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 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.

SEE ALSO

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

                                                             libnetlink(3)

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