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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 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 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.

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

   This  page  is  part of release 4.09 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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