Commit Graph

413 Commits

Author SHA1 Message Date
Mikolaj Golub
4d3dfd450a Unregister inet/inet6 pfil hooks on vnet destroy.
Discussed with:	andre
Approved by:	re (rodrigc)
2013-09-13 18:45:10 +00:00
Mark Johnston
57f6086735 Implement the ip, tcp, and udp DTrace providers. The probe definitions use
dynamic translation so that their arguments match the definitions for
these providers in Solaris and illumos. Thus, existing scripts for these
providers should work unmodified on FreeBSD.

Tested by:	gnn, hiren
MFC after:	1 month
2013-08-25 21:54:41 +00:00
Andre Oppermann
1b4381afbb Restructure the mbuf pkthdr to make it fit for upcoming capabilities and
features.  The changes in particular are:

o Remove rarely used "header" pointer and replace it with a 64bit protocol/
  layer specific union PH_loc for local use.  Protocols can flexibly overlay
  their own 8 to 64 bit fields to store information while the packet is
  worked on.

o Mechanically convert IP reassembly, IGMP/MLD and ATM to use pkthdr.PH_loc
  instead of pkthdr.header.

o Extend csum_flags to 64bits to allow for additional future offload
  information to be carried (e.g. iSCSI, IPsec offload, and others).

o Move the RSS hash type enumerator from abusing m_flags to its own 8bit
  rsstype field.  Adjust accessor macros.

o Add cosqos field to store Class of Service / Quality of Service information
  with the packet.  It is not yet supported in any drivers but allows us to
  get on par with Cisco/Juniper in routing applications (plus MPLS QoS) with
  a modernized ALTQ.

o Add four 8 bit fields l[2-5]hlen to store the relative header offsets
  from the start of the packet.  This is important for various offload
  capabilities and to relieve the drivers from having to parse the packet
  and protocol headers to find out location of checksums and other
  information.  Header parsing in drivers is a lot of copy-paste and
  unhandled corner cases which we want to avoid.

o Add another flexible 64bit union to map various additional persistent
  packet information, like ether_vtag, tso_segsz and csum fields.
  Depending on the csum_flags settings some fields may have different usage
  making it very flexible and adaptable to future capabilities.

o Restructure the CSUM flags to better signify their outbound (down the
  stack) and inbound (up the stack) use.  The CSUM flags used to be a bit
  chaotic and rather poorly documented leading to incorrect use in many
  places.  Bring clarity into their use through better naming.
  Compatibility mappings are provided to preserve the API.  The drivers
  can be corrected one by one and MFC'd without issue.

o The size of pkthdr stays the same at 48/56bytes (32/64bit architectures).

Sponsored by:	The FreeBSD Foundation
2013-08-24 19:51:18 +00:00
Andre Oppermann
b09dc7e328 Move ip_reassemble()'s use of the global M_FRAG mbuf flag to a protocol layer
specific flag instead.  The flag is only relevant while the packet stays in
the IP reassembly queue.

Discussed with:	trociny, glebius
2013-08-19 10:34:10 +00:00
Andrey V. Elsukov
5da0521fce Use new macros to implement ipstat and tcpstat using PCPU counters.
Change interface of kread_counters() similar ot kread() in the netstat(1).
2013-07-09 09:43:03 +00:00
Gleb Smirnoff
42a253e6a1 Fix kmod_*stat_inc() after r249276. The incorrect code actually
increased the pointer, not the memory it points to.

In collaboration with:	kib
Reported & tested by:	Ian FREISLICH <ianf clue.co.za>
Sponsored by:		Nginx, Inc.
2013-06-21 06:36:26 +00:00
Andre Oppermann
f89d4c3acf Back out r249318, r249320 and r249327 due to a heisenbug most
likely related to a race condition in the ipi_hash_lock with
the exact cause currently unknown but under investigation.
2013-05-06 16:42:18 +00:00
Andre Oppermann
e8b3186b6a Change certain heavily used network related mutexes and rwlocks to
reside on their own cache line to prevent false sharing with other
nearby structures, especially for those in the .bss segment.

NB: Those mutexes and rwlocks with variables next to them that get
changed on every invocation do not benefit from their own cache line.
Actually it may be net negative because two cache misses would be
incurred in those cases.
2013-04-09 21:02:20 +00:00
Gleb Smirnoff
5923c29332 Merge from projects/counters: TCP/IP stats.
Convert 'struct ipstat' and 'struct tcpstat' to counter(9).

