Commit Graph

32 Commits

Author SHA1 Message Date
Yue Haibing c956910d5a tipc: Remove unused function declarations
Commit d50ccc2d39 ("tipc: add 128-bit node identifier") declared but never
implemented tipc_node_id2hash().
Also commit 5c216e1d28 ("tipc: Allow run-time alteration of default link settings")
never implemented tipc_media_set_priority() and tipc_media_set_window(),
commit cad2929dc4 ("tipc: update a binding service via broadcast") only declared
tipc_named_bcast().

Since commit be07f05639 ("tipc: simplify the finalize work queue")
tipc_sched_net_finalize() is removed and declaration is unused.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20230802034659.39840-1-yuehaibing@huawei.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2023-08-03 12:51:45 +02:00
Jon Maloy 7823f04f34 tipc: introduce new unified address type for internal use
We introduce a simplified version of struct sockaddr_tipc, using
anonymous unions and structures. Apart from being nicer to work with,
this struct will come in handy when we in a later commit add another
address type.

Signed-off-by: Jon Maloy <jmaloy@redhat.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Acked-by: Hoang Le <hoang.h.le@dektech.com.au>
Acked-by: Tung Nguyen <tung.q.nguyen@dektech.com.au>
Acked-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2021-03-17 11:51:04 -07:00
Jon Maloy 5f75e0a0e9 tipc: make node number calculation reproducible
The 32-bit node number, aka node hash or node address, is calculated
based on the 128-bit node identity when it is not set explicitly by
the user. In future commits we will need to perform this hash operation
on peer nodes while feeling safe that we obtain the same result.

We do this by interpreting the initial hash as a network byte order
number. Whenever we need to use the number locally on a node
we must therefore translate it to host byte order to obtain an
architecure independent result.

Furthermore, given the context where we use this number, we must not
allow it to be zero unless the node identity also is zero. Hence, in
the rare cases when the xor-ed hash value may end up as zero we replace
it with a fix number, knowing that the code anyway is capable of
handling hash collisions.

Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2020-11-27 17:34:01 -08:00
Jon Maloy d50ccc2d39 tipc: add 128-bit node identifier
We add a 128-bit node identity, as an alternative to the currently used
32-bit node address.

For the sake of compatibility and to minimize message header changes
we retain the existing 32-bit address field. When not set explicitly by
the user, this field will be filled with a hash value generated from the
much longer node identity, and be used as a shorthand value for the
latter.

We permit either the address or the identity to be set by configuration,
but not both, so when the address value is set by a legacy user the
corresponding 128-bit node identity is generated based on the that value.

Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-03-23 13:12:18 -04:00
Jon Maloy 23fd3eace0 tipc: remove direct accesses to own_addr field in struct tipc_net
As a preparation to changing the addressing structure of TIPC we replace
all direct accesses to the tipc_net::own_addr field with the function
dedicated for this, tipc_own_addr().

There are no changes to program logics in this commit.

Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-03-23 13:12:18 -04:00
Jon Maloy b89afb116c tipc: allow closest-first lookup algorithm when legacy address is configured
The removal of an internal structure of the node address has an unwanted
side effect.
- Currently, if a user is sending an anycast message with destination
  domain 0, the tipc_namebl_translate() function will use the 'closest-
  first' algorithm to first look for a node local destination, and only
  when no such is found, will it resort to the cluster global 'round-
  robin' lookup algorithm.
- Current users can get around this, and enforce unconditional use of
  global round-robin by indicating a destination as Z.0.0 or Z.C.0.
- This option disappears when we make the node address flat, since the
  lookup algorithm has no way of recognizing this case. So, as long as
  there are node local destinations, the algorithm will always select
  one of those, and there is nothing the sender can do to change this.

We solve this by eliminating the 'closest-first' option, which was never
a good idea anyway, for non-legacy users, but only for those. To
distinguish between legacy users and non-legacy users we introduce a new
flag 'legacy_addr_format' in struct tipc_core, to be set when the user
configures a legacy-style Z.C.N node address. Hence, when a legacy user
indicates a zero lookup domain 'closest-first' is selected, and in all
other cases we use 'round-robin'.

Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-03-23 13:12:18 -04:00
Jon Maloy 2026364149 tipc: remove restrictions on node address values
Nominally, TIPC organizes network nodes into a three-level network
hierarchy consisting of the levels 'zone', 'cluster' and 'node'. This
hierarchy is reflected in the node address format, - it is sub-divided
into an 8-bit zone id, and 12 bit cluster id, and a 12-bit node id.

However, the 'zone' and 'cluster' levels have in reality never been
fully implemented,and never will be. The result of this has been
that the first 20 bits the node identity structure have been wasted,
and the usable node identity range within a cluster has been limited
to 12 bits. This is starting to become a problem.

In the following commits, we will need to be able to connect between
nodes which are using the whole 32-bit value space of the node address.
We therefore remove the restrictions on which values can be assigned
to node identity, -it is from now on only a 32-bit integer with no
assumed internal structure.

Isolation between clusters is now achieved only by setting different
values for the 'network id' field used during neighbor discovery, in
practice leading to the latter becoming the new cluster identity.

The rules for accepting discovery requests/responses from neighboring
nodes now become:

- If the user is using legacy address format on both peers, reception
  of discovery messages is subject to the legacy lookup domain check
  in addition to the cluster id check.

- Otherwise, the discovery request/response is always accepted, provided
  both peers have the same network id.

This secures backwards compatibility for users who have been using zone
or cluster identities as cluster separators, instead of the intended
'network id'.

Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-03-23 13:12:18 -04:00
Jon Maloy 928df1880e tipc: obsolete TIPC_ZONE_SCOPE
Publications for TIPC_CLUSTER_SCOPE and TIPC_ZONE_SCOPE are in all
aspects handled the same way, both on the publishing node and on the
receiving nodes.

Despite previous ambitions to the contrary, this is never going to change,
so we take the conseqeunce of this and obsolete TIPC_ZONE_SCOPE and related
macros/functions. Whenever a user is doing a bind() or a sendmsg() attempt
using ZONE_SCOPE we translate this internally to CLUSTER_SCOPE, while we
remain compatible with users and remote nodes still using ZONE_SCOPE.

Furthermore, the non-formalized scope value 0 has always been permitted
for use during lookup, with the same meaning as ZONE_SCOPE/CLUSTER_SCOPE.
We now permit it even as binding scope, but for compatibility reasons we
choose to not change the value of TIPC_CLUSTER_SCOPE.

Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-03-17 17:11:46 -04:00
Parthasarathy Bhuvaragan 9ff26e9fab tipc: introduce constants for tipc address validation
In this commit, we introduce defines for tipc address size,
offset and mask specification for Zone.Cluster.Node.
There is no functional change in this commit.

Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-07-26 14:26:42 -07:00
Jon Paul Maloy 35c55c9877 tipc: add neighbor monitoring framework
TIPC based clusters are by default set up with full-mesh link
connectivity between all nodes. Those links are expected to provide
a short failure detection time, by default set to 1500 ms. Because
of this, the background load for neighbor monitoring in an N-node
cluster increases with a factor N on each node, while the overall
monitoring traffic through the network infrastructure increases at
a ~(N * (N - 1)) rate. Experience has shown that such clusters don't
scale well beyond ~100 nodes unless we significantly increase failure
discovery tolerance.

This commit introduces a framework and an algorithm that drastically
reduces this background load, while basically maintaining the original
failure detection times across the whole cluster. Using this algorithm,
background load will now grow at a rate of ~(2 * sqrt(N)) per node, and
at ~(2 * N * sqrt(N)) in traffic overhead. As an example, each node will
now have to actively monitor 38 neighbors in a 400-node cluster, instead
of as before 399.

This "Overlapping Ring Supervision Algorithm" is completely distributed
and employs no centralized or coordinated state. It goes as follows:

- Each node makes up a linearly ascending, circular list of all its N
  known neighbors, based on their TIPC node identity. This algorithm
  must be the same on all nodes.

- The node then selects the next M = sqrt(N) - 1 nodes downstream from
  itself in the list, and chooses to actively monitor those. This is
  called its "local monitoring domain".

