1. NAME

libnetlink - A library for accessing the netlink service

2. SYNOPSIS

 
Sélectionnez
#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)
 

3. DESCRIPTION

libnetlink provides a higher level interface to

R 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 message 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

R rtnetlink(3) and

R 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.

4. BUGS

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

5. AUTHORS

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

6. SEE ALSO

R netlink(7),

R rtnetlink(7)
/usr/include/linux/rtnetlink.h