Instructions for time stamping outgoing packets are take from the
socket layer and later copied into the new skb.
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The overlap with the old SO_TIMESTAMP[NS] options is handled so
that time stamping in software (net_enable_timestamp()) is
enabled when SO_TIMESTAMP[NS] and/or SO_TIMESTAMPING_RX_SOFTWARE
is set. It's disabled if all of these are off.
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The additional per-packet information (16 bytes for time stamps, 1
byte for flags) is stored for all packets in the skb_shared_info
struct. This implementation detail is hidden from users of that
information via skb_* accessor functions. A separate struct resp.
union is used for the additional information so that it can be
stored/copied easily outside of skb_shared_info.
Compared to previous implementations (reusing the tstamp field
depending on the context, optional additional structures) this
is the simplest solution. It does not extend sk_buff itself.
TX time stamping is implemented in software if the device driver
doesn't support hardware time stamping.
The new semantic for hardware/software time stamping around
ndo_start_xmit() is based on two assumptions about existing
network device drivers which don't support hardware time
stamping and know nothing about it:
- they leave the new skb_shared_tx unmodified
- the keep the connection to the originating socket in skb->sk
alive, i.e., don't call skb_orphan()
Given that skb_shared_tx is new, the first assumption is safe.
The second is only true for some drivers. As a result, software
TX time stamping currently works with the bnx2 driver, but not
with the unmodified igb driver (the two drivers this patch series
was tested with).
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
User space can request hardware and/or software time stamping.
Reporting of the result(s) via a new control message is enabled
separately for each field in the message because some of the
fields may require additional computation and thus cause overhead.
User space can tell the different kinds of time stamps apart
and choose what suits its needs.
When a TX timestamp operation is requested, the TX skb will be cloned
and the clone will be time stamped (in hardware or software) and added
to the socket error queue of the skb, if the skb has a socket
associated with it.
The actual TX timestamp will reach userspace as a RX timestamp on the
cloned packet. If timestamping is requested and no timestamping is
done in the device driver (potentially this may use hardware
timestamping), it will be done in software after the device's
start_hard_xmit routine.
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Mapping from a struct timecounter to a time returned by functions like
ktime_get_real() is implemented. This is sufficient to use this code
in a network device driver which wants to support hardware time
stamping and transformation of hardware time stamps to system time.
The interface could have been made more versatile by not depending on
a time counter, but this wasn't done to avoid writing glue code
elsewhere.
The method implemented here is the one used and analyzed under the name
"assisted PTP" in the LCI PTP paper:
http://www.linuxclustersinstitute.org/conferences/archive/2008/PDF/Ohly_92221.pdf
Acked-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
So far struct clocksource acted as the interface between time/timekeeping.c
and hardware. This patch generalizes the concept so that a similar
interface can also be used in other contexts. For that it introduces
new structures and related functions *without* touching the existing
struct clocksource.
The reasons for adding these new structures to clocksource.[ch] are
* the APIs are clearly related
* struct clocksource could be cleaned up to use the new structs
* avoids proliferation of files with similar names (timesource.h?
timecounter.h?)
As outlined in the discussion with John Stultz, this patch adds
* struct cyclecounter: stateless API to hardware which counts clock cycles
* struct timecounter: stateful utility code built on a cyclecounter which
provides a nanosecond counter
* only the function to read the nanosecond counter; deltas are used internally
and not exposed to users of timecounter
The code does no locking of the shared state. It must be called at least
as often as the cycle counter wraps around to detect these wrap arounds.
Both is the responsibility of the timecounter user.
Acked-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Base versions handle constant folding now. For headers exposed to
userspace, we must only expose the __ prefixed versions.
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Use cpu_to_le32 directly as it handles constant folding now, replace direct
uses of __constant_cpu_to_{endian} as well.
