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 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)

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