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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 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 it‐
              self 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 mes‐
              sage 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 re‐
              ceived from a rtnetlink socket.

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


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



                                                                                       libnetlink(3)