If, for some strange reason, ieee80211_wep_encrypt() fails in
ieee80211_send_auth() free the SKB instead of sending out the
useless frame, in addition to the warning. This can't really
happen since the SKB was freshly allocated.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>
Signed-off-by: NLuca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210618133832.98f058d7a8b2.Ie605e6a10e72eae02f5734032826af48b85b6d11@changeidSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

ieee80211_mgd_assoc calls ieee80211_prep_connection which
might call ieee80211_prep_channel and set smps_mode to OFF.
That will override the previous setting of smps_mode in
ieee80211_mgd_assoc and HT SMPS will be set to "disabled"
in the association request frame.

Move the setting of smps_mode in ieee80211_mgd_assoc to
after the call to ieee80211_prep_connection.
Signed-off-by: NShaul Triebitz <shaul.triebitz@intel.com>
Signed-off-by: NLuca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210618133832.d8e5cc4b527f.Icf3a67fffbdd8c408c0cadfe43f8f4cffdc90acb@changeidSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

The code currently allows this for AP mode, but then ignores
it. Clarify that since the spec doesn't allow it in AP mode.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>
Signed-off-by: NLuca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210618133832.0465f8bcbe32.Iba39fc559ecfa887be00a5f3beabd881e5c86e54@changeidSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

Sending nulldata packets is important for sw AP link probing and detecting
4-address mode links. The checks that dropped these packets were apparently
added to work around an iwlwifi firmware bug with multi-TID aggregation.

Fixes: 41cbb0f5 ("mac80211: add support for HE")
Cc: stable@vger.kernel.org
Signed-off-by: NFelix Fietkau <nbd@nbd.name>
Link: https://lore.kernel.org/r/20210619101517.90806-1-nbd@nbd.nameSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

Preparation work for removing the "enum rtw_ieee80211_category" in
"drivers/staging/rtl8188eu/include/ieee80211.h" and
"drivers/staging/rtl8723bs/include/ieee80211.h".

This enum is similar to "enum ieee80211_category" from
"include/linux/ieee80211.h". However it defines the value '6' as
RTW_WLAN_CATEGORY_FT.

So add a corresponding value in "ieee80211_category"
Signed-off-by: NChristophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/66be0187869bd7dae1c0b0785a32db695ee9872e.1624108556.git.christophe.jaillet@wanadoo.frSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

The data go through mac80211_hwsim_tx_frame_no_nl() wasn't counted.
Signed-off-by: NNguyen Dinh Phi <phind.uet@gmail.com>
Link: https://lore.kernel.org/r/20210622152429.881230-1-phind.uet@gmail.comSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

This fixed the crash when setting channels to 2 or more when
communicating over virtio.
Signed-off-by: NWeilun Du <wdu@google.com>
Link: https://lore.kernel.org/r/20210506180530.3418576-1-wdu@google.comSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

Table 9-251—Supported VHT-MCS and NSS Set subfields, it has subfield VHT Extended
NSS BW Capable, its definition is:
Indicates whether the STA is capable of interpreting the Extended NSS BW
Support subfield of the VHT Capabilities Information field.

This patch is to add check for the subfield.
Signed-off-by: NWen Gong <wgong@codeaurora.org>
Link: https://lore.kernel.org/r/20210524033624.16993-1-wgong@codeaurora.orgSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

offload_flags has been introduced to indicate encap status of each interface.
An interface can encap offload at runtime, or if it has some extra limitations
it can simply override the flags, so it's more flexible to check offload_flags
in Tx path.
Signed-off-by: NRyder Lee <ryder.lee@mediatek.com>
Link: https://lore.kernel.org/r/177785418cf407808bf3a44760302d0647076990.1623961575.git.ryder.lee@mediatek.comSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

The software rate control cannot deal with encap offload, so fix it.
Signed-off-by: NRyder Lee <ryder.lee@mediatek.com>
Link: https://lore.kernel.org/r/20210617163113.75815-3-nbd@nbd.nameSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

Make ieee80211_tx_h_rate_ctrl() get called on dequeue to improve
performance since it reduces the turnaround time for rate control.
Signed-off-by: NRyder Lee <ryder.lee@mediatek.com>
Link: https://lore.kernel.org/r/20210617163113.75815-2-nbd@nbd.nameSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

