<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/net/netfilter/ipvs, branch linux-5.8.y</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>ipvs: Fix uninit-value in do_ip_vs_set_ctl()</title>
<updated>2020-10-29T09:08:27+00:00</updated>
<author>
<name>Peilin Ye</name>
<email>yepeilin.cs@gmail.com</email>
</author>
<published>2020-08-11T07:46:40+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=72720eaa6c337cfe0dfe2efac576124fff9bb61d'/>
<id>72720eaa6c337cfe0dfe2efac576124fff9bb61d</id>
<content type='text'>
[ Upstream commit c5a8a8498eed1c164afc94f50a939c1a10abf8ad ]

do_ip_vs_set_ctl() is referencing uninitialized stack value when `len` is
zero. Fix it.

Reported-by: syzbot+23b5f9e7caf61d9a3898@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=46ebfb92a8a812621a001ef04d90dfa459520fe2
Suggested-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Signed-off-by: Peilin Ye &lt;yepeilin.cs@gmail.com&gt;
Acked-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Reviewed-by: Simon Horman &lt;horms@verge.net.au&gt;
Signed-off-by: Pablo Neira Ayuso &lt;pablo@netfilter.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit c5a8a8498eed1c164afc94f50a939c1a10abf8ad ]

do_ip_vs_set_ctl() is referencing uninitialized stack value when `len` is
zero. Fix it.

Reported-by: syzbot+23b5f9e7caf61d9a3898@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=46ebfb92a8a812621a001ef04d90dfa459520fe2
Suggested-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Signed-off-by: Peilin Ye &lt;yepeilin.cs@gmail.com&gt;
Acked-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Reviewed-by: Simon Horman &lt;horms@verge.net.au&gt;
Signed-off-by: Pablo Neira Ayuso &lt;pablo@netfilter.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ipvs: clear skb-&gt;tstamp in forwarding path</title>
<updated>2020-10-29T09:07:49+00:00</updated>
<author>
<name>Julian Anastasov</name>
<email>ja@ssi.bg</email>
</author>
<published>2020-10-09T18:24:25+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=4cdfe55c067b457c69316d9c7cba3fd0f88039e3'/>
<id>4cdfe55c067b457c69316d9c7cba3fd0f88039e3</id>
<content type='text'>
[ Upstream commit 7980d2eabde82be86c5be18aa3d07e88ec13c6a1 ]

fq qdisc requires tstamp to be cleared in forwarding path

Reported-by: Evgeny B &lt;abt-admin@mail.ru&gt;
Link: https://bugzilla.kernel.org/show_bug.cgi?id=209427
Suggested-by: Eric Dumazet &lt;eric.dumazet@gmail.com&gt;
Fixes: 8203e2d844d3 ("net: clear skb-&gt;tstamp in forwarding paths")
Fixes: fb420d5d91c1 ("tcp/fq: move back to CLOCK_MONOTONIC")
Fixes: 80b14dee2bea ("net: Add a new socket option for a future transmit time.")
Signed-off-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Reviewed-by: Simon Horman &lt;horms@verge.net.au&gt;
Signed-off-by: Pablo Neira Ayuso &lt;pablo@netfilter.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 7980d2eabde82be86c5be18aa3d07e88ec13c6a1 ]

fq qdisc requires tstamp to be cleared in forwarding path

Reported-by: Evgeny B &lt;abt-admin@mail.ru&gt;
Link: https://bugzilla.kernel.org/show_bug.cgi?id=209427
Suggested-by: Eric Dumazet &lt;eric.dumazet@gmail.com&gt;
Fixes: 8203e2d844d3 ("net: clear skb-&gt;tstamp in forwarding paths")
Fixes: fb420d5d91c1 ("tcp/fq: move back to CLOCK_MONOTONIC")
Fixes: 80b14dee2bea ("net: Add a new socket option for a future transmit time.")
Signed-off-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Reviewed-by: Simon Horman &lt;horms@verge.net.au&gt;
Signed-off-by: Pablo Neira Ayuso &lt;pablo@netfilter.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ipvs: allow connection reuse for unconfirmed conntrack</title>
<updated>2020-08-19T06:26:31+00:00</updated>
<author>
<name>Julian Anastasov</name>
<email>ja@ssi.bg</email>
</author>
<published>2020-07-01T15:17:19+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=101df88a583759bd151bc770c7fc3390f6e317df'/>
<id>101df88a583759bd151bc770c7fc3390f6e317df</id>
<content type='text'>
[ Upstream commit f0a5e4d7a594e0fe237d3dfafb069bb82f80f42f ]

YangYuxi is reporting that connection reuse
is causing one-second delay when SYN hits
existing connection in TIME_WAIT state.
Such delay was added to give time to expire
both the IPVS connection and the corresponding
conntrack. This was considered a rare case
at that time but it is causing problem for
some environments such as Kubernetes.

