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.\" This manpage copyright 1998 by Andi Kleen. Subject to the GPL.
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.\" Based on the original comments from Alexey Kuznetsov
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.\" $Id: netlink.3,v 1.1 1999/05/14 17:17:24 freitag Exp $
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.TH NETLINK 3 1999-05-14 "Linux Man Page" "Linux Programmer's Manual"
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.SH NAME
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netlink \- Netlink macros
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.SH SYNOPSIS
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.nf
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2005-10-26 11:27:52 +00:00
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.\" FIXME what will glibc 2.1 use here?
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.B #include <asm/types.h>
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.br
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.B #include <linux/netlink.h>
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.br
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.BI "int NLMSG_ALIGN(size_t " len );
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.br
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.BI "int NLMSG_LENGTH(size_t " len );
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.br
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.BI "int NLMSG_SPACE(size_t " len );
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.br
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.BI "void *NLMSG_DATA(struct nlmsghdr *" nlh );
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.br
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.BI "struct nlmsghdr *NLMSG_NEXT(struct nlmsghdr *" nlh ", int " len );
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.br
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.BI "int NLMSG_OK(struct nlmsghdr *" nlh ", int " len );
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.br
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.BI "int NLMSG_PAYLOAD(struct nlmsghdr *" nlh ", int " len );
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.fi
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.SH DESCRIPTION
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.I <linux/netlink.h>
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defines several standard macros to access or create a netlink datagram.
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They are similar in spirit to the macros defined in
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.BR cmsg (3)
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for auxiliary data.
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The buffer passed to and from a netlink socket should
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be only accessed using these macros.
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.TP
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NLMSG_ALIGN
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Round the length of a netlink message up to align it properly.
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.TP
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NLMSG_LENGTH
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Gets the payload length as argument and returns the aligned length to store
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in the
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.B nlmsg_len
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field of the
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.IR nlmsghdr .
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.TP
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NLMSG_SPACE
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Return the number of bytes a netlink message with payload of the passed length
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would occupy.
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.TP
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NLMSG_DATA
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Return a pointer to the payload associated with the passed
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.IR nlmsghdr .
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.TP
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.\" FIXME this is bizarre, maybe the interface should be fixed.
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NLMSG_NEXT
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Get the next
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.I nlmsghdr
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in a multipart message.
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The caller must check if the current nlmsghdr didn't have the NLMSG_DONE
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set \(em this function doesn't return NULL on end.
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The length parameter is an lvalue containing the remaining length
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of the message buffer.
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This macro decrements it by the length of the message header.
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.TP
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NLMSG_OK
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Return true if the netlink message is not truncated and ok to parse.
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.TP
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NLMSG_PAYLOAD
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Return the length of the payload associated with the
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.IR nlmsghdr .
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.SH NOTES
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It is often better to use netlink via
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.B libnetlink
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than via the low level kernel interface.
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.SH "SEE ALSO"
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.BR netlink (7)
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.PP
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and ftp://ftp.inr.ac.ru/ip-routing/iproute2* for libnetlink
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