  This speeds up IP forwarding at extreme packet rates, and
makes accounting more precise.

Sponsored by:	Nginx, Inc.
2013-04-08 19:57:21 +00:00
Gleb Smirnoff
dc4ad05ecd Use m_get/m_gethdr instead of compat macros.
Sponsored by:	Nginx, Inc.
2013-03-15 12:55:30 +00:00
Sergey Kandaurov
46f2df9c13 ip_savecontrol() style fixes. No functional changes.
- fix indentation
- put the operator at the end of the line for long statements
- remove spaces between the type and the variable in a cast
- remove excessive parentheses

Tested by:	md5
2013-02-20 15:44:40 +00:00
Gleb Smirnoff
eb1b1807af Mechanically substitute flags from historic mbuf allocator with
malloc(9) flags within sys.

Exceptions:

- sys/contrib not touched
- sys/mbuf.h edited manually
2012-12-05 08:04:20 +00:00
Andrey V. Elsukov
ffdbf9da3b Remove the recently added sysctl variable net.pfil.forward.
Instead, add protocol specific mbuf flags M_IP_NEXTHOP and
M_IP6_NEXTHOP. Use them to indicate that the mbuf's chain
contains the PACKET_TAG_IPFORWARD tag. And do a tag lookup
only when this flag is set.

Suggested by:	andre
2012-11-02 01:20:55 +00:00
Andrey V. Elsukov
c1de64a495 Remove the IPFIREWALL_FORWARD kernel option and make possible to turn
on the related functionality in the runtime via the sysctl variable
net.pfil.forward. It is turned off by default.

Sponsored by:	Yandex LLC
Discussed with:	net@
MFC after:	2 weeks
2012-10-25 09:39:14 +00:00
Gleb Smirnoff
a7f707cd37 After r241923 the updated ip_len no longer needed. 2012-10-25 09:02:21 +00:00
Gleb Smirnoff
b6fcf6f9f5 Fix error in r241913 that had broken fragment reassembly. 2012-10-25 09:00:57 +00:00
Gleb Smirnoff
8ad458a471 Do not reduce ip_len by size of IP header in the ip_input()
before passing a packet to protocol input routines.
  For several protocols this mean that now protocol needs to
do subtraction itself, and for another half this means that
we do not need to add header length back to the packet.

  Make ip_stripoptions() to adjust ip_len, since now we enter
this function with a packet header whose ip_len does represent
length of entire packet, not payload only.
2012-10-23 08:33:13 +00:00
Gleb Smirnoff
8f134647ca Switch the entire IPv4 stack to keep the IP packet header
in network byte order. Any host byte order processing is
done in local variables and host byte order values are
never[1] written to a packet.

  After this change a packet processed by the stack isn't
modified at all[2] except for TTL.

  After this change a network stack hacker doesn't need to
scratch his head trying to figure out what is the byte order
at the given place in the stack.

[1] One exception still remains. The raw sockets convert host
byte order before pass a packet to an application. Probably
this would remain for ages for compatibility.

[2] The ip_input() still subtructs header len from ip->ip_len,
but this is planned to be fixed soon.

Reviewed by:	luigi, Maxim Dounin <mdounin mdounin.ru>
Tested by:	ray, Olivier Cochard-Labbe <olivier cochard.me>
2012-10-22 21:09:03 +00:00
Gleb Smirnoff
21d172a3f1 A step in resolving mess with byte ordering for AF_INET. After this change:
- All packets in NETISR_IP queue are in net byte order.
  - ip_input() is entered in net byte order and converts packet
    to host byte order right _after_ processing pfil(9) hooks.
  - ip_output() is entered in host byte order and converts packet
    to net byte order right _before_ processing pfil(9) hooks.
  - ip_fragment() accepts and emits packet in net byte order.
  - ip_forward(), ip_mloopback() use host byte order (untouched actually).
  - ip_fastforward() no longer modifies packet at all (except ip_ttl).
  - Swapping of byte order there and back removed from the following modules:
    pf(4), ipfw(4), enc(4), if_bridge(4).
  - Swapping of byte order added to ipfilter(4), based on __FreeBSD_version
  - __FreeBSD_version bumped.
  - pfil(9) manual page updated.

