Add OC_CMD_DETACH for "reconnectable abort"

OC_CMD_DETACH is similar to OC_CMD_CANCEL, except it does not tell the
server to invalidate the cookie when exiting.  So it is possible to
reconnect to the same session with "openconnect --cookie <foo>" later.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>

mainloop.c

@@ -105,7 +105,8 @@ int tun_mainloop(struct openconnect_info *vpninfo, int *timeout)
 
 /* Return value:
  *  = 0, when successfully paused (may call again)
- *  = -EINTR, if aborted locally via cmd_fd
+ *  = -EINTR, if aborted locally via OC_CMD_CANCEL
+ *  = -ECONNABORTED, if aborted locally via OC_CMD_DETACH
  *  = -EPIPE, if the remote end explicitly terminated the session
  *  = -EPERM, if the gateway sent 401 Unauthorized (cookie expired)
  *  < 0, for any other error
@@ -157,8 +158,12 @@ int openconnect_mainloop(struct openconnect_info *vpninfo,
 
 		poll_cmd_fd(vpninfo, 0);
 		if (vpninfo->got_cancel_cmd) {
-			vpninfo->quit_reason = "Aborted by caller";
-			ret = -EINTR;
+			if (vpninfo->cancel_type == OC_CMD_CANCEL) {
+				vpninfo->quit_reason = "Aborted by caller";
+				ret = -EINTR;
+			} else {
+				ret = -ECONNABORTED;
+			}
 			break;
 		}
 		if (vpninfo->got_pause_cmd) {
@@ -215,7 +220,8 @@ int openconnect_mainloop(struct openconnect_info *vpninfo,
 #endif
 	}
 
-	cstp_bye(vpninfo, vpninfo->quit_reason);
+	if (vpninfo->quit_reason)
+		cstp_bye(vpninfo, vpninfo->quit_reason);
 
 	os_shutdown_tun(vpninfo);
 	return ret < 0 ? ret : -EIO;

openconnect-internal.h

@@ -305,6 +305,7 @@ struct openconnect_info {
 	int cmd_fd_write;
 	int got_cancel_cmd;
 	int got_pause_cmd;
+	char cancel_type;
 
 	struct pkt *incoming_queue;
 	struct pkt *outgoing_queue;

openconnect.h

@@ -225,9 +225,21 @@ struct oc_stats {
 #define PRG_DEBUG	2
 #define PRG_TRACE	3
 
-/* byte commands to write into the cmd_fd */
+/* Byte commands to write into the cmd_fd:
+ *
+ *  CANCEL closes network connections, logs off the session (cookie)
+ *    and shuts down the tun device.
+ *  PAUSE closes network connections and returns. The caller is expected
+ *    to call openconnect_mainloop() again soon.
+ *  DETACH closes network connections and shuts down the tun device.
+ *    It is not legal to call openconnect_mainloop() again after this,
+ *    but a new instance of openconnect can be started using the same
+ *    cookie.
+ *  STATS calls the stats_handler.
+ */
 #define OC_CMD_CANCEL		'x'
 #define OC_CMD_PAUSE		'p'
+#define OC_CMD_DETACH		'd'
 #define OC_CMD_STATS		's'
 
 #define RECONNECT_INTERVAL_MIN	10

ssl.c

@@ -587,7 +587,9 @@ void check_cmd_fd(struct openconnect_info *vpninfo, fd_set *fds)
 
 	switch (cmd) {
 	case OC_CMD_CANCEL:
+	case OC_CMD_DETACH:
 		vpninfo->got_cancel_cmd = 1;
+		vpninfo->cancel_type = cmd;
 		break;
 	case OC_CMD_PAUSE:
 		vpninfo->got_pause_cmd = 1;