accf_http(9) [netbsd man page]

ACCF_HTTP(9)						   BSD Kernel Developer's Manual					      ACCF_HTTP(9)

NAME

     accf_http -- buffer incoming connections until a certain complete HTTP requests arrive

SYNOPSIS

     options INET
     pseudo-device accf_http

DESCRIPTION

     This is a filter to be placed on a socket that will be using accept() to receive incoming HTTP connections.

     Once installed on a listening socket, this filter is activated when a connection becomes ready to receive data (at which point accept(2)
     would usually return the connected descriptor to the application).  The filter prevents the descriptor from being returned immediately to the
     application via accept(2).  The descriptor is made available to the application via accept(2) only when one of the following conditions is
     met:

     1.   A complete, syntactically valid HTTP/1.0 or HTTP/1.1 HEAD or GET request has been buffered by the kernel.

     2.   The data buffered by the kernel cannot be part of a complete, syntactically valid HTTP 1.0 or HTTP/1.1 HEAD or GET request.

     The utility of accf_http is that a server will not have to context switch several times before performing the initial parsing of the request.
     This effectively reduces the amount of required CPU utilization to handle incoming requests by keeping active processes in preforking servers
     such as Apache low and reducing the size of the file descriptor set that needs to be managed by interfaces such as select(), poll() or
     kevent() based servers.

EXAMPLES

     If the accf_data accept filter is present in the kernel configuration, this will enable the http accept filter on the socket sok.

	     struct accept_filter_arg afa;

	     bzero(&afa, sizeof(afa));
	     strcpy(afa.af_name, "httpready");
	     setsockopt(sok, SOL_SOCKET, SO_ACCEPTFILTER, &afa, sizeof(afa));

SEE ALSO

     setsockopt(2), accept_filter(9)

HISTORY

     The accept filter mechanism and the accf_http filter were introduced in FreeBSD 4.0.  They were ported to NetBSD by Coyote Point Systems and
     appeared in NetBSD 5.0.

AUTHORS

     This manual page and the filter were written by Alfred Perlstein.

BSD
								 September 4, 2008							       BSD

ACCEPT_FILTER(9)					   BSD Kernel Developer's Manual					  ACCEPT_FILTER(9)

NAME

     accept_filter, accept_filt_add, accept_filt_del, accept_filt_generic_mod_event, accept_filt_get -- filter incoming connections

SYNOPSIS

     #define ACCEPT_FILTER_MOD
     #include <sys/param.h>
     #include <sys/kernel.h>
     #include <sys/sysctl.h>
     #include <sys/signalvar.h>
     #include <sys/socketvar.h>
     #include <netinet/accept_filter.h>

     int
     accept_filt_add(struct accept_filter *filt);

     int
     accept_filt_del(char *name);

     int
     accept_filt_generic_mod_event(module_t mod, int event, void *data);

     struct accept_filter *
     accept_filt_get(char *name);

DESCRIPTION

     Accept filters allow an application to request that the kernel pre-process incoming connections.  This manual page describes the kernel
     interface for accept filters.  User applications request accept filters via the setsockopt(2) system call, passing in an optname of
     SO_ACCEPTFILTER.

IMPLEMENTATION NOTES

     A module that wants to be an accept filter must provide a struct accept_filter to the system:

     struct accept_filter {
	     char    accf_name[16];
	     void    (*accf_callback)(struct socket *so, void *arg, int waitflag);
	     void *  (*accf_create)(struct socket *so, char *arg);
	     void    (*accf_destroy)(struct socket *so);
	     SLIST_ENTRY(accept_filter) accf_next;   /* next on the list */
     };

     The module should register it with the function accept_filt_add(), passing a pointer to a struct accept_filter, allocated with malloc(9).

     The accept filters currently provided with NetBSD (accf_data(9) and accf_http(9)) are implemented as pseudo-devices, but an accept filter may
     use any supported means of initializing and registering itself at system startup or later, including the module framework if supported by the
     running kernel.

     The fields of struct accept_filter are as follows:

     accf_name	    Name of the filter; this is how it will be accessed from userland.

     accf_callback  The callback that the kernel will do once the connection is established.  It is the same as a socket upcall and will be called
		    when the connection is established and whenever new data arrives on the socket, unless the callback modifies the socket's
		    flags.

     accf_create    Called whenever a setsockopt(2) installs the filter onto a listening socket.

     accf_destroy   Called whenever the user removes the accept filter on the socket.

     The accept_filt_del() function passed the same string used in accept_filter.accf_name during registration with accept_filt_add(), the kernel
     will then disallow and further userland use of the filter.

     The accept_filt_get() function is used internally to locate which accept filter to use via the setsockopt(2) system call.

     The accept_filt_generic_mod_event() function can be used by accept filters which are loadable kernel modules to add and delete themselves.

SEE ALSO

     setsockopt(2), accf_data(9), accf_http(9), malloc(9)

HISTORY

     The accept filter mechanism was introduced in FreeBSD 4.0.  It was ported to NetBSD by Coyote Point Systems, Inc. and appeared in NetBSD 5.0.

AUTHORS

     This manual page was written by Alfred Perlstein, Sheldon Hearn, and Jeroen Ruigrok van der Werven.

     The accept filter concept was pioneered by David Filo at Yahoo! and refined to be a loadable module system by Alfred Perlstein.

BSD
								 November 12, 2008							       BSD