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.\" $FreeBSD: releng/10.1/share/man/man4/udplite.4 265947 2014-05-13 06:09:01Z kevlo $
.\"
.Dd April 7, 2014
.Dt UDPLITE 4
.Os
.Sh NAME
.Nm udplite
.Nd Lightweight User Datagram Protocol
.Sh SYNOPSIS
.In sys/types.h
.In sys/socket.h
.In netinet/udplite.h
.Ft int
.Fn socket AF_INET SOCK_DGRAM IPPROTO_UDPLITE
.Sh DESCRIPTION
The
.Tn UDP-Lite
protocol provides a partial checksum which allows
corrupted packets to be transmitted to the receiving
application.
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.
.Pp
.Tn UDP-Lite
supports a number of socket options which can be set with
.Xr setsockopt 2
and tested with
.Xr getsockopt 2 :
.Bl -tag -width ".Dv UDPLITE_SEND_CSCOV"
.It Dv UDPLITE_SEND_CSCOV
This option sets the sender checksum coverage.
A value of zero indicates that the entire packet
is covered by the checksum. 
A value of 1 to 7 must be discarded by the receiver.
.It Dv UDPLITE_RECV_CSCOV
This option is the receiver-side analogue.
It is truly optional, i.e. 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 this value.
.El
.Sh ERRORS
A socket operation may fail with one of the following errors returned:
.Bl -tag -width Er
.It Bq Er EISCONN
when trying to establish a connection on a socket which
already has one, or when trying to send a datagram with the destination
address specified and the socket is already connected;
.It Bq Er ENOTCONN
when trying to send a datagram, but
no destination address is specified, and the socket has not been
connected;
.It Bq Er ENOBUFS
when the system runs out of memory for
an internal data structure;
.It Bq Er EADDRINUSE
when an attempt
is made to create a socket with a port which has already been
allocated;
.It Bq Er EADDRNOTAVAIL
when an attempt is made to create a
socket with a network address for which no network interface
exists.
.El
.Sh SEE ALSO
.Xr getsockopt 2 ,
.Xr recv 2 ,
.Xr send 2 ,
.Xr socket 2