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netlink - Netlink macros
#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);
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.
It is often better to use netlink via libnetlink than via the low level kernel interface.
netlink(7) ftp://ftp.inr.ac.ru/ip-routing/iproute2* for libnetlink