Reviewed by:	ray, luigi, eri, melifaro
Tested by:	glebius (LE), ray (BE)
2012-10-06 10:02:11 +00:00
Gleb Smirnoff
bf9840512a When ip_output()/ip6_output() is supplied a struct route *ro argument,
it skips FLOWTABLE lookup. However, the non-NULL ro has dual meaning
here: it may be supplied to provide route, and it may be supplied to
store and return to caller the route that ip_output()/ip6_output()
finds. In the latter case skipping FLOWTABLE lookup is pessimisation.

The difference between struct route filled by FLOWTABLE and filled
by rtalloc() family is that the former doesn't hold a reference on
its rtentry. Reference is hold by flow entry, and it is about to
be released in future. Thus, route filled by FLOWTABLE shouldn't
be passed to RTFREE() macro.

- Introduce new flag for struct route/route_in6, that marks route
  not holding a reference on rtentry.
- Introduce new macro RO_RTFREE() that cleans up a struct route
  depending on its kind.
- All callers to ip_output()/ip6_output() that do supply non-NULL
  but empty route should use RO_RTFREE() to free results of
  lookup.
- ip_output()/ip6_output() now do FLOWTABLE lookup always when
  ro->ro_rt == NULL.

Tested by:	tuexen (SCTP part)
2012-07-04 07:37:53 +00:00
Michael Tuexen
3cca425b29 Add a IP_RECVTOS socket option to receive for received UDP/IPv4
packets a cmsg of type IP_RECVTOS which contains the TOS byte.
Much like IP_RECVTTL does for TTL. This allows to implement a
protocol on top of UDP and implementing ECN.

MFC after: 3 days
2012-06-12 14:02:38 +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
Gleb Smirnoff
b365d954cc Remove last remnants of classful addressing:
- Remove ia_net, ia_netmask, ia_netbroadcast from struct in_ifaddr.
- Remove net.inet.ip.subnetsarelocal, I bet no one need it in 2011.
- fix bug when we were not forwarding to a host which matches classful
  net address. For example router having 192.168.x.y/16 network attached,
  would not forward traffic to 192.168.*.0, which are legal IPs in
  CIDR world.
- For compatibility, leave autoguessing of mask based on class.

Reviewed by:	andre, bz, rwatson
2011-10-15 16:28:06 +00:00
Bjoern A. Zeeb
ffe8cd7b10 Correct comments and debug logging in ipsec to better match reality.
MFC after:	3 days
2011-06-08 03:02:11 +00:00
Bjoern A. Zeeb
74e9dcf786 MfP4 CH=192004:
Move ip_defttl to raw_ip.c where it is actually used.  In an IPv6
only world we do not want to compile ip_input.c in for that and
it is a shared default with INET6.

Reviewed by:	gnn
Sponsored by:	The FreeBSD Foundation
Sponsored by:	iXsystems
MFC after:	4 days
2011-04-27 19:32:27 +00:00
Bjoern A. Zeeb
aae49dd304 MFp4 CH=191470:
Move the ipport_tick_callout and related functions from ip_input.c
to in_pcb.c.  The random source port allocation code has been merged
and is now local to in_pcb.c only.
Use a SYSINIT to get the callout started and no longer depend on
initialization from the inet code, which would not work in an IPv6
only setup.

Reviewed by:	gnn
Sponsored by:	The FreeBSD Foundation
Sponsored by:	iXsystems
MFC after:	4 days
2011-04-20 08:00:29 +00:00
Bjoern A. Zeeb
ec4f97277f MFp4 CH=191466:
Move fw_one_pass to where it belongs: it is a property of ipfw,
not of ip_input.

Reviewed by:	gnn
Sponsored by:	The FreeBSD Foundation
Sponsored by:	iXsystems
MFC after:	3 days
2011-04-20 07:55:33 +00:00
Rebecca Cran
6bccea7c2b Fix typos - remove duplicate "the".
PR:	bin/154928
Submitted by:	Eitan Adler <lists at eitanadler.com>
MFC after: 	3 days
2011-02-21 09:01:34 +00:00
Dimitry Andric
3e288e6238 After some off-list discussion, revert a number of changes to the
DPCPU_DEFINE and VNET_DEFINE macros, as these cause problems for various
people working on the affected files.  A better long-term solution is
still being considered.  This reversal may give some modules empty
set_pcpu or set_vnet sections, but these are harmless.

