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 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  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 5.13 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/.