pkg/38101: pkgsrc - misc/screen failed to start on tty if BREAK is pending

[Wolfgang.Stukenbrock%nagler-company.com@localhost]

>Number:         38101
>Category:       pkg
>Synopsis:       pkgsrc - misc/screen failed to start on tty if BREAK is pending
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Feb 25 09:40:00 +0000 2008
>Originator:     Wolfgang Stukenbock
>Release:        NetBSD 4.0 pkgsrc-2007Q4
>Organization:
Dr. Nagler & Company GmbH
        
>Environment:
        
        
System: NetBSD s010 4.0 NetBSD 4.0 (NSW-S010) #16: Wed Feb 20 12:51:34 CET 2008 
wgstuken@s012:/export/NetBSD-4.0/N+C-build/.OBJDIR_amd64/export/NetBSD-4.0/src/sys/arch/amd64/compile/NSW-S010
 amd64
Architecture: x86_64
Machine: amd64
>Description:
        The package screen-4.0.3 failes to start on a tty when a break is 
pending on that interface.
        We are using screen as a console-multiplexer for the serial console of 
several servers.
        Screen will be started during system boot in detached mode from an 
rc-file.
        If in such case a break signal is pending on one of the interfaces 
screen is gooing to open
        during startup, screen will catch a SIGINT some milliseconds after 
opening the affected
        interface. At this time the SIGINT will terminate screen, so that it 
will not come up.
        Later - after startup has completed - screen will ignore SIGINT on the 
interface, but that is too late ...

        The problem can be "fixed" by turning the "brkint" flag off on such 
interfaces. Accedently
        the distribution does not allow to set the brkint flag while opening 
the tty port.
        Setting this flag by a "exec !.. stty -brkint" on the just created 
window is too late,
        screen will not come there - it dies before.
        Therfore it makes sence to add the brkint to the flags recognized on 
the creation command line.

        Due to the fact that kern/28678 is still not fixed, the following patch 
will also add support
        to set vmin and vtime on the command line.
>How-To-Repeat:
        No realy easy to reproduce ...
        You need a machine and start screen during startup e.g. with
        "/usr/pkg/bin/screen -m -d -S cons_screen -c /root/.cons_screenrc".
        Than you need a permant pending BREAK signal on one tty-line - we have 
had this situation on one
        line of a cyclades card (cy - driver).
        The rc-file (/root/.cons_screenrc) for screen should contain something 
like
          "screen -h 10000 -t s011 2 /dev/dtyCY004 38400,cs8,ixon,ixoff,-istrip"
          "exec !.. stty min 1 time 0"
        Remark: the second line is required as workaround for the bug reported 
in kern/28678.

        Whenn you boot the machine, screen tries to start, but will get SIGINT 
and dies while setting up the window.
>Fix:
        The following patch will add support to process vmin, vtime and 
[-]brkint on the creation command line.
        With this patch you can start the window with
        "screen -h 10000 -t s011 2 /dev/dtyCY004 
38400,cs8,ixon,ixoff,-istrip,-brkint,vmin=1,vtime=0"
        without any problem.

        Remark: this fix should work on any architecture screen supports. This 
assumes that "m->tio.c_cc" is present
        on all architectures, but the screen implemantation assumes this too as 
fare as I've seen.

        I've send this info to "screen%uni-erlangen.de@localhost" too. This 
address is noted as the bug-report address in
        the doku files of screen.

        Start of Patch for tty.sh:

--- tty.sh.orig 2008-02-25 09:32:06.000000000 +0100
+++ tty.sh      2008-02-25 09:45:41.000000000 +0100
@@ -743,6 +743,22 @@
          m->tio.c_cflag &= ~CRTSCTS;
 #endif
        }
+      else if (!strncmp("brkint", opt, 6))
+       {
+IF{BRKINT}     m->tio.c_iflag |= BRKINT;
+       }
+      else if (!strncmp("-brkint", opt, 7))
+       {
+IF{BRKINT}     m->tio.c_iflag &= ~BRKINT;
+       }
+      else if (!strncmp("vmin=", opt, 5) && opt[5] >= '0' && opt[5] <= '9')
+       {
+         m->tio.c_cc[VMIN] = atoi(&opt[5]) & 0xff;
+       }
+      else if (!strncmp("vtime=", opt, 6) && opt[6] >= '0' && opt[6] <= '9')
+       {
+         m->tio.c_cc[VTIME] = atoi(&opt[6]) & 0xff;
+       }
       else
         return -1;
       while (*opt && !index(sep, *opt)) opt++;

>Unformatted: