1RTNETLINK(7)               Linux Programmer's Manual              RTNETLINK(7)
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NAME

6       rtnetlink - Linux IPv4 routing socket
7

SYNOPSIS

9       #include <asm/types.h>
10       #include <linux/netlink.h>
11       #include <linux/rtnetlink.h>
12       #include <sys/socket.h>
13
14       rtnetlink_socket = socket(AF_NETLINK, int socket_type, NETLINK_ROUTE);
15

DESCRIPTION

17       Rtnetlink  allows  the  kernel's routing tables to be read and altered.
18       It is used within the kernel to communicate between various subsystems,
19       though  this  usage  is not documented here, and for communication with
20       user-space programs.  Network routes, IP  addresses,  link  parameters,
21       neighbor setups, queueing disciplines, traffic classes and packet clas‐
22       sifiers may all be controlled through  NETLINK_ROUTE  sockets.   It  is
23       based on netlink messages; see netlink(7) for more information.
24
25   Routing attributes
26       Some  rtnetlink  messages  have  optional  attributes after the initial
27       header:
28
29           struct rtattr {
30               unsigned short rta_len;    /* Length of option */
31               unsigned short rta_type;   /* Type of option */
32               /* Data follows */
33           };
34
35       These attributes should be manipulated using only the RTA_*  macros  or
36       libnetlink, see rtnetlink(3).
37
38   Messages
39       Rtnetlink  consists  of  these  message  types (in addition to standard
40       netlink messages):
41
42       RTM_NEWLINK, RTM_DELLINK, RTM_GETLINK
43              Create, remove or  get  information  about  a  specific  network
44              interface.   These  messages contain an ifinfomsg structure fol‐
45              lowed by a series of rtattr structures.
46
47              struct ifinfomsg {
48                  unsigned char  ifi_family; /* AF_UNSPEC */
49                  unsigned short ifi_type;   /* Device type */
50                  int            ifi_index;  /* Interface index */
51                  unsigned int   ifi_flags;  /* Device flags  */
52                  unsigned int   ifi_change; /* change mask */
53              };
54
55              ifi_flags contains the device flags, see netdevice(7); ifi_index
56              is  the  unique interface index (since Linux 3.7, it is possible
57              to feed a nonzero value with the RTM_NEWLINK message, thus  cre‐
58              ating a link with the given ifindex); ifi_change is reserved for
59              future use and should be always set to 0xFFFFFFFF.
60
61                                 Routing attributes
62              rta_type         value type         description
63              ──────────────────────────────────────────────────────────
64              IFLA_UNSPEC      -                  unspecified.
65              IFLA_ADDRESS     hardware address   interface L2 address
66
67              IFLA_BROADCAST   hardware address   L2 broadcast address.
68              IFLA_IFNAME      asciiz string      Device name.
69              IFLA_MTU         unsigned int       MTU of the device.
70              IFLA_LINK        int                Link type.
71              IFLA_QDISC       asciiz string      Queueing discipline.
72              IFLA_STATS       see below          Interface Statistics.
73
74       The  value  type  for  IFLA_STATS  is  struct  rtnl_link_stats  (struct
75       net_device_stats in Linux 2.4 and earlier).
76
77       RTM_NEWADDR, RTM_DELADDR, RTM_GETADDR
78              Add,  remove  or receive information about an IP address associ‐
79              ated with an interface.  In Linux 2.2, an  interface  can  carry
80              multiple IP addresses, this replaces the alias device concept in
81              2.0.  In  Linux  2.2,  these  messages  support  IPv4  and  IPv6
82              addresses.  They contain an ifaddrmsg structure, optionally fol‐
83              lowed by rtattr routing attributes.
84
85              struct ifaddrmsg {
86                  unsigned char ifa_family;    /* Address type */
87                  unsigned char ifa_prefixlen; /* Prefixlength of address */
88                  unsigned char ifa_flags;     /* Address flags */
89                  unsigned char ifa_scope;     /* Address scope */
90                  int           ifa_index;     /* Interface index */
91              };
92
93              ifa_family is the address  family  type  (currently  AF_INET  or
94              AF_INET6),  ifa_prefixlen  is  the length of the address mask of
95              the address if defined for the family (like for IPv4), ifa_scope
96              is  the  address  scope, ifa_index is the interface index of the
97              interface the address is associated with.  ifa_flags is  a  flag
98              word  of IFA_F_SECONDARY for secondary address (old alias inter‐
99              face), IFA_F_PERMANENT for a permanent address set by  the  user
100              and other undocumented flags.
101
102                                       Attributes
103              rta_type        value type             description
104              ─────────────────────────────────────────────────────────────