This avoids calling back into tx handlers from within the rate control module.
Preparation for deferring rate control until tx dequeue
Signed-off-by: NFelix Fietkau <nbd@nbd.name>
Link: https://lore.kernel.org/r/20210617163113.75815-1-nbd@nbd.nameSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

This will allow the low level driver to query the rfkill
state.
Signed-off-by: NEmmanuel Grumbach <emmanuel.grumbach@intel.com>
Link: https://lore.kernel.org/r/20210616202826.9833-1-emmanuel.grumbach@intel.comSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

We shouldn't open-code led_trigger_blink() or led_trigger_event(),
use them instead of badly open-coding them. This also fixes the
locking, led_trigger_blink() and led_trigger_event() now use
read_lock_irqsave().

Link: https://lore.kernel.org/r/20210616212804.b19ba1c60353.I8ea1b4defd5e12fc20ef281291e602feeec336a6@changeidSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

If we have been keeping per-CPU statistics, consider them
regardless of USES_RSS, because we may not actually fill
those, for example in non-fast-RX cases when the connection
is not compatible with fast-RX. If we didn't fill them, the
additional data will be zero and not affect anything, and
if we did fill them then it's more correct to consider them.

This fixes an issue in mesh mode where some statistics are
not updated due to USES_RSS being set, but fast-RX isn't
used.
Reported-by: NThiraviyam Mariyappan <tmariyap@codeaurora.org>
Link: https://lore.kernel.org/r/20210610220814.13b35f5797c5.I511e9b33c5694e0d6cef4b6ae755c873d7c22124@changeidSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

In 2G band, a HE sta can only supports HT and HE, but not supports VHT.
In this case, default HE tx bitrate mask isn't filled, when we use iw to
set bitrates without any parameter.
Signed-off-by: NPing-Ke Shih <pkshih@realtek.com>
Link: https://lore.kernel.org/r/20210609075944.51130-1-pkshih@realtek.comSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

Function 'ieee80211_sta_set_rx_nss' is declared twice, so remove the
repeated declaration.
Signed-off-by: NShaokun Zhang <zhangshaokun@hisilicon.com>
Link: https://lore.kernel.org/r/1622196424-62403-1-git-send-email-zhangshaokun@hisilicon.comSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

Use newly introduced helper function ieee80211_is_tx_data to check if
frame is a data frame. Takes into account that hardware encapsulation
can be enabled for a frame and therefore no ieee80211 header is present.
Signed-off-by: NPhilipp Borgers <borgers@mi.fu-berlin.de>
Link: https://lore.kernel.org/r/20210519122019.92359-4-borgers@mi.fu-berlin.deSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

Data Frames with no ack flag set should be handled by the rate
controler. Make sure we reach the rate controler by returning early
from rate_control_send_low if the frame is a data frame with no ack
flag.
Signed-off-by: NPhilipp Borgers <borgers@mi.fu-berlin.de>
Link: https://lore.kernel.org/r/20210519122019.92359-3-borgers@mi.fu-berlin.deSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

Add a helper function that checks if a frame is a data frame. Frames
with hardware encapsulation enabled are data frames.
Signed-off-by: NPhilipp Borgers <borgers@mi.fu-berlin.de>
Link: https://lore.kernel.org/r/20210519122019.92359-2-borgers@mi.fu-berlin.deSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

There's no need to do some kind of weird err and RCU dance
just use sta_info_insert() directly.

Link: https://lore.kernel.org/r/20210517230754.55abd10056c0.I6f5a3b7b23347b2cdaf64e6d5ce1d9e904059654@changeidSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

We need to differentiate these frames since the ones we
currently put on the skb_queue_tdls_chsw have already
been converted to ethernet format, but now that we've
got a single place to enqueue to the sdata->skb_queue
this isn't hard. Just differentiate based on protocol
and adjust the code to queue the SKBs appropriately.

Link: https://lore.kernel.org/r/20210517230754.17034990abef.I5342f2183c0d246b18d36c511eb3b6be298a6572@changeidSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

This is a very long loop body, move it into its own function
instead, keeping only the kcov and free outside in the loop
body.

Link: https://lore.kernel.org/r/20210517230754.6bc6cdd68570.I28a86ebdb19601ca1965c4dc654cc49fc1064efa@changeidSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

We have a bunch of places that open-code the same to queue
an SKB to an interface, unify that.

