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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 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 check-
            sum 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 gener-
            ate 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