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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

       ip(7), ipv6(7), socket(7), udp(7)

       RFC 3828 for the Lightweight User Datagram Protocol (UDP-Lite)
       Documentation/networking/udplite.txt

COLOPHON

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