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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

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       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.