Fix #8: add support for running on multiple interfaces

This huge patch adds support for running on multiple interfaces.
There are quite a few changes to the setup and initialization of
the daemon.

Basically, this implmentation is the same as running multiple
instances of mdnsd v0.10, one per interface, sharing the same
.conf files for services to announce.

A later patch may add more granular support for filtering or selecting
which services are to be announced on which interface. Also, currently
mdnsd runs on all interfaces or one.  If you have seven interfaces and
only want to run on two of them, mdnsd won't support you right now.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

configure.ac

@@ -23,6 +23,11 @@ AC_C_CONST
 AC_REPLACE_FUNCS([pidfile strlcpy utimensat])
 AC_CONFIG_LIBOBJ_DIR([lib])
 
+AC_CHECK_MEMBERS([struct ip_mreqn.imr_ifindex], , ,
+[
+#include <netinet/in.h>
+])
+
 # Options
 AC_ARG_WITH([systemd],
 	[AS_HELP_STRING([--with-systemd=DIR], [Directory for systemd service files])],,

src/Makefile.am

@@ -6,7 +6,7 @@ AM_CPPFLAGS            += -I$(top_srcdir) -D_PIDFILEDIR=\"@runstatedir@\"
 sbin_PROGRAMS           = mdnsd
 bin_PROGRAMS            = mquery
 
-mdnsd_SOURCES           = mdnsd.c mdnsd.h addr.c conf.c
+mdnsd_SOURCES           = mdnsd.c mdnsd.h addr.c conf.c queue.h
 mdnsd_LDADD             = ../libmdnsd/libmdnsd.la $(LIBS) $(LIBOBJS)
 
 mquery_SOURCES          = mquery.c

src/addr.c

@@ -26,10 +26,12 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <errno.h>
 #include <ifaddrs.h>
 #include <netdb.h>
 #include <stdio.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
 #include <net/if.h>
 #include <netinet/in.h>
@@ -51,44 +53,9 @@
 #define IN_LINKLOCAL(addr) ((addr & IN_CLASSB_NET) == IN_LINKLOCALNETNUM)
 #endif
 
-/* Find default outbound *LAN* interface, i.e. skipping tunnels */
-static char *getifname(char *ifname, size_t len)
-{
-	uint32_t dest, gw, mask;
-	char buf[256], name[17];
-	FILE *fp;
-	int rc, flags, cnt, use, metric, mtu, win, irtt;
-	int found = 0;
-
-	fp = fopen("/proc/net/route", "r");
-	if (!fp)
-		return NULL;
-
-	while (fgets(buf, sizeof(buf), fp) != NULL) {
-		rc = sscanf(buf, "%16s %X %X %X %d %d %d %X %d %d %d\n",
-			   name, &dest, &gw, &flags, &cnt, &use, &metric,
-			   &mask, &mtu, &win, &irtt);
-
-		if (rc < 10 || !(flags & 1)) /* IFF_UP */
-			continue;
-
-		if (dest != 0 || mask != 0)
-			continue;
-
-		if (!ifname[0] || !strncmp(ifname, "tun", 3)) {
-			strlcpy(ifname, name, len);
-			found = 1;
-			break;
-		}
-	}
-	fclose(fp);
-
-	if (found)
-		return ifname;
-
-	return NULL;
-}
+static TAILQ_HEAD(iflist, iface) iface_list = TAILQ_HEAD_INITIALIZER(iface_list);
 
+#if 0	/* unused from v0.11 and later */
 /* Check if valid address */
 static int valid_addr(struct in_addr *ina)
 {
@@ -100,57 +67,126 @@ static int valid_addr(struct in_addr *ina)
 
 	return 1;
 }
+#endif	/* unused */
 
-/* Find IPv4 address of default outbound LAN interface */
-int getaddr(char *iface, struct in_addr *ina)
+struct iface *iface_iterator(int first)
+{
+	static struct iface *iface = NULL;
+
+	if (first)
+		iface = TAILQ_FIRST(&iface_list);
+	else
+		iface = TAILQ_NEXT(iface, link);
+
+	return iface;
+}
+
+struct iface *iface_find(const char *ifname)
+{
+	struct iface *iface;
+
+	for (iface = iface_iterator(1); iface; iface = iface_iterator(0)) {
+		if (strcmp(iface->ifname, ifname))
+			continue;
+
+		return iface;
+	}
+
+	return NULL;
+}
+
+int iface_update(char *ifname)
 {
 	struct ifaddrs *ifaddr, *ifa;
-	char ifname[IFNAMSIZ] = { 0 };
-	char buf[20] = { 0 };
+	struct iface *iface = NULL;
+	int changed = 0;
 	int rc = -1;
 
