Commit Graph

132 Commits

Author SHA1 Message Date
Alexander V. Chernikov
563ab4e400 Fix gateway setup for the interface routes.
Currently rinit1() and its IPv6 counterpart
  nd6_prefix_onlink_rtrequest() uses dummy null_sdl gateway address
  during route insertion and change it afterwards. This behaviour
  brings complications to the routing stack and the users of its
  upcoming notification system.

This change fixes both rinit1() and nd6_prefix_onlink_rtrequest()
  by filling in proper gateway in the beginning. It does not change any
  of the userland notifications as in both cases, they happen after
  the insertion and fixup process (rt_newaddrmsg_fib() and nd6_rtmsg()).

MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D20328
2019-05-22 21:20:15 +00:00
Bjoern A. Zeeb
30b450774e Update for IETF draft-ietf-6man-ipv6only-flag.
When we roam between networks and our link-state goes down, automatically remove
the IPv6-Only flag from the interface.  Otherwise we might switch from an
IPv6-only to and IPv4-only network and the flag would stay and we would prevent
IPv4 from working.

While the actual function call to clear the flag is under EXPERIMENTAL,
the eventhandler is not as we might want to re-use it for other
functionality on link-down event (such was re-calculate default routers
for example if there is more than one).

Reviewed by:	hrs
Differential Revision:	https://reviews.freebsd.org/D19487
2019-03-07 23:03:39 +00:00
Bjoern A. Zeeb
21231a7aa6 Update for IETF draft-ietf-6man-ipv6only-flag.
All changes are hidden behind the EXPERIMENTAL option and are not compiled
in by default.

Add ND6_IFF_IPV6_ONLY_MANUAL to be able to set the interface into no-IPv4-mode
manually without router advertisement options.  This will allow developers to
test software for the appropriate behaviour even on dual-stack networks or
IPv6-Only networks without the option being set in RA messages.
Update ifconfig to allow setting and displaying the flag.

Update the checks for the filters to check for either the automatic or the manual
flag to be set.  Add REVARP to the list of filtered IPv4-related protocols and add
an input filter similar to the output filter.

Add a check, when receiving the IPv6-Only RA flag to see if the receiving
interface has any IPv4 configured.  If it does, ignore the IPv6-Only flag.

Add a per-VNET global sysctl, which is on by default, to not process the automatic
RA IPv6-Only flag.  This way an administrator (if this is compiled in) has control
over the behaviour in case the node still relies on IPv4.
2019-03-06 23:31:42 +00:00
Gleb Smirnoff
a68cc38879 Mechanical cleanup of epoch(9) usage in network stack.
- Remove macros that covertly create epoch_tracker on thread stack. Such
  macros a quite unsafe, e.g. will produce a buggy code if same macro is
  used in embedded scopes. Explicitly declare epoch_tracker always.

- Unmask interface list IFNET_RLOCK_NOSLEEP(), interface address list
  IF_ADDR_RLOCK() and interface AF specific data IF_AFDATA_RLOCK() read
  locking macros to what they actually are - the net_epoch.
  Keeping them as is is very misleading. They all are named FOO_RLOCK(),
  while they no longer have lock semantics. Now they allow recursion and
  what's more important they now no longer guarantee protection against
  their companion WLOCK macros.
  Note: INP_HASH_RLOCK() has same problems, but not touched by this commit.

This is non functional mechanical change. The only functionally changed
functions are ni6_addrs() and ni6_store_addrs(), where we no longer enter
epoch recursively.

Discussed with:	jtl, gallatin
2019-01-09 01:11:19 +00:00
Bjoern A. Zeeb
201100c58b Initial implementation of draft-ietf-6man-ipv6only-flag.
This change defines the RA "6" (IPv6-Only) flag which routers
may advertise, kernel logic to check if all routers on a link
have the flag set and accordingly update a per-interface flag.

If all routers agree that it is an IPv6-only link, ether_output_frame(),
based on the interface flag, will filter out all ETHERTYPE_IP/ARP
frames, drop them, and return EAFNOSUPPORT to upper layers.

The change also updates ndp to show the "6" flag, ifconfig to
display the IPV6_ONLY nd6 flag if set, and rtadvd to allow
announcing the flag.

