Re: [Qemu-devel] PATCH: enabling TCP keepalives on VNC connections

["David S. Ahern" <daahern@cisco.com>]

Anthony Liguori wrote:
> David S. Ahern wrote:
>> Something is blocking this message from my gmail account; trying again
>> with this one.
>>
>> This patch enables TCP keepalives on VNC connections for linux hosts.
>> After 60-seconds of idle time, probes are sent every 12 seconds with the
>> connection resetting after 5 failed probes (ie., connection is closed if
>> no response received in 60-seconds).
>>
>> Signed-off-by: David Ahern <dsahern@gmail.com>
>>
>>
>> david
>>   diff --git a/vnc.c b/vnc.c
>> index ab1f044..7a8bbd7 100644
>> --- a/vnc.c
>> +++ b/vnc.c
>> @@ -32,6 +32,12 @@
>>  
>>  #define VNC_REFRESH_INTERVAL (1000 / 30)
>>  
>> +#ifdef __linux__
>> +#define VNC_TCP_KEEPIDLE  60
>> +#define VNC_TCP_KEEPINTVL 12
>> +#define VNC_TCP_KEEPCNT    5
>> +#endif
>>   
> 
> Should probe in configure and make an appropriate CONFIG_.  This is not
> necessarily a linux specific feature.

ok. I can only test on linux and mac os x; I do not have a means for
building on windows.

> 
>>  #include "vnc_keysym.h"
>>  #include "d3des.h"
>>  
>> @@ -2015,12 +2021,41 @@ static void vnc_listen_read(void *opaque)
>>      VncDisplay *vs = opaque;
>>      struct sockaddr_in addr;
>>      socklen_t addrlen = sizeof(addr);
>> +    int val;
>>  
>>      /* Catch-up */
>>      vga_hw_update();
>>  
>>      int csock = accept(vs->lsock, (struct sockaddr *)&addr, &addrlen);
>>      if (csock != -1) {
>> +#ifdef __linux__
>> +        /* best effort to enable keep alives */
>> +        val = 1;
>> +        if (setsockopt(csock, SOL_SOCKET, SO_KEEPALIVE,
>> +                       &val, sizeof(val)) < 0) {
>> +            fprintf(stderr, "VNC: failed to enable keepalives\n");
>> +        }
>>   
> 
> If we want to enable keep alive universally, wouldn't we also want it on
> the tcp: character devices?
> 

Ok. I can make a generic library call that takes the timers as input
options. If the timer is 0 means leave at OS default. What about other
accept() callers - e.g.,gdbstub?

I'll take a look at this end of next week after my vacation around this
weekend.

david