- It creates a domain record describing the monitoring domain, and
  piggy-backs this in the data area of all neighbor monitoring messages
  (LINK_PROTOCOL/STATE) leaving that node. This means that all nodes in
  the cluster eventually (default within 400 ms) will learn about
  its monitoring domain.

- Whenever a node discovers a change in its local domain, e.g., a node
  has been added or has gone down, it creates and sends out a new
  version of its node record to inform all neighbors about the change.

- A node receiving a domain record from anybody outside its local domain
  matches this against its own list (which may not look the same), and
  chooses to not actively monitor those members of the received domain
  record that are also present in its own list. Instead, it relies on
  indications from the direct monitoring nodes if an indirectly
  monitored node has gone up or down. If a node is indicated lost, the
  receiving node temporarily activates its own direct monitoring towards
  that node in order to confirm, or not, that it is actually gone.

- Since each node is actively monitoring sqrt(N) downstream neighbors,
  each node is also actively monitored by the same number of upstream
  neighbors. This means that all non-direct monitoring nodes normally
  will receive sqrt(N) indications that a node is gone.

- A major drawback with ring monitoring is how it handles failures that
  cause massive network partitionings. If both a lost node and all its
  direct monitoring neighbors are inside the lost partition, the nodes in
  the remaining partition will never receive indications about the loss.
  To overcome this, each node also chooses to actively monitor some
  nodes outside its local domain. Those nodes are called remote domain
  "heads", and are selected in such a way that no node in the cluster
  will be more than two direct monitoring hops away. Because of this,
  each node, apart from monitoring the member of its local domain, will
  also typically monitor sqrt(N) remote head nodes.

- As an optimization, local list status, domain status and domain
  records are marked with a generation number. This saves senders from
  unnecessarily conveying  unaltered domain records, and receivers from
  performing unneeded re-adaptations of their node monitoring list, such
  as re-assigning domain heads.

- As a measure of caution we have added the possibility to disable the
  new algorithm through configuration. We do this by keeping a threshold
  value for the cluster size; a cluster that grows beyond this value
  will switch from full-mesh to ring monitoring, and vice versa when
  it shrinks below the value. This means that if the threshold is set to
  a value larger than any anticipated cluster size (default size is 32)
  the new algorithm is effectively disabled. A patch set for altering the
  threshold value and for listing the table contents will follow shortly.

- This change is fully backwards compatible.

Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-06-15 14:06:28 -07:00
Jon Paul Maloy a6bf70f792 tipc: simplify include dependencies
When we try to add new inline functions in the code, we sometimes
run into circular include dependencies.

The main problem is that the file core.h, which really should be at
the root of the dependency chain, instead is a leaf. I.e., core.h
includes a number of header files that themselves should be allowed
to include core.h. In reality this is unnecessary, because core.h does
not need to know the full signature of any of the structs it refers to,
only their type declaration.

In this commit, we remove all dependencies from core.h towards any
other tipc header file.

As a consequence of this change, we can now move the function
tipc_own_addr(net) from addr.c to addr.h, and make it inline.

There are no functional changes in this commit.

Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-05-14 12:24:45 -04:00
Jon Paul Maloy d482994fca tipc: fix two bugs in secondary destination lookup
A message sent to a node after a successful name table lookup may still
find that the destination socket has disappeared, because distribution
of name table updates is non-atomic. If so, the message will be rejected
back to the sender with error code TIPC_ERR_NO_PORT. If the source
socket of the message has disappeared in the meantime, the message
should be dropped.

However, in the currrent code, the message will instead be subject to an
unwanted tertiary lookup, because the function tipc_msg_lookup_dest()
doesn't check if there is an error code present in the message before
performing the lookup. In the worst case, the message may now find the
old destination again, and be redirected once more, instead of being
dropped directly as it should be.

A second bug in this function is that the "prev_node" field in the message
is not updated after successful lookup, something that may have
unpredictable consequences.

The problems arising from those bugs occur very infrequently.

The third change in this function; the test on msg_reroute_msg_cnt() is
purely cosmetic, reflecting that the returned value never can be negative.

