wait for systemd tun device unit to be active before configuring dns (#…

…837)
openziti · Apr 29, 2024 · 94b479f · 94b479f
1 parent 90b416d
commit 94b479f
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Showing 3 changed files with 52 additions and 7 deletions.
diff --git a/programs/ziti-edge-tunnel/netif_driver/linux/resolvers.c b/programs/ziti-edge-tunnel/netif_driver/linux/resolvers.c
@@ -328,7 +328,53 @@ static bool set_systemd_resolved_link_setting(sd_bus *bus, const char *tun, cons
     return true;
 }
 
-bool try_libsystemd_resolver(void) {
+// wait for systemd to recognize the tun device before configuring, lest the configuration get overwritten
+static bool wait_for_tun(const char *name, sd_bus *bus, unsigned int timeout_ms) {
+    const unsigned int delay_ms = 250;
+    char systemd_path[128];
+    unsigned int iterations = timeout_ms / delay_ms;
+    bool active = false;
+    snprintf(systemd_path, sizeof(systemd_path), "/org/freedesktop/systemd1/unit/sys_2dsubsystem_2dnet_2ddevices_2d%s_2edevice", name);
+
+    ZITI_LOG(DEBUG, "waiting %d ms for systemd path '%s' to become active", timeout_ms, systemd_path);
+
+    for (int count = 0; count < iterations && active == false; count++, uv_sleep(delay_ms)) {
+        sd_bus_message *message = NULL;
+
+        int r = sd_bus_get_property_f(
+                bus,
+                "org.freedesktop.systemd1",
+                systemd_path,
+                "org.freedesktop.systemd1.Unit",
+                "ActiveState",
+                NULL,
+                &message,
+                "s"
+        );
+        if (r < 0) {
+            ZITI_LOG(VERBOSE, "failed to get ActiveState property: %s", strerror(-r));
+            continue;
+        }
+
+        const char *state = NULL;
+        r = sd_bus_message_read_f(message, "s", &state);
+        if (r < 0) {
+            ZITI_LOG(VERBOSE, "failed to read property: %s", strerror(-r));
+        } else {
+            if (state) {
+                ZITI_LOG(DEBUG, "device state (c=%d): %s", count, state);
+                if (strcmp(state, "active") == 0) {
+                    active = true;
+                }
+            }
+        }
+        sd_bus_message_unref_f(message);
+    }
+
+    return false;
+}
+
+bool try_libsystemd_resolver(const char *tun_name) {
     uv_once(&guard, init_libsystemd);
     if (!libsystemd_dl_success) {
         return false;
@@ -347,15 +393,14 @@ bool try_libsystemd_resolver(void) {
     r = sd_bus_open_system_f(&bus);
     if ((r >= 0) && (sd_bus_is_bus_client_f(bus) > 0)) {
         ZITI_LOG(DEBUG, "Connected to system DBus");
+        wait_for_tun(tun_name, bus, 3000);
         r = sd_bus_is_acquired_name(bus, RESOLVED_DBUS_NAME);
         if (r != 0) {
             ZITI_LOG(WARN, "libsystemd resolver unsuccessful. Falling back to legacy resolvers");
             return false;
         }
-        if (r == 0) {
-            ZITI_LOG(INFO, "systemd-resolved selected as DNS resolver manager");
-            return true;
-        }
+        ZITI_LOG(INFO, "systemd-resolved selected as DNS resolver manager");
+        return true;
     } else {
         ZITI_LOG(DEBUG, "Could not create system DBus client");
     }

diff --git a/programs/ziti-edge-tunnel/netif_driver/linux/resolvers.h b/programs/ziti-edge-tunnel/netif_driver/linux/resolvers.h
@@ -46,7 +46,7 @@
 #endif
 
 #ifndef EXCLUDE_LIBSYSTEMD_RESOLVER
-bool try_libsystemd_resolver(void);
+bool try_libsystemd_resolver(const char *tun_name);
 #endif
 bool is_systemd_resolved_primary_resolver(void);
 bool is_resolvconf_systemd_resolved(void);

diff --git a/programs/ziti-edge-tunnel/netif_driver/linux/tun.c b/programs/ziti-edge-tunnel/netif_driver/linux/tun.c
@@ -245,7 +245,7 @@ static void dns_update_systemd_resolve(const char* tun, unsigned int ifindex, co
 
 static void find_dns_updater() {
 #ifndef EXCLUDE_LIBSYSTEMD_RESOLVER
-    if(try_libsystemd_resolver()) {
+    if(try_libsystemd_resolver(dns_maintainer.tun_name)) {
         dns_updater = dns_update_systemd_resolved;
         return;
     }