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  addi-
       tion 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 cover-
              age 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 fil-
              ter: when enabled, it instructs the kernel to drop all packets which have a coverage less than the specified  cov-
              erage 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 3.25 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)