.TH libnetlink 3

.SH NAME

libnetlink \- A library for accessing the netlink service

.SH SYNOPSIS

.nf

#include <asm/types.h>

.br

#include <libnetlink.h>

.br

#include <linux/netlink.h>

.br

#include <linux/rtnetlink.h>

.sp

int rtnl_open(struct rtnl_handle *rth, unsigned subscriptions)

.sp

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

.sp

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

.sp

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

.sp

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)

.sp

int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n, pid_t peer,

	      unsigned groups, struct nlmsghdr *answer,

.br

	      int (*junk)(struct sockaddr_nl *,struct nlmsghdr *n, void *),

.br

	      void *jarg)

.sp

int rtnl_listen(struct rtnl_handle *rtnl,

	      int (*handler)(struct sockaddr_nl *, struct rtnl_ctrl_data *,

			     struct nlmsghdr *n, void *),

	      void *jarg)

.sp

int rtnl_from_file(FILE *rtnl,

	      int (*handler)(struct sockaddr_nl *,struct nlmsghdr *n, void *),

	      void *jarg)

.sp

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

.sp

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

.sp

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

.sp

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

.SH DESCRIPTION

libnetlink provides a higher level interface to

.BR 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.

.TP

rtnl_open

Open a rtnetlink socket and save the state into the

.B rth

handle. This handle is passed to all subsequent calls.

.B subscriptions

is a bitmap of the rtnetlink multicast groups the socket will be

a member of.

.TP

rtnl_wilddump_request

Request a full dump of the

.B type

database for

.B family

addresses.

.B type

is a rtnetlink message type.

.\" XXX

.TP

rtnl_dump_request

Request a full dump of the

.B type

data buffer into

.B buf

with maximum length of

.B len.

.B type

is a rtnetlink message type.

.TP

rtnl_dump_filter

Receive netlink data after a request and filter it.

The

.B filter

callback checks if the received message is wanted. It gets the source

address of the message, the message itself and

.B arg1

as arguments. 0 as return means that the filter passed, a negative

value is returned

by

.I rtnl_dump_filter

in case of error. NULL for

.I filter

means to not use a filter.

.B junk

is used to filter messages not destined to the local socket.

Only one message bundle is received. If there is a message

pending, this function does not block.

.TP

rtnl_listen

Receive netlink data after a request and pass it to

.I handler.

.B handler

is a callback that gets the message source address, anscillary data, the message

itself, and the

.B jarg

cookie as arguments. It will get called for all received messages.

Only one message bundle is received. If there is a message

pending this function does not block.

.TP

rtnl_from_file

Works like

.I rtnl_listen,

but reads a netlink message bundle from the file

.B file

and passes the messages to

.B handler

for parsing. The file should contain raw data as received from a rtnetlink socket.

.PP

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

.BR rtnetlink (3)

and

.BR 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.

.TP

rtnl_send

Send the rtnetlink message in

.B buf

of length

.B len

to handle

.B rth.

.TP

addattr32

Add a __u32 attribute of type

.B type

and with value

.B data

to netlink message

.B n,

which is part of a buffer of length

.B maxlen.

.TP

addattr_l

Add a variable length attribute of type

.B type

and with value

.B data

and

.B alen

length to netlink message

.B n,

which is part of a buffer of length

.B maxlen.

.B data

is copied.

.TP

rta_addattr32

Initialize the rtnetlink attribute

.B rta

with a __u32 data value.

.TP

rta_addattr32

Initialize the rtnetlink attribute

.B rta

with a variable length data value.

.SH BUGS

This library is meant for internal use, use libmnl for new programs.

The functions sometimes use fprintf and exit when a fatal error occurs.

This library should be named librtnetlink.

.SH AUTHORS

netlink/rtnetlink was designed and written by Alexey Kuznetsov.

Andi Kleen wrote the man page.

.SH SEE ALSO

.BR netlink (7),

.BR rtnetlink (7)

.br

/usr/include/linux/rtnetlink.h