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[thirdparty/man-pages.git] / man7 / udplite.7

.\" Copyright (c) 2008 by Gerrit Renker <gerrit@erg.abdn.ac.uk>
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.\" $Id: udplite.7,v 1.12 2008/07/23 15:22:22 gerrit Exp gerrit $
.\"
.TH udplite 7 (date) "Linux man-pages (unreleased)"
.SH NAME
udplite \- Lightweight User Datagram Protocol
.SH SYNOPSIS
.nf
.B #include <sys/socket.h>
.\" FIXME . see #defines under `BUGS',
.\"        when glibc supports this, add
.\"        #include <netinet/udplite.h>
.PP
.B sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDPLITE);
.fi
.SH DESCRIPTION
This is an implementation of the Lightweight User Datagram Protocol
(UDP-Lite), as described in RFC\ 3828.
.PP
UDP-Lite is an extension of UDP (RFC\ 768) to support variable-length
checksums.
This has advantages for some types of multimedia transport that
may be able to make use of slightly damaged datagrams,
rather than having them discarded by lower-layer protocols.
.PP
The variable-length checksum coverage is set via a
.BR setsockopt (2)
option.
If this option is not set, the only difference from UDP is
in using a different IP protocol identifier (IANA number 136).
.PP
The UDP-Lite implementation is a full extension of
.BR udp (7)\(emthat
is, it shares the same API and API behavior, and in addition
offers two socket options to control the checksum coverage.
.SS Address format
UDP-Litev4 uses the
.I sockaddr_in
address format described in
.BR ip (7).
UDP-Litev6 uses the
.I sockaddr_in6
address format described in
.BR ipv6 (7).
.SS Socket options
To set or get a UDP-Lite socket option, call
.BR getsockopt (2)
to read or
.BR setsockopt (2)
to write the option with the option level argument set to
.BR IPPROTO_UDPLITE .
In addition, all
.B IPPROTO_UDP
socket options are valid on a UDP-Lite socket.
See
.BR udp (7)
for more information.
.PP
The following two options are specific to UDP-Lite.
.TP
.B UDPLITE_SEND_CSCOV
This option sets the sender checksum coverage and takes an
.I int
as argument, with a checksum coverage value in the range 0..2^16-1.
.IP
A value of 0 means that the entire datagram is always covered.
Values from 1\-7 are illegal (RFC\ 3828, 3.1) and are rounded up to
the minimum coverage of 8.
.IP
With regard to IPv6 jumbograms (RFC\ 2675), the UDP-Litev6 checksum
coverage is limited to the first 2^16-1 octets, as per RFC\ 3828, 3.5.
Higher values are therefore silently truncated to 2^16-1.
If in doubt, the current coverage value can always be queried using
.BR getsockopt (2).
.TP
.B UDPLITE_RECV_CSCOV