Changes reverted:

------------------------------------------------------------------------
r215318 | dim | 2010-11-14 21:40:55 +0100 (Sun, 14 Nov 2010) | 4 lines

Instead of unconditionally emitting .globl's for the __start_set_xxx and
__stop_set_xxx symbols, only emit them when the set_vnet or set_pcpu
sections are actually defined.

------------------------------------------------------------------------
r215317 | dim | 2010-11-14 21:38:11 +0100 (Sun, 14 Nov 2010) | 3 lines

Apply the STATIC_VNET_DEFINE and STATIC_DPCPU_DEFINE macros throughout
the tree.

------------------------------------------------------------------------
r215316 | dim | 2010-11-14 21:23:02 +0100 (Sun, 14 Nov 2010) | 2 lines

Add macros to define static instances of VNET_DEFINE and DPCPU_DEFINE.
2010-11-22 19:32:54 +00:00
Dimitry Andric
31c6a0037e Apply the STATIC_VNET_DEFINE and STATIC_DPCPU_DEFINE macros throughout
the tree.
2010-11-14 20:38:11 +00:00
Bjoern A. Zeeb
1b48d24533 MFp4 CH=183052 183053 183258:
In protosw we define pr_protocol as short, while on the wire
  it is an uint8_t.  That way we can have "internal" protocols
  like DIVERT, SEND or gaps for modules (PROTO_SPACER).
  Switch ipproto_{un,}register to accept a short protocol number(*)
  and do an upfront check for valid boundries. With this we
  also consistently report EPROTONOSUPPORT for out of bounds
  protocols, as we did for proto == 0.  This allows a caller
  to not error for this case, which is especially important
  if we want to automatically call these from domain handling.

  (*) the functions have been without any in-tree consumer
  since the initial introducation, so this is considered save.

  Implement ip6proto_{un,}register() similarly to their legacy IP
  counter parts to allow modules to hook up dynamically.

Reviewed by:	philip, will
MFC after:	1 week
2010-09-02 17:43:44 +00:00
Will Andrews
54bfbd5153 Allow carp(4) to be loaded as a kernel module. Follow precedent set by
bridge(4), lagg(4) etc. and make use of function pointers and
pf_proto_register() to hook carp into the network stack.

Currently, because of the uncertainty about whether the unload path is free
of race condition panics, unloads are disallowed by default.  Compiling with
CARPMOD_CAN_UNLOAD in CFLAGS removes this anti foot shooting measure.

This commit requires IP6PROTOSPACER, introduced in r211115.

Reviewed by:	bz, simon
Approved by:	ken (mentor)
MFC after:	2 weeks
2010-08-11 00:51:50 +00:00
Bjoern A. Zeeb
82cea7e6f3 MFP4: @176978-176982, 176984, 176990-176994, 177441
"Whitspace" churn after the VIMAGE/VNET whirls.

Remove the need for some "init" functions within the network
stack, like pim6_init(), icmp_init() or significantly shorten
others like ip6_init() and nd6_init(), using static initialization
again where possible and formerly missed.

Move (most) variables back to the place they used to be before the
container structs and VIMAGE_GLOABLS (before r185088) and try to
reduce the diff to stable/7 and earlier as good as possible,
to help out-of-tree consumers to update from 6.x or 7.x to 8 or 9.

This also removes some header file pollution for putatively
static global variables.

Revert VIMAGE specific changes in ipfilter::ip_auth.c, that are
no longer needed.

Reviewed by:	jhb
Discussed with:	rwatson
Sponsored by:	The FreeBSD Foundation
Sponsored by:	CK Software GmbH
MFC after:	6 days
2010-04-29 11:52:42 +00:00
Bjoern A. Zeeb
1c044382c3 Avoid memory access after free. Use the (shortend) copy for the
ipsec mtu lookup as well.

