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

       rtnetlink, NETLINK_ROUTE - Linux IPv4 routing socket

       #include <&lt;asm/types.h>&gt;
       #include <&lt;linux/netlink.h>&gt;
       #include <&lt;linux/rtnetlink.h>&gt;
       #include <&lt;sys/socket.h>&gt;

       rtnetlink_socket = socket(PF_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 only manipulated using 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, ifi_change is reserved for future
              use and should be always set to 0xFFFFFFFF.

              tab(:);  c   l   l   l.    Routing   attributes   rta_type:value
              type:description           _          IFLA_UNSPEC:-:unspecified.
              IFLA_ADDRESS:hardware address:interface L2  address  IFLA_BROAD-
              CAST: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 dis-
              cipline.  IFLA_STATS:T{ see below T}:Interface Statistics.

              The value type for IFLA_STATS is struct net_device_stats.

              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 rtaddr 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.

              tab(:); c l l l.  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_BROAD-
              CAST:raw protocol  address:broadcast  address.   IFA_ANYCAST:raw
              protocol address:anycast address IFA_CACHEINFO:struct ifa_cache-
              info: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 source */
                  unsigned char rtm_src_len;  /* Length of destination */
                  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;

              tab(:);  l  l.   rtm_type:Route  type _ RTN_UNSPEC:unknown route
              RTN_UNICAST:a gateway or direct route RTN_LOCAL:a  local  inter-
              face  route  RTN_BROADCAST:T{ a local broadcast route (sent as a
              broadcast) T} RTN_ANYCAST:T{ a local broadcast route (sent as  a
              unicast)  T}  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:T{  refer to an external resolver (not imple-
              mented) T}

              tab(:);     l     l.      rtm_protocol:Route     origin.       _
              RTPROT_UNSPEC:unknown  RTPROT_REDIRECT:T{  by  an  ICMP redirect
              (currently    unused)    T}    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  &lt;linux/rtnetlink.h&gt;  for
              the routing daemon identifiers which are already assigned.

              rtm_scope is the distance to the destination:

              tab(:);  l  l.   RT_SCOPE_UNIVERSE:global route RT_SCOPE_SITE:T{
              interior   route   in   the   local   autonomous    system    T}
              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:

              tab(:);  l  l.  RTM_F_NOTIFY:T{ if the route changes, notify the
              user via rtnetlink T} RTM_F_CLONED:route is cloned from  another
              route RTM_F_EQUALIZE:a multipath equalizer (not yet implemented)

              rtm_table specifies the routing table

              tab(:);  l  l.   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

              tab(:); c l l l.  Attributes rta_type:value  type:description  _
              RTA_UNSPEC:-:ignored.   RTA_DST:protocol  address:Route destina-
              tion 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_MET-
              RICS:int:Route metric RTA_MULTIPATH:: RTA_PROTOINFO:: RTA_FLOW::

              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:

              tab(:); l l.  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:

              tab(:);  l  l.   NTF_PROXY:a  proxy arp entry NTF_ROUTER:an IPv6

              The rtaddr struct has the following meanings  for  the  rta_type

              tab(:);  l  l.  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;

              tab(:);  c  l l l.  Attributes rta_type:value type:Description _
              TCA_UNSPEC:-:unspecified TCA_KIND:asciiz string:Name of queueing
              discipline TCA_OPTIONS:byte sequence:Qdisc-specific options fol-
              low      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 3.05 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux                             1999-04-30                      RTNETLINK(7)