doc/developer/zebra.rst

   1 .. _zebra:
   2
   3 *****
   4 Zebra
   5 *****
   6
   7 .. _zebra-protocol:
   8
   9 Overview of the Zebra Protocol
  10 ==============================
  11
  12 The Zebra protocol (or ``ZAPI``) is used by protocol daemons to
  13 communicate with the **zebra** daemon.
  14
  15 Each protocol daemon may request and send information to and from the
  16 **zebra** daemon such as interface states, routing state,
  17 nexthop-validation, and so on.  Protocol daemons may also install
  18 routes with **zebra**. The **zebra** daemon manages which routes are
  19 installed into the forwarding table with the kernel. Some daemons use
  20 more than one ZAPI connection. This is supported: each ZAPI session is
  21 identified by a tuple of: ``{protocol, instance, session_id}``. LDPD
  22 is an example: it uses a second, synchronous ZAPI session to manage
  23 label blocks. The default value for ``session_id`` is zero; daemons
  24 who use multiple ZAPI sessions must assign unique values to the
  25 sessions' ids.
  26
  27 The Zebra protocol is a streaming protocol, with a common header. Version 0
  28 lacks a version field and is implicitly versioned. Version 1 and all subsequent
  29 versions have a version field.  Version 0 can be distinguished from all other
  30 versions by examining the 3rd byte of the header, which contains a marker value
  31 of 255 (in Quagga) or 254 (in FRR) for all versions except version 0. The
  32 marker byte corresponds to the command field in version 0, and the marker value
  33 is a reserved command in version 0.
  34
  35 Version History
  36 ---------------
  37
  38 - Version 0
  39
  40   Used by all versions of GNU Zebra and all version of Quagga up to and
  41   including Quagga 0.98. This version has no ``version`` field, and so is
  42   implicitly versioned as version 0.
  43
  44 - Version 1
  45
  46   Added ``marker`` and ``version`` fields, increased ``command`` field to 16
  47   bits. Used by Quagga versions 0.99.3 through 0.99.20.
  48
  49 - Version 2
  50
  51   Used by Quagga versions 0.99.21 through 0.99.23.
  52
  53 - Version 3
  54
  55   Added ``vrf_id`` field. Used by Quagga versions 0.99.23 until FRR fork.
  56
  57 - Version 4
  58
  59   Change marker value to 254 to prevent people mixing and matching Quagga and
  60   FRR daemon binaries. Used by FRR versions 2.0 through 3.0.3.
  61
  62 - Version 5
  63
  64   Increased VRF identifier field from 16 to 32 bits. Used by FRR versions 4.0
  65   through 5.0.1.
  66
  67 - Version 6
  68
  69   Removed the following commands:
  70
  71   * ZEBRA_IPV4_ROUTE_ADD
  72   * ZEBRA_IPV4_ROUTE_DELETE
  73   * ZEBRA_IPV6_ROUTE_ADD
  74   * ZEBRA_IPV6_ROUTE_DELETE
  75
  76   Used since FRR version 6.0.
  77
  78
  79 Zebra Protocol Definition
  80 =========================
  81
  82 Zebra Protocol Header Field Definitions
  83 ---------------------------------------
  84
  85 Length
  86    Total packet length including this header.
  87
  88 Marker
  89    Static marker. The marker value, when it exists, is 255 in all versions of
  90    Quagga. It is 254 in all versions of FRR. This is to allow version 0 headers
  91    (which do not include version explicitly) to be distinguished from versioned
  92    headers.
  93
  94 Version
  95    Zebra protocol version number. Clients should not continue processing
  96    messages past the version field for versions they do not recognise.
