Merge tag 'hwspinlock-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ohad/hwspinlock

Pull hwspinlock updates from Ohad Ben-Cohen:
 "Two small hwspinlock changes for better OMAP support, coming from
  Suman Anna"

* tag 'hwspinlock-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ohad/hwspinlock:
  hwspinlock: enable OMAP build for AM33xx, AM43xx & DRA7xx
  hwspinlock/omap: enable module before reading SYSSTATUS register
Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc

Pull more powerpc updates from Ben Herrenschmidt:
 "Here are some more powerpc bits for 3.17, essentially fixes.

  The biggest series, also aimed at -stable, is from Aneesh and is the
  result of weeks and weeks of debugging to find out why the heck or THP
  implementation was occasionally triggering multi-hit errors in our
  level 1 TLB.  It ended up being a combination of issues including
  subtleties as to how we should invalidate those special 'MPSS' pages
  we use to allow the use of 16M pages inside 4K/64K "base page size"
  segments (you really have to love our MMU !)

  Another interesting one in the "OMG" category is the series from
  Michael adding memory barriers to spin_is_locked().  That's also the
  result of many days of debugging to figure out why the semaphore code
  would occasionally crash in ways that made no sense.  It ended up
  being some creative lock stacking that was defeated by the fact that
  our locks allow a load inside the locked section to be re-ordered with
  the load of the lock value itself (I'm still of two mind about whether
  to kill that once and for all by putting a heavier barrier back into
  our lock implementation...).  The fixes come with a long explanation
  in the cset comments, feel free to read it if you feel like having a
  headache today"

* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc: (25 commits)
  powerpc/thp: Add tracepoints to track hugepage invalidate
  powerpc/mm: Use read barrier when creating real_pte
  powerpc/thp: Use ACCESS_ONCE when loading pmdp
  powerpc/thp: Invalidate with vpn in loop
  powerpc/thp: Handle combo pages in invalidate
  powerpc/thp: Invalidate old 64K based hash page mapping before insert of 4k pte
  powerpc/thp: Don't recompute vsid and ssize in loop on invalidate
  powerpc/thp: Add write barrier after updating the valid bit
  powerpc: reorder per-cpu NUMA information's initialization
  powerpc/perf/hv-24x7: Use kmem_cache_free
  powerpc/pseries/hvcserver: Fix endian issue in hvcs_get_partner_info
  powerpc: Hard disable interrupts in xmon
  powerpc: remove duplicate definition of TEXASR_FS
  powerpc/pseries: Avoid deadlock on removing ddw
  powerpc/pseries: Failure on removing device node
  powerpc/boot: Use correct zlib types for comparison
  powerpc/powernv: Interface to register/unregister opal dump region
  printk: Add function to return log buffer address and size
  powerpc: Add POWER8 features to CPU_FTRS_POSSIBLE/ALWAYS
  powerpc/ppc476: Disable BTAC
  ...
iwlwifi: mvm: disable scheduled scan to prevent firmware crash

There are firmwares which don't support scheduled scan.
Disable it for now.
Linus's system encoutered this issue.
Thanks to David Spinadel for his help.

Tested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
mm, hugetlb_cgroup: align hugetlb cgroup limit to hugepage size

Memcg aligns memory.limit_in_bytes to PAGE_SIZE as part of the resource
counter since it makes no sense to allow a partial page to be charged.

As a result of the hugetlb cgroup using the resource counter, it is also
aligned to PAGE_SIZE but makes no sense unless aligned to the size of
the hugepage being limited.

Align hugetlb cgroup limit to hugepage size.

Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
drivers/mfd/rtsx_usb.c: export device table

The rtsx_usb driver contains the table for the devices it supports but
doesn't export it.  As a result, no alias is generated and it doesn't
get loaded automatically.

Via https://bugzilla.novell.com/show_bug.cgi?id=890096

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reported-by: Marcel Witte <wittemar@googlemail.com>
Cc: Roger Tseng <rogerable@realtek.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm: fix CROSS_MEMORY_ATTACH help text grammar

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge branch 'akpm' (fixes from Andrew Morton)

Merge leftovers from Andrew Morton:
 "A few leftovers.