-	if (!iface)
-		iface = getifname(ifname, sizeof(ifname));
-	DBG("Default interface: %s", iface ? iface : "N/A");
-
 	rc = getifaddrs(&ifaddr);
-	if (rc)
-		return -1;
+	if (rc) {
+		ERR("Failed fetching system interfaces: %s", strerror(errno));
+		return 0;
+	}
+
+	if (ifname)
+		iface = iface_find(ifname);
 
 	for (ifa = ifaddr; ifa; ifa = ifa->ifa_next) {
+		struct in_addr ina;
+		char buf[20];
+
 		if (!ifa->ifa_addr)
 			continue;
 
 		if (ifa->ifa_flags & IFF_LOOPBACK)
-			continue;
+			continue; /* skip for now, mDNSResponder has it as fallback */
 
 		if (!(ifa->ifa_flags & IFF_MULTICAST))
 			continue;
 
+		if (!(ifa->ifa_flags & IFF_UP))
+			continue; /* skip for now, not enabled */
+
 		if (ifa->ifa_addr->sa_family != AF_INET)
 			continue;
 
-		if (iface && strcmp(iface, ifa->ifa_name))
+		if (ifname && strcmp(ifname, ifa->ifa_name))
 			continue;
 
-		rc = getnameinfo(ifa->ifa_addr, sizeof(struct sockaddr_in),
-				 buf, sizeof(buf), NULL, 0, NI_NUMERICHOST);
-		if (!rc) {
-			if (!inet_aton(buf, ina))
-				continue;
-			if (!valid_addr(ina))
-				continue;
+		/* Validate IP address */
+		rc = getnameinfo(ifa->ifa_addr, sizeof(struct sockaddr_in), buf, sizeof(buf), NULL, 0, NI_NUMERICHOST);
+		if (rc)
+			continue;
+
+		/* Use address from getnameinfo() */
+		if (!inet_aton(buf, &ina))
+			continue;
 
+		if (!ifname)
+			iface = iface_find(ifa->ifa_name);
+
+		if (!iface) {
+			iface = calloc(1, sizeof(*iface));
+			if (!iface) {
+				ERR("Failed allocating memory for iface %s: %s", ifa->ifa_name, strerror(errno));
+				exit(1);
+			}
+			TAILQ_INSERT_TAIL(&iface_list, iface, link);
+
+			strlcpy(iface->ifname, ifa->ifa_name, sizeof(iface->ifname));
+			iface->ifindex = if_nametoindex(ifa->ifa_name);
+			iface->sd = -1;
+		} else {
+			iface->unused = 0;
+		}
+
+		if (iface->inaddr.s_addr != ina.s_addr) {
 			DBG("Found interface %s, address %s", ifa->ifa_name, buf);
-			break;
+			iface->inaddr = ina;
+			iface->changed = 1;
+			changed++;
 		}
+		iface = NULL;
+
+		if (ifname)
+			break;
 	}
 	freeifaddrs(ifaddr);
 
-	if (rc || IN_ZERONET(ntohl(ina->s_addr)))
-		return -1;
+	return changed;
+}
 
-	DBG("Using address: %s", inet_ntoa(*ina));
+void iface_init(char *ifname)
+{
+	iface_update(ifname);
+}
 
-	return 0;
+void iface_exit(void)
+{
+	struct iface *iface, *tmp;
+
+	TAILQ_FOREACH_SAFE(iface, &iface_list, link, tmp) {
+		TAILQ_REMOVE(&iface_list, iface, link);
+		free(iface);
+	}
 }