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Add a more flexible BSS lookup function so that mac80211 or
other drivers can actually use this for getting the BSS to
connect to.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This patch introduces cfg80211_unlink_bss, a function to
allow a driver to remove a BSS from the internal list and
make it not show up in scan results any more -- this is
to be used when the driver detects that the BSS is no
longer available.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
When cfg80211 users have their own allocated data in the per-BSS
private data, they will need to free this when the BSS struct is
destroyed. Add a free_priv method and fix one place where the BSS
was kfree'd rather than released properly.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This patch adds basic scan capability to cfg80211/nl80211 and
changes mac80211 to use it. The BSS list that cfg80211 maintains
is made driver-accessible with a private area in each BSS struct,
but mac80211 doesn't yet use it. That's another large project.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
The atomic requirement for the TSF callbacks
is outdated. get_tsf() is only called by
ieee80211_rx_bss_info() which is indirectly
called by the work queue ieee80211_sta_work().
In the same context are called several other
non-atomic functions, too.
And the atomic requirement causes problems
for drivers of USB wifi cards.
Signed-off-by: Alina Friedrichsen <x-alina@gmx.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6:
ASoC: Only register AC97 bus if it's not done already
ALSA: hda - Add snd_hda_multi_out_dig_cleanup()
ALSA: hda - Add missing terminator in slave dig-out array
ALSA: hda - Change HP dv7 (103c:30f4) quirk from hp-m4 to hp-dv5 model
ALSA: hda - Register (new) devices at reconfig
ALSA: mtpav - Fix initial value for input hwport
ALSA: hda - add id for Intel IbexPeak integrated HDMI codec
ALSA: hda - compute checksum in HDMI audio infoframe
ALSA: hda - enable HDMI audio pin out at module loading time
ALSA: hda - allow multi-channel HDMI audio playback when ELD is not present
ASoC: Update SDP3430 machine driver for snd_soc_card
ALSA: hda - Add quirk for Asus z37e (1043:8284)
sound: Remove OSSlib stuff from linux/soundcard.h
ASoC: WM8990: Fix kcontrol's private value use in put callback
ASoC: TLV320AIC3X: Fix kcontrol's private value use in put callback
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6: (32 commits)
wimax: fix oops in wimax_dev_get_by_genl_info() when looking up non-wimax iface
net: 4 bytes kernel memory disclosure in SO_BSDCOMPAT gsopt try #2
netxen: fix compile waring "label ‘set_32_bit_mask’ defined but not used" on IA64 platform
bnx2: Update version to 1.9.2 and copyright.
bnx2: Fix jumbo frames error handling.
bnx2: Update 5709 firmware.
bnx2: Update 5706/5708 firmware.
3c505: do not set pcb->data.raw beyond its size
Documentation/connector/cn_test.c: don't use gfp_any()
net: don't use in_atomic() in gfp_any()
IRDA: cnt is off by 1
netxen: remove pcie workaround
sun3: print when lance_open() fails
qlge: bugfix: Add missing rx buf clean index on early exit.
qlge: bugfix: Fix RX scaling values.
qlge: bugfix: Fix TSO breakage.
qlge: bugfix: Add missing dev_kfree_skb_any() call.
qlge: bugfix: Add missing put_page() call.
qlge: bugfix: Fix fatal error recovery hang.
qlge: bugfix: Use netif_receive_skb() and vlan_hwaccel_receive_skb().
...
The problem is that in_atomic() will return false inside spinlocks if
CONFIG_PREEMPT=n. This will lead to deadlockable GFP_KERNEL allocations
from spinlocked regions.
Secondly, if CONFIG_PREEMPT=y, this bug solves itself because networking
will instead use GFP_ATOMIC from this callsite. Hence we won't get the
might_sleep() debugging warnings which would have informed us of the buggy
callsites.
Solve both these problems by switching to in_interrupt(). Now, if someone
runs a gfp_any() allocation from inside spinlock we will get the warning
if CONFIG_PREEMPT=y.
I reviewed all callsites and most of them were too complex for my little
brain and none of them documented their interface requirements. I have no
idea what this patch will do.
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
With the new system call defines we get this on uml:
arch/um/sys-i386/built-in.o: In function `sys_call_table':
(.rodata+0x308): undefined reference to `sys_sigprocmask'
Reason for this is that uml passes the preprocessor option
-Dsigprocmask=kernel_sigprocmask to gcc when compiling the kernel.
