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RTNETLINK(7)		   Linux Programmer's Manual		  RTNETLINK(7)

NAME
       rtnetlink - Linux IPv4 routing socket

SYNOPSIS
       #include	<asm/types.h>
       #include	<linux/if_link.h>
       #include	<linux/netlink.h>
       #include	<linux/rtnetlink.h>
       #include	<sys/socket.h>

       rtnetlink_socket	= socket(AF_NETLINK, int socket_type, NETLINK_ROUTE);

DESCRIPTION
       Rtnetlink  allows  the  kernel's	routing	tables to be read and altered.
       It is used within the kernel to communicate between various subsystems,
       though  this  usage  is not documented here, and	for communication with
       user-space programs.  Network routes, IP	 addresses,  link  parameters,
       neighbor	setups,	queueing disciplines, traffic classes and packet clas-
       sifiers may all be controlled through  NETLINK_ROUTE  sockets.	It  is
       based on	netlink	messages; see netlink(7) for more information.

   Routing attributes
       Some  rtnetlink	messages  have	optional  attributes after the initial
       header:

	   struct rtattr {
	       unsigned	short rta_len;	  /* Length of option */
	       unsigned	short rta_type;	  /* Type of option */
	       /* Data follows */
	   };

       These attributes	should be manipulated using only the RTA_*  macros  or
       libnetlink, see rtnetlink(3).

   Messages
       Rtnetlink  consists  of	these  message	types (in addition to standard
       netlink messages):

       RTM_NEWLINK, RTM_DELLINK, RTM_GETLINK
	      Create, remove or	get information	about a	specific  network  in-
	      terface.	These messages contain an ifinfomsg structure followed
	      by a series of rtattr structures.

	      struct ifinfomsg {
		  unsigned char	 ifi_family; /*	AF_UNSPEC */
		  unsigned short ifi_type;   /*	Device type */
		  int		 ifi_index;  /*	Interface index	*/
		  unsigned int	 ifi_flags;  /*	Device flags  */
		  unsigned int	 ifi_change; /*	change mask */
	      };

	      ifi_flags	contains the device flags, see netdevice(7); ifi_index
	      is  the  unique interface	index (since Linux 3.7,	it is possible
	      to feed a	nonzero	value with the RTM_NEWLINK message, thus  cre-
	      ating a link with	the given ifindex); ifi_change is reserved for
	      future use and should be always set to 0xFFFFFFFF.

				 Routing attributes
	      rta_type	       value type	  description
	      ----------------------------------------------------------
	      IFLA_UNSPEC      -		  unspecified.

	      IFLA_ADDRESS     hardware	address	  interface L2 address
	      IFLA_BROADCAST   hardware	address	  L2 broadcast address.
	      IFLA_IFNAME      asciiz string	  Device name.
	      IFLA_MTU	       unsigned	int	  MTU of the device.
	      IFLA_LINK	       int		  Link type.
	      IFLA_QDISC       asciiz string	  Queueing discipline.
	      IFLA_STATS       see below	  Interface Statistics.

	      The value	type for IFLA_STATS is struct rtnl_link_stats  (struct
	      net_device_stats in Linux	2.4 and	earlier).

       RTM_NEWADDR, RTM_DELADDR, RTM_GETADDR
	      Add,  remove  or receive information about an IP address associ-
	      ated with	an interface.  In Linux	2.2, an	 interface  can	 carry
	      multiple IP addresses, this replaces the alias device concept in
	      2.0.  In Linux 2.2, these	messages support  IPv4	and  IPv6  ad-
	      dresses.	 They  contain an ifaddrmsg structure, optionally fol-
	      lowed by rtattr routing attributes.

	      struct ifaddrmsg {
		  unsigned char	ifa_family;    /* Address type */
		  unsigned char	ifa_prefixlen; /* Prefixlength of address */
		  unsigned char	ifa_flags;     /* Address flags	*/
		  unsigned char	ifa_scope;     /* Address scope	*/
		  int		ifa_index;     /* Interface index */
	      };

	      ifa_family is the	address	 family	 type  (currently  AF_INET  or
	      AF_INET6),  ifa_prefixlen	 is  the length	of the address mask of
	      the address if defined for the family (like for IPv4), ifa_scope
	      is  the  address	scope, ifa_index is the	interface index	of the
	      interface	the address is associated with.	 ifa_flags is  a  flag
	      word  of IFA_F_SECONDARY for secondary address (old alias	inter-
	      face), IFA_F_PERMANENT for a permanent address set by  the  user
	      and other	undocumented flags.

