man3/netlink.3

   1 .\" This manpage copyright 1998 by Andi Kleen.
   2 .\"
   3 .\" SPDX-License-Identifier: GPL-1.0-or-later
   4 .\"
   5 .\" Based on the original comments from Alexey Kuznetsov
   6 .\" $Id: netlink.3,v 1.1 1999/05/14 17:17:24 freitag Exp $
   7 .\"
   8 .TH netlink 3 (date) "Linux man-pages (unreleased)"
   9 .SH NAME
  10 netlink \- Netlink macros
  11 .SH LIBRARY
  12 Standard C library
  13 .RI ( libc ", " \-lc )
  14 .SH SYNOPSIS
  15 .nf
  16 .B #include <asm/types.h>
  17 .B #include <linux/netlink.h>
  18 .PP
  19 .BI "int NLMSG_ALIGN(size_t " len );
  20 .BI "int NLMSG_LENGTH(size_t " len );
  21 .BI "int NLMSG_SPACE(size_t " len );
  22 .BI "void *NLMSG_DATA(struct nlmsghdr *" nlh );
  23 .BI "struct nlmsghdr *NLMSG_NEXT(struct nlmsghdr *" nlh ", int " len );
  24 .BI "int NLMSG_OK(struct nlmsghdr *" nlh ", int " len );
  25 .BI "int NLMSG_PAYLOAD(struct nlmsghdr *" nlh ", int " len );
  26 .fi
  27 .SH DESCRIPTION
  28 .I <linux/netlink.h>
  29 defines several standard macros to access or create a netlink datagram.
  30 They are similar in spirit to the macros defined in
  31 .BR cmsg (3)
  32 for auxiliary data.
  33 The buffer passed to and from a netlink socket should
  34 be accessed using only these macros.
  35 .TP
  36 .BR NLMSG_ALIGN ()
  37 Round the length of a netlink message up to align it properly.
  38 .TP
  39 .BR NLMSG_LENGTH ()
  40 Given the payload length,
  41 .IR len ,
  42 this macro returns the aligned length to store in the
  43 .I nlmsg_len
  44 field of the
  45 .IR nlmsghdr .
  46 .TP
  47 .BR NLMSG_SPACE ()
  48 Return the number of bytes that a netlink message with payload of
  49 .I len
  50 would occupy.
  51 .TP
  52 .BR NLMSG_DATA ()
  53 Return a pointer to the payload associated with the passed
  54 .IR nlmsghdr .
  55 .TP
  56 .\" this is bizarre, maybe the interface should be fixed.
  57 .BR NLMSG_NEXT ()
  58 Get the next
  59 .I nlmsghdr
  60 in a multipart message.
  61 The caller must check if the current
  62 .I nlmsghdr
  63 didn't have the
  64 .B NLMSG_DONE
  65 set\(emthis function doesn't return NULL on end.
  66 The
  67 .I len
  68 argument is an lvalue containing the remaining length
  69 of the message buffer.
  70 This macro decrements it by the length of the message header.
  71 .TP
  72 .BR NLMSG_OK ()
  73 Return true if the netlink message is not truncated and
  74 is in a form suitable for parsing.
  75 .TP
  76 .BR NLMSG_PAYLOAD ()
  77 Return the length of the payload associated with the
  78 .IR nlmsghdr .
  79 .SH STANDARDS
  80 These macros are nonstandard Linux extensions.
  81 .SH NOTES
  82 It is often better to use netlink via
  83 .I libnetlink
  84 than via the low-level kernel interface.
  85 .SH SEE ALSO
  86 .BR libnetlink (3),
  87 .BR netlink (7)