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

       rtnetlink - Linux IPv4 routing socket

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

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

       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

	   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).

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

	      Create, remove or	 get  information  about  a  specific  network
	      interface.   These  messages contain an ifinfomsg structure fol-
	      lowed 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).

	      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
	      addresses.  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.

	      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.

	      Create,  remove  or  receive  information about a network route.
	      These messages contain  an  rtmsg	 structure  with  an  optional
	      sequence 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
	      RTN_ANYCAST	a  local broadcast route (sent as a uni-
	      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

	      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
	      between  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
				  local 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
	      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

	      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_METRICS     int		 Route metric

	      Fill these values in!

	      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

	      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

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

	      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;

	      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

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

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

       rtnetlink is a new feature of Linux 2.2.

       This manual page is incomplete.

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

       This page is part of release 4.10 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

Linux				  2013-03-05			  RTNETLINK(7)