[Qemu-devel] [PATCH] add VNC reverse connections

[Eddie Kohler]

Hi all,

This patch against current CVS adds VNC reverse connections, where the server 
connects actively to a waiting client, as in "-vnc rev:5500" or "-vnc 
rev:read.cs.ucla.edu:5500".  This is quite useful if the user expects to run 
QEMU many times in succession (for example, is debugging a toy OS), and 
doesn't want to reopen a VNC client each time.

Eddie

Index: qemu-doc.texi
===================================================================
RCS file: /sources/qemu/qemu/qemu-doc.texi,v
retrieving revision 1.179
diff -u -r1.179 qemu-doc.texi
--- qemu-doc.texi       14 Jan 2008 22:09:11 -0000      1.179
+++ qemu-doc.texi       16 Jan 2008 07:25:30 -0000
@@ -429,10 +429,16 @@
 Connections will be allowed over UNIX domain sockets where @var{path} is the
 location of a unix socket to listen for connections on.
 
address@hidden @var{rev}:@var{interface}:@var{port}
+
+Makes a reverse connection to a VNC viewer listening on
address@hidden on port @var{port}. Optionally, @var{interface} can be
+omitted in which case QEMU will connect to @var{port} on the local machine.
+
 @item none
 
-VNC is initialized by not started. The monitor @code{change} command can be 
used
-to later start the VNC server.
+VNC is initialized but not started. The monitor @code{change} command
+can be used to later start the VNC server.
 
 @end table
 
Index: vnc.c
===================================================================
RCS file: /sources/qemu/qemu/vnc.c,v
retrieving revision 1.33
diff -u -r1.33 vnc.c
--- vnc.c       14 Jan 2008 21:45:55 -0000      1.33
+++ vnc.c       16 Jan 2008 07:25:30 -0000
@@ -1898,6 +1898,22 @@
     return 0;
 }
 
+static void vnc_connect(VncState *vs)
+{
+    VNC_DEBUG("New client on socket %d\n", vs->csock);
+    socket_set_nonblock(vs->csock);
+    qemu_set_fd_handler2(vs->csock, NULL, vnc_client_read, NULL, vs);
+    vnc_write(vs, "RFB 003.008\n", 12);
+    vnc_flush(vs);
+    vnc_read_when(vs, protocol_version, 12);
+    memset(vs->old_data, 0, vs->ds->linesize * vs->ds->height);
+    memset(vs->dirty_row, 0xFF, sizeof(vs->dirty_row));
+    vs->has_resize = 0;
+    vs->has_hextile = 0;
+    vs->ds->dpy_copy = NULL;
+    vnc_update_client(vs);
+}
+
 static void vnc_listen_read(void *opaque)
 {
     VncState *vs = opaque;
@@ -1909,18 +1925,7 @@
 
     vs->csock = accept(vs->lsock, (struct sockaddr *)&addr, &addrlen);
     if (vs->csock != -1) {
-       VNC_DEBUG("New client on socket %d\n", vs->csock);
-        socket_set_nonblock(vs->csock);
-       qemu_set_fd_handler2(vs->csock, NULL, vnc_client_read, NULL, opaque);
-       vnc_write(vs, "RFB 003.008\n", 12);
-       vnc_flush(vs);
-       vnc_read_when(vs, protocol_version, 12);
-       memset(vs->old_data, 0, vs->ds->linesize * vs->ds->height);
-       memset(vs->dirty_row, 0xFF, sizeof(vs->dirty_row));
-       vs->has_resize = 0;
-       vs->has_hextile = 0;
-       vs->ds->dpy_copy = NULL;
-        vnc_update_client(vs);
+       vnc_connect(vs);
     }
 }
 
@@ -2087,6 +2092,7 @@
     VncState *vs = ds ? (VncState *)ds->opaque : vnc_state;
     const char *options;
     int password = 0;
+    int reverse = 0;
 #if CONFIG_VNC_TLS
     int tls = 0, x509 = 0;
 #endif
@@ -2179,6 +2185,13 @@
        }
 #endif
     }
+    if (strstart(display, "rev:", &p)) {
+       reverse = 1;
+       display = p;
+       if (!strchr(display, ':')) {
+           display = p - 1;
+       }
+    }
 #ifndef _WIN32
     if (strstart(display, "unix:", &p)) {
        addr = (struct sockaddr *)&uaddr;
@@ -2196,7 +2209,9 @@
        memset(uaddr.sun_path, 0, 108);
        snprintf(uaddr.sun_path, 108, "%s", p);
 
-       unlink(uaddr.sun_path);
+       if (!reverse) {
+           unlink(uaddr.sun_path);
+       }
     } else
 #endif
     {
@@ -2210,7 +2225,7 @@
            return -1;
        }
 
-       iaddr.sin_port = htons(ntohs(iaddr.sin_port) + 5900);
+       iaddr.sin_port = htons(ntohs(iaddr.sin_port) + (reverse ? 0 : 5900));
 
        vs->lsock = socket(PF_INET, SOCK_STREAM, 0);
        if (vs->lsock == -1) {
@@ -2233,6 +2248,22 @@
        }
     }
 
+    if (reverse) {
+       if (connect(vs->lsock, addr, addrlen) == -1) {
+           fprintf(stderr, "Connection to VNC client failed\n");
+           close(vs->lsock);
+           vs->lsock = -1;
+           free(vs->display);
+           vs->display = NULL;
+           return -1;
+       } else {
+           vs->csock = vs->lsock;
+           vs->lsock = -1;
+           vnc_connect(vs);
+           return 0;
+       }
+    }
+
     if (bind(vs->lsock, addr, addrlen) == -1) {
        fprintf(stderr, "bind() failed\n");
        close(vs->lsock);