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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

       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  auxilliary  data.  The  buffer passed to and from a netlink socket
       should be only accessed using these macros.

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

       NLMSG_LENGTH
              Gets  the  payload  length  as  argument  and returns the
              aligned length to store in the  nlmsg_len  field  of  the
              nlmsghdr.

       NLMSG_SPACE
              Return the number of bytes a netlink message with payload
              of the passed length 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 length parameter 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.

NOTES

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

SEE ALSO

       netlink(7)

       ftp://ftp.inr.ac.ru/ip-routing/iproute2* for libnetlink