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Linux 2.6 - man page for rtnetlink (linux section 7)

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

	      Create,  remove  or get information about a specific network interface.  These mes-
	      sages 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 creating 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 associated  with  an  inter-
	      face.   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 followed 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_pre-
	      fixlen  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 interface), 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 con-
	      tain an rtmsg structure with an optional sequence of rtattr  structures  following.
	      For  RTM_GETROUTE,  setting  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 (currently
	      RTPROT_KERNEL	by the kernel
	      RTPROT_BOOT	during boot
	      RTPROT_STATIC	by the administrator

	      Values  larger  than RTPROT_STATIC are not interpreted by the kernel, 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 au-
				  tonomous 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 RT_TABLE_DEFAULT.

	      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 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_cacheinfo 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 files.

	      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 3.55 of the Linux man-pages project.  A description of the
       project,    and	  information	 about	  reporting    bugs,	can    be    found     at

Linux					    2013-03-05				     RTNETLINK(7)

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