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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 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.

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 ALSO
       udp(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  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2008-12-03                        UDPLITE(7)