Link: https://lore.kernel.org/r/20210517230754.113b65febd5a.Ie0e1d58a2885e75f242cb6e06f3b9660117fef93@changeidSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

QoS Data Frames that were sent with a No Ack policy should be ignored by
the minstrel statistics. There will never be an Ack for these frames so
there is no way to draw conclusions about the success of the transmission.
Signed-off-by: NPhilipp Borgers <borgers@mi.fu-berlin.de>
Link: https://lore.kernel.org/r/20210517120145.132814-1-borgers@mi.fu-berlin.deSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

The "ap_info->tbtt_info_len" and "length" variables are the same value
but it is confusing how the names are mixed up.  Let's use "length"
everywhere for consistency.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/YJaMNzZENkYFAYQX@mwandaSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

We no longer need to put any limits here, hardware will and
mac80211-hwsim can do whatever it likes. The reason we had
this was some accounting code (still mentioned in the comment)
but that code was deleted in commit c781944b ("cfg80211:
Remove unused cfg80211_can_use_iftype_chan()").

Link: https://lore.kernel.org/r/20210506221159.d1d61db1d31c.Iac4da68d54b9f1fdc18a03586bbe06aeb9515425@changeidSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

Variable 'ret' is set to -ENODEV but this value is never read as it
is overwritten with a new value later on, hence it is a redundant
assignment and can be removed.

Clean up the following clang-analyzer warning:

net/mac80211/debugfs_netdev.c:60:2: warning: Value stored to 'ret' is
never read [clang-analyzer-deadcode.DeadStores]
Reported-by: NAbaci Robot <abaci@linux.alibaba.com>
Signed-off-by: NYang Li <yang.lee@linux.alibaba.com>
Link: https://lore.kernel.org/r/1619774483-116805-1-git-send-email-yang.lee@linux.alibaba.comSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

Variable 'ps' is set to wdev->ps but this value is never read as it is
overwritten with a new value later on, hence it is a redundant
assignment and can be removed.

Cleans up the following clang-analyzer warning:

net/wireless/wext-compat.c:1170:7: warning: Value stored to 'ps' during
its initialization is never read [clang-analyzer-deadcode.DeadStores]
Reported-by: NAbaci Robot <abaci@linux.alibaba.com>
Signed-off-by: NYang Li <yang.lee@linux.alibaba.com>
Link: https://lore.kernel.org/r/1619603945-116891-1-git-send-email-yang.lee@linux.alibaba.comSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

Fix the following out-of-bounds warning:

net/wireless/wext-spy.c:178:2: warning: 'memcpy' offset [25, 28] from the object at 'threshold' is out of the bounds of referenced subobject 'low' with type 'struct iw_quality' at offset 20 [-Warray-bounds]

The problem is that the original code is trying to copy data into a
couple of struct members adjacent to each other in a single call to
memcpy(). This causes a legitimate compiler warning because memcpy()
overruns the length of &threshold.low and &spydata->spy_thr_low. As
these are just a couple of struct members, fix this by using direct
assignments, instead of memcpy().

This helps with the ongoing efforts to globally enable -Warray-bounds
and get us closer to being able to tighten the FORTIFY_SOURCE routines
on memcpy().

Link: https://github.com/KSPP/linux/issues/109Reported-by: Nkernel test robot <lkp@intel.com>
Signed-off-by: NGustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: NKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210422200032.GA168995@embeddedorSigned-off-by: NJohannes Berg <johannes.berg@intel.com>

Mat Martineau says:

====================
mptcp: Connection-time 'C' flag and two fixes

Here are six more patches from the MPTCP tree.

Most of them add support for the 'C' flag in the MPTCP connection-time
option headers. This flag affects how the initial address and port are
treated by each peer. Normally one peer may send MP_JOIN requests to the
remote address and port that were used when initiating the MPTCP
connection. The 'C' bit indicates that MP_JOINs should only be sent to
remote addresses that have been advertised with ADD_ADDR.

The other two patches are unrelated improvements.

Patches 1-4: Add the 'C' flag feature, a sysctl to optionally enable it,
and a selftest.

Patch 5: Adjust rp_filter settings in a selftest.

Patch 6: Improve rbuf cleanup for MPTCP sockets.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The current cleanup rbuf tries a bit too hard to avoid acquiring
the subflow socket lock. We may end-up delaying the needed ack,
or skip acking a blocked subflow.