Further changes to tcpdump (contrib code) are availble and will
be upstreamed.

Tested the code (slightly earlier version) with 2 FreeBSD
IPv6 routers, a FreeBSD laptop on ethernet as well as wifi,
and with Win10 and OSX clients (which did not fall over with
the "6" flag set but not understood).

We may also want to (a) implement and RX filter, and (b) over
time enahnce user space to, say, stop dhclient from running
when the interface flag is set.  Also we might want to start
IPv6 before IPv4 in the future.

All the code is hidden under the EXPERIMENTAL option and not
compiled by default as the draft is a work-in-progress and
we cannot rely on the fact that IANA will assign the bits
as requested by the draft and hence they may change.

Dear 6man, you have running code.

Discussed with:	Bob Hinden, Brian E Carpenter
2018-10-30 20:08:48 +00:00
Andrew Turner
5f901c92a8 Use the new VNET_DEFINE_STATIC macro when we are defining static VNET
variables.

Reviewed by:	bz
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D16147
2018-07-24 16:35:52 +00:00
Matt Macy
d7c5a620e2 ifnet: Replace if_addr_lock rwlock with epoch + mutex
Run on LLNW canaries and tested by pho@

gallatin:
Using a 14-core, 28-HTT single socket E5-2697 v3 with a 40GbE MLX5
based ConnectX 4-LX NIC, I see an almost 12% improvement in received
packet rate, and a larger improvement in bytes delivered all the way
to userspace.

When the host receiving 64 streams of netperf -H $DUT -t UDP_STREAM -- -m 1,
I see, using nstat -I mce0 1 before the patch:

InMpps OMpps  InGbs  OGbs err TCP Est %CPU syscalls csw     irq GBfree
4.98   0.00   4.42   0.00 4235592     33   83.80 4720653 2149771   1235 247.32
4.73   0.00   4.20   0.00 4025260     33   82.99 4724900 2139833   1204 247.32
4.72   0.00   4.20   0.00 4035252     33   82.14 4719162 2132023   1264 247.32
4.71   0.00   4.21   0.00 4073206     33   83.68 4744973 2123317   1347 247.32
4.72   0.00   4.21   0.00 4061118     33   80.82 4713615 2188091   1490 247.32
4.72   0.00   4.21   0.00 4051675     33   85.29 4727399 2109011   1205 247.32
4.73   0.00   4.21   0.00 4039056     33   84.65 4724735 2102603   1053 247.32

After the patch

InMpps OMpps  InGbs  OGbs err TCP Est %CPU syscalls csw     irq GBfree
5.43   0.00   4.20   0.00 3313143     33   84.96 5434214 1900162   2656 245.51
5.43   0.00   4.20   0.00 3308527     33   85.24 5439695 1809382   2521 245.51
5.42   0.00   4.19   0.00 3316778     33   87.54 5416028 1805835   2256 245.51
5.42   0.00   4.19   0.00 3317673     33   90.44 5426044 1763056   2332 245.51
5.42   0.00   4.19   0.00 3314839     33   88.11 5435732 1792218   2499 245.52
5.44   0.00   4.19   0.00 3293228     33   91.84 5426301 1668597   2121 245.52

Similarly, netperf reports 230Mb/s before the patch, and 270Mb/s after the patch

Reviewed by:	gallatin
Sponsored by:	Limelight Networks
Differential Revision:	https://reviews.freebsd.org/D15366
2018-05-18 20:13:34 +00:00
Eric van Gyzen
0bbfb20fe5 Update the MTU in affected routes when IPv6 RA changes the MTU
ip6_calcmtu() only looks at the interface MTU if neither the TCP hostcache
nor the route provides an MTU.  Update the routes so they do not provide
stale MTUs.

This fixes UNH IPv6 conformance test cases v6LC_4_1_08 and v6LC_4_1_09,
which use a RA to reduce the link MTU from 1500 to 1280.

