NETLINK(3)		   Linux Programmers Manual		   NETLINK(3)



NAME
       netlink - Netlink macros

SYNOPSIS
       #include 
       #include 

       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
        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 only be accessed using 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 didnt have the NLMSG_DONE  set
	      this  function  doesnt 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 ok to
	      parse.

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

CONFORMING TO
       These macros are non-standard Linux extensions.

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

SEE ALSO
       netlink(7)
       and ftp://ftp.inr.ac.ru/ip-routing/iproute2* for libnetlink

COLOPHON
       This  page  is  part of release 3.05 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.



GNU				  1999-05-14			    NETLINK(3)