View source for FreeBSD APIs

I'm documenting [[FreeBSD|FreeBSD's]] departures from known standards/APIUE/UNP as I come across them in various man pages and source code. The entirety of the FreeBSD man pages can be browsed at http://www.freebsd.org/cgi/man.cgi. This page serves as a companion to "[[Linux APIs]]" and "[[POSIX]]".

==File descriptors==
* <tt>[[kqueue|kqueue(2)]]</tt>, introduced in FreeBSD 4.1, is FreeBSD's "better <tt>poll(2)</tt>", ala <tt>[[epoll|epoll(7)]]</tt> on [[Linux APIs|Linux]].
* <tt>[https://man.freebsd.org/cgi/man.cgi?query=accept_filter accept_filter(9)]</tt>
* <tt>getfh()</tt> and <tt>openfh()</tt>, similar to Linux's <tt>name_to_handle_at()</tt> and <tt>open_by_handle_at()</tt>

== Socket Options ==
=== SOL_SOCKET===
* SO_ACCEPTFILTER (Introduced in FreeBSD 4.0): Apply an <tt>accept_filter(9)</tt> kernel module to the <tt>listen(2)ing</tt> socket. The connection will not be <tt>accept(2)able</tt> until the filter is satisfied. <tt>accf_data(9)</tt>, satisfied by the receipt of any connection payload data, is roughly equivalent to [[Linux APIs#IPPROTO_TCP|Linux's]] TCP_DEFER_ACCEPT.
=== IPPROTO_TCP ===
* TCP_NOPUSH: Normally, every write operation to a TCP socket will result in an attempt to set the [[TCP]] PSH bit and transmit the queued data. With TCP_NOPUSH set, packets will be coalesced until either the MSS is reached, or the socket is closed. Compare to [[Linux APIs#IPPROTO_TCP|Linux's]] TCP_CORK.
** It is my experience that clearing this flag will result in the transmission of queued data, but I cannot find documentation supporting this. Tony Finch's [http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/netinet/tcp_usrreq.c.diff?r1=1.52&r2=1.53 kernel patch] seems to have been applied to FreeBSD 4.5, providing this behavior.
[[CATEGORY:FreeBSD]]