Reported and tested by:	Farrell Woods <Farrell_Woods@Dell.com>
Reviewed by:	dab, melifaro
Discussed with:	ae
MFC after:	1 week
Sponsored by:	Dell EMC
Differential Revision:	https://reviews.freebsd.org/D14257
2018-02-12 19:49:20 +00:00
Andrey V. Elsukov
a406128960 Follow the RFC6980 and silently ignore following IPv6 NDP messages
that had the IPv6 fragmentation header:
 o  Neighbor Solicitation
 o  Neighbor Advertisement
 o  Router Solicitation
 o  Router Advertisement
 o  Redirect

Introduce M_FRAGMENTED mbuf flag, and set it after IPv6 fragment reassembly
is completed. Then check the presence of this flag in correspondig ND6
handling routines.

PR:		224247
MFC after:	2 weeks
2017-12-15 12:37:32 +00:00
Pedro F. Giffuni
51369649b0 sys: further adoption of SPDX licensing ID tags.
Mainly focus on files that use BSD 3-Clause license.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.
2017-11-20 19:43:44 +00:00
Alan Somers
559b42968c Constrain IPv6 routes to single FIBs when net.add_addr_allfibs=0
sys/netinet6/icmp6.c
	Use the interface's FIB for source address selection in ICMPv6 error
	responses.

sys/netinet6/in6.c
	In in6_newaddrmsg, announce arrival of local addresses on the
	interface's FIB only.  In in6_lltable_rtcheck, use a per-fib ND6
	cache instead of a single cache.

sys/netinet6/in6_src.c
	In in6_selectsrc, use the caller's fib instead of the default fib.
	In in6_selectsrc_socket, remove a superfluous check.

sys/netinet6/nd6.c
	In nd6_lle_event, use the interface's fib for routing socket
	messages.  In nd6_is_new_addr_neighbor, check all FIBs when trying
	to determine whether an address is a neighbor.  Also, simplify the
	code for point to point interfaces.

sys/netinet6/nd6.h
sys/netinet6/nd6.c
sys/netinet6/nd6_rtr.c
	Make defrouter_select fib-aware, and make all of its callers pass in
	the interface fib.

sys/netinet6/nd6_nbr.c
	When inputting a Neighbor Solicitation packet, consider the
	interface fib instead of the default fib for DAD.  Output NS and
	Neighbor Advertisement packets on the correct fib.

sys/netinet6/nd6_rtr.c
	Allow installing the same host route on different interfaces in
	different FIBs.  If rt_add_addr_allfibs=0, only install or delete
	the prefix route on the interface fib.

tests/sys/netinet/fibs_test.sh
	Clear some expected failures, but add a skip for the newly revealed
	BUG217871.

PR:		196361
Submitted by:	Erick Turnquist <jhujhiti@adjectivism.org>
Reported by:	Jason Healy <jhealy@logn.net>
Reviewed by:	asomers
MFC after:	3 weeks
Sponsored by:	Spectra Logic Corp
Differential Revision:	https://reviews.freebsd.org/D9451
2017-03-17 16:50:37 +00:00
Mark Johnston
62280740d6 Remove a bogus KASSERT from nd6_prefix_unlink().
The caller may unlink a prefix before purging referencing addresses. An
identical assertion in nd6_prefix_del() verifies that the addresses are
purged before the prefix is freed.

PR:		215372
X-MFC With:	r306829
2016-12-19 19:21:28 +00:00
Mark Johnston
d748f7efcd Lock the ND prefix list and add refcounting for prefixes.
This change extends the nd6 lock to protect the ND prefix list as well
as the list of advertising routers associated with each prefix. To handle
cases where the nd6 lock must be dropped while iterating over either the
prefix or default router lists, a generation counter is used to track
modifications to the lists. Additionally, a new mutex is used to serialize
prefix on-link/off-link transitions. This mutex must be acquired before
the nd6 lock and is held while updating the routing table in
nd6_prefix_onlink() and nd6_prefix_offlink().

