Le mercredi 30 novembre 2011 à 14:36 -0800, Stephen Hemminger a écrit :

> (Almost) nobody uses RED because they can't figure it out.
> According to Wikipedia, VJ says that:
>  "there are not one, but two bugs in classic RED."

RED is useful for high throughput routers, I doubt many linux machines
act as such devices.

I was considering adding Adaptative RED (Sally Floyd, Ramakrishna
Gummadi, Scott Shender), August 2001

In this version, maxp is dynamic (from 1% to 50%), and user only have to
setup min_th (target average queue size)
(max_th and wq (burst in linux RED) are automatically setup)

By the way it seems we have a small bug in red_change()

if (skb_queue_empty(&sch->q))
	red_end_of_idle_period(&q->parms);

First, if queue is empty, we should call
red_start_of_idle_period(&q->parms);

Second, since we dont use anymore sch->q, but q->qdisc, the test is
meaningless.

Oh well...

[PATCH] sch_red: fix red_change()

Now RED is classful, we must check q->qdisc->q.qlen, and if queue is empty,
we start an idle period, not end it.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This reverts commit 81d54ec8.

If we take the "try_again" goto, due to a checksum error,
the 'len' has already been truncated.  So we won't compute
the same values as the original code did.
Reported-by: paul bilke <fsmail@conspiracy.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

When in user-stp mode, bridge master do not follow state of its slaves, so
after the following sequence of events it can stuck forever in no-carrier
state:
1) turn stp off
2) put all slaves down - master device will follow their state and also go in
no-carrier state
3) turn stp on with bridge-stp script returning 0 (go to the user-stp mode)
Now bridge master won't follow slaves' state and will never reach running
state.

This patch solves the problem by making user-stp and kernel-stp behavior
similar regarding master following slaves' states.
Signed-off-by: Vitalii Demianets <vitas@nppfactor.kiev.ua>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Otherwise we won't notice the peer GENID change.
Reported-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Within nested statements, the break statement terminates only the
do, for, switch, or while statement that immediately encloses it,
So replace the break with goto.
Signed-off-by: RongQing.Li <roy.qing.li@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Since commit a4a710c4 (pkt_sched: Change PSCHED_SHIFT from 10 to
6) it seems RED/GRED are broken.

red_calc_qavg_from_idle_time() computes a delay in us units, but this
delay is now 16 times bigger than real delay, so the final qavg result
smaller than expected.

Use standard kernel time services since there is no need to obfuscate
them.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Only use the primary address of the bond device
for master_ip. This will prevent changing the ARP source
address in Active-Backup mode whenever a secondry address
is added to the bond device.
Signed-off-by: Henrik Saavedra Persson <henrik.e.persson@ericsson.com>
Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: David S. Miller <davem@drr.davemloft.net>

After commit f2c31e32 (fix NULL dereferences in check_peer_redir()),
dst_get_neighbour() should be guarded by rcu_read_lock() /
rcu_read_unlock() section.
Reported-by: Miles Lane <miles.lane@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

We need rcu_read_lock() protection before using dst_get_neighbour(), and
we must cache its value (pass it to __teql_resolve())

teql_master_xmit() is called under rcu_read_lock_bh() protection, its
not enough.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Since commit 230dec61 (net/fec: add imx6q enet support) the FEC driver is no 
longer built by default for i.MX SoCs.

Let the FEC driver be built by default again.
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless into for-davem

"cfg->drvid" comes from the user so there is a possibility they
didn't NUL terminate it properly.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

These strings come from the user.  We strcpy() them inside
cf_command() so we should check that they are NULL terminated and
return an error if not.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

A recent fix to the the NetLabel code caused build problem with
configurations that did not have IPv6 enabled; see below:

 netlabel_kapi.c: In function 'netlbl_cfg_unlbl_map_add':
 netlabel_kapi.c:165:4:
  error: implicit declaration of function 'netlbl_af6list_add'

This patch fixes this problem by making the IPv6 specific code conditional
on the IPv6 configuration flags as we done in the rest of NetLabel and the
network stack as a whole.  We have to move some variable declarations
around as a result so things may not be quite as pretty, but at least it
builds cleanly now.