  97
  98 Command
  99    The Zebra protocol command.
 100
 101
 102 Current Version
 103 ^^^^^^^^^^^^^^^
 104
 105 ::
 106
 107    Version 5, 6
 108
 109     0                   1                   2                   3
 110     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 111    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 112    |             Length            |     Marker    |    Version    |
 113    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 114    |                             VRF ID                            |
 115    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 116    |            Command            |
 117    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 118
 119
 120 Past Versions
 121 ^^^^^^^^^^^^^
 122
 123 ::
 124
 125    Version 0
 126
 127     0                   1                   2                   3
 128     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 129    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 130    |             Length            |    Command    |
 131    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 132
 133 ::
 134
 135    Version 1, 2
 136
 137     0                   1                   2                   3
 138     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 139    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 140    |             Length            |     Marker    |    Version    |
 141    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 142    |            Command            |
 143    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 144
 145
 146 ::
 147
 148    Version 3, 4
 149
 150     0                   1                   2                   3
 151     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 152    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 153    |             Length            |     Marker    |    Version    |
 154    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 155    |             VRF ID            |            Command            |
 156    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 157
 158
 159 Zebra Protocol Commands
 160 -----------------------
 161
 162 +------------------------------------+-------+
 163 | Command                            | Value |
 164 +====================================+=======+
 165 | ZEBRA_INTERFACE_ADD                | 0     |
 166 +------------------------------------+-------+
 167 | ZEBRA_INTERFACE_DELETE             | 1     |
 168 +------------------------------------+-------+
 169 | ZEBRA_INTERFACE_ADDRESS_ADD        | 2     |
 170 +------------------------------------+-------+
 171 | ZEBRA_INTERFACE_ADDRESS_DELETE     | 3     |
 172 +------------------------------------+-------+
 173 | ZEBRA_INTERFACE_UP                 | 4     |
 174 +------------------------------------+-------+
 175 | ZEBRA_INTERFACE_DOWN               | 5     |
 176 +------------------------------------+-------+
 177 | ZEBRA_INTERFACE_SET_MASTER         | 6     |
 178 +------------------------------------+-------+
 179 | ZEBRA_INTERFACE_SET_PROTODOWN      | 7     |
 180 +------------------------------------+-------+
 181 | ZEBRA_ROUTE_ADD                    | 8     |
 182 +------------------------------------+-------+
 183 | ZEBRA_ROUTE_DELETE                 | 9     |
 184 +------------------------------------+-------+
 185 | ZEBRA_ROUTE_NOTIFY_OWNER           | 10    |
 186 +------------------------------------+-------+
 187 | ZEBRA_REDISTRIBUTE_ADD             | 11    |
 188 +------------------------------------+-------+
 189 | ZEBRA_REDISTRIBUTE_DELETE          | 12    |
 190 +------------------------------------+-------+
 191 | ZEBRA_REDISTRIBUTE_DEFAULT_ADD     | 13    |
 192 +------------------------------------+-------+
 193 | ZEBRA_REDISTRIBUTE_DEFAULT_DELETE  | 14    |
 194 +------------------------------------+-------+
 195 | ZEBRA_ROUTER_ID_ADD                | 15    |
 196 +------------------------------------+-------+
 197 | ZEBRA_ROUTER_ID_DELETE             | 16    |
 198 +------------------------------------+-------+
 199 | ZEBRA_ROUTER_ID_UPDATE             | 17    |
 200 +------------------------------------+-------+
 201 | ZEBRA_HELLO                        | 18    |
 202 +------------------------------------+-------+
 203 | ZEBRA_CAPABILITIES                 | 19    |