This causes SYSCALL_DEFINE3(sigprocmask, ...) to be expanded to
SYSCALL_DEFINEx(3, kernel_sigprocmask, ...) and finally to a system
call named sys_kernel_sigprocmask. However sys_sigprocmask is missing
because of this.
To avoid macro expansion for the system call name just concatenate the
name at first define instead of carrying it through severel levels.
This was pointed out by Al Viro.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: WANG Cong <wangcong@zeuux.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I enabled all cgroup subsystems when compiling kernel, and then:
# mount -t cgroup -o net_cls xxx /mnt
# mkdir /mnt/0
This showed up immediately:
BUG: MAX_LOCKDEP_SUBCLASSES too low!
turning off the locking correctness validator.
It's caused by the cgroup hierarchy lock:
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss->root == root)
mutex_lock_nested(&ss->hierarchy_mutex, i);
}
Now we have 9 cgroup subsystems, and the above 'i' for net_cls is 8, but
MAX_LOCKDEP_SUBCLASSES is 8.
This patch uses different lockdep keys for different subsystems.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
timers: fix TIMER_ABSTIME for process wide cpu timers
timers: split process wide cpu clocks/timers, fix
x86: clean up hpet timer reinit
timers: split process wide cpu clocks/timers, remove spurious warning
timers: split process wide cpu clocks/timers
signal: re-add dead task accumulation stats.
x86: fix hpet timer reinit for x86_64
sched: fix nohz load balancer on cpu offline
The POSIX timer interface allows for absolute time expiry values through the
TIMER_ABSTIME flag, therefore we have to synchronize the timer to the clock
every time we start it.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
To decrease the chance of a missed enable, always enable the timer when we
sample it, we'll always disable it when we find that there are no active timers
in the jiffy tick.
This fixes a flood of warnings reported by Mike Galbraith.
Reported-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Using u32 in this header breaks the build of iptables.
Signed-off-by: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Fix regression due to 5a6fe12595,
"Do not account for the address space used by hugetlbfs using VM_ACCOUNT"
which added an argument to the function hugetlb_file_setup() but not to
the macro hugetlb_file_setup().
Reported-by: Chris Clayton <chris2553@googlemail.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6: (23 commits)
bridge: Fix LRO crash with tun
IPv6: fix to set device name when new IPv6 over IPv6 tunnel device is created.
gianfar: Fix boot hangs while bringing up gianfar ethernet
netfilter: xt_sctp: sctp chunk mapping doesn't work
netfilter: ctnetlink: fix echo if not subscribed to any multicast group
netfilter: ctnetlink: allow changing NAT sequence adjustment in creation
netfilter: nf_conntrack_ipv6: don't track ICMPv6 negotiation message
netfilter: fix tuple inversion for Node information request
netxen: fix msi-x interrupt handling
de2104x: force correct order when writing to rx ring
tun: Fix unicast filter overflow
drivers/isdn: introduce missing kfree
drivers/atm: introduce missing kfree
sunhme: Don't match PCI devices in SBUS probe.
9p: fix endian issues [attempt 3]
net_dma: call dmaengine_get only if NET_DMA enabled
3c509: Fix resume from hibernation for PnP mode.
sungem: Soft lockup in sungem on Netra AC200 when switching interface up
RxRPC: Fix a potential NULL dereference
r8169: Don't update statistics counters when interface is down
...
When overcommit is disabled, the core VM accounts for pages used by anonymous
shared, private mappings and special mappings. It keeps track of VMAs that
should be accounted for with VM_ACCOUNT and VMAs that never had a reserve
with VM_NORESERVE.
Overcommit for hugetlbfs is much riskier than overcommit for base pages
due to contiguity requirements. It avoids overcommiting on both shared and
private mappings using reservation counters that are checked and updated
during mmap(). This ensures (within limits) that hugepages exist in the
future when faults occurs or it is too easy to applications to be SIGKILLed.