As nf_conntrack_tcp_packet() can decide to
release the conntrack in TIME_WAIT state and
to replace it with a fresh NEW conntrack, we
can use this to allow rescheduling just by
tuning our check: if the conntrack is
confirmed we can not schedule it to different
real server and the one-second delay still
applies but if new conntrack was created,
we are free to select new real server without
any delays.

YangYuxi lists some of the problem reports:

- One second connection delay in masquerading mode:
https://marc.info/?t=151683118100004&amp;r=1&amp;w=2

- IPVS low throughput #70747
https://github.com/kubernetes/kubernetes/issues/70747

- Apache Bench can fill up ipvs service proxy in seconds #544
https://github.com/cloudnativelabs/kube-router/issues/544

- Additional 1s latency in `host -&gt; service IP -&gt; pod`
https://github.com/kubernetes/kubernetes/issues/90854

Fixes: f719e3754ee2 ("ipvs: drop first packet to redirect conntrack")
Co-developed-by: YangYuxi &lt;yx.atom1@gmail.com&gt;
Signed-off-by: YangYuxi &lt;yx.atom1@gmail.com&gt;
Signed-off-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Reviewed-by: Simon Horman &lt;horms@verge.net.au&gt;
Signed-off-by: Pablo Neira Ayuso &lt;pablo@netfilter.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit f0a5e4d7a594e0fe237d3dfafb069bb82f80f42f ]

YangYuxi is reporting that connection reuse
is causing one-second delay when SYN hits
existing connection in TIME_WAIT state.
Such delay was added to give time to expire
both the IPVS connection and the corresponding
conntrack. This was considered a rare case
at that time but it is causing problem for
some environments such as Kubernetes.

As nf_conntrack_tcp_packet() can decide to
release the conntrack in TIME_WAIT state and
to replace it with a fresh NEW conntrack, we
can use this to allow rescheduling just by
tuning our check: if the conntrack is
confirmed we can not schedule it to different
real server and the one-second delay still
applies but if new conntrack was created,
we are free to select new real server without
any delays.

YangYuxi lists some of the problem reports:

- One second connection delay in masquerading mode:
https://marc.info/?t=151683118100004&amp;r=1&amp;w=2

- IPVS low throughput #70747
https://github.com/kubernetes/kubernetes/issues/70747

- Apache Bench can fill up ipvs service proxy in seconds #544
https://github.com/cloudnativelabs/kube-router/issues/544

- Additional 1s latency in `host -&gt; service IP -&gt; pod`
https://github.com/kubernetes/kubernetes/issues/90854

Fixes: f719e3754ee2 ("ipvs: drop first packet to redirect conntrack")
Co-developed-by: YangYuxi &lt;yx.atom1@gmail.com&gt;
Signed-off-by: YangYuxi &lt;yx.atom1@gmail.com&gt;
Signed-off-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Reviewed-by: Simon Horman &lt;horms@verge.net.au&gt;
Signed-off-by: Pablo Neira Ayuso &lt;pablo@netfilter.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ipvs: fix the connection sync failed in some cases</title>
<updated>2020-07-21T23:21:34+00:00</updated>
<author>
<name>guodeqing</name>
<email>geffrey.guo@huawei.com</email>
</author>
<published>2020-07-16T08:12:08+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=8210e344ccb798c672ab237b1a4f241bda08909b'/>
<id>8210e344ccb798c672ab237b1a4f241bda08909b</id>
<content type='text'>
The sync_thread_backup only checks sk_receive_queue is empty or not,
there is a situation which cannot sync the connection entries when
sk_receive_queue is empty and sk_rmem_alloc is larger than sk_rcvbuf,
the sync packets are dropped in __udp_enqueue_schedule_skb, this is
because the packets in reader_queue is not read, so the rmem is
not reclaimed.

Here I add the check of whether the reader_queue of the udp sock is
empty or not to solve this problem.

