UDPLITE(7) Linux Programmer's Manual UDPLITE(7)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), i.e., it
shares the same API and API behaviour, 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 check‐
sum 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 gener‐
ate a warning message in the system log.
ERRORS
All errors documented for udp(7) may be returned. UDP-Lite does not
add further errors.
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
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.
SEE ALSOudp(7), ip(7), ipv6(7), socket(7)
RFC 3828 for the Lightweight User Datagram Protocol (UDP-Lite)
Documentation/networking/udplite.txt
COLOPHON
This page is part of release 3.22 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/.
Linux 2008-12-03 UDPLITE(7)