Some additional IPv6 conditionals were added to the NetLabel code as well
for the sake of consistency.
Reported-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Paul Moore <pmoore@redhat.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

The check from commit 30c2235c is incomplete and cannot prevent
cases like key_len = 0x80000000 (INT_MAX + 1).  In that case, the
left-hand side of the check (INT_MAX - key_len), which is unsigned,
becomes 0xffffffff (UINT_MAX) and bypasses the check.

However this shouldn't be a security issue.  The function is called
from the following two code paths:

 1) setsockopt()

 2) sctp_auth_asoc_set_secret()

In case (1), sca_keylength is never going to exceed 65535 since it's
bounded by a u16 from the user API.  As such, the key length will
never overflow.

In case (2), sca_keylength is computed based on the user key (1 short)
and 2 * key_vector (3 shorts) for a total of 7 * USHRT_MAX, which still
will not overflow.

In other words, this overflow check is not really necessary.  Just
make it more correct.
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Cc: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The previous commit 30c2235c is incomplete and cannot prevent integer
overflows. For example, when key_len is 0x80000000 (INT_MAX + 1), the
left-hand side of the check, (INT_MAX - key_len), which is unsigned,
becomes 0xffffffff (UINT_MAX) and bypasses the check.
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

We need to set np->mcast_hops to it's default value at this moment
otherwise when we use it and found it's value is -1, the logic to
get default hop limit doesn't take multicast into account and will
return wrong hop limit(IPV6_DEFAULT_HOPLIMIT) which is for unicast.
Signed-off-by: Li Wei <lw@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

I just hit this during my testing. Isn't there another bug lurking?

BUG kmalloc-8: Redzone overwritten

INFO: 0xc0000000de9dec48-0xc0000000de9dec4b. First byte 0x0 instead of 0xcc
INFO: Allocated in .__seq_open_private+0x30/0xa0 age=0 cpu=5 pid=3896
	.__kmalloc+0x1e0/0x2d0
	.__seq_open_private+0x30/0xa0
	.seq_open_net+0x60/0xe0
	.dev_mc_seq_open+0x4c/0x70
	.proc_reg_open+0xd8/0x260
	.__dentry_open.clone.11+0x2b8/0x400
	.do_last+0xf4/0x950
	.path_openat+0xf8/0x480
	.do_filp_open+0x48/0xc0
	.do_sys_open+0x140/0x250
	syscall_exit+0x0/0x40

dev_mc_seq_ops uses dev_seq_start/next/stop but only allocates
sizeof(struct seq_net_private) of private data, whereas it expects
sizeof(struct dev_iter_state):

struct dev_iter_state {
	struct seq_net_private p;
	unsigned int pos; /* bucket << BUCKET_SPACE + offset */
};

Create dev_seq_open_ops and use it so we don't have to expose
struct dev_iter_state.

[ Problem added by commit f04565dd (dev: use name hash for
  dev_seq_ops) -Eric ]
Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

When a packet is supposed to sent be as an a-MPDU, mac80211 sets
IEEE80211_TX_CTL_AMPDU to let the driver know. On the other
hand, mac80211 configures the driver for aggregration with the
ampdu_action callback.
There is race between these two mechanisms since the following
scenario can occur when the BA agreement is torn down:

Tx softIRQ	 			drv configuration
==========				=================

check OPERATIONAL bit
Set the TX_CTL_AMPDU bit in the packet

					clear OPERATIONAL bit
					stop Tx AGG
Pass Tx packet to the driver.

In that case the driver would get a packet with TX_CTL_AMPDU set
although it has already been notified that the BA session has been
torn down.

To fix this, we need to synchronize all the Qdisc activity after we
cleared the OPERATIONAL bit. After that step, all the following
packets will be buffered until the driver reports it is ready to get
new packets for this RA / TID. This buffering allows not to run into
another race that would send packets with TX_CTL_AMPDU unset while
the driver hasn't been requested to tear down the BA session yet.

