Section (7) udplite
udplite — Lightweight User Datagram Protocol
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)(emthat is, it shares the same API and API behavior, and in addition offers two socket options to control the checksum coverage.
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,
options are valid on a UDP-Lite socket. See udp(7) for more
The following two options are specific to UDP-Lite.
This option sets the sender checksum coverage and takes an
intas 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).
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
lessthan the specified coverage value.
When the value of
UDPLITE_RECV_CSCOVexceeds the actual packet coverage, incoming packets are silently dropped, but may generate a warning message in the system log.
All errors documented for udp(7) may be returned. UDP-Lite does not add further errors.
Basic UDP-Litev4 statistics counters.
Basic UDP-Litev6 statistics counters.
Where glibc support is missing, the following definitions are needed:
#define IPPROTO_UDPLITE 136 #define UDPLITE_SEND_CSCOV 10 #define UDPLITE_RECV_CSCOV 11
RFC 3828 for the Lightweight User Datagram Protocol (UDP-Lite).
Documentation/networking/udplite.txt in the
Linux kernel source tree
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Copyright (c) 2008 by Gerrit Renker <gerriterg.abdn.ac.uk>
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$Id: udplite.7,v 1.12 2008/07/23 15:22:22 gerrit Exp gerrit $