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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
          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 4.09 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/.



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