 204 +------------------------------------+-------+
 205 | ZEBRA_NEXTHOP_REGISTER             | 20    |
 206 +------------------------------------+-------+
 207 | ZEBRA_NEXTHOP_UNREGISTER           | 21    |
 208 +------------------------------------+-------+
 209 | ZEBRA_NEXTHOP_UPDATE               | 22    |
 210 +------------------------------------+-------+
 211 | ZEBRA_INTERFACE_NBR_ADDRESS_ADD    | 23    |
 212 +------------------------------------+-------+
 213 | ZEBRA_INTERFACE_NBR_ADDRESS_DELETE | 24    |
 214 +------------------------------------+-------+
 215 | ZEBRA_INTERFACE_BFD_DEST_UPDATE    | 25    |
 216 +------------------------------------+-------+
 217 | ZEBRA_IMPORT_ROUTE_REGISTER        | 26    |
 218 +------------------------------------+-------+
 219 | ZEBRA_IMPORT_ROUTE_UNREGISTER      | 27    |
 220 +------------------------------------+-------+
 221 | ZEBRA_IMPORT_CHECK_UPDATE          | 28    |
 222 +------------------------------------+-------+
 223 | ZEBRA_BFD_DEST_REGISTER            | 29    |
 224 +------------------------------------+-------+
 225 | ZEBRA_BFD_DEST_DEREGISTER          | 30    |
 226 +------------------------------------+-------+
 227 | ZEBRA_BFD_DEST_UPDATE              | 31    |
 228 +------------------------------------+-------+
 229 | ZEBRA_BFD_DEST_REPLAY              | 32    |
 230 +------------------------------------+-------+
 231 | ZEBRA_REDISTRIBUTE_ROUTE_ADD       | 33    |
 232 +------------------------------------+-------+
 233 | ZEBRA_REDISTRIBUTE_ROUTE_DEL       | 34    |
 234 +------------------------------------+-------+
 235 | ZEBRA_VRF_UNREGISTER               | 35    |
 236 +------------------------------------+-------+
 237 | ZEBRA_VRF_ADD                      | 36    |
 238 +------------------------------------+-------+
 239 | ZEBRA_VRF_DELETE                   | 37    |
 240 +------------------------------------+-------+
 241 | ZEBRA_VRF_LABEL                    | 38    |
 242 +------------------------------------+-------+
 243 | ZEBRA_INTERFACE_VRF_UPDATE         | 39    |
 244 +------------------------------------+-------+
 245 | ZEBRA_BFD_CLIENT_REGISTER          | 40    |
 246 +------------------------------------+-------+
 247 | ZEBRA_BFD_CLIENT_DEREGISTER        | 41    |
 248 +------------------------------------+-------+
 249 | ZEBRA_INTERFACE_ENABLE_RADV        | 42    |
 250 +------------------------------------+-------+
 251 | ZEBRA_INTERFACE_DISABLE_RADV       | 43    |
 252 +------------------------------------+-------+
 253 | ZEBRA_NEXTHOP_LOOKUP_MRIB          | 44    |
 254 +------------------------------------+-------+
 255 | ZEBRA_INTERFACE_LINK_PARAMS        | 45    |
 256 +------------------------------------+-------+
 257 | ZEBRA_MPLS_LABELS_ADD              | 46    |
 258 +------------------------------------+-------+
 259 | ZEBRA_MPLS_LABELS_DELETE           | 47    |
 260 +------------------------------------+-------+
 261 | ZEBRA_MPLS_LABELS_REPLACE          | 48    |
 262 +------------------------------------+-------+
 263 | ZEBRA_IPMR_ROUTE_STATS             | 49    |
 264 +------------------------------------+-------+
 265 | ZEBRA_LABEL_MANAGER_CONNECT        | 50    |
 266 +------------------------------------+-------+
 267 | ZEBRA_LABEL_MANAGER_CONNECT_ASYNC  | 51    |
 268 +------------------------------------+-------+
 269 | ZEBRA_GET_LABEL_CHUNK              | 52    |
 270 +------------------------------------+-------+
 271 | ZEBRA_RELEASE_LABEL_CHUNK          | 53    |
 272 +------------------------------------+-------+
 273 | ZEBRA_FEC_REGISTER                 | 54    |
 274 +------------------------------------+-------+
 275 | ZEBRA_FEC_UNREGISTER               | 55    |
 276 +------------------------------------+-------+
 277 | ZEBRA_FEC_UPDATE                   | 56    |
 278 +------------------------------------+-------+
 279 | ZEBRA_ADVERTISE_DEFAULT_GW         | 57    |
 280 +------------------------------------+-------+
 281 | ZEBRA_ADVERTISE_SVI_MACIP          | 58    |
 282 +------------------------------------+-------+
 283 | ZEBRA_ADVERTISE_SUBNET             | 59    |
 284 +------------------------------------+-------+
 285 | ZEBRA_ADVERTISE_ALL_VNI            | 60    |
 286 +------------------------------------+-------+
 287 | ZEBRA_LOCAL_ES_ADD                 | 61    |