105              IFA_UNSPEC      -                      unspecified.
106              IFA_ADDRESS     raw protocol address   interface address
107              IFA_LOCAL       raw protocol address   local address
108              IFA_LABEL       asciiz string          name of the interface
109              IFA_BROADCAST   raw protocol address   broadcast address.
110              IFA_ANYCAST     raw protocol address   anycast address
111              IFA_CACHEINFO   struct ifa_cacheinfo   Address information.
112
113       RTM_NEWROUTE, RTM_DELROUTE, RTM_GETROUTE
114              Create,  remove  or  receive  information about a network route.
115              These messages contain  an  rtmsg  structure  with  an  optional
116              sequence of rtattr structures following.  For RTM_GETROUTE, set‐
117              ting rtm_dst_len and rtm_src_len to 0 means you get all  entries
118              for  the  specified routing table.  For the other fields, except
119              rtm_table and rtm_protocol, 0 is the wildcard.
120
121              struct rtmsg {
122                  unsigned char rtm_family;   /* Address family of route */
123                  unsigned char rtm_dst_len;  /* Length of destination */
124                  unsigned char rtm_src_len;  /* Length of source */
125                  unsigned char rtm_tos;      /* TOS filter */
126
127                  unsigned char rtm_table;    /* Routing table ID */
128                  unsigned char rtm_protocol; /* Routing protocol; see below */
129                  unsigned char rtm_scope;    /* See below */
130                  unsigned char rtm_type;     /* See below */
131
132                  unsigned int  rtm_flags;
133              };
134
135              rtm_type          Route type
136              ───────────────────────────────────────────────────────────
137              RTN_UNSPEC        unknown route
138              RTN_UNICAST       a gateway or direct route
139              RTN_LOCAL         a local interface route
140              RTN_BROADCAST     a  local  broadcast  route  (sent  as  a
141                                broadcast)
142              RTN_ANYCAST       a  local broadcast route (sent as a uni‐
143                                cast)
144              RTN_MULTICAST     a multicast route
145              RTN_BLACKHOLE     a packet dropping route
146              RTN_UNREACHABLE   an unreachable destination
147              RTN_PROHIBIT      a packet rejection route
148              RTN_THROW         continue routing lookup in another table
149              RTN_NAT           a network address translation rule
150              RTN_XRESOLVE      refer  to  an  external  resolver   (not
151                                implemented)
152
153              rtm_protocol      Route origin.
154              ─────────────────────────────────────────────
155              RTPROT_UNSPEC     unknown
156              RTPROT_REDIRECT   by  an ICMP redirect (cur‐
157                                rently unused)
158              RTPROT_KERNEL     by the kernel
159              RTPROT_BOOT       during boot
160              RTPROT_STATIC     by the administrator
161
162              Values larger than RTPROT_STATIC are not interpreted by the ker‐
163              nel,  they  are  just for user information.  They may be used to
164              tag the source  of  a  routing  information  or  to  distinguish
165              between  multiple  routing daemons.  See <linux/rtnetlink.h> for
166              the routing daemon identifiers which are already assigned.
167
168              rtm_scope is the distance to the destination:
169
170              RT_SCOPE_UNIVERSE   global route
171              RT_SCOPE_SITE       interior  route   in   the
172                                  local autonomous system
173              RT_SCOPE_LINK       route on this link
174              RT_SCOPE_HOST       route on the local host
175              RT_SCOPE_NOWHERE    destination doesn't exist
176
177              The  values  between  RT_SCOPE_UNIVERSE  and  RT_SCOPE_SITE  are
178              available to the user.
179
180              The rtm_flags have the following meanings:
181
182              RTM_F_NOTIFY     if the route changes, notify the  user  via
183                               rtnetlink
184              RTM_F_CLONED     route is cloned from another route
185              RTM_F_EQUALIZE   a multipath equalizer (not yet implemented)
186
187              rtm_table specifies the routing table
188
189              RT_TABLE_UNSPEC    an unspecified routing table
190              RT_TABLE_DEFAULT   the default table
191              RT_TABLE_MAIN      the main table
192              RT_TABLE_LOCAL     the local table
193
194              The user may assign arbitrary values between RT_TABLE_UNSPEC and
195              RT_TABLE_DEFAULT.
196
197                                       Attributes
198              rta_type        value type         description
199              ──────────────────────────────────────────────────────────────
200              RTA_UNSPEC      -                  ignored.
201              RTA_DST         protocol address   Route destination address.
