udplite(7) - man - phpMan

Che Dong

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 ad‐
vantages for some types of multimedia transport that may be able to make use of slightly dam‐
aged 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 from 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 sock‐
addr_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 IP‐‐
PROTO_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 in‐
structs 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

COLOPHON
This page is part of release 5.10 of the Linux man-pages project. A description of the
project, information about reporting bugs, and the latest version of this page, can be found
at https://www.kernel.org/doc/man-pages/.

Linux 2017-09-15 UDPLITE(7)