 288 +------------------------------------+-------+
 289 | ZEBRA_LOCAL_ES_DEL                 | 62    |
 290 +------------------------------------+-------+
 291 | ZEBRA_VNI_ADD                      | 63    |
 292 +------------------------------------+-------+
 293 | ZEBRA_VNI_DEL                      | 64    |
 294 +------------------------------------+-------+
 295 | ZEBRA_L3VNI_ADD                    | 65    |
 296 +------------------------------------+-------+
 297 | ZEBRA_L3VNI_DEL                    | 66    |
 298 +------------------------------------+-------+
 299 | ZEBRA_REMOTE_VTEP_ADD              | 67    |
 300 +------------------------------------+-------+
 301 | ZEBRA_REMOTE_VTEP_DEL              | 68    |
 302 +------------------------------------+-------+
 303 | ZEBRA_MACIP_ADD                    | 69    |
 304 +------------------------------------+-------+
 305 | ZEBRA_MACIP_DEL                    | 70    |
 306 +------------------------------------+-------+
 307 | ZEBRA_IP_PREFIX_ROUTE_ADD          | 71    |
 308 +------------------------------------+-------+
 309 | ZEBRA_IP_PREFIX_ROUTE_DEL          | 72    |
 310 +------------------------------------+-------+
 311 | ZEBRA_REMOTE_MACIP_ADD             | 73    |
 312 +------------------------------------+-------+
 313 | ZEBRA_REMOTE_MACIP_DEL             | 74    |
 314 +------------------------------------+-------+
 315 | ZEBRA_DUPLICATE_ADDR_DETECTION     | 75    |
 316 +------------------------------------+-------+
 317 | ZEBRA_PW_ADD                       | 76    |
 318 +------------------------------------+-------+
 319 | ZEBRA_PW_DELETE                    | 77    |
 320 +------------------------------------+-------+
 321 | ZEBRA_PW_SET                       | 78    |
 322 +------------------------------------+-------+
 323 | ZEBRA_PW_UNSET                     | 79    |
 324 +------------------------------------+-------+
 325 | ZEBRA_PW_STATUS_UPDATE             | 80    |
 326 +------------------------------------+-------+
 327 | ZEBRA_RULE_ADD                     | 81    |
 328 +------------------------------------+-------+
 329 | ZEBRA_RULE_DELETE                  | 82    |
 330 +------------------------------------+-------+
 331 | ZEBRA_RULE_NOTIFY_OWNER            | 83    |
 332 +------------------------------------+-------+
 333 | ZEBRA_TABLE_MANAGER_CONNECT        | 84    |
 334 +------------------------------------+-------+
 335 | ZEBRA_GET_TABLE_CHUNK              | 85    |
 336 +------------------------------------+-------+
 337 | ZEBRA_RELEASE_TABLE_CHUNK          | 86    |
 338 +------------------------------------+-------+
 339 | ZEBRA_IPSET_CREATE                 | 87    |
 340 +------------------------------------+-------+
 341 | ZEBRA_IPSET_DESTROY                | 88    |
 342 +------------------------------------+-------+
 343 | ZEBRA_IPSET_ENTRY_ADD              | 89    |
 344 +------------------------------------+-------+
 345 | ZEBRA_IPSET_ENTRY_DELETE           | 90    |
 346 +------------------------------------+-------+
 347 | ZEBRA_IPSET_NOTIFY_OWNER           | 91    |
 348 +------------------------------------+-------+
 349 | ZEBRA_IPSET_ENTRY_NOTIFY_OWNER     | 92    |
 350 +------------------------------------+-------+
 351 | ZEBRA_IPTABLE_ADD                  | 93    |
 352 +------------------------------------+-------+
 353 | ZEBRA_IPTABLE_DELETE               | 94    |
 354 +------------------------------------+-------+
 355 | ZEBRA_IPTABLE_NOTIFY_OWNER         | 95    |
 356 +------------------------------------+-------+
 357 | ZEBRA_VXLAN_FLOOD_CONTROL          | 96    |
 358 +------------------------------------+-------+
 359 | ZEBRA_VXLAN_SG_ADD                 | 97    |
 360 +------------------------------------+-------+
 361 | ZEBRA_VXLAN_SG_DEL                 | 98    |
 362 +------------------------------------+-------+
 363 | ZEBRA_VXLAN_SG_REPLAY              | 99    |
 364 +------------------------------------+-------+
 365 | ZEBRA_MLAG_PROCESS_UP              | 100   |
 366 +------------------------------------+-------+
 367 | ZEBRA_MLAG_PROCESS_DOWN            | 101   |
 368 +------------------------------------+-------+
 369 | ZEBRA_MLAG_CLIENT_REGISTER         | 102   |
 370 +------------------------------------+-------+
 371 | ZEBRA_MLAG_CLIENT_UNREGISTER       | 103   |
