libnetlink(3)						     Library Functions Manual						     libnetlink(3)

NAME

       libnetlink - A library for accessing the netlink service

SYNOPSIS

       #include <asm/types.h>
       #include <libnetlink.h>
       #include <linux/netlink.h>
       #include <linux/rtnetlink.h>

       int rtnl_open(struct rtnl_handle *rth, unsigned subscriptions)

       int rtnl_wilddump_request(struct rtnl_handle *rth, int family, int type)

       int rtnl_send(struct rtnl_handle *rth, char *buf, int len)

       int rtnl_dump_request(struct rtnl_handle *rth, int type, void *req, int len)

       int rtnl_dump_filter(struct rtnl_handle *rth,
		      int (*filter)(struct sockaddr_nl *, struct nlmsghdr *n, void *),
		      void *arg1,
		      int (*junk)(struct sockaddr_nl *,struct nlmsghdr *n, void *),
		      void *arg2)

       int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n, pid_t peer,
		  unsigned groups, struct nlmsghdr *answer,
		  int (*junk)(struct sockaddr_nl *,struct nlmsghdr *n, void *),
		  void *jarg)

       int rtnl_listen(struct rtnl_handle *rtnl,
		  int (*handler)(struct sockaddr_nl *,struct nlmsghdr *n, void *),
		  void *jarg)

       int rtnl_from_file(FILE *rtnl,
		  int (*handler)(struct sockaddr_nl *,struct nlmsghdr *n, void *),
		  void *jarg)

       int addattr32(struct nlmsghdr *n, int maxlen, int type, __u32 data)

       int addattr_l(struct nlmsghdr *n, int maxlen, int type, void *data, int alen)

       int rta_addattr32(struct rtattr *rta, int maxlen, int type, __u32 data)

       int rta_addattr_l(struct rtattr *rta, int maxlen, int type, void *data, int alen)

DESCRIPTION

       libnetlink provides a higher level interface to rtnetlink(7).  The read functions return 0 on success and a negative errno on failure.  The
       send functions return the amount of data sent, or -1 on error.

       rtnl_open
	      Open a rtnetlink socket and save the state into the rth handle. This handle is passed to all subsequent calls.  subscriptions  is  a
	      bitmap of the rtnetlink multicast groups the socket will be a member of.

       rtnl_wilddump_request
	      Request a full dump of the type database for family addresses.  type is a rtnetlink message type.

       rtnl_dump_request
	      Request a full dump of the type data buffer into buf with maximum length of len.	type is a rtnetlink message type.

       rtnl_dump_filter
	      Receive  netlink	data  after  a	request  and filter it.  The filter callback checks if the received message is wanted. It gets the
	      source address of the message, the message itself and arg1 as arguments. 0 as return means that the filter passed, a negative  value
	      is  returned  by	rtnl_dump_filter in case of error. NULL for filter means to not use a filter.  junk is used to filter messages not
	      destined to the local socket.  Only one message bundle is received. Unless there is no  message  pending,  this  function  does  not
	      block.

       rtnl_listen
	      Receive  netlink	data after a request and pass it to handler.  handler is a callback that gets the message source address, the mes-
	      sage itself, and the jarg cookie as arguments. It will get called for all received messages.  Only one message bundle  is  received.
	      Unless there is no message pending this function does not block.

       rtnl_from_file
	      Works  like  rtnl_listen,  but reads a netlink message bundle from the file file and passes the messages to handler for parsing. The
	      file contains raw data as received from a rtnetlink socket.

       The following functions are useful to construct custom rtnetlink messages. For simple database dumping with filtering it is better  to  use
       the  higher  level functions above. See rtnetlink(3) and netlink(3) on how to generate a rtnetlink message. The following utility functions
       require a continuous buffer that already contains a netlink message header and a rtnetlink request.

       rtnl_send
	      Send the rtnetlink message in buf of length len to handle rth.

       addattr32
	      Add a __u32 attribute of type type and with value data to netlink message n, which is part of a buffer of length maxlen.

       addattr_l
	      Add a variable length attribute of type type and with value data and alen length to netlink message n, which is part of a buffer	of
	      length maxlen.  data is copied.

       rta_addattr32
	      Initialize the rtnetlink attribute rta with a __u32 data value.

       rta_addattr32
	      Initialize the rtnetlink attribute rta with a variable length data value.

BUGS

       The functions sometimes use fprintf and exit when a fatal error occurs.	This library should be named librtnetlink.

AUTHORS

       netlink/rtnetlink was designed and written by Alexey Kuznetsov.	Andi Kleen wrote the man page.

SEE ALSO

       netlink(7), rtnetlink(7)
       /usr/include/linux/rtnetlink.h

																     libnetlink(3)