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-rw-r--r--unix/tclUnixSock.c75
1 files changed, 56 insertions, 19 deletions
diff --git a/unix/tclUnixSock.c b/unix/tclUnixSock.c
index 5ace251..52b089c 100644
--- a/unix/tclUnixSock.c
+++ b/unix/tclUnixSock.c
@@ -858,6 +858,17 @@ TcpGetHandleProc(
return TCL_OK;
}
+/*
+ *----------------------------------------------------------------------
+ *
+ * TcpAsyncCallback --
+ *
+ * Called by the event handler that CreateClientSocket sets up
+ * internally for [socket -async] to get notified when the
+ * asyncronous connection attempt has succeeded or failed.
+ *
+ *----------------------------------------------------------------------
+ */
static void
TcpAsyncCallback(
ClientData clientData, /* The socket state. */
@@ -883,6 +894,18 @@ TcpAsyncCallback(
* Side effects:
* Opens a socket.
*
+ * Remarks:
+ * A single host name may resolve to more than one IP address, e.g. for
+ * an IPv4/IPv6 dual stack host. For handling asyncronously connecting
+ * sockets in the background for such hosts, this function can act as a
+ * coroutine. On the first call, it sets up the control variables for the
+ * two nested loops over the local and remote addresses. Once the first
+ * connection attempt is in progress, it sets up itself as a writable
+ * event handler for that socket, and returns. When the callback occurs,
+ * control is transferred to the "reenter" label, right after the initial
+ * return and the loops resume as if they had never been interrupted.
+ * For syncronously connecting sockets, the loops work the usual way.
+ *
*----------------------------------------------------------------------
*/
@@ -892,14 +915,14 @@ CreateClientSocket(
TcpState *state)
{
socklen_t optlen;
- int in_coro = (state->addr != NULL);
+ int async_callback = (state->addr != NULL);
int status;
int async = state->flags & TCP_ASYNC_CONNECT;
- if (in_coro) {
- goto coro_continue;
+ if (async_callback) {
+ goto reenter;
}
-
+
for (state->addr = state->addrlist; state->addr != NULL;
state->addr = state->addr->ai_next) {
@@ -976,12 +999,13 @@ CreateClientSocket(
TcpAsyncCallback, state);
return TCL_OK;
- coro_continue:
+ reenter:
Tcl_DeleteFileHandler(state->fds.fd);
/*
- * Read the error state from the socket, to see if the async
- * connection has succeeded or failed and store the status in
- * the socket state for later retrieval by [fconfigure -error]
+ * Read the error state from the socket to see if the async
+ * connection has succeeded or failed. As this clears the
+ * error condition, we cache the status in the socket state
+ * struct for later retrieval by [fconfigure -error].
*/
optlen = sizeof(int);
getsockopt(state->fds.fd, SOL_SOCKET, SO_ERROR,
@@ -996,22 +1020,35 @@ CreateClientSocket(
out:
- if (async) {
+ if (async_callback) {
+ /*
+ * An asynchonous connection has finally succeeded or failed.
+ */
CLEAR_BITS(state->flags, TCP_ASYNC_CONNECT);
TcpWatchProc(state, state->filehandlers);
TclUnixSetBlockingMode(state->fds.fd, TCL_MODE_BLOCKING);
- }
- if (status < 0) {
- if (in_coro) {
- Tcl_NotifyChannel(state->channel, TCL_WRITABLE);
- } else {
- if (interp != NULL) {
- Tcl_AppendResult(interp, "couldn't open socket: ",
- Tcl_PosixError(interp), NULL);
- }
- return TCL_ERROR;
+ /*
+ * We need to forward the writable event that brought us here, bcasue
+ * upon reading of getsockopt(SO_ERROR), at least some OSes clear the
+ * writable state from the socket, and so a subsequent select() on
+ * behalf of a script level [fileevent] would not fire. It doesn't
+ * hurt that this is also called in the successful case and will save
+ * the event mechanism one roundtrip through select().
+ */
+ Tcl_NotifyChannel(state->channel, TCL_WRITABLE);
+
+ } else if (status != 0) {
+ /*
+ * Failure for either a synchronous connection, or an async one that
+ * failed before it could enter background mode, e.g. because an
+ * invalid -myaddr was given.
+ */
+ if (interp != NULL) {
+ Tcl_AppendResult(interp, "couldn't open socket: ",
+ Tcl_PosixError(interp), NULL);
}
+ return TCL_ERROR;
}
return TCL_OK;
}