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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 cov-
       erage.

   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 informa-
       tion.

       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 lim-
	      ited 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)
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