libtailscale: EBADF on bad tailscale_listener_close fd

Signed-off-by: David Crawshaw <[email protected]>

Author: crawshaw

tailscale.go

@@ -201,6 +201,9 @@ func TsnetListenerClose(ld C.int) C.int {
 	defer listeners.mu.Unlock()
 
 	l := listeners.m[ld]
+	if l == nil {
+		return C.EBADF
+	}
 	err := l.ln.Close()
 	delete(listeners.m, ld)
 

tailscale.h

@@ -103,7 +103,10 @@ extern int tailscale_listen(tailscale sd, const char* network, const char* addr,
 
 // tailscale_listener_close closes the listener.
 //
-// Returns zero on success or -1 on error, call tailscale_errmsg for details.
+// Returns:
+// 	0     - success
+// 	EBADF - listener is not a valid tailscale_listener
+// 	-1    - call tailscale_errmsg for details
 extern int tailscale_listener_close(tailscale_listener listener);
 
 // tailscale_accept accepts a connection on a tailscale_listener.

tsnetctest/tsnetctest.go

@@ -112,6 +112,10 @@ int test_conn() {
 	if ((ret = tailscale_listener_close(ln)) != 0) {
 		return set_err(s1, 'a');
 	}
+	if ((ret = tailscale_listener_close(ln)) != EBADF) {
+		snprintf(err, errlen, "double tailscale_listener_close = %d (%s), want EBADF", errno, strerror(errno));
+		return 1;
+	}
 
 	if ((ret = tailscale_loopback(s1, addr, addrlen, proxy_cred, local_api_cred)) != 0) {
 		return set_err(s1, 'b');