As hugetlbfs makes its own reservations of a different unit to the base page
size, VM_ACCOUNT should never be set. Even if the units were correct, we would
double account for the usage in the core VM and hugetlbfs. VM_NORESERVE may
be set because an application can request no reserves be made for hugetlbfs
at the risk of getting killed later.
With commit fc8744adc8, VM_NORESERVE and
VM_ACCOUNT are getting unconditionally set for hugetlbfs-backed mappings. This
breaks the accounting for both the core VM and hugetlbfs, can trigger an
OOM storm when hugepage pools are too small lockups and corrupted counters
otherwise are used. This patch brings hugetlbfs more in line with how the
core VM treats VM_NORESERVE but prevents VM_ACCOUNT being set.
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This kills of HAVE_ALLOC_SKB and HAVE_ALIGNABLE_SKB.
Nothing in-tree uses them and nothing in-tree has used them
since 2.0.x times.
Signed-off-by: David S. Miller <davem@davemloft.net>
Removed OSSlib stuff from linux/soundcard.h to fix the warnings for
'make headers_check'.
This patch breaks building against OSSlib with the kernel headers
instead of its own headers. It should still work with any
version of the library from the 2003 onwards which provide
their own headers for the latest interface.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Jaswinder Singh Rajput <jaswinder@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This adds support for the SSB PMU.
A PMU is found on Low-Power devices.
Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
In certain cases it is required to perform board specific actions
before activating libertas G-SPI interface. These actions may include
power up of the chip, GPIOs setup, proper pin-strapping and SPI
controller config.
This patch adds ability to call board specific setup/teardown methods
Signed-off-by: Mike Rapoport <mike@compulab.co.il>
Acked-by: Andrey Yurovsky <andrey@cozybit.com>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This lets userspace request to get the currently set
regulatory domain.
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Giving the signal in dB isn't much more useful to userspace
than giving the signal in unspecified units. This removes
some radiotap information for zd1211 (the only driver using
this flag), but it helps a lot for getting cfg80211-based
scanning which won't support dB, and zd1211 being dB is a
little fishy anyway.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: Bruno Randolf <bruno@thinktube.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
* 'drm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6:
drm/i915: select framebuffer support automatically
drm/i915: add get_vblank_counter function for GM45
drm/i915: capture last_vblank count at IRQ uninstall time too
drm/i915: Unlock mutex on i915_gem_fault() error path
drm/i915: Quiet the message on get/setparam ioctl with an unknown value.
drm/i915: skip LVDS initialization on Apple Mac Mini
drm/i915: sync SDVO code with stable userland modesetting driver
drm/i915: Unref the object after failing to set tiling mode.
drm/i915: add fence register management to execbuf
drm/i915: Return error from i915_gem_object_get_fence_reg() when failing.
drm/i915: Set up an MTRR covering the GTT at driver load.
drm/i915: Skip SDVO/HDMI init when the chipset tells us it's not present.
drm/i915: Suppress GEM teardown on X Server exit in KMS mode.
drm/radeon: fix ioremap conflict with AGP mappings
i915: fix unneeded locking in i915 LVDS get modes code.
Architectures other than mips and x86 are not using ticket spinlocks.
Therefore, the contention on the lock is meaningless, since there is
nobody known to be waiting on it (arguably /fairly/ unfair locks).
Dummy it out to return 0 on other architectures.
Signed-off-by: Kyle McMartin <kyle@redhat.com>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch optimises the Ethernet header comparison to use 2-byte
and 4-byte xors instead of memcmp. In order to facilitate this,
the actual comparison is now carried out by the callers of the
shared dev_gro_receive function.
This has a significant impact when receiving 1500B packets through
10GbE.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch prepares for the move of the same_flow checks out of
dev_gro_receive. As such we need to remember the number of held
packets since doing a loop just to count them every time is silly.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Several devices need to insert some "pre headers" in front of the
main packet data when they transmit a packet.
Currently we allocate only 16 bytes of pad room and this ends up not
being enough for some types of hardware (NIU, usb-net, s390 qeth,
etc.)
So increase this to 32.
Note that drivers still need to check in their transmit routine
whether enough headroom exists, and if not use skb_realloc_headroom().