  I have a bunch of OCFS2 patches which are still out for review and
  which I might sneak along after -rc1.  Partly my fault - I should send
  my review pokes out earlier"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  mm: fix CROSS_MEMORY_ATTACH help text grammar
  drivers/mfd/rtsx_usb.c: export device table
  mm, hugetlb_cgroup: align hugetlb cgroup limit to hugepage size
timekeeping: Another fix to the VSYSCALL_OLD update_vsyscall

Benjamin Herrenschmidt pointed out that I further missed modifying
update_vsyscall after the wall_to_mono value was changed to a
timespec64.  This causes issues on powerpc32, which expects a 32bit
timespec.

This patch fixes the problem by properly converting from a timespec64 to
a timespec before passing the value on to the arch-specific vsyscall
logic.

[ Thomas is currently on vacation, but reviewed it and wanted me to send
  this fix on to you directly. ]

Cc: LKML <linux-kernel@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge tag 'rdma-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland/infiniband

Pull infiniband/rdma updates from Roland Dreier:
 "Main set of InfiniBand/RDMA updates for 3.17 merge window:

   - MR reregistration support
   - MAD support for RMPP in userspace
   - iSER and SRP initiator updates
   - ocrdma hardware driver updates
   - other fixes..."

* tag 'rdma-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland/infiniband: (52 commits)
  IB/srp: Fix return value check in srp_init_module()
  RDMA/ocrdma: report asic-id in query device
  RDMA/ocrdma: Update sli data structure for endianness
  RDMA/ocrdma: Obtain SL from device structure
  RDMA/uapi: Include socket.h in rdma_user_cm.h
  IB/srpt: Handle GID change events
  IB/mlx5: Use ARRAY_SIZE instead of sizeof/sizeof[0]
  IB/mlx4: Use ARRAY_SIZE instead of sizeof/sizeof[0]
  RDMA/amso1100: Check for integer overflow in c2_alloc_cq_buf()
  IPoIB: Remove unnecessary test for NULL before debugfs_remove()
  IB/mad: Add user space RMPP support
  IB/mad: add new ioctl to ABI to support new registration options
  IB/mad: Add dev_notice messages for various umad/mad registration failures
  IB/mad: Update module to [pr|dev]_* style print messages
  IB/ipoib: Avoid multicast join attempts with invalid P_key
  IB/umad: Update module to [pr|dev]_* style print messages
  IB/ipoib: Avoid flushing the workqueue from worker context
  IB/ipoib: Use P_Key change event instead of P_Key polling mechanism
  IB/ipath: Add P_Key change event support
  mlx4_core: Add support for secure-host and SMP firewall
  ...
Merge branch 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild

Pull kbuild updates from Michal Marek:
 - make clean also considers $(extra-m) and $(extra-) to be consistent
 - cleanup and fixes in scripts/Makefile.host
 - allow to override the name of the Python 2 executable with make
   PYTHON=... (only needed for ia64 in practice)
 - option to split debugingo into *.dwo files to save disk space if the
   compiler supports it (CONFIG_DEBUG_INFO_SPLIT)
 - option to use dwarf4 debuginfo if the compiler supports it
   (CONFIG_DEBUG_INFO_DWARF4)
 - fix for disabling certain warnings with clang
 - fix for unneeded rebuild with dash when a command contains
   backslashes

* 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  kbuild: Fix handling of backslashes in *.cmd files
  kbuild, LLVMLinux: Supress warnings unless W=1-3
  Kbuild: Add a option to enable dwarf4 v2
  kbuild: Support split debug info v4
  kbuild: allow to override Python command name
  kbuild: clean-up and bug fix of scripts/Makefile.host
  kbuild: clean up scripts/Makefile.host
  kbuild: drop shared library support from Makefile.host
  kbuild: fix a bug of C++ host program handling
  kbuild: fix a typo in scripts/Makefile.host
  scripts/Makefile.clean: clean also $(extra-m) and $(extra-)
Merge branch 'misc' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild

Pull misc kbuild updates from Michal Marek:
 "This is the non-critical part of kbuild for 3.17-rc1:

   - make help hint to use make -s with make kernelrelease et al.
   - moved a kbuild document to Documentation/kbuild where it belongs
   - four new Coccinelle scripts, one dropped and one fixed
   - new make kselftest target to run various tests on the kernel"

* 'misc' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  kbuild: kselftest - new make target to build and run kernel selftests
  Coccinelle: Script to replace if and BUG with BUG_ON
  Coccinelle: Script to detect incorrect argument to sizeof
  Coccinelle: Script to use ARRAY_SIZE instead of division of two sizeofs
  Coccinelle: Script to detect cast after memory allocation
  coccinelle/null: solve parse error
  Documentation: headers_install.txt is part of kbuild
  kbuild: make -s should be used with kernelrelease/kernelversion/image_name
Revert "macvlan: simplify the structure port"

This reverts commit a188a54d11629bef2169052297e61f3767ca8ce5.

It causes crashes

====================
[   80.643286] BUG: unable to handle kernel NULL pointer dereference at 0000000000000878
[   80.670103] IP: [<ffffffff810832e4>] try_to_grab_pending+0x64/0x1f0
[   80.691289] PGD 22c102067 PUD 235bf0067 PMD 0
[   80.706611] Oops: 0002 [#1] SMP
[   80.717836] Modules linked in: macvlan nfsd lockd nfs_acl exportfs auth_rpcgss sunrpc oid_registry ioatdma ixgbe(-) mdio igb dca
[   80.757935] CPU: 37 PID: 6724 Comm: rmmod Not tainted 3.16.0-net-next-08-12-2014-FCoE+ #1
[   80.785688] Hardware name: Intel Corporation S2600CO/S2600CO, BIOS SE5C600.86B.02.03.0003.041920141333 04/19/2014
[   80.820310] task: ffff880235a9eae0 ti: ffff88022e844000 task.ti: ffff88022e844000
[   80.845770] RIP: 0010:[<ffffffff810832e4>]  [<ffffffff810832e4>] try_to_grab_pending+0x64/0x1f0
[   80.875326] RSP: 0018:ffff88022e847b28  EFLAGS: 00010046
[   80.893251] RAX: 0000000000037a6a RBX: 0000000000000878 RCX: 0000000000000000
[   80.917187] RDX: ffff880235a9eae0 RSI: 0000000000000001 RDI: ffffffff810832db
[   80.941125] RBP: ffff88022e847b58 R08: 0000000000000000 R09: 0000000000000000
[   80.965056] R10: 0000000000000001 R11: 0000000000000001 R12: ffff88022e847b70
[   80.988994] R13: 0000000000000000 R14: ffff88022e847be8 R15: ffffffff81ebe440
[   81.012929] FS:  00007fab90b07700(0000) GS:ffff88043f7a0000(0000) knlGS:0000000000000000
[   81.040400] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   81.059757] CR2: 0000000000000878 CR3: 0000000235a42000 CR4: 00000000001407e0
[   81.083689] Stack:
[   81.090739]  ffff880235a9eae0 0000000000000878 ffff88022e847b70 0000000000000000
[   81.116253]  ffff88022e847be8 ffffffff81ebe440 ffff88022e847b98 ffffffff810847f1
[   81.141766]  ffff88022e847b78 0000000000000286 ffff880234200000 0000000000000000
[   81.167282] Call Trace:
[   81.175768]  [<ffffffff810847f1>] __cancel_work_timer+0x31/0x170
[   81.195985]  [<ffffffff8108494b>] cancel_work_sync+0xb/0x10
[   81.214769]  [<ffffffffa015ae68>] macvlan_port_destroy+0x28/0x60 [macvlan]
