Let us take a closer look at the acceptfilter apache windows with the support of our Server management support services at Bobcares.

AcceptFilter Directive

This directive configures optimizations for a Protocol’s Listener Sockets and its syntax is as follows:

AcceptFilter protocol accept_filter

Based on the Protocol type, the acceptfilter apache windows enables specific operating system optimizations for a listening socket. The main notion is that the kernel will not allocate a socket to the server process until either data or a full HTTP Request in the buffering stage. At the moment, it only support the Accept Filters from FreeBSD, TCP DEFER ACCEPT from Linux, and AcceptEx() from Windows.

When none is the argument, it will disable any acceptfilters for that protocol. This is useful for protocols that need a server to first provide data, such as ftp: or nntp:

AcceptFilter nntp none

The default protocol names for port 443 are https and http for all other ports. Add the protocol argument to the Listen directive to signal the usage of another protocol with the listening port.

On FreeBSD, the default values are:

AcceptFilter http httpready
AcceptFilter https dataready

At the kernel level, the httpready accept filter buffers complete HTTP requests. When the kernel receives an entire request, it sends it to the server. Only the accf data filter is utilized because HTTPS requests are encrypted.

On Linux, the default values are:

AcceptFilter http data
AcceptFilter https data

TCP DEFER ACCEPT in Linux does not support buffering http requests. Any value other than none enables TCP DEFER ACCEPT on that listener.

Windows’ default values are:

AcceptFilter http connect
AcceptFilter https connect

The mpm winnt interrupts the AcceptFilter to enable the AcceptEx() API and does not support http protocol buffering. Connect uses the AcceptEx() API to acquire network endpoint addresses, but unlike none, it does not wait for the initial data transmission.

None on Windows uses accept() instead of AcceptEx() and does not recycle sockets between connections. This is useful for network adapters that have lost driver support, as well as some virtual network providers such as vpn drivers and spam, virus, or spyware filters.

The data AcceptFilter (Windows)

The Windows data accept filter will wait until the data transmission and the initial data buffer and network endpoint addresses were acquired from the single AcceptEx() invocation in versions 2.4.23 and earlier. This implementation is currently in the deactivation stage due to a denial of service attack.

On Windows, current releases of httpd default to the connect filter and will fall back to connect if data is supplied. Prior release users are urged to add an explicit connect option to their AcceptFilter, as seen above.

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Conclusion

To conclude we have learned more about using the acceptfilter apache on windows and the various configurations with it with the assistance of our Server management support services.