NETLINK(3)		   Linux Programmer's Manual		    NETLINK(3)



NAME
       netlink - Netlink macros

SYNOPSIS
       #include <asm/types.h>
       #include <linux/netlink.h>

       int NLMSG_ALIGN(size_t len);
       int NLMSG_LENGTH(size_t len);
       int NLMSG_SPACE(size_t len);
       void *NLMSG_DATA(struct nlmsghdr *nlh);
       struct nlmsghdr *NLMSG_NEXT(struct nlmsghdr *nlh, int len);
       int NLMSG_OK(struct nlmsghdr *nlh, int len);
       int NLMSG_PAYLOAD(struct nlmsghdr *nlh, int len);

DESCRIPTION
       <linux/netlink.h> defines several standard macros to access or create a
       netlink datagram.  They are similar in spirit to the macros defined  in
       cmsg(3)	for  auxiliary	data.  The buffer passed to and from a netlink
       socket should be accessed using only these macros.

       NLMSG_ALIGN()
	      Round the length of a netlink message up to align it properly.

       NLMSG_LENGTH()
	      Given the payload length, len, this macro	 returns  the  aligned
	      length to store in the nlmsg_len field of the nlmsghdr.

       NLMSG_SPACE()
	      Return  the  number of bytes that a netlink message with payload
	      of len would occupy.

       NLMSG_DATA()
	      Return a pointer to the payload associated with the passed nlms-
	      ghdr.

       NLMSG_NEXT()
	      Get  the	next nlmsghdr in a multipart message.  The caller must
	      check if the current nlmsghdr didn't have the  NLMSG_DONE	 set--
	      this  function  doesn't return NULL on end.  The len argument is
	      an lvalue containing the remaining length of the message buffer.
	      This macro decrements it by the length of the message header.

       NLMSG_OK()
	      Return  true if the netlink message is not truncated and is in a
	      form suitable for parsing.

       NLMSG_PAYLOAD()
	      Return the length of the payload associated with the nlmsghdr.

CONFORMING TO
       These macros are nonstandard Linux extensions.

NOTES
       It is often better to use netlink via libnetlink than via the low-level
       kernel interface.

SEE ALSO
       libnetlink(3), netlink(7)

COLOPHON
       This  page  is  part of release 4.10 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest	  version     of     this    page,    can    be	   found    at
       https://www.kernel.org/doc/man-pages/.



GNU				  2014-03-20			    NETLINK(3)