				       Attributes
	      rta_type	      value type	     description
	      -------------------------------------------------------------
	      IFA_UNSPEC      -			     unspecified.
	      IFA_ADDRESS     raw protocol address   interface address
	      IFA_LOCAL	      raw protocol address   local address
	      IFA_LABEL	      asciiz string	     name of the interface
	      IFA_BROADCAST   raw protocol address   broadcast address.
	      IFA_ANYCAST     raw protocol address   anycast address
	      IFA_CACHEINFO   struct ifa_cacheinfo   Address information.

       RTM_NEWROUTE, RTM_DELROUTE, RTM_GETROUTE
	      Create,  remove  or  receive  information	about a	network	route.
	      These messages contain an	rtmsg structure	with an	 optional  se-
	      quence  of  rtattr structures following.	For RTM_GETROUTE, set-
	      ting rtm_dst_len and rtm_src_len to 0 means you get all  entries
	      for  the	specified routing table.  For the other	fields,	except
	      rtm_table	and rtm_protocol, 0 is the wildcard.

	      struct rtmsg {
		  unsigned char	rtm_family;   /* Address family	of route */
		  unsigned char	rtm_dst_len;  /* Length	of destination */
		  unsigned char	rtm_src_len;  /* Length	of source */
		  unsigned char	rtm_tos;      /* TOS filter */

		  unsigned char	rtm_table;    /* Routing table ID */
		  unsigned char	rtm_protocol; /* Routing protocol; see below */
		  unsigned char	rtm_scope;    /* See below */
		  unsigned char	rtm_type;     /* See below */

		  unsigned int	rtm_flags;
	      };

	      rtm_type		Route type
	      -----------------------------------------------------------
	      RTN_UNSPEC	unknown	route
	      RTN_UNICAST	a gateway or direct route
	      RTN_LOCAL		a local	interface route
	      RTN_BROADCAST	a  local  broadcast  route  (sent  as  a
				broadcast)
	      RTN_ANYCAST	a  local broadcast route (sent as a uni-
				cast)
	      RTN_MULTICAST	a multicast route
	      RTN_BLACKHOLE	a packet dropping route
	      RTN_UNREACHABLE	an unreachable destination
	      RTN_PROHIBIT	a packet rejection route
	      RTN_THROW		continue routing lookup	in another table
	      RTN_NAT		a network address translation rule
	      RTN_XRESOLVE	refer to an external resolver  (not  im-
				plemented)

	      rtm_protocol	Route origin.
	      ---------------------------------------------
	      RTPROT_UNSPEC	unknown
	      RTPROT_REDIRECT	by  an ICMP redirect (cur-
				rently unused)
	      RTPROT_KERNEL	by the kernel
	      RTPROT_BOOT	during boot
	      RTPROT_STATIC	by the administrator

	      Values larger than RTPROT_STATIC are not interpreted by the ker-
	      nel,  they  are  just for	user information.  They	may be used to
	      tag the source of	a routing information or  to  distinguish  be-
	      tween multiple routing daemons.  See _linux/rtnetlink.h_ for the
	      routing daemon identifiers which are already assigned.

	      rtm_scope	is the distance	to the destination:

	      RT_SCOPE_UNIVERSE	  global route
	      RT_SCOPE_SITE	  interior route in the	 lo-
				  cal autonomous system
	      RT_SCOPE_LINK	  route	on this	link
	      RT_SCOPE_HOST	  route	on the local host
	      RT_SCOPE_NOWHERE	  destination doesn't exist

	      The  values  between  RT_SCOPE_UNIVERSE  and  RT_SCOPE_SITE  are
	      available	to the user.

	      The rtm_flags have the following meanings:

	      RTM_F_NOTIFY     if the route changes, notify the	 user  via
			       rtnetlink
	      RTM_F_CLONED     route is	cloned from another route
	      RTM_F_EQUALIZE   a multipath equalizer (not yet implemented)

	      rtm_table	specifies the routing table

	      RT_TABLE_UNSPEC	 an unspecified	routing	table
	      RT_TABLE_DEFAULT	 the default table
	      RT_TABLE_MAIN	 the main table
	      RT_TABLE_LOCAL	 the local table

	      The user may assign arbitrary values between RT_TABLE_UNSPEC and
	      RT_TABLE_DEFAULT.