[   81.237844]  [<ffffffffa015b930>] macvlan_uninit+0x40/0x50 [macvlan]
[   81.259209]  [<ffffffff816bf6e2>] rollback_registered_many+0x1a2/0x2c0
[   81.281140]  [<ffffffff816bf81a>] unregister_netdevice_many+0x1a/0xb0
[   81.302786]  [<ffffffffa015a4ff>] macvlan_device_event+0x1ef/0x240 [macvlan]
[   81.326439]  [<ffffffff8108a13d>] notifier_call_chain+0x4d/0x70
[   81.346366]  [<ffffffff8108a201>] raw_notifier_call_chain+0x11/0x20
[   81.367439]  [<ffffffff816bf25b>] call_netdevice_notifiers_info+0x3b/0x70
[   81.390228]  [<ffffffff816bf2a1>] call_netdevice_notifiers+0x11/0x20
[   81.411587]  [<ffffffff816bf6bd>] rollback_registered_many+0x17d/0x2c0
[   81.433518]  [<ffffffff816bf925>] unregister_netdevice_queue+0x75/0x110
[   81.455735]  [<ffffffff816bfb2b>] unregister_netdev+0x1b/0x30
[   81.475094]  [<ffffffffa0039b50>] ixgbe_remove+0x170/0x1d0 [ixgbe]
[   81.495886]  [<ffffffff813512a2>] pci_device_remove+0x32/0x60
[   81.515246]  [<ffffffff814c75c4>] __device_release_driver+0x64/0xd0
[   81.536321]  [<ffffffff814c76f8>] driver_detach+0xc8/0xd0
[   81.554530]  [<ffffffff814c656e>] bus_remove_driver+0x4e/0xa0
[   81.573888]  [<ffffffff814c828b>] driver_unregister+0x2b/0x60
[   81.593246]  [<ffffffff8135143e>] pci_unregister_driver+0x1e/0xa0
[   81.613749]  [<ffffffffa005db18>] ixgbe_exit_module+0x1c/0x2e [ixgbe]
[   81.635401]  [<ffffffff810e738b>] SyS_delete_module+0x15b/0x1e0
[   81.655334]  [<ffffffff8187a395>] ? sysret_check+0x22/0x5d
[   81.673833]  [<ffffffff810abd2d>] ? trace_hardirqs_on_caller+0x11d/0x1e0
[   81.696339]  [<ffffffff8132bfde>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[   81.717985]  [<ffffffff8187a369>] system_call_fastpath+0x16/0x1b
[   81.738199] Code: 00 48 83 3d 6e bb da 00 00 48 89 c2 0f 84 67 01 00 00 fa 66 0f 1f 44 00 00 49 89 14 24 e8 b5 4b 02 00 45 84 ed 0f 85 ac 00 00 00 <f0> 0f ba 2b 00 72 1d 31 c0 48 8b 5d d8 4c 8b 65 e0 4c 8b 6d e8
[   81.807026] RIP  [<ffffffff810832e4>] try_to_grab_pending+0x64/0x1f0
[   81.828468]  RSP <ffff88022e847b28>
[   81.840384] CR2: 0000000000000878
[   81.851731] ---[ end trace 9f6c7232e3464e11 ]---
====================

This bug could be triggered by these steps:

modprobe ixgbe ; modprobe macvlan
ip link add link p96p1 address 00:1B:21:6E:06:00 macvlan0 type macvlan
ip link add link p96p1 address 00:1B:21:6E:06:01 macvlan1 type macvlan
ip link add link p96p1 address 00:1B:21:6E:06:02 macvlan2 type macvlan
ip link add link p96p1 address 00:1B:21:6E:06:03 macvlan3 type macvlan
rmmod ixgbe

Reported-by: "Keller, Jacob E" <jacob.e.keller@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: xilinx: Remove .owner field for driver

There is no need to init .owner field.

Based on the patch from Peter Griffin <peter.griffin@linaro.org>
"mmc: remove .owner field for drivers using module_platform_driver"

This patch removes the superflous .owner field for drivers which
use the module_platform_driver API, as this is overriden in
platform_driver_register anyway."