PR:		kern/145736
Submitted by:	Peter Molnar (peter molnar.cc)
MFC after:	3 days
2010-04-21 10:21:34 +00:00
Kip Macy
3059584e2a - boot-time size the ipv4 flowtable and the maximum number of flows
- increase flow cleaning frequency and decrease flow caching time
  when near the flow limit
- stop allocating new flows when within 3% of maxflows don't start
  allocating again until below 12.5%

MFC after:	7 days
2010-03-22 23:04:12 +00:00
Kip Macy
d4121a02c0 - restructure flowtable to support ipv6
- add a name argument to flowtable_alloc for printing with ddb commands
- extend ddb commands to print destination address or 4-tuples
- don't parse ports in ulp header if FL_HASH_ALL is not passed
- add kern_flowtable_insert to enable more generic use of flowtable
  (e.g. system calls for adding entries)
- don't hash loopback addresses
- cleanup whitespace
- keep statistics per-cpu for per-cpu flowtables to avoid cache line contention
- add sysctls to accumulate stats and report aggregate

MFC after:	7 days
2010-03-12 05:03:26 +00:00
Bjoern A. Zeeb
9802380e41 Split up ip_drain() into an outer lock and iterator part and
a "locked" version that will only handle a single network stack
instance. The latter is called directly from ip_destroy().

Hook up an ip_destroy() function to release resources from the
legacy IP network layer upon virtual network stack teardown.

Sponsored by:	ISPsystem
Reviewed by:	rwatson
MFC After:	5 days
2010-02-20 19:59:52 +00:00
Robert Watson
99b96cf934 Correct spelling typo in ip_input comment.
Pointed out by:	N.J. Mann <njm at njm.me.uk>,
		John Nielsen <john at jnielsen.net>, julian (!), lstewart
MFC after:	2 days
2009-10-24 09:18:26 +00:00
Robert Watson
0d3d0d74ea Improve grammar in ip_input comment while attempting to maintain what
might be its meaning.

MFC after:	3 days
2009-10-23 13:35:00 +00:00
Robert Watson
6426657e9f Rewrap ip_input() comment so that it prints more nicely.
MFC after:	3 days
2009-10-18 11:23:56 +00:00
Julian Elischer
0b4b0b0fee Virtualize the pfil hooks so that different jails may chose different
packet filters. ALso allows ipfw to be enabled on on ejail and disabled
on another. In 8.0 it's a global setting.

Sitting aroung in tree waiting to commit for: 2 months
MFC after:	2 months
2009-10-11 05:59:43 +00:00
Robert Watson
315e3e38fa Many network stack subsystems use a single global data structure to hold
all pertinent statatistics for the subsystem.  These structures are
sometimes "borrowed" by kernel modules that require a place to store
statistics for similar events.

Add KPI accessor functions for statistics structures referenced by kernel
modules so that they no longer encode certain specifics of how the data
structures are named and stored.  This change is intended to make it
easier to move to per-CPU network stats following 8.0-RELEASE.

The following modules are affected by this change:

      if_bridge
      if_cxgb
      if_gif
      ip_mroute
      ipdivert
      pf

In practice, most of these statistics consumers should, in fact, maintain
their own statistics data structures rather than borrowing structures
from the base network stack.  However, that change is too agressive for
this point in the release cycle.

Reviewed by:	bz
Approved by:	re (kib)
2009-08-02 19:43:32 +00:00
Robert Watson
530c006014 Merge the remainder of kern_vimage.c and vimage.h into vnet.c and
vnet.h, we now use jails (rather than vimages) as the abstraction
for virtualization management, and what remained was specific to
virtual network stacks.  Minor cleanups are done in the process,
and comments updated to reflect these changes.

Reviewed by:	bz
Approved by:	re (vimage blanket)
2009-08-01 19:26:27 +00:00
Robert Watson
a511354af4 Back out the moving in r195782 of V_ip_id's initialization from the top
back to the bottom of ip_init() as found in 7.x.  I missed the fact that
the bottom half of the init routine only runs in the !VNET case.

Submitted by:	zec
Approved by:	re (vimage blanket)
2009-07-20 19:40:09 +00:00
Robert Watson
0a4747d4d0 Garbage collect vnet module registrations that have neither constructors
nor destructors, as there's no actual work to do.

In most cases, the constructors weren't needed because of the existing
protocol initialization functions run by net_init_domain() as part of
VNET_MOD_NET, or they were eliminated when support for static
initialization of virtualized globals was added.

Garbage collect dependency references to modules without constructors or
destructors, notably VNET_MOD_INET and VNET_MOD_INET6.