Address the above extending the conditions used to trigger the cleanup
to reflect more closely what TCP does and invoking tcp_cleanup_rbuf()
on all the active subflows.

Note that we can't replicate the exact tests implemented in
tcp_cleanup_rbuf(), as MPTCP lacks some of the required info - e.g.
ping-pong mode.
Signed-off-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NMat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

To turn rp_filter off we should:

  echo 0 > /proc/sys/net/ipv4/conf/default/rp_filter

and

  echo 0 > /proc/sys/net/ipv4/conf/all/rp_filter

before NIC created.
Co-developed-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NYonglong Li <liyonglong@chinatelecom.cn>
Signed-off-by: NMat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch added a new argument '-d' for mptcp_join.sh script, to invoke
the testcases for the MP_CAPABLE 'C' flag.
Acked-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NGeliang Tang <geliangtang@gmail.com>
Signed-off-by: NMat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch added a new flag named deny_join_id0 in struct
mptcp_options_received. Set it when MP_CAPABLE with the flag
MPTCP_CAP_DENYJOIN_ID0 is received.

Also add a new flag remote_deny_join_id0 in struct mptcp_pm_data. When the
flag deny_join_id0 is set, set this remote_deny_join_id0 flag.

In mptcp_pm_create_subflow_or_signal_addr, if the remote_deny_join_id0 flag
is set, and the remote address id is zero, stop this connection.
Suggested-by: NFlorian Westphal <fw@strlen.de>
Acked-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NGeliang Tang <geliangtang@gmail.com>
Signed-off-by: NMat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch defined a new flag MPTCP_CAP_DENY_JOIN_ID0 for the third bit,
labeled "C" of the MP_CAPABLE option.

Add a new flag allow_join_id0 in struct mptcp_out_options. If this flag is
set, send out the MP_CAPABLE option with the flag MPTCP_CAP_DENY_JOIN_ID0.
Acked-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NGeliang Tang <geliangtang@gmail.com>
Signed-off-by: NMat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch added a new sysctl, named allow_join_initial_addr_port, to
control whether allow peers to send join requests to the IP address and
port number used by the initial subflow.
Suggested-by: NFlorian Westphal <fw@strlen.de>
Acked-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NGeliang Tang <geliangtang@gmail.com>
Signed-off-by: NMat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Xin Long says:

====================
sctp: implement RFC8899: Packetization Layer Path MTU Discovery for SCTP transport

Overview(From RFC8899):

  In contrast to PMTUD, Packetization Layer Path MTU Discovery
  (PLPMTUD) [RFC4821] introduces a method that does not rely upon
  reception and validation of PTB messages.  It is therefore more
  robust than Classical PMTUD.  This has become the recommended
  approach for implementing discovery of the PMTU [BCP145].

  It uses a general strategy in which the PL sends probe packets to
  search for the largest size of unfragmented datagram that can be sent
  over a network path.  Probe packets are sent to explore using a
  larger packet size.  If a probe packet is successfully delivered (as
  determined by the PL), then the PLPMTU is raised to the size of the
  successful probe.  If a black hole is detected (e.g., where packets
  of size PLPMTU are consistently not received), the method reduces the
  PLPMTU.

SCTP Probe Packets:

  As the RFC suggested, the probe packets consist of an SCTP common header
  followed by a HEARTBEAT chunk and a PAD chunk. The PAD chunk is used to
  control the length of the probe packet.  The HEARTBEAT chunk is used to
  trigger the sending of a HEARTBEAT ACK chunk to confirm this probe on
  the HEARTBEAT sender.

  The HEARTBEAT chunk also carries a Heartbeat Information parameter that
  includes the probe size to help an implementation associate a HEARTBEAT
  ACK with the size of probe that was sent. The sender use the nonce and
  the probe size to verify the information returned.