Reviewed by:	ae, tuexen (SCTP bits)
Tested by:	Jason Wolfe <jason@llnw.com>,
		Larry Rosenman <ler@lerctr.org>
MFC after:	2 months
Differential Revision:	https://reviews.freebsd.org/D8125
2016-10-07 21:10:53 +00:00
Mark Johnston
c26158449e Reduce the number of conditional statements in nd6_prefix_onlink().
MFC after:	1 week
2016-10-07 21:03:18 +00:00
Mark Johnston
7b0e84b7c8 Combine several checks in nd6_prefix_offlink() into one.
MFC after:	1 week
2016-10-07 21:02:30 +00:00
Mark Johnston
7782accf13 Fix whitespace around prototypes in nd6_rtr.c.
MFC after:	1 week
2016-10-07 00:36:18 +00:00
Mark Johnston
07c1f95976 Fix a typo.
MFC after:	1 week
2016-10-07 00:35:28 +00:00
Mark Johnston
a88d6d7e07 Shorten and simplify some of the loops in pfxlist_onlink_check().
No functional change intended.

MFC after:	1 week
2016-10-07 00:34:57 +00:00
Mark Johnston
0bbf244e9f Rename ndpr_refcnt to ndpr_addrcnt.
This field counts derived addresses and is not a true refcount for prefix
objects, so the previous name was misleading.

MFC after:	1 week
2016-09-24 01:14:25 +00:00
Mark Johnston
1b28988b44 Exploit r301213 to fix in6 ifaddr locking in pfxlist_onlink_check().
Reviewed by:	ae, hrs
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D6639
2016-06-02 17:21:57 +00:00
Mark Johnston
20b5f02214 Clean up callers of nd6_prelist_add().
nd6_prelist_add() sets *newp if and only if it is successful, so there's no
need for code that handles the case where the return value is 0 and
*newp == NULL. Fix some style bugs in nd6_prelist_add() while here.

MFC after:	1 week
2016-05-07 03:41:29 +00:00
Mark Johnston
83631b16a7 Remove two useless local variables from prelist_update().
MFC after:	1 week
2016-05-07 03:32:29 +00:00
Pedro F. Giffuni
a4641f4eaa sys/net*: minor spelling fixes.
No functional change.
2016-05-03 18:05:43 +00:00
Pedro F. Giffuni
155d72c498 sys/net* : for pointers replace 0 with NULL.
Mostly cosmetical, no functional change.

Found with devel/coccinelle.
2016-04-15 17:30:33 +00:00
Mark Johnston
ff63037da1 Modify defrouter_remove() to perform the router lookup before removal.
This allows some simplification of its callers. No functional change
intended.

Tested by:	Larry Rosenman (as part of a larger change)
MFC after:	1 month
2016-03-17 19:01:44 +00:00
Mark Johnston
4de485fe5f Lock the NDP default router list and count defrouter references.
This addresses a number of race conditions that can cause crashes as a
result of unsynchronized access to the list.

PR:		206904
Tested by:	Larry Rosenman <ler@lerctr.org>,
		Kevin Bowling <kevin.bowling@kev009.com>
MFC after:	2 months
Differential Revision: https://reviews.freebsd.org/D5315
2016-02-25 20:12:05 +00:00
Mark Johnston
38dd603f8c Use pfxrtr_del() instead of freeing advertising routers directly.
MFC after:	1 week
2016-02-17 23:55:24 +00:00
Mark Johnston
01869be58e Rename the flags field of struct nd_defrouter to "raflags".
This field contains the flags inherited from the corresponding router
advertisement message and is not for storing private state.

MFC after:	1 week
2016-02-12 21:15:57 +00:00
Mark Johnston
a4a7c8254c Simplify defrtrlist_update() slightly in preparation for future changes.
No functional change intended.

MFC after:	1 week
2016-02-12 21:06:48 +00:00
Mark Johnston
baebd3e54f Remove superfluous return statements from the neighbour discovery code.
MFC after:	1 week
2016-02-12 20:55:22 +00:00
Mark Johnston
fc31564185 Fix style around allocations from M_IP6NDP.
- Don't cast the return value of malloc(9).
- Use M_ZERO instead of explicitly calling bzero(9).

MFC after:	1 week
2016-02-12 20:52:53 +00:00
Alexander V. Chernikov
61eee0e202 MFP r287070,r287073: split radix implementation and route table structure.
There are number of radix consumers in kernel land (pf,ipfw,nfs,route)
  with different requirements. In fact, first 3 don't have _any_ requirements
  and first 2 does not use radix locking. On the other hand, routing
  structure do have these requirements (rnh_gen, multipath, custom
  to-be-added control plane functions, different locking).
Additionally, radix should not known anything about its consumers internals.