202              RTA_SRC         protocol address   Route source address.
203              RTA_IIF         int                Input interface index.
204              RTA_OIF         int                Output interface index.
205              RTA_GATEWAY     protocol address   The gateway of the route
206              RTA_PRIORITY    int                Priority of route.
207              RTA_PREFSRC
208              RTA_METRICS     int                Route metric
209              RTA_MULTIPATH
210              RTA_PROTOINFO
211              RTA_FLOW
212              RTA_CACHEINFO
213
214              Fill these values in!
215
216       RTM_NEWNEIGH, RTM_DELNEIGH, RTM_GETNEIGH
217              Add, remove or receive information about a neighbor table  entry
218              (e.g., an ARP entry).  The message contains an ndmsg structure.
219
220              struct ndmsg {
221                  unsigned char ndm_family;
222                  int           ndm_ifindex;  /* Interface index */
223                  __u16         ndm_state;    /* State */
224                  __u8          ndm_flags;    /* Flags */
225                  __u8          ndm_type;
226              };
227
228              struct nda_cacheinfo {
229                  __u32         ndm_confirmed;
230                  __u32         ndm_used;
231                  __u32         ndm_updated;
232                  __u32         ndm_refcnt;
233              };
234
235              ndm_state is a bit mask of the following states:
236
237              NUD_INCOMPLETE   a currently resolving cache entry
238              NUD_REACHABLE    a confirmed working cache entry
239              NUD_STALE        an expired cache entry
240              NUD_DELAY        an entry waiting for a timer
241              NUD_PROBE        a cache entry that is currently reprobed
242              NUD_FAILED       an invalid cache entry
243              NUD_NOARP        a device with no destination cache
244              NUD_PERMANENT    a static entry
245
246              Valid ndm_flags are:
247
248              NTF_PROXY    a proxy arp entry
249              NTF_ROUTER   an IPv6 router
250
251              The  rtattr  struct  has the following meanings for the rta_type
252              field:
253
254              NDA_UNSPEC      unknown type
255              NDA_DST         a neighbor cache n/w layer destination address
256              NDA_LLADDR      a neighbor cache link layer address
257              NDA_CACHEINFO   cache statistics.
258
259              If the rta_type field is NDA_CACHEINFO, then a struct nda_cache‐
260              info header follows
261
262       RTM_NEWRULE, RTM_DELRULE, RTM_GETRULE
263              Add, delete or retrieve a routing rule.  Carries a struct rtmsg
264
265       RTM_NEWQDISC, RTM_DELQDISC, RTM_GETQDISC
266              Add,  remove or get a queueing discipline.  The message contains
267              a struct tcmsg and may be followed by a series of attributes.
268
269              struct tcmsg {
270                  unsigned char    tcm_family;
271                  int              tcm_ifindex;   /* interface index */
272                  __u32            tcm_handle;    /* Qdisc handle */
273                  __u32            tcm_parent;    /* Parent qdisc */
274                  __u32            tcm_info;
275              };
276
277                                        Attributes
278              rta_type     value type           Description
279              ────────────────────────────────────────────────────────────────
280              TCA_UNSPEC   -                    unspecified
281              TCA_KIND     asciiz string        Name of queueing discipline
282              TCA_OPTIONS  byte sequence        Qdisc-specific options follow
283              TCA_STATS    struct tc_stats      Qdisc statistics.
284              TCA_XSTATS   qdisc-specific       Module-specific statistics.
285              TCA_RATE     struct tc_estimator  Rate limit.
286
287              In addition, various other qdisc-module-specific attributes  are
288              allowed.   For  more  information  see  the  appropriate include
289              files.
290
291       RTM_NEWTCLASS, RTM_DELTCLASS, RTM_GETTCLASS
292              Add, remove or get a traffic class.  These  messages  contain  a
293              struct tcmsg as described above.
294
295       RTM_NEWTFILTER, RTM_DELTFILTER, RTM_GETTFILTER
296              Add,  remove  or  receive  information  about  a traffic filter.
297              These messages contain a struct tcmsg as described above.
298

VERSIONS

300       rtnetlink is a new feature of Linux 2.2.
301

BUGS

303       This manual page is incomplete.
304

SEE ALSO

306       cmsg(3), rtnetlink(3), ip(7), netlink(7)
307

COLOPHON

309       This page is part of release 5.02 of the Linux  man-pages  project.   A
310       description  of  the project, information about reporting bugs, and the
311       latest    version    of    this    page,    can     be     found     at
312       https://www.kernel.org/doc/man-pages/.
313
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316Linux                             2017-09-15                      RTNETLINK(7)
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