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udplite — Lightweight User Datagram Protocol
#include <sys/socket.h>
sockfd =
socket( |
AF_INET, |
| SOCK_DGRAM, | |
IPPROTO_UDPLITE); |
This is an implementation of the Lightweight User Datagram Protocol (UDP-Lite), as described in RFC 3828.
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.
The variable-length checksum coverage is set via a setsockopt(2) option. If this option is not set, the only difference to UDP is in using a different IP protocol identifier (IANA number 136).
The UDP-Lite implementation is a full extension of udp(7), i.e., it shares the same API and API behaviour, and in addition offers two socket options to control the checksum coverage.
UDP-Litev4 uses the sockaddr_in address format
described in ip(7). UDP-Litev6 uses
the sockaddr_in6
address format described in ipv6(7).
To set or get a UDP-Lite socket option, call getsockopt(2) to read or
setsockopt(2) to write
the option with the option level argument set to IPPROTO_UDPLITE. In addition,
all IPPROTO_UDP socket
options are valid on a UDP-Lite socket. See udp(7) for more
information.
The following two options are specific to UDP-Lite.
UDPLITE_SEND_CSCOVThis option sets the sender checksum coverage and
takes an int as argument, with
a checksum coverage value in the range 0..2^16-1.
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.
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 getsockopt(2).
UDPLITE_RECV_CSCOVThis is the receiver-side analogue and uses the
same argument format and value range as UDPLITE_SEND_CSCOV. This option is
not required to enable traffic with partial checksum
coverage. Its function is that of a traffic filter:
when enabled, it instructs the kernel to drop all
packets which have a coverage less than the
specified coverage value.
When the value of UDPLITE_RECV_CSCOV exceeds the
actual packet coverage, incoming packets are silently
dropped, but may generate a warning message in the
system log.
/proc/net/snmp − basic
UDP-Litev4 statistics counters.
/proc/net/snmp6 −
basic UDP-Litev6 statistics counters.
Where glibc support is missing, the following definitions are needed:
#define IPPROTO_UDPLITE 136 #define UDPLITE_SEND_CSCOV 10 #define UDPLITE_RECV_CSCOV 11
ip(7), ipv6(7), socket(7), udp(7)
RFC 3828 for the Lightweight User Datagram Protocol (UDP-Lite).
Documentation/networking/udplite.txt in the
Linux kernel source tree
This page is part of release 3.52 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man−pages/.
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Copyright (c) 2008 by Gerrit Renker <gerriterg.abdn.ac.uk> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END $Id: udplite.7,v 1.12 2008/07/23 15:22:22 gerrit Exp gerrit $ |