облегченный протокол дейтаграмм пользователя (Lightweight User Datagram Protocol)
Имя (Name)
udplite - Lightweight User Datagram Protocol
Синопсис (Synopsis)
#include <sys/socket.h>
sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDPLITE);
Описание (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
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.
Ошибки (Error)
All errors documented for udp(7) may be returned. UDP-Lite does
not add further errors.
Файлы (Files)
/proc/net/snmp
Basic UDP-Litev4 statistics counters.
/proc/net/snmp6
Basic UDP-Litev6 statistics counters.
Версии (Versions)
UDP-Litev4/v6 first appeared in Linux 2.6.20.
Ошибки (баги) (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
Смотри также (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
