UDPLITE

Section: Linux Programmer's Manual (7)
Updated: 2014-07-08
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NAME

udplite - Lightweight User Datagram Protocol  

SYNOPSIS

#include <sys/socket.h>

sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDPLITE);  

DESCRIPTION

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)---that is, it shares the same API and API behavior, and in addition offers two socket options to control the checksum coverage.  

Address format

UDP-Litev4 uses the sockaddr_in address format described in ip(7). UDP-Litev6 uses the sockaddr_in6 address format described in ipv6(7).  

Socket options

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_CSCOV
This 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_CSCOV
This 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.

 

ERRORS

All errors documented for udp(7) may be returned. UDP-Lite does not add further errors.  

FILES

/proc/net/snmp - basic UDP-Litev4 statistics counters.
/proc/net/snmp6 - basic UDP-Litev6 statistics counters.  

VERSIONS

UDP-Litev4/v6 first appeared in Linux 2.6.20.  

BUGS

Where glibc support is missing, the following definitions are needed:

#define IPPROTO_UDPLITE     136
#define UDPLITE_SEND_CSCOV  10
#define UDPLITE_RECV_CSCOV  11
 

SEE ALSO

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


 

Index

NAME
SYNOPSIS
DESCRIPTION
Address format
Socket options
ERRORS
FILES
VERSIONS
BUGS
SEE ALSO

This document was created by man2html, using the manual pages.
Time: 02:55:20 GMT, September 18, 2014