Detailed Implementation on SCTP:

                       +------+
              +------->| Base |-----------------+ Connectivity
              |        +------+                 | or BASE_PLPMTU
              |           |                     | confirmation failed
              |           |                     v
              |           | Connectivity    +-------+
              |           | and BASE_PLPMTU | Error |
              |           | confirmed       +-------+
              |           |                     | Consistent
              |           v                     | connectivity
   Black Hole |       +--------+                | and BASE_PLPMTU
    detected  |       | Search |<---------------+ confirmed
              |       +--------+
              |          ^  |
              |          |  |
              |    Raise |  | Search
              |    timer |  | algorithm
              |  expired |  | completed
              |          |  |
              |          |  v
              |   +-----------------+
              +---| Search Complete |
                  +-----------------+

  When PLPMTUD is enabled, it's in Base state, and starts to probe with
  BASE_PLPMTU (1200). If this probe succeeds, it goes to Search state;
  If this probe fails, it goes to Error state under which pl.pmtu goes
  down to MIN_PLPMTU (512) and keeps probing with BASE_PLPMTU until it
  succeeds and goes to Search state.

  During the Search state, the probe size is growing by a Big step (32)
  every time when the last probe succeeds at the beginning. Once a probe
  (such as 1420) fails after trying MAX_PROBES (3) times, the probe_size
  goes back to the last one (1420 - 32 = 1388), meanwhile 'probe_high'
  is set to 1420 and the growing step becomes a Small one (4). Then the
  probe is continuing with a Small step grown each round. Until it gets
  the optimal size (such as 1400) when probe with its next probe size
  (1404) fails, it sync this size to pathmtu and goes to Complete state.

  In Complete state, it will only does a probe check for the pathmtu just
  set, if it fails, which means a Black Hole is detected and it goes back
  to Base state. If it succeeds, it goes back to Search state again, and
  probe is continuing with growing a Small step (1400 + 4). If this probe
  fails, probe_high is set and goes back to 1388 and then Complete state,
  which is kind of a loop normally. However if the env's pathmtu changes
  to a big size somehow, this probe will succeed and then probe continues
  with growing a Big step (1400 + 32) each round until another probe fails.

PTB Messages Process:

  PLPMTUD doesn't rely on these package to find the pmtu, and shouldn't
  trust it either. When processing them, it only changes the probe_size
  to PL_PTB_SIZE(info - hlen) if 'pl.pmtu < PL_PTB_SIZE < the current
  probe_size' druing Search state. As this could help probe_size to get
  to the optimal size faster, for exmaple:

  pl.pmtu = 1388, probe_size = 1420, while the env's pathmtu = 1400.
  When probe_size is 1420, a Toobig packet with 1400 comes back. If probe
  size changes to use 1400, it will save quite a few rounds to get there.
  But of course after having this value, PLPMTUD will still verify it on
  its own before using it.

Patches:

  - Patch 1-6: introduce some new constants/variables from the RFC, systcl
    and members in transport, APIs for the following patches, chunks and
    a timer for the probe sending and some codes for the probe receiving.

  - Patch 7-9: implement the state transition on the tx path, rx path and
    toobig ICMP packet processing. This is the main algorithm part.

  - Patch 10: activate this feature

  - Patch 11-14: improve the process for ICMP packets for SCTP over UDP,
    so that it can also be covered by this feature.

Tests:

  - do sysctl and setsockopt tests for this feature's enabling and disabling.

  - get these pr_debug points for this feature by
      # cat /sys/kernel/debug/dynamic_debug/control | grep PLP
    and enable them on kernel dynamic debug, then play with the pathmtu and
    check if the state transition and plpmtu change match the RFC.

  - do the above tests for SCTP over IPv4/IPv6 and SCTP over UDP.

v1->v2:
  - See Patch 06/14.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Previously, sctp over udp was using udp tunnel's icmp err process, which
only does sk lookup on sctp side. However for sctp's icmp error process,
there are more things to do, like syncing assoc pmtu/retransmit packets
for toobig type err, and starting proto_unreach_timer for unreach type
err etc.

Now after adding PLPMTUD, which also requires to process toobig type err
on sctp side. This patch is to process icmp err on sctp side by parsing
the type/code/info in .encap_err_lookup and call sctp's icmp processing
functions. Note as the 'redirect' err process needs to know the outer
ip(v6) header's, we have to leave it to udp(v6)_err to handle it.
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Acked-by: NMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch is to extract sctp_v4_err_handle() from sctp_v4_err() to
only handle the icmp err after the sock lookup, and it also makes
the code clearer.

sctp_v4_err_handle() will be used in sctp over udp's err handling
in the following patch.
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Acked-by: NMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>