<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/net/core/dst.c, branch linux-4.19.y</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>ipv6: remove max_size check inline with ipv4</title>
<updated>2024-01-15T17:23:44+00:00</updated>
<author>
<name>Jon Maxwell</name>
<email>jmaxwell37@gmail.com</email>
</author>
<published>2024-01-13T00:53:08+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=95372b040ae689293c6863b90049f1af68410c8b'/>
<id>95372b040ae689293c6863b90049f1af68410c8b</id>
<content type='text'>
commit af6d10345ca76670c1b7c37799f0d5576ccef277 upstream.

In ip6_dst_gc() replace:

  if (entries &gt; gc_thresh)

With:

  if (entries &gt; ops-&gt;gc_thresh)

Sending Ipv6 packets in a loop via a raw socket triggers an issue where a
route is cloned by ip6_rt_cache_alloc() for each packet sent. This quickly
consumes the Ipv6 max_size threshold which defaults to 4096 resulting in
these warnings:

[1]   99.187805] dst_alloc: 7728 callbacks suppressed
[2] Route cache is full: consider increasing sysctl net.ipv6.route.max_size.
.
.
[300] Route cache is full: consider increasing sysctl net.ipv6.route.max_size.

When this happens the packet is dropped and sendto() gets a network is
unreachable error:

remaining pkt 200557 errno 101
remaining pkt 196462 errno 101
.
.
remaining pkt 126821 errno 101

Implement David Aherns suggestion to remove max_size check seeing that Ipv6
has a GC to manage memory usage. Ipv4 already does not check max_size.

Here are some memory comparisons for Ipv4 vs Ipv6 with the patch:

Test by running 5 instances of a program that sends UDP packets to a raw
socket 5000000 times. Compare Ipv4 and Ipv6 performance with a similar
program.

Ipv4:

Before test:

MemFree:        29427108 kB
Slab:             237612 kB

ip6_dst_cache       1912   2528    256   32    2 : tunables    0    0    0
xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
ip_dst_cache        2881   3990    192   42    2 : tunables    0    0    0

During test:

MemFree:        29417608 kB
Slab:             247712 kB

ip6_dst_cache       1912   2528    256   32    2 : tunables    0    0    0
xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
ip_dst_cache       44394  44394    192   42    2 : tunables    0    0    0

After test:

MemFree:        29422308 kB
Slab:             238104 kB

ip6_dst_cache       1912   2528    256   32    2 : tunables    0    0    0
xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
ip_dst_cache        3048   4116    192   42    2 : tunables    0    0    0

Ipv6 with patch:

Errno 101 errors are not observed anymore with the patch.

Before test:

MemFree:        29422308 kB
Slab:             238104 kB

ip6_dst_cache       1912   2528    256   32    2 : tunables    0    0    0
xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
ip_dst_cache        3048   4116    192   42    2 : tunables    0    0    0

During Test:

MemFree:        29431516 kB
Slab:             240940 kB

ip6_dst_cache      11980  12064    256   32    2 : tunables    0    0    0
xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
ip_dst_cache        3048   4116    192   42    2 : tunables    0    0    0

After Test:

MemFree:        29441816 kB
Slab:             238132 kB

ip6_dst_cache       1902   2432    256   32    2 : tunables    0    0    0
xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
ip_dst_cache        3048   4116    192   42    2 : tunables    0    0    0

Tested-by: Andrea Mayer &lt;andrea.mayer@uniroma2.it&gt;
Signed-off-by: Jon Maxwell &lt;jmaxwell37@gmail.com&gt;
Reviewed-by: David Ahern &lt;dsahern@kernel.org&gt;
Link: https://lore.kernel.org/r/20230112012532.311021-1-jmaxwell37@gmail.com
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
Signed-off-by: Suraj Jitindar Singh &lt;surajjs@amazon.com&gt;
Cc: &lt;stable@vger.kernel.org&gt; # 4.19.x
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit af6d10345ca76670c1b7c37799f0d5576ccef277 upstream.

