.,ruby: enable accept to be called as TsnetAccept & fix gem

This fixes calling accept on the updates listen socket strategy by
embedding the accept behavior into the Go exported library, avoiding the
mandatory requirement for building a separate object from the C library.

Author: raggi

ruby/Gemfile.lock

@@ -14,6 +14,7 @@ GEM
       rake
 
 PLATFORMS
+  arm64-darwin-22
   x86_64-linux-gnu
 
 DEPENDENCIES

ruby/lib/tailscale.rb

@@ -5,6 +5,9 @@
 require 'tailscale/version'
 require 'ffi'
 require 'rbconfig'
+require 'base64'
+require 'net/http'
+require 'json'
 
 # Tailscale provides an embedded tailscale network interface for ruby programs.
 class Tailscale 
@@ -36,8 +39,7 @@ module Libtailscale
         attach_function :TsnetSetLogFD, [:int, :int], :int
         attach_function :TsnetDial, [:int, :string, :string, :pointer], :int, blocking: true
         attach_function :TsnetListen, [:int, :string, :string, :pointer], :int
-        attach_function :close, [:int], :int
-        attach_function :tailscale_accept, [:int, :pointer], :int, blocking: true
+        attach_function :TsnetAccept, [:int, :pointer], :int, blocking: true
         attach_function :TsnetErrmsg, [:int, :pointer, :size_t], :int
         attach_function :TsnetLoopback, [:int, :pointer, :size_t, :pointer, :pointer], :int
     end
@@ -82,6 +84,7 @@ def initialize(ts, listener)
         # write.
         def accept
             @ts.assert_open
+            IO.select [IO.for_fd(@listener)]
             conn = FFI::MemoryPointer.new(:int)
             Error.check @ts, Libtailscale::TsnetAccept(@listener, conn)
             IO::new conn.read_int
@@ -90,7 +93,7 @@ def accept
         # Close the listener.
         def close
             @ts.assert_open
-            Error.check @ts, Libtailscale::close(@listener)
+            IO.for_fd(@listener).close
         end
     end
 
@@ -225,9 +228,8 @@ def set_log_fd(log_fd)
     end
 
     # Dial a network address. +network+ is one of "tcp" or "udp". +addr+ is the
-    # remote address to connect to, and +local_addr+ is the local address to
-    # bind to. This method blocks until the connection is established.
-    def dial(network, addr, local_addr)
+    # remote address to connect to. This method blocks until the connection is established.
+    def dial(network, addr)
         assert_open
         conn = FFI::MemoryPointer.new(:int)
         Error.check self, Libtailscale::TsnetDial(@t, network, addr, conn)

ruby/test/tailscale/test_tailscale.rb

@@ -22,11 +22,28 @@ def test_dial_sorta_works
         # TODO: make a more useful test when we can make a server to connect to.
         ts = newts
         ts.start
-        c = ts.dial "udp", "100.100.100.100:53", ""
+        c = ts.dial "udp", "100.100.100.100:53"
         c.close
         ts.close
     end
 
+    # Requires a solution to be logged in:
+    # def test_listen_accept_dial_close
+    #     ts = newts
+    #     ts.up
+    #     hn = ts.local_api.status["Self"]["HostName"]
+    #     s = ts.listen "tcp", ":1999"
+    #     c = ts.dial "tcp", "#{hn}:1999"
+    #     ss = s.accept
+    #     c.write "hello"
+    #     assert_equal "hello", ss.read(5)
+    #     ss.write "world"
+    #     assert_equal "world", c.read(5)
+    #     ss.close
+    #     c.close
+    #     ts.close
+    # end
+
     def newts
         t = Tailscale::new
         unless ENV['VERBOSE']

tailscale.c

@@ -20,6 +20,7 @@ extern int TsnetSetControlURL(int sd, char* str);
 extern int TsnetSetEphemeral(int sd, int ephemeral);
 extern int TsnetSetLogFD(int sd, int fd);
 extern int TsnetListen(int sd, char* net, char* addr, int* listenerOut);
+extern int TsnetAccept(int ld, int* connOut);
 extern int TsnetLoopback(int sd, char* addrOut, size_t addrLen, char* proxyOut, char* localOut);
 
 tailscale tailscale_new() {
@@ -47,27 +48,7 @@ int tailscale_listen(tailscale sd, const char* network, const char* addr, tailsc
 }
 
 int tailscale_accept(tailscale_listener ld, tailscale_conn* conn_out) {
-	struct msghdr msg = {0};
-
-	char mbuf[256];
-	struct iovec io = { .iov_base = mbuf, .iov_len = sizeof(mbuf) };
-	msg.msg_iov = &io;
-	msg.msg_iovlen = 1;
-
-	char cbuf[256];
-	msg.msg_control = cbuf;
-	msg.msg_controllen = sizeof(cbuf);
-
-	if (recvmsg(ld, &msg, 0) == -1) {
-		return -1;
-	}
-
-	struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
-	unsigned char* data = CMSG_DATA(cmsg);
-
-	int fd = *(int*)data;
-	*conn_out = fd;
-	return 0;
+	return TsnetAccept(ld, (int*)conn_out);
 }
 
 int tailscale_set_dir(tailscale sd, const char* dir) {

tailscale.go

@@ -17,6 +17,7 @@ import (
 	"syscall"
 	"unsafe"
 
+	"golang.org/x/sys/unix"
 	"tailscale.com/hostinfo"
 	"tailscale.com/tsnet"
 	"tailscale.com/types/logger"
@@ -254,6 +255,41 @@ func TsnetListen(sd C.int, network, addr *C.char, listenerOut *C.int) C.int {
 	return 0
 }
 
+//export TsnetAccept
+func TsnetAccept(listenerFd C.int, connOut *C.int) C.int {
+	listeners.mu.Lock()
+	ln := listeners.m[listenerFd]
+	listeners.mu.Unlock()
+
+	if ln == nil {
+		return C.EBADF
+	}
+
+	buf := make([]byte, unix.CmsgLen(int(unsafe.Sizeof((C.int)(0)))))
+	_, oobn, _, _, err := syscall.Recvmsg(int(listenerFd), nil, buf, 0)
+	if err != nil {
+		return ln.s.recErr(err)
+	}
+
+	scms, err := syscall.ParseSocketControlMessage(buf[:oobn])
+	if err != nil {
+		return ln.s.recErr(err)
+	}
+	if len(scms) != 1 {
+		return ln.s.recErr(fmt.Errorf("libtailscale: got %d control messages, want 1", len(scms)))
+	}
+	fds, err := syscall.ParseUnixRights(&scms[0])
+	if err != nil {
+		return ln.s.recErr(err)
+	}
+	if len(fds) != 1 {
+		return ln.s.recErr(fmt.Errorf("libtailscale: got %d FDs, want 1", len(fds)))
+	}
+	*connOut = (C.int)(fds[0])
+
+	return 0
+}
+
 func newConn(s *server, netConn net.Conn, connOut *C.int) error {
 	fds, err := syscall.Socketpair(syscall.AF_LOCAL, syscall.SOCK_STREAM, 0)
 	if err != nil {