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
tcp: don't use timestamp from repaired skb-s to calculate RTT (v2)

We don't know right timestamp for repaired skb-s. Wrong RTT estimations
isn't good, because some congestion modules heavily depends on it.

This patch adds the TCPCB_REPAIRED flag, which is included in
TCPCB_RETRANS.

Thanks to Eric for the advice how to fix this issue.

This patch fixes the warning:
[  879.562947] WARNING: CPU: 0 PID: 2825 at net/ipv4/tcp_input.c:3078 tcp_ack+0x11f5/0x1380()
[  879.567253] CPU: 0 PID: 2825 Comm: socket-tcpbuf-l Not tainted 3.16.0-next-20140811 #1
[  879.567829] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  879.568177]  0000000000000000 00000000c532680c ffff880039643d00 ffffffff817aa2d2
[  879.568776]  0000000000000000 ffff880039643d38 ffffffff8109afbd ffff880039d6ba80
[  879.569386]  ffff88003a449800 000000002983d6bd 0000000000000000 000000002983d6bc
[  879.569982] Call Trace:
[  879.570264]  [<ffffffff817aa2d2>] dump_stack+0x4d/0x66
[  879.570599]  [<ffffffff8109afbd>] warn_slowpath_common+0x7d/0xa0
[  879.570935]  [<ffffffff8109b0ea>] warn_slowpath_null+0x1a/0x20
[  879.571292]  [<ffffffff816d0a05>] tcp_ack+0x11f5/0x1380
[  879.571614]  [<ffffffff816d10bd>] tcp_rcv_established+0x1ed/0x710
[  879.571958]  [<ffffffff816dc9da>] tcp_v4_do_rcv+0x10a/0x370
[  879.572315]  [<ffffffff81657459>] release_sock+0x89/0x1d0
[  879.572642]  [<ffffffff816c81a0>] do_tcp_setsockopt.isra.36+0x120/0x860
[  879.573000]  [<ffffffff8110a52e>] ? rcu_read_lock_held+0x6e/0x80
[  879.573352]  [<ffffffff816c8912>] tcp_setsockopt+0x32/0x40
[  879.573678]  [<ffffffff81654ac4>] sock_common_setsockopt+0x14/0x20
[  879.574031]  [<ffffffff816537b0>] SyS_setsockopt+0x80/0xf0
[  879.574393]  [<ffffffff817b40a9>] system_call_fastpath+0x16/0x1b
[  879.574730] ---[ end trace a17cbc38eb8c5c00 ]---

v2: moving setting of skb->when for repaired skb-s in tcp_write_xmit,
    where it's set for other skb-s.

Fixes: 431a91242d8d ("tcp: timestamp SYN+DATA messages")
Fixes: 740b0f1841f6 ("tcp: switch rtt estimations to usec resolution")
Cc: Eric Dumazet <edumazet@google.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: xgene: Check negative return value of xgene_enet_get_ring_size()

xgene_enet_get_ring_size() returns a negative value in case of an error,
but its only caller in xgene_enet_create_desc_ring() currently uses the
return value directly as u32. Instead, check for a negative value first and
error out in case. Also move the call to xgene_enet_get_ring_size() before
devm_kzalloc() so we don't need to free anything in the error path.

This fixes the following issue reported by the Coverity Scanner:

** CID 1231336:  Improper use of negative value  (NEGATIVE_RETURNS)
/drivers/net/ethernet/apm/xgene/xgene_enet_main.c: 596 in xgene_enet_create_desc_ring()

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: ethernet: ibm: ehea: Remove duplicate object from Makefile

In the Makefile, ehea_phyp.o is included twice in the list of
object files compile into ehea.o.

This change removes one instance.

Signed-off-by: Andreas Ruprecht <rupran@einserver.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
sit: Fix ipip6_tunnel_lookup device matching criteria

As of 4fddbf5d78 ("sit: strictly restrict incoming traffic to tunnel link device"),
when looking up a tunnel, tunnel's underlying interface (t->parms.link)
is verified to match incoming traffic's ingress device.

