The TCP_DEFER_ACCEPT socket option is not natively supported by Windows.

WSL team are working with Windows networking team on this issue, but fix likely won't make it in RS3.

Doesn't block Apache2 from starting, just a warning. Pile-on below if otherwise.

Thanks @bitcrazed for reporting the issue. Your analysis above seems spot on.

Add the following line to the end of the /etc/apache2/apache2.conf file:

AcceptFilter http none

If you have this warning after enabling SSL (https), just add the following line to the end of the file :

/etc/apache2/apache2.conf

AcceptFilter https none

Keep in mind that this would just hide errors.

I have added both http and https

AcceptFilter https none
AcceptFilter http none

Hello,

I have added

AcceptFilter https none
AcceptFilter http none

This worked on start, however, when I give restart it continues with the same error.

@bitcrazed is there an issue somewhere open for the fix that can be tracked / voted on or is this it? Applications based on Apache Thrift currently do not work on WSL due to TCP_DEFER_ACCEPT not being available, eg. MapD

Thrift: Thu Aug 23 10:41:00 2018 TServerSocket::listen() setsockopt() TCP_DEFER_ACCEPT Protocol not available

#1953 (comment)

The TCP_DEFER_ACCEPT socket option is not natively supported by Windows.

WSL team are working with Windows networking team on this issue, but fix likely won't make it in RS3.

This is one of the main issues tracking this problem, so please subscribe to this issue if you're interested in future progress. @tara-raj will triage with the team and get back to you.

Hi @tara-raj, has there been any progress on this issue internally?

This is another one that should have been stubbed to do nothing back in 2016 (like every GNU/FOSS configure script on the planet does). Question rhetorical natch. Pretty sure it can be configured away with AcceptFilter http none but I haven't tried.

@therealkenc there does indeed appear to be a way to configure Apache to work around it, however, it's not Apache specific.

it's not Apache specific

That's rhetorical also.

Identifying other use-cases here is always good. Or at least, it never hurts.

That's rhetorical also.

Yes, although the fact that MapD (OmniSci) does not work due to Apache Thrift not working because of this is not rhetorical

due to Apache Thrift not working

Add #undef TCP_DEFER_ACCEPT here should make it go.

Is there plan to fix this?

@lion-wang based on the lack of response from MS it appears unlikely, but who knows.

While it has been pointed out that it's possible in some cases to change a configuration flag and in other cases to recompile to work around this issue, both of those options (especially the second) come with their own potential issues so supporting this on the MS side would still be preferable (aside from the efficiency of fixing in one place (WSL) instead of every dependent project having to do so).

instead of every dependent project having to do so

Since these seem to be de rigueur this week

/*  sockopt-stub.c

    sudo apt-install build-essential
    cd ~ && mkdir -p ~/build && cd build
    gcc -fPIC -c -o sockopt-stub.o sockopt-stub.c
    gcc -shared -o sockopt-stub.so sockopt-stub.o -ldl
    export LD_PRELOAD="$PWD/sockopt-stub.so"
    # ... run stuff    
 */
#define _GNU_SOURCE
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <dlfcn.h>

typedef int (*setsockopt_)(int sockfd, int level, int optname,
                      const void *optval, socklen_t optlen);
int setsockopt(int sockfd, int level, int optname,
                      const void *optval, socklen_t optlen)
{
    static setsockopt_ fn = (setsockopt_)(dlsym(RTLD_NEXT, "setsockopt"));
    if (level == IPPROTO_TCP && optname == TCP_DEFER_ACCEPT) {
        return 0;
    }
    return fn(sockfd, level, optname, optval, optlen);
}

Totally untested; I haven't run it even once. But that should get you there without having to recompile.

Thanks @therealkenc this is great, we are going to try this as a workaround.

(the point remains though - instead of every dependent project having to do so ~ instead of every user having to modify their system)

Same problem here...

Well it did not seem to have made it to 1903

@thevictor13 I suppose there's a possibility that "Full System Call Compatibility" will fix this issue (although, what do I know?) in WSL2: https://devblogs.microsoft.com/commandline/announcing-wsl-2/. This may be (part of) the reason this issue has not had any love from MS.

Hmm, makes sense. Thanks for the link! I'll keep an eye on it.

Just updated to WSL2 and no more error.

Still have it on WSL 2. Scratch that. I hadn't converted the distro.

For those as dumb as I am:

wsl --set-version Ubuntu 2

Yeah, make as @BenMorel said, if you have Windows 10 Build 18917 or higher. Other requirements.
Otherwise you have an option to ignore warning.

set-version

unknown command : --set-version

set-version

unknown command : --set-version

Yeah, make as @BenMorel said, if you have Windows 10 Build 18917 or higher. Other requirements.
Otherwise you have an option to ignore warning.

AcceptFilter https none
AcceptFilter http none