UDPLITE(7)                (2017-09-15)                 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 dis-
          carded 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 from UDP is in using a different IP protocol
          identifier (IANA number 136).

          The UDP-Lite implementation is a full extension of
          udp(7)-that is, it shares the same API and API behavior, and
          in addition offers two socket options to control the check-
          sum 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.

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               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 there-
               fore 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 par-
               tial 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

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          This page is part of release 5.10 of the Linux man-pages
          project.  A description of the project, information about
          reporting bugs, and the latest version of this page, can be
          found at https://www.kernel.org/doc/man-pages/.

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