man3/netlink.3

   1 .\" This manpage copyright 1998 by Andi Kleen.
   2 .\"
   3 .\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
   4 .\" Subject to the GPL.
   5 .\" %%%LICENSE_END
   6 .\"
   7 .\" Based on the original comments from Alexey Kuznetsov
   8 .\" $Id: netlink.3,v 1.1 1999/05/14 17:17:24 freitag Exp $
   9 .\"
  10 .TH NETLINK 3 2014-03-20 "GNU" "Linux Programmer's Manual"
  11 .SH NAME
  12 netlink \- Netlink macros
  13 .SH SYNOPSIS
  14 .nf
  15 .B #include <asm/types.h>
  16 .B #include <linux/netlink.h>
  17 .PP
  18 .BI "int NLMSG_ALIGN(size_t " len );
  19 .BI "int NLMSG_LENGTH(size_t " len );
  20 .BI "int NLMSG_SPACE(size_t " len );
  21 .BI "void *NLMSG_DATA(struct nlmsghdr *" nlh );
  22 .BI "struct nlmsghdr *NLMSG_NEXT(struct nlmsghdr *" nlh ", int " len );
  23 .BI "int NLMSG_OK(struct nlmsghdr *" nlh ", int " len );
  24 .BI "int NLMSG_PAYLOAD(struct nlmsghdr *" nlh ", int " len );
  25 .fi
  26 .SH DESCRIPTION
  27 .I <linux/netlink.h>
  28 defines several standard macros to access or create a netlink datagram.
  29 They are similar in spirit to the macros defined in
  30 .BR cmsg (3)
  31 for auxiliary data.
  32 The buffer passed to and from a netlink socket should
  33 be accessed using only these macros.
  34 .TP
  35 .BR NLMSG_ALIGN ()
  36 Round the length of a netlink message up to align it properly.
  37 .TP
  38 .BR NLMSG_LENGTH ()
  39 Given the payload length,
  40 .IR len ,
  41 this macro returns the aligned length to store in the
  42 .I nlmsg_len
  43 field of the
  44 .IR nlmsghdr .
  45 .TP
  46 .BR NLMSG_SPACE ()
  47 Return the number of bytes that a netlink message with payload of
  48 .I len
  49 would occupy.
  50 .TP
  51 .BR NLMSG_DATA ()
  52 Return a pointer to the payload associated with the passed
  53 .IR nlmsghdr .
  54 .TP
  55 .\" this is bizarre, maybe the interface should be fixed.
  56 .BR NLMSG_NEXT ()
  57 Get the next
  58 .I nlmsghdr
  59 in a multipart message.
  60 The caller must check if the current
  61 .I nlmsghdr
  62 didn't have the
  63 .B NLMSG_DONE
  64 set\(emthis function doesn't return NULL on end.
  65 The
  66 .I len
  67 argument is an lvalue containing the remaining length
  68 of the message buffer.
  69 This macro decrements it by the length of the message header.
  70 .TP
  71 .BR NLMSG_OK ()
  72 Return true if the netlink message is not truncated and
  73 is in a form suitable for parsing.
  74 .TP
  75 .BR NLMSG_PAYLOAD ()
  76 Return the length of the payload associated with the
  77 .IR nlmsghdr .
  78 .SH CONFORMING TO
  79 These macros are nonstandard Linux extensions.
  80 .SH NOTES
  81 It is often better to use netlink via
  82 .I libnetlink
  83 than via the low-level kernel interface.
  84 .SH SEE ALSO
  85 .BR libnetlink (3),
  86 .BR netlink (7)