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 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

COLOPHON

       This  page is part of release 3.55 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)