However the comparison was incorrectly based on skb->dev->iflink.

Instead, dev->ifindex should be used, which correctly represents the
interface from which the IP stack hands the ipip6 packets.

This allows setting up sit tunnels bound to vlan interfaces (otherwise
incoming ipip6 traffic on the vlan interface was dropped due to
ipip6_tunnel_lookup match failure).

Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
tcp: fix tcp_release_cb() to dispatch via address family for mtu_reduced()

Make sure we use the correct address-family-specific function for
handling MTU reductions from within tcp_release_cb().

Previously AF_INET6 sockets were incorrectly always using the IPv6
code path when sometimes they were handling IPv4 traffic and thus had
an IPv4 dst.

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Diagnosed-by: Willem de Bruijn <willemb@google.com>
Fixes: 563d34d057862 ("tcp: dont drop MTU reduction indications")
Reviewed-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
tcp: don't allow syn packets without timestamps to pass tcp_tw_recycle logic

tcp_tw_recycle heavily relies on tcp timestamps to build a per-host
ordering of incoming connections and teardowns without the need to
hold state on a specific quadruple for TCP_TIMEWAIT_LEN, but only for
the last measured RTO. To do so, we keep the last seen timestamp in a
per-host indexed data structure and verify if the incoming timestamp
in a connection request is strictly greater than the saved one during
last connection teardown. Thus we can verify later on that no old data
packets will be accepted by the new connection.

During moving a socket to time-wait state we already verify if timestamps
where seen on a connection. Only if that was the case we let the
time-wait socket expire after the RTO, otherwise normal TCP_TIMEWAIT_LEN
will be used. But we don't verify this on incoming SYN packets. If a
connection teardown was less than TCP_PAWS_MSL seconds in the past we
cannot guarantee to not accept data packets from an old connection if
no timestamps are present. We should drop this SYN packet. This patch
closes this loophole.

Please note, this patch does not make tcp_tw_recycle in any way more
usable but only adds another safety check:
Sporadic drops of SYN packets because of reordering in the network or
in the socket backlog queues can happen. Users behing NAT trying to
connect to a tcp_tw_recycle enabled server can get caught in blackholes
and their connection requests may regullary get dropped because hosts
behind an address translator don't have synchronized tcp timestamp clocks.
tcp_tw_recycle cannot work if peers don't have tcp timestamps enabled.

In general, use of tcp_tw_recycle is disadvised.

Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
tcp: fix ssthresh and undo for consecutive short FRTO episodes

Fix TCP FRTO logic so that it always notices when snd_una advances,
indicating that any RTO after that point will be a new and distinct
loss episode.

Previously there was a very specific sequence that could cause FRTO to
fail to notice a new loss episode had started:

(1) RTO timer fires, enter FRTO and retransmit packet 1 in write queue
(2) receiver ACKs packet 1
(3) FRTO sends 2 more packets
(4) RTO timer fires again (should start a new loss episode)

The problem was in step (3) above, where tcp_process_loss() returned
early (in the spot marked "Step 2.b"), so that it never got to the
logic to clear icsk_retransmits. Thus icsk_retransmits stayed
non-zero. Thus in step (4) tcp_enter_loss() would see the non-zero
icsk_retransmits, decide that this RTO is not a new episode, and
decide not to cut ssthresh and remember the current cwnd and ssthresh
for undo.

There were two main consequences to the bug that we have
observed. First, ssthresh was not decreased in step (4). Second, when
there was a series of such FRTO (1-4) sequences that happened to be
followed by an FRTO undo, we would restore the cwnd and ssthresh from
before the entire series started (instead of the cwnd and ssthresh
from before the most recent RTO). This could result in cwnd and
ssthresh being restored to values much bigger than the proper values.

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Fixes: e33099f96d99c ("tcp: implement RFC5682 F-RTO")
Signed-off-by: David S. Miller <davem@davemloft.net>