send_question(struct uloop_fd *u, char *question, int type)
 {
+	size_t cmsg_data[( CMSG_SPACE(sizeof(struct in_pktinfo)) / sizeof(size_t)) + 1];
 	unsigned char buffer[MAX_NAME_LEN];
 	struct dns_header h = { 0 };
 	struct dns_question q = { 0 };
 	struct msghdr m = { 0 };
 	struct iovec iov[3] = { {0}, {0}, {0} };
 	struct sockaddr_in a = { 0 };
+	struct in_pktinfo *pkti;
+	struct cmsghdr *cmsg;
+	struct in_addr in;
 	int len;
 
 	a.sin_family = AF_INET;
@@ -92,6 +96,20 @@ dns_send_question(struct uloop_fd *u, char *question, int type)
 	m.msg_iov = iov;
 	m.msg_iovlen = 3;
 
+	memset(cmsg_data, 0, sizeof(cmsg_data));
+	m.msg_control = cmsg_data;
+	m.msg_controllen = CMSG_LEN(sizeof(struct in_pktinfo));
+
+	cmsg = CMSG_FIRSTHDR(&m);
+	cmsg->cmsg_len = m.msg_controllen;
+	cmsg->cmsg_level = IPPROTO_IP;
+	cmsg->cmsg_type = IP_PKTINFO;
+
+	inet_aton(iface_ip, &in);
+
+	pkti = (struct in_pktinfo*) CMSG_DATA(cmsg);
+	pkti->ipi_ifindex = iface_index;
+
 	iov[0].iov_base = &h;
 	iov[0].iov_len = sizeof(struct dns_header);
 
diff --git a/main.c b/main.c
index a6c99b5..cc17903 100644
--- a/main.c
+++ b/main.c
@@ -42,6 +42,7 @@
 static struct uloop_timeout reconnect;
 char *iface_name = "eth0";
 const char *iface_ip;
+int iface_index;
 
 static int
 parse_answer(struct uloop_fd *u, uint8_t *buffer, int len, uint8_t **b, int *rlen, int cache)
@@ -185,7 +186,6 @@ reconnect_socket(struct uloop_timeout *timeout)
 
 		uloop_fd_add(&listener, ULOOP_READ);
 		sleep(5);
-		dns_send_question(&listener, "_services._dns-sd._tcp.local", TYPE_PTR);
 		dns_send_question(&listener, "_services._dns-sd._udp.local", TYPE_PTR);
 		announce_init(&listener);
 	}
@@ -226,7 +226,15 @@ main(int argc, char **argv)
 		fprintf(stderr, "failed to read ip for %s\n", iface_name);
 		return -1;
 	}
-	fprintf(stderr, "interface %s has ip %s\n", iface_name, iface_ip);
+
+	iface_index = get_iface_index(iface_name);
+
+	if (!iface_index) {
+		fprintf(stderr, "failed to read index for %s\n", iface_name);
+		return -1;
+	}
+
+	fprintf(stderr, "interface %s has ip %s and index %d\n", iface_name, iface_ip, iface_index);
 	signal_setup();
 
 	if (dns_init())
diff --git a/util.c b/util.c
index a4a117b..1708a40 100644
--- a/util.c
+++ b/util.c
@@ -98,6 +98,28 @@ get_iface_ipv4(const char *ifname)
 	return ret;
 }
 
+int
+get_iface_index(const char *ifname)
+{
+	struct ifreq ir;
+	int sock;
+
+	sock = socket(AF_INET, SOCK_DGRAM, 0);
+	if (sock < 0)
+		return 0;
+
+	memset(&ir, 0, sizeof(struct ifreq));
+
+	strncpy(ir.ifr_name, ifname, sizeof(ir.ifr_name));
+
+	if (ioctl(sock, SIOCGIFINDEX, &ir) < 0)
+		return 0;
+
+	close(sock);
+
+	return ir.ifr_ifindex;
+}
+
 char*
 get_hostname(void)
 {
@@ -116,15 +138,19 @@ socket_setup(int fd, const char *ip)
 	uint8_t ttl = 255;
 	int yes = 1;
 	int no = 0;
-	struct sockaddr_in sa;
+	struct sockaddr_in sa = { 0 };
+	struct in_addr in;
+
+	inet_aton(iface_ip, &in);
 
 	sa.sin_family = AF_INET;
 	sa.sin_port = htons(MCAST_PORT);
 	inet_pton(AF_INET, MCAST_ADDR, &sa.sin_addr);
 
 	memset(&mreq, 0, sizeof(mreq));
-	mreq.imr_address.s_addr = htonl(INADDR_ANY);
+	mreq.imr_address.s_addr = in.s_addr;
 	mreq.imr_multiaddr = sa.sin_addr;
+	mreq.imr_ifindex = iface_index;
 
 	if (setsockopt(fd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl)) < 0)
 		fprintf(stderr, "ioctl failed: IP_MULTICAST_TTL\n");
@@ -132,6 +158,13 @@ socket_setup(int fd, const char *ip)
 	if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes)) < 0)
 		fprintf(stderr, "ioctl failed: SO_REUSEADDR\n");
 
+	/* Some network drivers have issues with dropping membership of
+	 * mcast groups when the iface is down, but don't allow rejoining
+	 * when it comes back up. This is an ugly workaround
+	 * -- this was copied from avahi --
+	 */
+	setsockopt(fd, IPPROTO_IP, IP_DROP_MEMBERSHIP, &mreq, sizeof(mreq));
+
 	if (setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0) {
 		fprintf(stderr, "failed to join multicast group: %s\n", strerror(errno));
 		close(fd);
diff --git a/util.h b/util.h
index 6c73904..fe9f1ea 100644
--- a/util.h
+++ b/util.h
@@ -22,6 +22,7 @@
 extern int debug;
 extern struct uloop_fd listener;
 extern const char *iface_ip;
+extern int iface_index;
 
 void *memdup(void *d, int l);
 
@@ -29,6 +30,7 @@ extern void signal_setup(void);
 extern int socket_setup(int fd, const char *ip);
 extern char* get_hostname(void);
 extern const char* get_iface_ipv4(const char *ifname);
+extern int get_iface_index(const char *ifname);
 extern uint32_t rand_time_delta(uint32_t t);
 
 #endif