udplite(7) Miscellaneous Information 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 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
Linux man-pages 6.9.1 2024-05-02 udplite(7)
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