This commit corrects the two bugs described above.

Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-03-29 13:47:36 -07:00
Ying Xue 3474753954 tipc: make tipc node address support net namespace
If net namespace is supported in tipc, each namespace will be treated
as a separate tipc node. Therefore, every namespace must own its
private tipc node address. This means the "tipc_own_addr" global
variable of node address must be moved to tipc_net structure to
satisfy the requirement. It's turned out that users also can assign
node address for every namespace.

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Tested-by: Tero Aho <Tero.Aho@coriant.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-01-12 16:24:33 -05:00
Ying Xue 1da465683a tipc: make tipc broadcast link support net namespace
TIPC broadcast link is statically established and its relevant states
are maintained with the global variables: "bcbearer", "bclink" and
"bcl". Allowing different namespace to own different broadcast link
instances, these variables must be moved to tipc_net structure and
broadcast link instances would be allocated and initialized when
namespace is created.

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Tested-by: Tero Aho <Tero.Aho@coriant.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-01-12 16:24:33 -05:00
Ying Xue f2f9800d49 tipc: make tipc node table aware of net namespace
Global variables associated with node table are below:
- node table list (node_htable)
- node hash table list (tipc_node_list)
- node table lock (node_list_lock)
- node number counter (tipc_num_nodes)
- node link number counter (tipc_num_links)

To make node table support namespace, above global variables must be
moved to tipc_net structure in order to keep secret for different
namespaces. As a consequence, these variables are allocated and
initialized when namespace is created, and deallocated when namespace
is destroyed. After the change, functions associated with these
variables have to utilize a namespace pointer to access them. So
adding namespace pointer as a parameter of these functions is the
major change made in the commit.

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Tested-by: Tero Aho <Tero.Aho@coriant.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-01-12 16:24:32 -05:00
Ying Xue 859fc7c0ce tipc: cleanup core.c and core.h files
Only the works of initializing and shutting down tipc module are done
in core.h and core.c files, so all stuffs which are not closely
associated with the two tasks should be moved to appropriate places.

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Tested-by: Tero Aho <Tero.Aho@coriant.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-01-12 16:24:31 -05:00
Andreas Bofjäll b3f0f5c357 tipc: explicitly include core.h in addr.h
The inline functions in addr.h uses tipc_own_addr which is exported by
core.h, but addr.h never actually includes it. It works because it is
explicitly included where this is used, but it looks a bit strange.

Include core.h in addr.h explicitly to make the dependency clearer.

Signed-off-by: Andreas Bofjäll <andreas.bofjall@ericsson.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-02-13 17:49:13 -05:00
Paul Gortmaker 617d3c7a50 tipc: compress out gratuitous extra carriage returns
Some of the comment blocks are floating in limbo between two
functions, or between blocks of code.  Delete the extra line
feeds between any comment and its associated following block
of code, to be consistent with the majority of the rest of
the kernel.  Also delete trailing newlines at EOF and fix
a couple trivial typos in existing comments.

This is a 100% cosmetic change with no runtime impact.  We get
rid of over 500 lines of non-code, and being blank line deletes,
they won't even show up as noise in git blame.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-04-30 15:53:56 -04:00
Allan Stephens 336ebf5bf5 tipc: Add routines for safe checking of node's network address
Introduces routines that test whether a given network address is
equal to a node's own network address or if it lies within the node's
own network cluster, and which work properly regardless of whether
the node is using the default network address <0.0.0> or a non-zero
network address that is assigned later on. In essence, these routines
ensure that address <0.0.0> is treated as an alias for "this node",
regardless of which network address the node is actually using.

Old users of the pre-existing more strict match in_own_cluster()
have been accordingly redirected to what is now called
in_own_cluster_exact() --- which does not extend matching to <0,0,0>.

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-04-19 15:46:39 -04:00
Paul Gortmaker 1f3de471ad tipc: make zone/cluster mask constants a define
This allows them to be available for easy re-use in other places
and avoids trivial mistakes caused by  "count the f's and 0's".

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2011-05-10 16:03:54 -04:00
Allan Stephens a3796f895f tipc: Add network address mask helper routines
Introduces a pair of helper routines that convert the network address
for a TIPC node into the network address for its cluster or zone.

