Re: [Qemu-devel] PATCH: Put Psuedo-TTY in rawmode for char devices

[Daniel P. Berrange]

Re-posting patch for review/inclusion...

On Tue, Apr 22, 2008 at 01:50:57AM +0100, Daniel P. Berrange wrote:
> If running a QEMU instance with a serial/parallel device connected to a
> Psuedo-TTY, eg  '-serial pty',  every \r\n sequence output by the guest
> is getting translated into a \n\n sequence by the TTY layer. So clients
> interacting with the serial port via a TTY done get the correct \r\n
> sequence and text marches to the right and wraps. This is because the 
> TTY is not put into rawmode when QEMU sets it up. 
> 
> The following patch is a re-diff of a patch applied to Xen's QEMU code.
> It uses cfmakeraw() to ensure the TTY is put into rawmode, thus avoiding
> the incorrect \r\n translations. It also switches to tcsetattr() on the
> slave_fd instead of master_fd - although this is effectively the same on
> Linux, only slave_fd works on Solaris. Finally it stops using the 'name'
> arg to openpty() which is a security risk because its buffer size is
> undefined. Instead it makes use of the ptsname() function.

Here is the patch re-diff to apply cleanly to latest SVN checkout of
QEMU codebase.

   Signed-off-by: Daniel P. Berrange <address@hidden>

Regards,
Daniel

Index: vl.c
===================================================================
--- vl.c        (revision 4291)
+++ vl.c        (working copy)
@@ -2273,24 +2273,20 @@
 static CharDriverState *qemu_chr_open_pty(void)
 {
     struct termios tty;
-    char slave_name[1024];
     int master_fd, slave_fd;
 
 #if defined(__linux__)
     /* Not satisfying */
-    if (openpty(&master_fd, &slave_fd, slave_name, NULL, NULL) < 0) {
+    if (openpty(&master_fd, &slave_fd, NULL, NULL, NULL) < 0) {
         return NULL;
     }
 #endif
 
-    /* Disabling local echo and line-buffered output */
-    tcgetattr (master_fd, &tty);
-    tty.c_lflag &= ~(ECHO|ICANON|ISIG);
-    tty.c_cc[VMIN] = 1;
-    tty.c_cc[VTIME] = 0;
-    tcsetattr (master_fd, TCSAFLUSH, &tty);
+    /* Set raw attributes on the pty. */
+    cfmakeraw(&tty);
+    tcsetattr(slave_fd, TCSAFLUSH, &tty);
 
-    fprintf(stderr, "char device redirected to %s\n", slave_name);
+    fprintf(stderr, "char device redirected to %s\n", ptsname(master_fd));
     return qemu_chr_open_fd(master_fd, master_fd);
 }
 


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