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 rtnl_ctrl_data *,
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. If there is a 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, anscillary data, the message
itself, and the
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.
- 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 should contain 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
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.
AUTHORS
netlink/rtnetlink was designed and written by Alexey Kuznetsov. Andi Kleen wrote the man page.