This is a cosmetic change designed to avoid future errors caused by
the incorrect use of address bitmasks, and does not alter the existing
operation of TIPC.

Signed-off-by: Allan Stephens <Allan.Stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2011-03-13 16:35:16 -04:00
Allan Stephens 51a8e4dee7 tipc: Remove prototype code for supporting inter-cluster routing
Eliminates routines and data structures that were intended to allow
TIPC to route messages to other clusters. Currently, TIPC supports only
networks consisting of a single cluster within a single zone, so this
code is unnecessary.

Signed-off-by: Allan Stephens <Allan.Stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2011-01-01 13:57:48 -08:00
Allan Stephens 08c80e9a03 tipc: Remove prototype code for supporting slave nodes
Simplifies routines and data structures that were intended to allow
TIPC to support slave nodes (i.e. nodes that did not have links to
all of the other nodes in its cluster, forcing TIPC to route messages
that it could not deliver directly through a non-slave node).

Currently, TIPC supports only networks containing non-slave nodes,
so this code is unnecessary.

Note: The latest edition of the TIPC 2.0 Specification has eliminated
the concept of slave nodes entirely.

Signed-off-by: Allan Stephens <Allan.Stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2011-01-01 13:57:48 -08:00
Allan Stephens 80e0c33064 tipc: Reduce footprint by un-inlining address routines
Convert address-related inline routines that are more than one
line into standard functions, thereby eliminating a significant
amount of repeated code.

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2010-05-12 23:02:26 -07:00
Allan Stephens c68ca7b720 tipc: add tipc_ prefix to fcns targeted for un-inlining
These functions have enough code in them such that they
seem like sensible targets for un-inlining.  Prior to doing
that, this adds the tipc_ prefix to the functions, so that
in the event of a panic dump or similar, the subsystem from
which the functions come from is immediately clear.

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2010-05-12 23:02:25 -07:00
Ilpo Järvinen 86121fe5b4 [TIPC]: Kill unused static inline (x5)
All these static inlines are unused:

in_own_zone     1 (net/tipc/addr.h)
msg_dataoctet   1 (net/tipc/msg.h)
msg_direct      1 (include/net/tipc/tipc_msg.h)
msg_options     1 (include/net/tipc/tipc_msg.h)
tipc_nmap_get   1 (net/tipc/bcast.h)

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-02-07 18:17:13 -08:00
YOSHIFUJI Hideaki c430728526 [NET] TIPC: Fix whitespace errors.
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-02-10 23:20:15 -08:00
Per Liden 4323add677 [TIPC] Avoid polluting the global namespace
This patch adds a tipc_ prefix to all externally visible symbols.

Signed-off-by: Per Liden <per.liden@ericsson.com>
2006-01-18 00:45:16 +01:00
Per Liden 593a5f22d8 [TIPC] More updates of file headers
Updated copyright notice to include the year the file was
actually created. Information about file creation dates
was extracted from the files in the old CVS repository
at tipc.sourceforge.net.

Signed-off-by: Per Liden <per.liden@nospam.ericsson.com>
2006-01-12 14:06:39 -08:00
Per Liden 9da1c8b694 [TIPC] Update of file headers
The copyright statements from different parts of Ericsson
have been merged into one.

Signed-off-by: Per Liden <per.liden@nospam.ericsson.com>
2006-01-12 14:06:38 -08:00
Per Liden 9ea1fd3c1a [TIPC] License header update
The license header in each file now more clearly state that this
code is licensed under a dual BSD/GPL. Before this was only
evident if you looked at the MODULE_LICENSE line in core.c.

Signed-off-by: Per Liden <per.liden@nospam.ericsson.com>
2006-01-12 14:06:36 -08:00
Per Liden b97bf3fd8f [TIPC] Initial merge
TIPC (Transparent Inter Process Communication) is a protocol designed for
intra cluster communication. For more information see
http://tipc.sourceforge.net

Signed-off-by: Per Liden <per.liden@nospam.ericsson.com>
2006-01-12 14:06:31 -08:00