Fixes: 2276f58ac589 ("udp: use a separate rx queue for packet reception")
Reported-by: zhouxudong &lt;zhouxudong8@huawei.com&gt;
Signed-off-by: guodeqing &lt;geffrey.guo@huawei.com&gt;
Acked-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Signed-off-by: Pablo Neira Ayuso &lt;pablo@netfilter.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The sync_thread_backup only checks sk_receive_queue is empty or not,
there is a situation which cannot sync the connection entries when
sk_receive_queue is empty and sk_rmem_alloc is larger than sk_rcvbuf,
the sync packets are dropped in __udp_enqueue_schedule_skb, this is
because the packets in reader_queue is not read, so the rmem is
not reclaimed.

Here I add the check of whether the reader_queue of the udp sock is
empty or not to solve this problem.

Fixes: 2276f58ac589 ("udp: use a separate rx queue for packet reception")
Reported-by: zhouxudong &lt;zhouxudong8@huawei.com&gt;
Signed-off-by: guodeqing &lt;geffrey.guo@huawei.com&gt;
Acked-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Signed-off-by: Pablo Neira Ayuso &lt;pablo@netfilter.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>treewide: replace '---help---' in Kconfig files with 'help'</title>
<updated>2020-06-13T16:57:21+00:00</updated>
<author>
<name>Masahiro Yamada</name>
<email>masahiroy@kernel.org</email>
</author>
<published>2020-06-13T16:50:22+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=a7f7f6248d9740d710fd6bd190293fe5e16410ac'/>
<id>a7f7f6248d9740d710fd6bd190293fe5e16410ac</id>
<content type='text'>
Since commit 84af7a6194e4 ("checkpatch: kconfig: prefer 'help' over
'---help---'"), the number of '---help---' has been gradually
decreasing, but there are still more than 2400 instances.

This commit finishes the conversion. While I touched the lines,
I also fixed the indentation.

There are a variety of indentation styles found.

  a) 4 spaces + '---help---'
  b) 7 spaces + '---help---'
  c) 8 spaces + '---help---'
  d) 1 space + 1 tab + '---help---'
  e) 1 tab + '---help---'    (correct indentation)
  f) 1 tab + 1 space + '---help---'
  g) 1 tab + 2 spaces + '---help---'

In order to convert all of them to 1 tab + 'help', I ran the
following commend:

  $ find . -name 'Kconfig*' | xargs sed -i 's/^[[:space:]]*---help---/\thelp/'

Signed-off-by: Masahiro Yamada &lt;masahiroy@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Since commit 84af7a6194e4 ("checkpatch: kconfig: prefer 'help' over
'---help---'"), the number of '---help---' has been gradually
decreasing, but there are still more than 2400 instances.

This commit finishes the conversion. While I touched the lines,
I also fixed the indentation.

There are a variety of indentation styles found.

  a) 4 spaces + '---help---'
  b) 7 spaces + '---help---'
  c) 8 spaces + '---help---'
  d) 1 space + 1 tab + '---help---'
  e) 1 tab + '---help---'    (correct indentation)
  f) 1 tab + 1 space + '---help---'
  g) 1 tab + 2 spaces + '---help---'

In order to convert all of them to 1 tab + 'help', I ran the
following commend:

  $ find . -name 'Kconfig*' | xargs sed -i 's/^[[:space:]]*---help---/\thelp/'

Signed-off-by: Masahiro Yamada &lt;masahiroy@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>sysctl: pass kernel pointers to -&gt;proc_handler</title>
<updated>2020-04-27T06:07:40+00:00</updated>
<author>
<name>Christoph Hellwig</name>
<email>hch@lst.de</email>
</author>
<published>2020-04-24T06:43:38+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=32927393dc1ccd60fb2bdc05b9e8e88753761469'/>
<id>32927393dc1ccd60fb2bdc05b9e8e88753761469</id>
<content type='text'>
Instead of having all the sysctl handlers deal with user pointers, which
is rather hairy in terms of the BPF interaction, copy the input to and
from  userspace in common code.  This also means that the strings are
always NUL-terminated by the common code, making the API a little bit
safer.

As most handler just pass through the data to one of the common handlers
a lot of the changes are mechnical.

Signed-off-by: Christoph Hellwig &lt;hch@lst.de&gt;
Acked-by: Andrey Ignatov &lt;rdna@fb.com&gt;
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Instead of having all the sysctl handlers deal with user pointers, which
is rather hairy in terms of the BPF interaction, copy the input to and
from  userspace in common code.  This also means that the strings are
always NUL-terminated by the common code, making the API a little bit
safer.