Reviewed by:	bz
Approved by:	re (vimage blanket)
2009-07-20 13:55:33 +00:00
Robert Watson
5ee847d3ac Reimplement and/or implement vnet list locking by replacing a mostly
unused custom mutex/condvar-based sleep locks with two locks: an
rwlock (for non-sleeping use) and sxlock (for sleeping use).  Either
acquired for read is sufficient to stabilize the vnet list, but both
must be acquired for write to modify the list.

Replace previous no-op read locking macros, used in various places
in the stack, with actual locking to prevent race conditions.  Callers
must declare when they may perform unbounded sleeps or not when
selecting how to lock.

Refactor vnet sysinits so that the vnet list and locks are initialized
before kernel modules are linked, as the kernel linker will use them
for modules loaded by the boot loader.

Update various consumers of these KPIs based on whether they may sleep
or not.

Reviewed by:	bz
Approved by:	re (kib)
2009-07-19 14:20:53 +00:00
Robert Watson
1e77c1056a Remove unused VNET_SET() and related macros; only VNET_GET() is
ever actually used.  Rename VNET_GET() to VNET() to shorten
variable references.

Discussed with:	bz, julian
Reviewed by:	bz
Approved by:	re (kensmith, kib)
2009-07-16 21:13:04 +00:00
Robert Watson
eddfbb763d Build on Jeff Roberson's linker-set based dynamic per-CPU allocator
(DPCPU), as suggested by Peter Wemm, and implement a new per-virtual
network stack memory allocator.  Modify vnet to use the allocator
instead of monolithic global container structures (vinet, ...).  This
change solves many binary compatibility problems associated with
VIMAGE, and restores ELF symbols for virtualized global variables.

Each virtualized global variable exists as a "reference copy", and also
once per virtual network stack.  Virtualized global variables are
tagged at compile-time, placing the in a special linker set, which is
loaded into a contiguous region of kernel memory.  Virtualized global
variables in the base kernel are linked as normal, but those in modules
are copied and relocated to a reserved portion of the kernel's vnet
region with the help of a the kernel linker.

Virtualized global variables exist in per-vnet memory set up when the
network stack instance is created, and are initialized statically from
the reference copy.  Run-time access occurs via an accessor macro, which
converts from the current vnet and requested symbol to a per-vnet
address.  When "options VIMAGE" is not compiled into the kernel, normal
global ELF symbols will be used instead and indirection is avoided.

This change restores static initialization for network stack global
variables, restores support for non-global symbols and types, eliminates
the need for many subsystem constructors, eliminates large per-subsystem
structures that caused many binary compatibility issues both for
monitoring applications (netstat) and kernel modules, removes the
per-function INIT_VNET_*() macros throughout the stack, eliminates the
need for vnet_symmap ksym(2) munging, and eliminates duplicate
definitions of virtualized globals under VIMAGE_GLOBALS.

Bump __FreeBSD_version and update UPDATING.

Portions submitted by:  bz
Reviewed by:            bz, zec
Discussed with:         gnn, jamie, jeff, jhb, julian, sam
Suggested by:           peter
Approved by:            re (kensmith)
2009-07-14 22:48:30 +00:00
Robert Watson
64aeca7b42 Initialize in_ifaddr_lock using RW_SYSINIT() instead of in ip_init(),
so that it doesn't run multiple times if VIMAGE is being used.

Discussed with:	bz
MFC after:	6 weeks
2009-06-25 14:44:00 +00:00
Robert Watson
2d9cfabad4 Add a new global rwlock, in_ifaddr_lock, which will synchronize use of the
in_ifaddrhead and INADDR_HASH address lists.

Previously, these lists were used unsynchronized as they were effectively
never changed in steady state, but we've seen increasing reports of
writer-writer races on very busy VPN servers as core count has gone up
(and similar configurations where address lists change frequently and
concurrently).

For the time being, use rwlocks rather than rmlocks in order to take
advantage of their better lock debugging support.  As a result, we don't
enable ip_input()'s read-locking of INADDR_HASH until an rmlock conversion
is complete and a performance analysis has been done.  This means that one
class of reader-writer races still exists.

MFC after:      6 weeks
Reviewed by:    bz
2009-06-25 11:52:33 +00:00