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 to UDP is in using a different
IP protocol identifier (IANA number 136).
The UDP-Lite implementation is a full extension of
udp(7), i.e., it
shares the same API and API behaviour, and in addition offers two socket
options to control the checksum coverage.
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.
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
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.
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 3.44 of the Linux
man-pages project. A
description of the project, and information about reporting bugs, can be found
at
http://www.kernel.org/doc/man-pages/.