Re: Serious problem with base 7.0.4 on Windows

[Michael Davidsaver via Tech-talk <tech-talk at aps.anl.gov>]

On 6/20/20 5:01 AM, Mark Rivers via Tech-talk wrote:
> 
>> Could it be, that this commit removed the functionality that we need for  Windows ?
> 
> Yes, that is the problem.  These core-talk threads discuss it.
> 
> https://epics.anl.gov/core-talk/2020/msg01064.php
> https://epics.anl.gov/core-talk/2020/msg01071.php

I've committed what should be a fix on the 7.0 branch.
I was planning to get confirmation before announcing on tech-talk.
Since this is already being talked about though, here it is:

https://github.com/epics-base/epics-base/commit/19146a597b42bc5f03aed1d97ccef56b4c4d0fac

>> Does `git revert db6e7c7a22b73f70a8b93e2` help ?
> 
> The patch I posted basically reverts that commit.  But it is not quite that simple because base 7.0.4 changes the EPICS-specific way that __declspec(dllimport)/export is specified in base.  It no longer epicsShareFunc.

The fix can be slightly smaller as I've convinced myself that
only the unintentional change to epicsSocketEnableAddressReuseDuringTimeWaitState()
causes problems.  The intentional change to epicsSocketEnableAddressUseForDatagramFanout()
seems to be ok.


> Mark
> 
> 
> ________________________________
> From: Torsten Bögershausen <torsten.bogershausen at ess.eu>
> Sent: Saturday, June 20, 2020 2:03 AM
> To: Mark Rivers; 'tech-talk'
> Subject: Re: Serious problem with base 7.0.4 on Windows
> 
> Could it be, that this commit removed the functionality that we need for
> Windows ?
> 
> commit db6e7c7a22b73f70a8b93e2aa4b6fa505e0218a6
> Author: Michael Davidsaver <mdavidsaver at gmail.com>
> Date:   Wed Feb 5 10:30:58 2020 -0800
>      use one osdSockAddrReuse impl for all targets
>          drop win32 specialization of osdSockAddrReuse
> 
> After reading
> <https://docs.microsoft.com/en-us/windows/win32/winsock/using-so-reuseaddr-and-so-exclusiveaddruse>
> 
> it seems clear that there a different understandings what
> SO_REUSEADDR should do, compared UNIX - Windows.
> 
> Does `git revert db6e7c7a22b73f70a8b93e2` help ?
> 
> 
> On 19/06/20 22:40, Mark Rivers via Tech-talk wrote:
>> Folks,
>>
>> I just want to give a heads-up that I have found a serious problem in
>> base 7.0.4 on Windows.  Running a single IOC on a computer works fine.
>> However, additional IOCs started on the same machine cannot be reached
>> with Channel Access.
>>
>> I assume there will be a patch release soon.  Meanwhile this patch
>> (actually a new file) will fix the problem.
>>
>> corvette:local/epics/base-7.0.4>git diff R7.0.4 modules/libcom/
>>
>> diff --git a/modules/libcom/src/osi/os/WIN32/osdSockAddrReuse.cpp
>> b/modules/libcom/src/osi/os/WIN32/osdSockAddrReuse.cpp
>>
>> new file mode 100644
>>
>> index 0000000..cc13605
>>
>> --- /dev/null
>>
>> +++ b/modules/libcom/src/osi/os/WIN32/osdSockAddrReuse.cpp
>>
>> @@ -0,0 +1,44 @@
>>
>> +
>>
>> +/*************************************************************************\
>>
>> +* Copyright (c) 2002 The University of Chicago, as Operator of Argonne
>>
>> +*     National Laboratory.
>>
>> +* Copyright (c) 2002 The Regents of the University of California, as
>>
>> +*     Operator of Los Alamos National Laboratory.
>>
>> +* EPICS BASE Versions 3.13.7
>>
>> +* and higher are distributed subject to a Software License Agreement found
>>
>> +* in file LICENSE that is included with this distribution.
>>
>> +\*************************************************************************/
>>
>> +
>>
>> +/*
>>
>> + * Author: Jeff Hill
>>
>> + */
>>
>> +
>>
>> +#define epicsExportSharedSymbols
>>
>> +#include "osiSock.h"
>>
>> +#include "errlog.h"
>>
>> +
>>
>> +/*
>>
>> + * Note: WINSOCK appears to assign a different functionality for
>>
>> + * SO_REUSEADDR compared to other OS. With WINSOCK SO_REUSEADDR indicates
>>
>> + * that simultaneously servers can bind to the same TCP port on the
>> same host!
>>
>> + * Also, servers are always enabled to reuse a port immediately after
>>
>> + * they exit ( even if SO_REUSEADDR isnt set ).
>>
>> + */
>>
>> +LIBCOM_API void epicsStdCall
>>
>> +    epicsSocketEnableAddressReuseDuringTimeWaitState ( SOCKET s )
>>
>> +{
>>
>> +}
>>
>> +
>>
>> +LIBCOM_API void epicsStdCall
>>
>> +    epicsSocketEnableAddressUseForDatagramFanout ( SOCKET s )
>>
>> +{
>>
>> +    int yes = true;
>>
>> +    int status;
>>
>> +    status = setsockopt ( s, SOL_SOCKET, SO_REUSEADDR,
>>
>> +        (char *) & yes, sizeof ( yes ) );
>>
>> +    if ( status < 0 ) {
>>
>> +        errlogPrintf (
>>
>> +            "epicsSocketEnablePortUseForDatagramFanout: "
>>
>> +            "unable to set SO_REUSEADDR?\n");
>>
>> +    }
>>
>> +}
>>
>> Mark
>>