In ip6_dst_gc() replace:

  if (entries &gt; gc_thresh)

With:

  if (entries &gt; ops-&gt;gc_thresh)

Sending Ipv6 packets in a loop via a raw socket triggers an issue where a
route is cloned by ip6_rt_cache_alloc() for each packet sent. This quickly
consumes the Ipv6 max_size threshold which defaults to 4096 resulting in
these warnings:

[1]   99.187805] dst_alloc: 7728 callbacks suppressed
[2] Route cache is full: consider increasing sysctl net.ipv6.route.max_size.
.
.
[300] Route cache is full: consider increasing sysctl net.ipv6.route.max_size.

When this happens the packet is dropped and sendto() gets a network is
unreachable error:

remaining pkt 200557 errno 101
remaining pkt 196462 errno 101
.
.
remaining pkt 126821 errno 101

Implement David Aherns suggestion to remove max_size check seeing that Ipv6
has a GC to manage memory usage. Ipv4 already does not check max_size.

Here are some memory comparisons for Ipv4 vs Ipv6 with the patch:

Test by running 5 instances of a program that sends UDP packets to a raw
socket 5000000 times. Compare Ipv4 and Ipv6 performance with a similar
program.

Ipv4:

Before test:

MemFree:        29427108 kB
Slab:             237612 kB

ip6_dst_cache       1912   2528    256   32    2 : tunables    0    0    0
xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
ip_dst_cache        2881   3990    192   42    2 : tunables    0    0    0

During test:

MemFree:        29417608 kB
Slab:             247712 kB

ip6_dst_cache       1912   2528    256   32    2 : tunables    0    0    0
xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
ip_dst_cache       44394  44394    192   42    2 : tunables    0    0    0

After test:

MemFree:        29422308 kB
Slab:             238104 kB

ip6_dst_cache       1912   2528    256   32    2 : tunables    0    0    0
xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
ip_dst_cache        3048   4116    192   42    2 : tunables    0    0    0

Ipv6 with patch:

Errno 101 errors are not observed anymore with the patch.

Before test:

MemFree:        29422308 kB
Slab:             238104 kB

ip6_dst_cache       1912   2528    256   32    2 : tunables    0    0    0
xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
ip_dst_cache        3048   4116    192   42    2 : tunables    0    0    0

During Test:

MemFree:        29431516 kB
Slab:             240940 kB

ip6_dst_cache      11980  12064    256   32    2 : tunables    0    0    0
xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
ip_dst_cache        3048   4116    192   42    2 : tunables    0    0    0

After Test:

MemFree:        29441816 kB
Slab:             238132 kB

ip6_dst_cache       1902   2432    256   32    2 : tunables    0    0    0
xfrm_dst_cache         0      0    320   25    2 : tunables    0    0    0
ip_dst_cache        3048   4116    192   42    2 : tunables    0    0    0

Tested-by: Andrea Mayer &lt;andrea.mayer@uniroma2.it&gt;
Signed-off-by: Jon Maxwell &lt;jmaxwell37@gmail.com&gt;
Reviewed-by: David Ahern &lt;dsahern@kernel.org&gt;
Link: https://lore.kernel.org/r/20230112012532.311021-1-jmaxwell37@gmail.com
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
Signed-off-by: Suraj Jitindar Singh &lt;surajjs@amazon.com&gt;
Cc: &lt;stable@vger.kernel.org&gt; # 4.19.x
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net/dst: use a smaller percpu_counter batch for dst entries accounting</title>
<updated>2024-01-15T17:23:44+00:00</updated>
<author>
<name>Eric Dumazet</name>
<email>edumazet@google.com</email>
</author>
<published>2024-01-13T00:53:06+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=9635bd0a5296e2e725c6b33e530d0ef582e2f64e'/>
<id>9635bd0a5296e2e725c6b33e530d0ef582e2f64e</id>
<content type='text'>
commit cf86a086a18095e33e0637cb78cda1fcf5280852 upstream.

percpu_counter_add() uses a default batch size which is quite big
on platforms with 256 cpus. (2*256 -&gt; 512)

This means dst_entries_get_fast() can be off by +/- 2*(nr_cpus^2)
(131072 on servers with 256 cpus)

Reduce the batch size to something more reasonable, and
add logic to ip6_dst_gc() to call dst_entries_get_slow()
before calling the _very_ expensive fib6_run_gc() function.

