Re: Socket options KPI

[Iain Hibbert <plunky%rya-online.net@localhost>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Fri, 18 Jan 2008, Elad Efrat wrote:

> I have a patch to make a large portion of the network code use a new
> "struct sockopt" (inspired by similar work done in FreeBSD, with input
> from dyoung@ and yamt@) instead of passing socket options in mbufs.
>
> The work is incomplete - although I think the majority of the code was
> covered.

I have been corresponding intermittently with Elad on this (he has run out
of time lately and I was busy last month), and the KPI has evolved to be
somewhat less complex.  I wrote a manpage (attached) and have uploaded the
(I think complete now) kernel patch to:

        http://www.netbsd.org/~plunky/sockopt-20080502a.diff

comments?
iain

(some code does still use mbufs, this to be addressed later)

(Elad has done most of the hard work, I've just shuffled around a bit of
whitespace to get credits)
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.7 (NetBSD)

iQEVAwUBSBq78/FJxoMWDXVDAQLVNQf+Kz7E6ZBWq6AotoYQVyF/Jz62rk43INqt
oHyZ/4jlm/4Osbd+F6luU0jiW4lyPqwe1i4WOyPe96XsKjq2EozMmbKgp7nbLxh6
9OxIZl+B9OR2/RJklpV3BROK7UJlV7UeHm6pxnoo5Ljkz/EssNfvjh94Gnccy4mU
Hi5H9+dW/OUEMtdVXu8fGSEIk+atoAUqwQmF+Yrrlex8on1kOYdJlDZwGTbEySnd
vM2K+FZlcMzScJ+y5ogvAYc0xjsQblc8inoQPyq7Rh3e2V8YbYQtQORtQXg95KUh
KMJiXWD6w5y0VoJefK9tShJkosODLbQaHpkOsKnQO3DegMN9pkDjPQ==
=qfRD
-----END PGP SIGNATURE-----

.\"     $NetBSD: sockopt.9$
.\"
.\" Copyright (c) 2008 Iain Hibbert
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd May 1, 2008
.Dt SOCKOPT 9
.Os
.Sh NAME
.Nm sockopt_init ,
.Nm sockopt_destroy ,
.Nm sockopt_set ,
.Nm sockopt_setint ,
.Nm sockopt_get ,
.Nm sockopt_getint
.Nd socket options handling
.Sh SYNOPSIS
.In sys/socketvar.h
.Ft void
.Fn sockopt_init "struct sockopt *sopt" "int level" "int name" "size_t size"
.Ft void
.Fn sockopt_destroy "struct sockopt *sopt"
.Ft int
.Fn sockopt_set "struct sockopt *sopt" "const void *value" "size_t size"
.Ft int
.Fn sockopt_setint "struct sockopt *sopt" "int value"
.Ft int
.Fn sockopt_get "struct sockopt *sopt" "void *value" "size_t size"
.Ft int
.Fn sockopt_getint "struct sockopt *sopt" "int *value"
.Sh DESCRIPTION
The sockopt structure is used to pass a socket option and associated
value:
.Bd -literal -offset indent
struct sockopt {
        int             sopt_level;             /* option level */
        int             sopt_name;              /* option name */
        size_t          sopt_size;              /* data length */
        void *          sopt_data;              /* data pointer */
        uint8_t         sopt_buf[sizeof(int)];  /* internal storage */
};
.Ed
.Pp
The internal storage is used for the common case of values up to integer
size so that memory allocation is not required and sopt_data will point
to this in that case.
.Pp
Note: a sockopt structure may only be used for a single level/name/size
combination.
If the structure is to be re-used, it must be destroyed and re-initialized
with the new values.
.Sh OPTIONS
.Bl -tag -width xxxx
.It Cd "options DIAGNOSTIC"
Kernels compiled with the
.Dv DIAGNOSTIC
option will perform basic sanity checks on socket options operations.
.El
.Sh FUNCTIONS
.Bl -tag -width xxxx
.It Fn sockopt_init "sopt" "level" "name" "size"
Initialise sockopt storage.
If
.Ar size
is given,
.Fn sockopt_init
will arrange for sopt_data to point to a buffer of
.Ar size
bytes for the sockopt value.
.It Fn sockopt_destroy "sopt"
Destroy sockopt storage, releasing any allocated memory.
.It Fn sockopt_set "sopt" "value" "size"
Copy in sockopt value.
The sockopt structure must contain a data field of
.Ar size
bytes or be previously unset, in which case a data buffer may be
allocated.
.It Fn sockopt_setint "sopt" "value"
Common case of set sockopt integer value.
The sockpt structure must contain an int sized data field or be previously
unset, in which case the data pointer will be set to the internal storage.
.It Fn sockopt_get "sopt" "value" "size"
Copy out sockopt value.
Will return
.Dv EINVAL 
if an incorrect data size is given.
.It Fn sockopt_getint "sopt" "value"
Common case of get sockopt integer value.
.El
.Sh CODE REFERENCES
This section describes places within the
.Nx
source tree where code implementing socket options can be found.
All pathnames are relative to
.Pa /usr/src .
.Pp
The function prototypes and sockopt structure are defined in the
.Pa sys/sys/socketvar.h
header file, and the socket options implementation is in
.Pa sys/kern/uipc_socket.c .
.Sh SEE ALSO
.Xr errno 2 ,
.Xr malloc 9
.Sh HISTORY
The socket options code first appeared in
.Nx 5.0 .