 372 +------------------------------------+-------+
 373 | ZEBRA_MLAG_FORWARD_MSG             | 104   |
 374 +------------------------------------+-------+
 375 | ZEBRA_ERROR                        | 105   |
 376 +------------------------------------+-------+
 377 | ZEBRA_CLIENT_CAPABILITIES          | 106   |
 378 +------------------------------------+-------+
 379 | ZEBRA_OPAQUE_MESSAGE               | 107   |
 380 +------------------------------------+-------+
 381 | ZEBRA_OPAQUE_REGISTER              | 108   |
 382 +------------------------------------+-------+
 383 | ZEBRA_OPAQUE_UNREGISTER            | 109   |
 384 +------------------------------------+-------+
 385 | ZEBRA_NEIGH_DISCOVER               | 110   |
 386 +------------------------------------+-------+
 387
 388 Dataplane batching
 389 ==================
 390
 391 Dataplane batching is an optimization feature that reduces the processing
 392 time involved in the user space to kernel space transition for every message we
 393 want to send.
 394
 395 Design
 396 -----------
 397
 398 With our dataplane abstraction, we create a queue of dataplane context objects
 399 for the messages we want to send to the kernel. In a separate pthread, we
 400 loop over this queue and send the context objects to the appropriate
 401 dataplane. A batching enhancement tightly integrates with the dataplane
 402 context objects so they are able to be batch sent to dataplanes that support
 403 it.
 404
 405 There is one main change in the dataplane code. It does not call
 406 kernel-dependent functions one-by-one, but instead it hands a list of work down
 407 to the kernel level for processing.
 408
 409 Netlink
 410 ^^^^^^^
 411
 412 At the moment, this is the only dataplane that allows for batch sending
 413 messages to it.
 414
 415 When messages must be sent to the kernel, they are consecutively added
 416 to the batch represented by the `struct nl_batch`. Context objects are firstly
 417 encoded to their binary representation. All the encoding functions use the same
 418 interface: take a context object, a buffer and a size of the buffer as an
 419 argument. It is important that they should handle a situation in which a message
 420 wouldn't fit in the buffer and return a proper error. To achieve a zero-copy
 421 (in the user space only) messages are encoded to the same buffer which will
 422 be passed to the kernel. Hence, we can theoretically hit the boundary of the
 423 buffer.
 424
 425 Messages stored in the batch are sent if one of the conditions occurs:
 426
 427 - When an encoding function returns the buffer overflow error. The context
 428   object that caused this error is re-added to the new, empty batch.
 429
 430 - When the size of the batch hits certain limit.
 431
 432 - When the namespace of a currently being processed context object is
 433   different from all the previous ones. They have to be sent through
 434   distinct sockets, so the messages cannot share the same buffer.
 435
 436 - After the last message from the list is processed.
 437
 438 As mentioned earlier, there is a special threshold which is smaller than
 439 the size of the underlying buffer. It prevents the overflow error and thus
 440 eliminates the case, in which a message is encoded twice.
 441
 442 The buffer used in the batching is global, since allocating that big amount of
 443 memory every time wouldn't be most effective. However, its size can be changed
 444 dynamically, using hidden vtysh command:
 445 ``zebra kernel netlink batch-tx-buf (1-1048576) (1-1048576)``. This feature is
 446 only used in tests and shouldn't be utilized in any other place.
 447
 448 For every failed message in the batch, the kernel responds with an error
 449 message. Error messages are kept in the same order as they were sent, so parsing the
 450 response is straightforward. We use the two pointer technique to match
 451 requests with responses and then set appropriate status of dataplane context
 452 objects. There is also a global receive buffer and it is assumed that whatever
 453 the kernel sends it will fit in this buffer. The payload of netlink error messages
 454 consists of a error code and the original netlink message of the request, so
 455 the batch response won't be bigger than the batch request increased by
 456 some space for the headers.