This race occurs in practice and iwlwifi complains with a WARN_ON
when it happens.

Cc: stable@kernel.org
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

If addBA responses comes in just after addba_resp_timer has
expired mac80211 will still accept it and try to open the
aggregation session. This causes drivers to be confused and
in some cases even crash.

This patch fixes the race condition and makes sure that if
addba_resp_timer has expired addBA response is not longer
accepted and we do not try to open half-closed session.

Cc: stable@vger.kernel.org
Signed-off-by: Nikolay Martynov <mar.kolya@gmail.com>
[some adjustments]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

Revert a hunk in drivers/net/wireless/ath/ath9k/hw.c introduced by
commit 2577c6e8 (ath9k_hw: Add
support for AR946/8x chipsets) that caused a nasty regression to
appear on my Acer Ferrari One (the box locks up entirely at random
times after the wireless has been started without any way to get
debug information out of it).
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

rtl_lps_leave can be called from interrupt context, so we have to
disable interrupts when taking lps_lock.

Below is full lockdep info about deadlock:

[   93.815269] =================================
[   93.815390] [ INFO: inconsistent lock state ]
[   93.815472] 2.6.41.1-3.offch.fc15.x86_64.debug #1
[   93.815556] ---------------------------------
[   93.815635] inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
[   93.815743] swapper/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
[   93.815832]  (&(&rtlpriv->locks.lps_lock)->rlock){+.?...}, at: [<ffffffffa025dad6>] rtl_lps_leave+0x26/0x103 [rtlwifi]
[   93.815947] {SOFTIRQ-ON-W} state was registered at:
[   93.815947]   [<ffffffff8108e10d>] __lock_acquire+0x369/0xd0c
[   93.815947]   [<ffffffff8108efb3>] lock_acquire+0xf3/0x13e
[   93.815947]   [<ffffffff814e981d>] _raw_spin_lock+0x45/0x79
[   93.815947]   [<ffffffffa025de34>] rtl_swlps_rf_awake+0x5a/0x76 [rtlwifi]
[   93.815947]   [<ffffffffa025aec0>] rtl_op_config+0x12a/0x32a [rtlwifi]
[   93.815947]   [<ffffffffa01d614b>] ieee80211_hw_config+0x124/0x129 [mac80211]
[   93.815947]   [<ffffffffa01e0af3>] ieee80211_dynamic_ps_disable_work+0x32/0x47 [mac80211]
[   93.815947]   [<ffffffff81075aa5>] process_one_work+0x205/0x3e7
[   93.815947]   [<ffffffff81076753>] worker_thread+0xda/0x15d
[   93.815947]   [<ffffffff8107a119>] kthread+0xa8/0xb0
[   93.815947]   [<ffffffff814f3184>] kernel_thread_helper+0x4/0x10
[   93.815947] irq event stamp: 547822
[   93.815947] hardirqs last  enabled at (547822): [<ffffffff814ea1a7>] _raw_spin_unlock_irqrestore+0x45/0x61
[   93.815947] hardirqs last disabled at (547821): [<ffffffff814e9987>] _raw_spin_lock_irqsave+0x22/0x8e
[   93.815947] softirqs last  enabled at (547790): [<ffffffff810623ed>] _local_bh_enable+0x13/0x15
[   93.815947] softirqs last disabled at (547791): [<ffffffff814f327c>] call_softirq+0x1c/0x30
[   93.815947]
[   93.815947] other info that might help us debug this:
[   93.815947]  Possible unsafe locking scenario:
[   93.815947]
[   93.815947]        CPU0