As most handler just pass through the data to one of the common handlers
a lot of the changes are mechnical.

Signed-off-by: Christoph Hellwig &lt;hch@lst.de&gt;
Acked-by: Andrey Ignatov &lt;rdna@fb.com&gt;
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ipvs: fix uninitialized variable warning</title>
<updated>2020-03-30T19:17:53+00:00</updated>
<author>
<name>Haishuang Yan</name>
<email>yanhaishuang@cmss.chinamobile.com</email>
</author>
<published>2020-03-30T03:20:15+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=e19680f8347ec0e335ae90801fbe42d85d7b385a'/>
<id>e19680f8347ec0e335ae90801fbe42d85d7b385a</id>
<content type='text'>
If outer_proto is not set, GCC warning as following:

In file included from net/netfilter/ipvs/ip_vs_core.c:52:
net/netfilter/ipvs/ip_vs_core.c: In function 'ip_vs_in_icmp':
include/net/ip_vs.h:233:4: warning: 'outer_proto' may be used uninitialized in this function [-Wmaybe-uninitialized]
 233 |    printk(KERN_DEBUG pr_fmt(msg), ##__VA_ARGS__); \
     |    ^~~~~~
net/netfilter/ipvs/ip_vs_core.c:1666:8: note: 'outer_proto' was declared here
1666 |  char *outer_proto;
     |        ^~~~~~~~~~~

Fixes: 73348fed35d0 ("ipvs: optimize tunnel dumps for icmp errors")
Signed-off-by: Haishuang Yan &lt;yanhaishuang@cmss.chinamobile.com&gt;
Acked-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Signed-off-by: Pablo Neira Ayuso &lt;pablo@netfilter.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
If outer_proto is not set, GCC warning as following:

In file included from net/netfilter/ipvs/ip_vs_core.c:52:
net/netfilter/ipvs/ip_vs_core.c: In function 'ip_vs_in_icmp':
include/net/ip_vs.h:233:4: warning: 'outer_proto' may be used uninitialized in this function [-Wmaybe-uninitialized]
 233 |    printk(KERN_DEBUG pr_fmt(msg), ##__VA_ARGS__); \
     |    ^~~~~~
net/netfilter/ipvs/ip_vs_core.c:1666:8: note: 'outer_proto' was declared here
1666 |  char *outer_proto;
     |        ^~~~~~~~~~~

Fixes: 73348fed35d0 ("ipvs: optimize tunnel dumps for icmp errors")
Signed-off-by: Haishuang Yan &lt;yanhaishuang@cmss.chinamobile.com&gt;
Acked-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Signed-off-by: Pablo Neira Ayuso &lt;pablo@netfilter.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ipvs: optimize tunnel dumps for icmp errors</title>
<updated>2020-03-27T17:31:01+00:00</updated>
<author>
<name>Haishuang Yan</name>
<email>yanhaishuang@cmss.chinamobile.com</email>
</author>
<published>2020-03-15T13:25:41+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=73348fed35d023e998cbd303a28400f2c0ec30a3'/>
<id>73348fed35d023e998cbd303a28400f2c0ec30a3</id>
<content type='text'>
After strip GRE/UDP tunnel header for icmp errors, it's better to show
"GRE/UDP" instead of "IPIP" in debug message.

Signed-off-by: Haishuang Yan &lt;yanhaishuang@cmss.chinamobile.com&gt;
Acked-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Signed-off-by: Pablo Neira Ayuso &lt;pablo@netfilter.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
After strip GRE/UDP tunnel header for icmp errors, it's better to show
"GRE/UDP" instead of "IPIP" in debug message.

Signed-off-by: Haishuang Yan &lt;yanhaishuang@cmss.chinamobile.com&gt;
Acked-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Signed-off-by: Pablo Neira Ayuso &lt;pablo@netfilter.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ipvs: fix spelling mistake "to" -&gt; "too"</title>
<updated>2020-01-24T07:12:06+00:00</updated>
<author>
<name>Colin Ian King</name>
<email>colin.king@canonical.com</email>
</author>
<published>2020-01-23T00:43:28+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=971485a0d681954677ec6a7ed990359aceabc06e'/>
<id>971485a0d681954677ec6a7ed990359aceabc06e</id>
<content type='text'>
There is a spelling mistake in a IP_VS_ERR_RL message. Fix it.