So, radix code now uses tiny 'struct radix_head' structure along with
  internal 'struct radix_mask_head' instead of 'struct radix_node_head'.
  Existing consumers still uses the same 'struct radix_node_head' with
  slight modifications: they need to pass pointer to (embedded)
  'struct radix_head' to all radix callbacks.

Routing code now uses new 'struct rib_head' with different locking macro:
  RADIX_NODE_HEAD prefix was renamed to RIB_ (which stands for routing
  information base).

New net/route_var.h header was added to hold routing subsystem internal
  data. 'struct rib_head' was placed there. 'struct rtentry' will also
  be moved there soon.
2016-01-25 06:33:15 +00:00
Alexander V. Chernikov
e8b0643eee Add new rt_foreach_fib_walk_del() function for deleting route entries
by filter function instead of picking into routing table details in
  each consumer.
Remove now-unused rt_expunge() (eliminating last external RTF_RNH_LOCKED
 user).
This simplifies future nexthops/mulitipath changes and rtrequest1_fib()
  locking refactoring.

Actual changes:
Add "rt_chain" field to permit rte grouping while doing batched delete
  from routing table (thus growing rte 200->208 on amd64).
Add "rti_filter" /  "rti_filterdata" / "rti_spare" fields to rt_addrinfo
  to pass filter function to various routing subsystems in standard way.
Convert all rt_expunge() customers to new rt_addinfo-based api and eliminate
  rt_expunge().
2015-11-30 05:51:14 +00:00
Eric van Gyzen
17a036563d Fix the handling of IPv6 On-Link Redirects.
On receipt of a redirect message, install an interface route for the
redirected destination.  On removal of the corresponding Neighbor Cache
entry, remove the interface route.

This requires changes in rtredirect_fib() to cope with an AF_LINK
address for the gateway and with the absence of RTF_GATEWAY.

This fixes the "Redirected On-Link" test cases in the Tahi IPv6 Ready Logo
Phase 2 test suite.

Unrelated to the above, fix a recursion on the radix node head lock
triggered by the Tahi Redirected to Alternate Router test cases.

When I first wrote this patch in October 2012, all Section 2
(Neighbor Discovery) test cases passed on 10-CURRENT, 9-STABLE,
and 8-STABLE.  cem@ recently rebased the 10.x patch onto head and reported
that it passes Tahi.  (Thanks!)

These other test cases also passed in 2012:

* the RTF_MODIFIED case, with IPv4 and IPv6 (using a
  RTF_HOST|RTF_GATEWAY route for the destination)

* the redirected-to-self case, with IPv4 and IPv6

* a valid IPv4 redirect

All testing in 2012 was done with WITNESS and INVARIANTS.

Tested by:    EMC / Isilon Storage Division via Conrad Meyer (cem) in 2015,
              Mark Kelley <mark_kelley@dell.com> in 2012,
              TC Telkamp <terence_telkamp@dell.com> in 2012
PR:           152791
Reviewed by:  melifaro (current rev), bz (earlier rev)
Approved by:  kib (mentor)
MFC after:    1 month
Relnotes:     yes
Sponsored by: Dell Inc.
Differential Revision: https://reviews.freebsd.org/D3602
2015-09-14 19:17:25 +00:00
Alexander V. Chernikov
2caee4be35 Rename rt_foreach_fib() to rt_foreach_fib_walk().
Suggested by:	julian
2015-08-10 20:50:31 +00:00
Alexander V. Chernikov
4bdf0b6a9a MFP r274295:
* Move interface route cleanup to route.c:rt_flushifroutes()
* Convert most of "for (fibnum = 0; fibnum < rt_numfibs; fibnum++)" users
  to use new rt_foreach_fib() instead of hand-rolling cycles.
2015-08-08 18:14:59 +00:00
Xin LI
dd3856601d Mitigate Local Denial of Service with IPv6 Router Advertisements
and log attack attempts.

