diff --git a/man7/udplite.7 b/man7/udplite.7 new file mode 100644 index 000000000..136d7eed1 --- /dev/null +++ b/man7/udplite.7 @@ -0,0 +1,152 @@ +.\" Copyright (c) 2008 by Gerrit Renker +.\" +.\" 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. +.\" +.\" Since the Linux kernel and libraries are constantly changing, this +.\" manual page may be incorrect or out-of-date. The author(s) assume no +.\" responsibility for errors or omissions, or for damages resulting from +.\" the use of the information contained herein. The author(s) may not +.\" have taken the same level of care in the production of this manual, +.\" which is licensed free of charge, as they might when working +.\" professionally. +.\" +.\" Formatted or processed versions of this manual, if unaccompanied by +.\" the source, must acknowledge the copyright and authors of this work. +.\" +.\" $Id: udplite.7,v 1.12 2008/07/23 15:22:22 gerrit Exp gerrit $ +.\" +.TH UDPLITE 7 2008-08-08 "Linux" "Linux Programmer's Manual" +.SH NAME +udplite \- Lightweight User Datagram Protocol +.SH SYNOPSIS +.B #include +.br +.\" FIXME . see #defines under `BUGS', +.\" when glibc supports this, add +.\" #include +.sp +.B s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDPLITE); +.SH 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 +.BR 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 +.BR udp (7), +i.e., it shares the same API and API behaviour, and in addition +offers two socket options to control the checksum coverage. +.SS "Address Format" +UDP-Litev4 uses the +.I sockaddr_in +address format described in +.BR ip (7). +UDP-Litev6 uses the +.I sockaddr_in6 +address format described in +.BR ipv6 (7). +.SS "Socket Options" +To set or get a UDP-Lite socket option, call +.BR getsockopt (2) +to read or +.BR setsockopt (2) +to write the option with the option level argument set to +.BR IPPROTO_UDPLITE . +In addition, all +.B IPPROTO_UDP +socket options are valid on a UDP-Lite socket. +See +.BR udp (7) +for more information. + +The following two options are specific to UDP-Lite. +.TP +.BR UDPLITE_SEND_CSCOV +This option sets the sender checksum coverage and takes an +.I 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 +.BR getsockopt (2). +.TP +.BR UDPLITE_RECV_CSCOV +This is the receiver-side analogue and uses uses the same argument format +and value range as +.BR 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 +.I less +than the specified coverage value. + +When the value of +.B UDPLITE_RECV_CSCOV +exceeds the actual packet coverage, incoming packets are silently dropped, +but may generate a warning message in the system log. +.\" SO_NO_CHECK exists and is supported by UDPv4, but is +.\" commented out in socket(7), hence also commented out here +.\".PP +.\"Since UDP-Lite mandates checksums, checksumming can not be disabled +.\"via the +.\".B SO_NO_CHECK +.\"option from +.\".BR socket (7). +.SH ERRORS +All errors documented for +.BR udp (7) +may be returned. +UDP-Lite does not add further errors. +.SH BUGS +.\" FIXME . remove this section once glibc supports UDP-Lite +Where glibc support is missing, the following definitions are needed: +.in +4n +.nf + +#define IPPROTO_UDPLITE 136 +.\" The following two are defined in the kernel in linux/net/udplite.h +#define UDPLITE_SEND_CSCOV 10 +#define UDPLITE_RECV_CSCOV 11 +.fi +.in +.SH FILES +.I /proc/net/snmp +\- basic UDP-Litev4 statistics counters. +.br +.I /proc/net/snmp6 +\- basic UDP-Litev6 statistics counters. +.SH VERSIONS +UDP-Litev4/v6 first appeared in Linux 2.6.20. +.SH "SEE ALSO" +.BR udp (7), +.BR ip (7), +.BR ipv6 (7), +.BR socket (7) + +RFC\ 3828 for the Lightweight User Datagram Protocol (UDP-Lite) +.br +.I Documentation/networking/udplite.txt