From: Guus Sliepen <guus@meshlink.io>
Date: Thu, 13 Aug 2020 20:48:06 +0000 (+0200)
Subject: Add local discovery support for macOS.
X-Git-Url: https://git.meshlink.io/?a=commitdiff_plain;h=baeb6c0ea8746dc2387cbbb186874821223b0835;p=meshlink

Add local discovery support for macOS.

This implements the pfroute counterpart to Linux's netlink interface.
Pfroute doesn't allow easy querying the current interfaces and addresses,
so we use getifaddrs() for that.
---

diff --git a/src/discovery.c b/src/discovery.c
index 6fec9a24..eb29c735 100644
--- a/src/discovery.c
+++ b/src/discovery.c
@@ -1,7 +1,10 @@
+#define __APPLE_USE_RFC_3542
 #include "system.h"
 
 #if defined(__APPLE__) || defined(__unix) && !defined(__linux)
+#include <net/if.h>
 #include <net/route.h>
+#include <netinet/in.h>
 #elif defined(__linux)
 #include <asm/types.h>
 #include <net/if.h>
@@ -26,6 +29,18 @@
 #define MESHLINK_MDNS_NAME_KEY "name"
 #define MESHLINK_MDNS_FINGERPRINT_KEY "fingerprint"
 
+#ifndef MSG_NOSIGNAL
+#define MSG_NOSIGNAL 0
+#endif
+
+#ifndef IPV6_ADD_MEMBERSHIP
+#define IPV6_ADD_MEMBERSHIP IPV6_JOIN_GROUP
+#endif
+
+#ifndef IPV6_DROP_MEMBERSHIP
+#define IPV6_DROP_MEMBERSHIP IPV6_LEAVE_GROUP
+#endif
+
 static const sockaddr_t mdns_address_ipv4 = {
 	.in.sin_family = AF_INET,
 	.in.sin_addr.s_addr = 0xfb0000e0,
@@ -99,6 +114,9 @@ static void send_mdns_packet_ipv4(meshlink_handle_t *mesh, int fd, int index, co
 	// Send the packet
 	ssize_t result = sendmsg(fd, &msg, MSG_DONTWAIT | MSG_NOSIGNAL);
 #else
+	(void)index;
+	(void)src;
+
 	// Send the packet
 	ssize_t result = sendto(fd, data, len, MSG_DONTWAIT | MSG_NOSIGNAL, &dest->sa, SALEN(dest->sa));
 #endif
@@ -145,6 +163,9 @@ static void send_mdns_packet_ipv6(meshlink_handle_t *mesh, int fd, int index, co
 	// Send the packet
 	ssize_t result = sendmsg(fd, &msg, MSG_DONTWAIT | MSG_NOSIGNAL);
 #else
+	(void)index;
+	(void)src;
+
 	// Send the packet
 	ssize_t result = sendto(fd, data, len, MSG_DONTWAIT | MSG_NOSIGNAL, &dest->sa, SALEN(dest->sa));
 #endif
@@ -444,11 +465,11 @@ static void netlink_parse_addr(meshlink_handle_t *mesh, const struct nlmsghdr *n
 			if(rta->rta_len == 8) {
 				addr.address.sa.sa_family = AF_INET;
 				memcpy(&addr.address.in.sin_addr, ptr + 4, 4);
-				addr.address.in.sin_port = 5353;
+				addr.address.in.sin_port = ntohs(5353);
 			} else if(rta->rta_len == 20) {
 				addr.address.sa.sa_family = AF_INET6;
 				memcpy(&addr.address.in6.sin6_addr, ptr + 4, 16);
-				addr.address.in6.sin6_port = 5353;
+				addr.address.in6.sin6_port = ntohs(5353);
 				addr.address.in6.sin6_scope_id = ifa->ifa_index;
 			} else {
 				addr.address.sa.sa_family = AF_UNKNOWN;
@@ -539,10 +560,61 @@ static void netlink_io_handler(event_loop_t *loop, void *data, int flags) {
 	}
 }
 #elif defined(RTM_NEWADDR)
+static void pfroute_parse_iface(meshlink_handle_t *mesh, const struct rt_msghdr *rtm) {
+	const struct if_msghdr *ifm = (const struct if_msghdr *)rtm;
+
+	if(ifm->ifm_flags & IFF_UP && ifm->ifm_flags & IFF_MULTICAST && !(ifm->ifm_flags & IFF_LOOPBACK)) {
+		iface_up(mesh, ifm->ifm_index);
+	} else {
+		iface_down(mesh, ifm->ifm_index);
+	}
+}
+
+static void pfroute_parse_addr(meshlink_handle_t *mesh, const struct rt_msghdr *rtm) {
+	const struct ifa_msghdr *ifam = (const struct ifa_msghdr *)rtm;
+	const char *p = (const char *)(ifam + 1);
+
+	for(unsigned int i = 1; i; i <<= 1) {
+		if(!(ifam->ifam_addrs & i)) {
+			continue;
+		}
+
+		const sockaddr_t *sa = (const sockaddr_t *)p;
+
+		if(i == RTA_IFA) {
+			discovery_address_t addr = {
+				.index = ifam->ifam_index,
+			};
+
+			if(sa->sa.sa_family == AF_INET) {
+				addr.address.in = sa->in;
+				addr.address.in.sin_port = ntohs(5353);
+			} else if(sa->sa.sa_family == AF_INET6) {
+				addr.address.in6 = sa->in6;
+				addr.address.in6.sin6_port = ntohs(5353);
+			} else {
+				addr.address.sa.sa_family = AF_UNKNOWN;
+			}
+
+			if(addr.address.sa.sa_family != AF_UNKNOWN) {
+				if(ifam->ifam_type == RTM_NEWADDR) {
+					addr_add(mesh, &addr);
+				} else {
+					addr_del(mesh, &addr);
+				}
+			}
+
+			break;
+		}
+
+		size_t len = (sa->sa.sa_len + 3) & ~3;
+		p += len;
+	}
+}
+
 static void pfroute_io_handler(event_loop_t *loop, void *data, int flags) {
 	(void)flags;
 	(void)data;
-	static time_t prev_update;
 	meshlink_handle_t *mesh = loop->data;
 
