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 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 nlms-
              ghdr.

       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 nlmsghdr.

       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 remain-
              ing 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 nonstandard 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 3.25 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)