				       Attributes
	      rta_type	      value type	 description
	      --------------------------------------------------------------
	      RTA_UNSPEC      -			 ignored.
	      RTA_DST	      protocol address	 Route destination address.
	      RTA_SRC	      protocol address	 Route source address.
	      RTA_IIF	      int		 Input interface index.
	      RTA_OIF	      int		 Output	interface index.
	      RTA_GATEWAY     protocol address	 The gateway of	the route
	      RTA_PRIORITY    int		 Priority of route.
	      RTA_PREFSRC
	      RTA_METRICS     int		 Route metric
	      RTA_MULTIPATH
	      RTA_PROTOINFO
	      RTA_FLOW
	      RTA_CACHEINFO

	      Fill these values	in!

       RTM_NEWNEIGH, RTM_DELNEIGH, RTM_GETNEIGH
	      Add, remove or receive information about a neighbor table	 entry
	      (e.g., an	ARP entry).  The message contains an ndmsg structure.

	      struct ndmsg {
		  unsigned char	ndm_family;
		  int		ndm_ifindex;  /* Interface index */
		  __u16		ndm_state;    /* State */
		  __u8		ndm_flags;    /* Flags */
		  __u8		ndm_type;
	      };

	      struct nda_cacheinfo {
		  __u32		ndm_confirmed;
		  __u32		ndm_used;
		  __u32		ndm_updated;
		  __u32		ndm_refcnt;
	      };

	      ndm_state	is a bit mask of the following states:

	      NUD_INCOMPLETE   a currently resolving cache entry
	      NUD_REACHABLE    a confirmed working cache entry
	      NUD_STALE	       an expired cache	entry
	      NUD_DELAY	       an entry	waiting	for a timer
	      NUD_PROBE	       a cache entry that is currently reprobed
	      NUD_FAILED       an invalid cache	entry
	      NUD_NOARP	       a device	with no	destination cache
	      NUD_PERMANENT    a static	entry

	      Valid ndm_flags are:

	      NTF_PROXY	   a proxy arp entry
	      NTF_ROUTER   an IPv6 router

	      The  rtattr  struct  has the following meanings for the rta_type
	      field:

	      NDA_UNSPEC      unknown type
	      NDA_DST	      a	neighbor cache n/w layer destination address
	      NDA_LLADDR      a	neighbor cache link layer address
	      NDA_CACHEINFO   cache statistics.

	      If the rta_type field is NDA_CACHEINFO, then a struct nda_cache-
	      info header follows

       RTM_NEWRULE, RTM_DELRULE, RTM_GETRULE
	      Add, delete or retrieve a	routing	rule.  Carries a struct	rtmsg

       RTM_NEWQDISC, RTM_DELQDISC, RTM_GETQDISC
	      Add,  remove or get a queueing discipline.  The message contains
	      a	struct tcmsg and may be	followed by a series of	attributes.

	      struct tcmsg {
		  unsigned char	   tcm_family;
		  int		   tcm_ifindex;	  /* interface index */
		  __u32		   tcm_handle;	  /* Qdisc handle */
		  __u32		   tcm_parent;	  /* Parent qdisc */
		  __u32		   tcm_info;
	      };

					Attributes
	      rta_type	   value type		Description
	      ----------------------------------------------------------------
	      TCA_UNSPEC   -			unspecified
	      TCA_KIND	   asciiz string	Name of	queueing discipline
	      TCA_OPTIONS  byte	sequence	Qdisc-specific options follow
	      TCA_STATS	   struct tc_stats	Qdisc statistics.
	      TCA_XSTATS   qdisc-specific	Module-specific	statistics.
	      TCA_RATE	   struct tc_estimator	Rate limit.

	      In addition, various other qdisc-module-specific attributes  are
	      allowed.	 For  more  information	 see  the  appropriate include
	      files.

       RTM_NEWTCLASS, RTM_DELTCLASS, RTM_GETTCLASS
	      Add, remove or get a traffic class.  These  messages  contain  a
	      struct tcmsg as described	above.

       RTM_NEWTFILTER, RTM_DELTFILTER, RTM_GETTFILTER
	      Add,  remove  or	receive	 information  about  a traffic filter.
	      These messages contain a struct tcmsg as described above.

VERSIONS
       rtnetlink is a new feature of Linux 2.2.

BUGS
       This manual page	is incomplete.

SEE ALSO
       cmsg(3),	rtnetlink(3), ip(7), netlink(7)

COLOPHON
       This page is part of release 3.74 of the	Linux  man-pages  project.   A
       description  of	the project, information about reporting bugs, and the
       latest	 version    of	  this	  page,	   can	   be	  found	    at
       http://www.kernel.org/doc/man-pages/.

Linux				  2013-03-05			  RTNETLINK(7)

NAME | SYNOPSIS | DESCRIPTION | VERSIONS | BUGS | SEE ALSO | COLOPHON

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