 	struct {
@@ -570,13 +642,12 @@ static void pfroute_io_handler(event_loop_t *loop, void *data, int flags) {
 
 		switch(msg.rtm.rtm_type) {
 		case RTM_IFINFO:
+			pfroute_parse_iface(mesh, &msg.rtm);
+			break;
+
 		case RTM_NEWADDR:
 		case RTM_DELADDR:
-			if(loop->now.tv_sec > prev_update + 5) {
-				prev_update = loop->now.tv_sec;
-				handle_network_change(mesh, 1);
-			}
-
+			pfroute_parse_addr(mesh, &msg.rtm);
 			break;
 
 		default:
@@ -594,6 +665,8 @@ bool discovery_start(meshlink_handle_t *mesh) {
 	// Set up multicast sockets for mDNS
 	static const int one = 1;
 	static const int ttl = 255;
+	static const uint8_t one8 = 1;
+	static const uint8_t ttl8 = 255;
 
 	int fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
 	sockaddr_t sa4 = {
@@ -601,9 +674,9 @@ bool discovery_start(meshlink_handle_t *mesh) {
 		.in.sin_port = ntohs(5353),
 	};
 	setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
+	setsockopt(fd, IPPROTO_IP, IP_MULTICAST_LOOP, &one8, sizeof(one8));
+	setsockopt(fd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl8, sizeof(ttl8));
 	bind(fd, &sa4.sa, SALEN(sa4.sa));
-	setsockopt(fd, IPPROTO_IP, IP_MULTICAST_LOOP, &one, sizeof(one));
-	setsockopt(fd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl));
 	io_add(&mesh->loop, &mesh->discovery.sockets[0], mdns_io_handler, &mesh->discovery.sockets[0], fd, IO_READ);
 
 	sockaddr_t sa6 = {
@@ -613,9 +686,10 @@ bool discovery_start(meshlink_handle_t *mesh) {
 	fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);
 	setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
 	setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));
-	bind(fd, &sa6.sa, SALEN(sa6.sa));
 	setsockopt(fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &one, sizeof(one));
 	setsockopt(fd, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &ttl, sizeof(ttl));
+	setsockopt(fd, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &ttl, sizeof(ttl));
+	bind(fd, &sa6.sa, SALEN(sa6.sa));
 	io_add(&mesh->loop, &mesh->discovery.sockets[1], mdns_io_handler, &mesh->discovery.sockets[1], fd, IO_READ);
 
 #if defined(__linux)
@@ -646,6 +720,51 @@ bool discovery_start(meshlink_handle_t *mesh) {
 		logger(mesh, MESHLINK_WARNING, "Could not open PF_ROUTE socket: %s", strerror(errno));
 	}
 
+	struct ifaddrs *ifa = NULL;
+
+	if(getifaddrs(&ifa) == -1) {
+		logger(mesh, MESHLINK_ERROR, "Could not get list of interface addresses: %s", strerror(errno));
+		return true;
+	}
+
+	for(struct ifaddrs *ifap = ifa; ifap; ifap = ifap->ifa_next) {
+		if(!ifap->ifa_name) {
+			continue;
+		}
+
+		int index = if_nametoindex(ifap->ifa_name);
+
+		if(ifap->ifa_flags & IFF_UP && ifap->ifa_flags & IFF_MULTICAST && !(ifap->ifa_flags & IFF_LOOPBACK)) {
+			iface_up(mesh, index);
+		}
+
+		if(!ifap->ifa_addr) {
+			continue;
+		}
+
+		discovery_address_t addr  = {
+			.index = index,
+		};
+
+		sockaddr_t *sa = (sockaddr_t *)ifap->ifa_addr;
+
+		if(sa->sa.sa_family == AF_INET) {
+			memcpy(&addr.address.in, &sa->in, sizeof(sa->in));
+			addr.address.in.sin_port = ntohs(5353);
+		} else if(sa->sa.sa_family == AF_INET6) {
+			memcpy(&addr.address.in6, &sa->in6, sizeof(sa->in6));
+			addr.address.in6.sin6_port = ntohs(5353);
+		} else {
+			addr.address.sa.sa_family = AF_UNKNOWN;
+		}
+
+		if(addr.address.sa.sa_family != AF_UNKNOWN) {
+			addr_add(mesh, &addr);
+		}
+	}
+
+	freeifaddrs(ifa);
+
 #endif
 
 	return true;