udplite (7)
Leading comments
Copyright (c) 2008 by Gerrit Renker <gerrit@erg.abdn.ac.uk> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. ...
NAME
udplite - Lightweight User Datagram ProtocolSYNOPSIS
#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)---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