[   93.815947]        ----
[   93.815947]   lock(&(&rtlpriv->locks.lps_lock)->rlock);
[   93.815947]   <Interrupt>
[   93.815947]     lock(&(&rtlpriv->locks.lps_lock)->rlock);
[   93.815947]
[   93.815947]  *** DEADLOCK ***
[   93.815947]
[   93.815947] no locks held by swapper/0.
[   93.815947]
[   93.815947] stack backtrace:
[   93.815947] Pid: 0, comm: swapper Not tainted 2.6.41.1-3.offch.fc15.x86_64.debug #1
[   93.815947] Call Trace:
[   93.815947]  <IRQ>  [<ffffffff814dfd00>] print_usage_bug+0x1e7/0x1f8
[   93.815947]  [<ffffffff8101a849>] ? save_stack_trace+0x2c/0x49
[   93.815947]  [<ffffffff8108d55c>] ? print_irq_inversion_bug.part.18+0x1a0/0x1a0
[   93.815947]  [<ffffffff8108dc8a>] mark_lock+0x106/0x220
[   93.815947]  [<ffffffff8108e099>] __lock_acquire+0x2f5/0xd0c
[   93.815947]  [<ffffffff810152af>] ? native_sched_clock+0x34/0x36
[   93.830125]  [<ffffffff810152ba>] ? sched_clock+0x9/0xd
[   93.830125]  [<ffffffff81080181>] ? sched_clock_local+0x12/0x75
[   93.830125]  [<ffffffffa025dad6>] ? rtl_lps_leave+0x26/0x103 [rtlwifi]
[   93.830125]  [<ffffffff8108efb3>] lock_acquire+0xf3/0x13e
[   93.830125]  [<ffffffffa025dad6>] ? rtl_lps_leave+0x26/0x103 [rtlwifi]
[   93.830125]  [<ffffffff814e981d>] _raw_spin_lock+0x45/0x79
[   93.830125]  [<ffffffffa025dad6>] ? rtl_lps_leave+0x26/0x103 [rtlwifi]
[   93.830125]  [<ffffffff81422467>] ? skb_dequeue+0x62/0x6d
[   93.830125]  [<ffffffffa025dad6>] rtl_lps_leave+0x26/0x103 [rtlwifi]
[   93.830125]  [<ffffffffa025f677>] _rtl_pci_ips_leave_tasklet+0xe/0x10 [rtlwifi]
[   93.830125]  [<ffffffff8106281f>] tasklet_action+0x8d/0xee
[   93.830125]  [<ffffffff810629ce>] __do_softirq+0x112/0x25a
[   93.830125]  [<ffffffff814f327c>] call_softirq+0x1c/0x30
[   93.830125]  [<ffffffff81010bf6>] do_softirq+0x4b/0xa1
[   93.830125]  [<ffffffff81062d7d>] irq_exit+0x5d/0xcf
[   93.830125]  [<ffffffff814f3b7e>] do_IRQ+0x8e/0xa5
[   93.830125]  [<ffffffff814ea533>] common_interrupt+0x73/0x73
[   93.830125]  <EOI>  [<ffffffff8108b825>] ? trace_hardirqs_off+0xd/0xf
[   93.830125]  [<ffffffff812bb6d5>] ? intel_idle+0xe5/0x10c
[   93.830125]  [<ffffffff812bb6d1>] ? intel_idle+0xe1/0x10c
[   93.830125]  [<ffffffff813f8d5e>] cpuidle_idle_call+0x11c/0x1fe
[   93.830125]  [<ffffffff8100e2ef>] cpu_idle+0xab/0x101
[   93.830125]  [<ffffffff814c6373>] rest_init+0xd7/0xde
[   93.830125]  [<ffffffff814c629c>] ? csum_partial_copy_generic+0x16c/0x16c
[   93.830125]  [<ffffffff81d4bbb0>] start_kernel+0x3dd/0x3ea
[   93.830125]  [<ffffffff81d4b2c4>] x86_64_start_reservations+0xaf/0xb3
[   93.830125]  [<ffffffff81d4b140>] ? early_idt_handlers+0x140/0x140
[   93.830125]  [<ffffffff81d4b3ca>] x86_64_start_kernel+0x102/0x111

Resolves:
https://bugzilla.redhat.com/show_bug.cgi?id=755154

Reported-by: vjain02@students.poly.edu
Reported-and-tested-by: Oliver Paukstadt <pstadt@sourcentral.org>
Cc: stable@vger.kernel.org
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

Nikolay noticed (by code review) that mac80211 can
attempt to stop an aggregation session while it is
already being stopped. So to fix it, check whether
stop is already being done and bail out if so.

