New plug_closing error type for 'user abort'.

This is generated when setup of a network connection is cancelled by
deliberate user action, namely, pressing ^C or ^D or the like at a
get_userpass_input prompt presented during proxy setup.

It's handled just like normal socket setup errors, except that it
omits the call to seat_connection_fatal, on the grounds that in this
one case of connection-setup failure, the user doesn't need to be
_informed_ that the connection failed - they already know, because
they failed it themself on purpose.

network.h

@@ -55,6 +55,7 @@ typedef enum PlugCloseType {
     PLUGCLOSE_NORMAL,
     PLUGCLOSE_ERROR,
     PLUGCLOSE_BROKEN_PIPE,
+    PLUGCLOSE_USER_ABORT,
 } PlugCloseType;
 
 struct PlugVtable {
@@ -112,6 +113,16 @@ struct PlugVtable {
      *    distinguishes the particular error condition signalled by
      *    EPIPE / ERROR_BROKEN_PIPE, which ssh/sharing.c needs to
      *    recognise and handle specially in one situation.
+     *
+     *  - PLUGCLOSE_USER_ABORT means that the close has happened as a
+     *    result of some kind of deliberate user action (e.g. hitting
+     *    ^C at a password prompt presented by a proxy socket setup
+     *    phase). This can be used to suppress interactive error
+     *    messages sent to the user (such as dialog boxes), on the
+     *    grounds that the user already knows. However, 'error_msg'
+     *    will still contain some appropriate text, so that
+     *    non-interactive error reporting (e.g. event logs) can still
+     *    record why the connection terminated.
      */
     void (*closing)(Plug *p, PlugCloseType type, const char *error_msg);
 
@@ -242,6 +253,8 @@ static inline void plug_closing_normal(Plug *p)
 { p->vt->closing(p, PLUGCLOSE_NORMAL, NULL); }
 static inline void plug_closing_error(Plug *p, const char *msg)
 { p->vt->closing(p, PLUGCLOSE_ERROR, msg); }
+static inline void plug_closing_user_abort(Plug *p)
+{ p->vt->closing(p, PLUGCLOSE_USER_ABORT, "User aborted connection setup"); }
 static inline void plug_receive(Plug *p, int urg, const char *data, size_t len)
 { p->vt->receive(p, urg, data, len); }
 static inline void plug_sent (Plug *p, size_t bufsize)

otherbackends/raw.c

@@ -79,6 +79,7 @@ static void raw_closing(Plug *plug, PlugCloseType type, const char *error_msg)
             seat_notify_remote_disconnect(raw->seat);
         }
         logevent(raw->logctx, error_msg);
+        if (type != PLUGCLOSE_USER_ABORT)
             seat_connection_fatal(raw->seat, "%s", error_msg);
     } else {
         /* Otherwise, the remote side closed the connection normally. */

otherbackends/rlogin.c

@@ -107,6 +107,7 @@ static void rlogin_closing(Plug *plug, PlugCloseType type,
     if (type != PLUGCLOSE_NORMAL) {
         /* A socket error has occurred. */
         logevent(rlogin->logctx, error_msg);
+        if (type != PLUGCLOSE_USER_ABORT)
             seat_connection_fatal(rlogin->seat, "%s", error_msg);
     }
     /* Otherwise, the remote side closed the connection normally. */

otherbackends/supdup.c

@@ -594,6 +594,7 @@ static void supdup_closing(Plug *plug, PlugCloseType type,
     }
     if (type != PLUGCLOSE_NORMAL) {
         logevent(supdup->logctx, error_msg);
+        if (type != PLUGCLOSE_USER_ABORT)
             seat_connection_fatal(supdup->seat, "%s", error_msg);
     }
     /* Otherwise, the remote side closed the connection normally. */

otherbackends/telnet.c

@@ -656,6 +656,7 @@ static void telnet_closing(Plug *plug, PlugCloseType type,
     }
     if (type != PLUGCLOSE_NORMAL) {
         logevent(telnet->logctx, error_msg);
+        if (type != PLUGCLOSE_USER_ABORT)
             seat_connection_fatal(telnet->seat, "%s", error_msg);
     }
     /* Otherwise, the remote side closed the connection normally. */

proxy/sshproxy.c

@@ -13,18 +13,6 @@
 
 const bool ssh_proxy_supported = true;
 
-/*
- * TODO for future work:
- *
- * If the user manually aborts the attempt to make the proxy SSH
- * connection (e.g. by hitting ^C at a userpass prompt, or refusing to
- * accept the proxy server's host key), then I think it would be nicer
- * if we didn't give a connection_fatal error box. If I've aborted the
- * connection deliberately, I don't need to be told it happened, and
- * I'd rather not have the UI annoyance of clicking away an extra
- * error dialog.
- */
-
 typedef struct SshProxy {
     char *errmsg;
     Conf *conf;
@@ -318,6 +306,8 @@ static void sshproxy_send_close(SshProxy *sp)
 
     if (sp->errmsg)
         plug_closing_error(sp->plug, sp->errmsg);
+    else if (!sp->conn_established && backend_exitcode(sp->backend) == 0)
+        plug_closing_user_abort(sp->plug);
     else
         plug_closing_normal(sp->plug);
 }

ssh/ssh.c

@@ -606,7 +606,9 @@ static void ssh_socket_log(Plug *plug, PlugLogType type, SockAddr *addr,
 static void ssh_closing(Plug *plug, PlugCloseType type, const char *error_msg)
 {
     Ssh *ssh = container_of(plug, Ssh, plug);
-    if (type != PLUGCLOSE_NORMAL) {
+    if (type == PLUGCLOSE_USER_ABORT) {
+        ssh_user_close(ssh, "%s", error_msg);
+    } else if (type != PLUGCLOSE_NORMAL) {
         ssh_remote_error(ssh, "%s", error_msg);
     } else if (ssh->bpp) {
         ssh->bpp->input_eof = true;