Tunneling, IPSEC, and other encapsulation methods can cause the
padding area to be used up.
Signed-off-by: David S. Miller <davem@davemloft.net>
Rename the async_*_special() functions to async_*_domain(), which
describes the purpose of these functions much better.
[Broke up long lines to silence checkpatch]
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Adds code to set up fence registers at execbuf time on pre-965 chips as
necessary. Also fixes up a few bugs in the pre-965 tile register support
(get_order != ffs). The number of fences available to the kernel defaults
to the hw limit minus 3 (for legacy X front/back/depth), but a new parameter
allows userspace to override that as needed.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@linux.ie>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6:
PCI PM: make the PM core more careful with drivers using the new PM framework
PCI PM: Read power state from device after trying to change it on resume
PCI PM: Do not disable and enable bridges during suspend-resume
PCI: PCIe portdrv: Simplify suspend and resume
PCI PM: Fix saving of device state in pci_legacy_suspend
PCI PM: Check if the state has been saved before trying to restore it
PCI PM: Fix handling of devices without drivers
PCI: return error on failure to read PCI ROMs
PCI: properly clean up ASPM link state on device remove
Impact: fix spurious BUG_ON() triggered under load
module_refcount() isn't reliable outside stop_machine(), as demonstrated
by Karsten Keil <kkeil@suse.de>, networking can trigger it under load
(an inc on one cpu and dec on another while module_refcount() is tallying
can give false results, for example).
Almost noone should be using __module_get, but that's another issue.
Cc: Karsten Keil <kkeil@suse.de>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Based upon a patch from Atsushi Nemoto <anemo@mba.ocn.ne.jp>
--------------------
The commit 649274d993 ("net_dma:
acquire/release dma channels on ifup/ifdown") added unconditional call
of dmaengine_get() to net_dma. The API should be called only if
NET_DMA was enabled.
--------------------
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Bit 11 in intel PDC definitions is meant for OS capability to handle
hardware coordination of P-states. In Linux we have always supported
hwardware coordination of P-states. Just let the BIOSes know that we
support it, by setting this bit.
Some BIOSes use this bit to choose between hardware or software coordination
and without this change below, BIOSes switch to software coordination, which
is not very optimal in terms of power consumption and extra wakeups from idle.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Mike Galbraith reported that the new warning in thread_group_cputimer()
triggers en masse with Amarok running.
Oleg Nesterov observed:
Can't fastpath_timer_check()->thread_group_cputimer() have the
false warning too? Suppose we had the timer, then posix_cpu_timer_del()
removes this timer, but task_cputime_zero(&sig->cputime_expires) still
not true.
Remove the spurious debug warning.
Reported-by: Mike Galbraith <efault@gmx.de>
Explained-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Unlike a normal socket path, the tuntap device send path does
not have any accounting. This means that the user-space sender
may be able to pin down arbitrary amounts of kernel memory by
continuing to send data to an end-point that is congested.
Even when this isn't an issue because of limited queueing at
most end points, this can also be a problem because its only
response to congestion is packet loss. That is, when those
local queues at the end-point fills up, the tuntap device will
start wasting system time because it will continue to send
data there which simply gets dropped straight away.
Of course one could argue that everybody should do congestion
control end-to-end, unfortunately there are people in this world
still hooked on UDP, and they don't appear to be going away
anywhere fast. In fact, we've always helped them by performing
accounting in our UDP code, the sole purpose of which is to
provide congestion feedback other than through packet loss.
This patch attempts to apply the same bandaid to the tuntap device.
It creates a pseudo-socket object which is used to account our
packets just as a normal socket does for UDP. Of course things
are a little complex because we're actually reinjecting traffic
back into the stack rather than out of the stack.
The stack complexities however should have been resolved by preceding
patches. So this one can simply start using skb_set_owner_w.
For now the accounting is essentially disabled by default for
backwards compatibility. In particular, we set the cap to INT_MAX.
This is so that existing applications don't get confused by the
sudden arrival EAGAIN errors.
In future we may wish (or be forced to) do this by default.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