Signed-off-by: Colin Ian King &lt;colin.king@canonical.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
There is a spelling mistake in a IP_VS_ERR_RL message. Fix it.

Signed-off-by: Colin Ian King &lt;colin.king@canonical.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: add bool confirm_neigh parameter for dst_ops.update_pmtu</title>
<updated>2019-12-25T06:28:54+00:00</updated>
<author>
<name>Hangbin Liu</name>
<email>liuhangbin@gmail.com</email>
</author>
<published>2019-12-22T02:51:09+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=bd085ef678b2cc8c38c105673dfe8ff8f5ec0c57'/>
<id>bd085ef678b2cc8c38c105673dfe8ff8f5ec0c57</id>
<content type='text'>
The MTU update code is supposed to be invoked in response to real
networking events that update the PMTU. In IPv6 PMTU update function
__ip6_rt_update_pmtu() we called dst_confirm_neigh() to update neighbor
confirmed time.

But for tunnel code, it will call pmtu before xmit, like:
  - tnl_update_pmtu()
    - skb_dst_update_pmtu()
      - ip6_rt_update_pmtu()
        - __ip6_rt_update_pmtu()
          - dst_confirm_neigh()

If the tunnel remote dst mac address changed and we still do the neigh
confirm, we will not be able to update neigh cache and ping6 remote
will failed.

So for this ip_tunnel_xmit() case, _EVEN_ if the MTU is changed, we
should not be invoking dst_confirm_neigh() as we have no evidence
of successful two-way communication at this point.

On the other hand it is also important to keep the neigh reachability fresh
for TCP flows, so we cannot remove this dst_confirm_neigh() call.

To fix the issue, we have to add a new bool parameter for dst_ops.update_pmtu
to choose whether we should do neigh update or not. I will add the parameter
in this patch and set all the callers to true to comply with the previous
way, and fix the tunnel code one by one on later patches.

v5: No change.
v4: No change.
v3: Do not remove dst_confirm_neigh, but add a new bool parameter in
    dst_ops.update_pmtu to control whether we should do neighbor confirm.
    Also split the big patch to small ones for each area.
v2: Remove dst_confirm_neigh in __ip6_rt_update_pmtu.

Suggested-by: David Miller &lt;davem@davemloft.net&gt;
Reviewed-by: Guillaume Nault &lt;gnault@redhat.com&gt;
Acked-by: David Ahern &lt;dsahern@gmail.com&gt;
Signed-off-by: Hangbin Liu &lt;liuhangbin@gmail.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
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The MTU update code is supposed to be invoked in response to real
networking events that update the PMTU. In IPv6 PMTU update function
__ip6_rt_update_pmtu() we called dst_confirm_neigh() to update neighbor
confirmed time.

But for tunnel code, it will call pmtu before xmit, like:
  - tnl_update_pmtu()
    - skb_dst_update_pmtu()
      - ip6_rt_update_pmtu()
        - __ip6_rt_update_pmtu()
          - dst_confirm_neigh()

If the tunnel remote dst mac address changed and we still do the neigh
confirm, we will not be able to update neigh cache and ping6 remote
will failed.

So for this ip_tunnel_xmit() case, _EVEN_ if the MTU is changed, we
should not be invoking dst_confirm_neigh() as we have no evidence
of successful two-way communication at this point.

On the other hand it is also important to keep the neigh reachability fresh
for TCP flows, so we cannot remove this dst_confirm_neigh() call.

To fix the issue, we have to add a new bool parameter for dst_ops.update_pmtu
to choose whether we should do neigh update or not. I will add the parameter
in this patch and set all the callers to true to comply with the previous
way, and fix the tunnel code one by one on later patches.

v5: No change.
v4: No change.
v3: Do not remove dst_confirm_neigh, but add a new bool parameter in
    dst_ops.update_pmtu to control whether we should do neighbor confirm.
    Also split the big patch to small ones for each area.
v2: Remove dst_confirm_neigh in __ip6_rt_update_pmtu.

Suggested-by: David Miller &lt;davem@davemloft.net&gt;
Reviewed-by: Guillaume Nault &lt;gnault@redhat.com&gt;
Acked-by: David Ahern &lt;dsahern@gmail.com&gt;
Signed-off-by: Hangbin Liu &lt;liuhangbin@gmail.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
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