Also move setting the STOPPING state into the lock
so things are properly atomic.

Cc: stable@vger.kernel.org
Reported-by: Nikolay Martynov <mar.kolya@gmail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

MAC addresses have a fixed length. The current
policy allows passing < ETH_ALEN bytes, which
might result in reading beyond the buffer.

Cc: stable@vger.kernel.org
Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

To perform PHY calibration and set a different EA value by chip ID,
Whenever the NIC chip power on, ie booting or resuming, we need to
force HW to calibrate PHY parameter again, and also set a proper EA
value which gather from experiment.

Those procedures help to reduce compatible issues(NIC is unable to link
up in some special case) in giga speed.
Signed-off-by: AriesLee <AriesLee@jmicron.com>
Signed-off-by: Guo-Fu Tseng <cooldavid@cooldavid.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Now inetpeer is the place where we cache redirect information for ipv4
destinations, we must be able to invalidate informations when a route is
added/removed on host.

As inetpeer is not yet namespace aware, this patch adds a shared
redirect_genid, and a per inetpeer redirect_genid. This might be changed
later if inetpeer becomes ns aware.

Cache information for one inerpeer is valid as long as its
redirect_genid has the same value than global redirect_genid.
Reported-by: Arkadiusz Miśkiewicz <a.miskiewicz@gmail.com>
Tested-by: Arkadiusz Miśkiewicz <a.miskiewicz@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

poll() call may be blocked by concurrent reading from the same stream
socket.
Signed-off-by: Alexey Moiseytsev <himeraster@gmail.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

We're trying to check if any options are defined which isn't wha the
existing code does due to confusing & and &&.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

When using l2tp over ipsec, the tunnel will hang when rekeying
occurs. Reason is that the transformer bundle attached to the dst entry
is now in STATE_DEAD and thus xfrm_output_one() drops all packets
(XfrmOutStateExpired increases).

Fix this by calling __sk_dst_check (which drops the stale dst
if xfrm dst->check callback finds that the bundle is no longer valid).

Cc: James Chapman <jchapman@katalix.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Better use sk_reset_timer() / sk_stop_timer() helpers to make sure we
dont access already freed/reused memory later.
Reported-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Tested-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

commit 88491d81 ("drivers/net: Kconfig
& Makefile cleanup") changed the type of these options to bool, but
they select code that could (and still can) be built as modules.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

The pmtu informations on the inetpeer are visible for output and
input routes. On packet forwarding, we might propagate a learned
pmtu to the sender. As we update the pmtu informations of the
inetpeer on demand, the original sender of the forwarded packets
might never notice when the pmtu to that inetpeer increases.
So use the mtu of the outgoing device on packet forwarding instead
of the pmtu to the final destination.
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

We move all mtu handling from dst_mtu() down to the protocol
layer. So each protocol can implement the mtu handling in
a different manner.
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

We plan to invoke the dst_opt->default_mtu() method unconditioally
from dst_mtu(). So rename the method to dst_opt->mtu() to match
the name with the new meaning.
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

As it is, we return null as the default mtu of blackhole routes.
This may lead to a propagation of a bogus pmtu if the default_mtu
method of a blackhole route is invoked. So return dst->dev->mtu
as the default mtu instead.
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Skip entries from foreign network namespaces.
Signed-off-by: Jorge Boncompte [DTI2] <jorge@dti2.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

This was copy and pasted from the IPv4 code.  We're calling the
ip4 version of that function and map4 is NULL.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

We can not update iph->daddr in ip_options_rcv_srr(), It is too early.
When some exception ocurred later (eg. in ip_forward() when goto
sr_failed) we need the ip header be identical to the original one as
ICMP need it.

Add a field 'nexthop' in struct ip_options to save nexthop of LSRR
or SSRR option.
Signed-off-by: Li Wei <lw@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>