Submitted by:	hrs
Security:	FreeBSD-SA-15:09.nd6
Security:	CVE-2015-2923
2015-04-07 20:20:09 +00:00
Alexander V. Chernikov
0c5d4bde90 Use in6_localip() instead of hand-rolled cycle.
MFC after:	2 weeks
2014-01-18 20:54:55 +00:00
Alexander V. Chernikov
9080e7d023 Add in6_prepare_ifra() function to ease preparing in-kernel IPv6
address requests.

MFC after:	2 weeks
2014-01-18 20:32:59 +00:00
Alexander V. Chernikov
1dc8f6a82c Introduce IN6_MASK_ADDR() macro to unify various hand-rolled code
to do IPv6 addr & mask in different places.

MFC after:	2 weeks
2014-01-08 22:13:32 +00:00
Gleb Smirnoff
76039bc84f The r48589 promised to remove implicit inclusion of if_var.h soon. Prepare
to this event, adding if_var.h to files that do need it. Also, include
all includes that now are included due to implicit pollution via if_var.h

Sponsored by:	Netflix
Sponsored by:	Nginx, Inc.
2013-10-26 17:58:36 +00:00
Hiroki Sato
7d26db1792 - Use time_uptime instead of time_second in data structures for
PF_INET6 in kernel.  This fixes various malfunction when the wall time
  clock is changed.  Bump __FreeBSD_version to 1000041.

- Use clock_gettime(CLOCK_MONOTONIC_FAST) in userland utilities.

MFC after:	1 month
2013-08-05 20:13:02 +00:00
Qing Li
378aa8d85e Delete the nd6 entries associated with an off-link prefix
if the same prefix cannot be found on an alternative
interface.

Reviewed by:	hrs
MFC after:	1 week
2013-06-24 05:01:13 +00:00
Andrey V. Elsukov
73cb2f38f2 Reduce the overhead of locking, use IF_AFDATA_RLOCK() when we are doing
simple lookups.

Sponsored by:	Yandex LLC
MFC after:	1 week
2012-11-16 12:12:02 +00:00
Xin LI
6f56329a25 Remove __P.
Submitted by:	kevlo
Reviewed by:	md5(1)
MFC after:	2 months
2012-10-22 21:49:56 +00:00
Andre Oppermann
c9b652e3e8 Mechanically remove the last stray remains of spl* calls from net*/*.
They have been Noop's for a long time now.
2012-10-18 13:57:24 +00:00
Bjoern A. Zeeb
81d5d46b3c Add multi-FIB IPv6 support to the core network stack supplementing
the original IPv4 implementation from r178888:

- Use RT_DEFAULT_FIB in the IPv4 implementation where noticed.
- Use rt*fib() KPI with explicit RT_DEFAULT_FIB where applicable in
  the NFS code.
- Use the new in6_rt* KPI in TCP, gif(4), and the IPv6 network stack
  where applicable.
- Split in6_rtqtimo() and in6_mtutimo() as done in IPv4 and equally
  prevent multiple initializations of callouts in in6_inithead().
- Use wrapper functions where needed to preserve the current KPI to
  ease MFCs.  Use BURN_BRIDGES to indicate expected future cleanup.
- Fix (related) comments (both technical or style).
- Convert to rtinit() where applicable and only use custom loops where
  currently not possible otherwise.
- Multicast group, most neighbor discovery address actions and faith(4)
  are locked to the default FIB.  Individual IPv6 addresses will only
  appear in the default FIB, however redirect information and prefixes
  of connected subnets are automatically propagated to all FIBs by
  default (mimicking IPv4 behavior as closely as possible).

Sponsored by:	Cisco Systems, Inc.
2012-02-03 13:08:44 +00:00
John Baldwin
137f91e80f Convert all users of IF_ADDR_LOCK to use new locking macros that specify
either a read lock or write lock.

Reviewed by:	bz
MFC after:	2 weeks
2012-01-05 19:00:36 +00:00
Bjoern A. Zeeb
9d9b92f299 Mark a couple of file local functions static and stop exporting them.
MFC after:	1 week
2012-01-05 01:14:35 +00:00
John Baldwin
3b0b2840be Use queue(3) macros instead of home-rolled versions in several places in
the INET6 code.  This includes retiring the 'ndpr_next' and 'pfr_next'
macros.

Submitted by:	pluknet (earlier version)
Reviewed by:	pluknet
2011-12-29 18:25:18 +00:00