Signed-off-by: Eric Dumazet &lt;edumazet@google.com&gt;
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
Signed-off-by: Suraj Jitindar Singh &lt;surajjs@amazon.com&gt;
Cc: &lt;stable@vger.kernel.org&gt; # 4.19.x
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit cf86a086a18095e33e0637cb78cda1fcf5280852 upstream.

percpu_counter_add() uses a default batch size which is quite big
on platforms with 256 cpus. (2*256 -&gt; 512)

This means dst_entries_get_fast() can be off by +/- 2*(nr_cpus^2)
(131072 on servers with 256 cpus)

Reduce the batch size to something more reasonable, and
add logic to ip6_dst_gc() to call dst_entries_get_slow()
before calling the _very_ expensive fib6_run_gc() function.

Signed-off-by: Eric Dumazet &lt;edumazet@google.com&gt;
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
Signed-off-by: Suraj Jitindar Singh &lt;surajjs@amazon.com&gt;
Cc: &lt;stable@vger.kernel.org&gt; # 4.19.x
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: add a route cache full diagnostic message</title>
<updated>2024-01-15T17:23:44+00:00</updated>
<author>
<name>Peter Oskolkov</name>
<email>posk@google.com</email>
</author>
<published>2024-01-13T00:53:05+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=47468fae2704151503214f4d4327c164118247fd'/>
<id>47468fae2704151503214f4d4327c164118247fd</id>
<content type='text'>
commit 22c2ad616b74f3de2256b242572ab449d031d941 upstream.

In some testing scenarios, dst/route cache can fill up so quickly
that even an explicit GC call occasionally fails to clean it up. This leads
to sporadically failing calls to dst_alloc and "network unreachable" errors
to the user, which is confusing.

This patch adds a diagnostic message to make the cause of the failure
easier to determine.

Signed-off-by: Peter Oskolkov &lt;posk@google.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Suraj Jitindar Singh &lt;surajjs@amazon.com&gt;
Cc: &lt;stable@vger.kernel.org&gt; # 4.19.x
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 22c2ad616b74f3de2256b242572ab449d031d941 upstream.

In some testing scenarios, dst/route cache can fill up so quickly
that even an explicit GC call occasionally fails to clean it up. This leads
to sporadically failing calls to dst_alloc and "network unreachable" errors
to the user, which is confusing.

This patch adds a diagnostic message to make the cause of the failure
easier to determine.

Signed-off-by: Peter Oskolkov &lt;posk@google.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Suraj Jitindar Singh &lt;surajjs@amazon.com&gt;
Cc: &lt;stable@vger.kernel.org&gt; # 4.19.x
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>netfilter: nf_tables: add tunnel support</title>
<updated>2018-08-03T19:12:12+00:00</updated>
<author>
<name>Pablo Neira Ayuso</name>
<email>pablo@netfilter.org</email>
</author>
<published>2018-08-02T18:51:39+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=af308b94a2a4a5a27bec9028354c4df444a7c8ba'/>
<id>af308b94a2a4a5a27bec9028354c4df444a7c8ba</id>
<content type='text'>
This patch implements the tunnel object type that can be used to
configure tunnels via metadata template through the existing lightweight
API from the ingress path.

Signed-off-by: Pablo Neira Ayuso &lt;pablo@netfilter.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This patch implements the tunnel object type that can be used to
configure tunnels via metadata template through the existing lightweight
API from the ingress path.

Signed-off-by: Pablo Neira Ayuso &lt;pablo@netfilter.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net/ipv6: move metrics from dst to rt6_info</title>
<updated>2018-04-18T03:41:16+00:00</updated>
<author>
<name>David Ahern</name>
<email>dsahern@gmail.com</email>
</author>
<published>2018-04-18T00:33:16+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=d4ead6b34b67fd711639324b6465a050bcb197d4'/>
<id>d4ead6b34b67fd711639324b6465a050bcb197d4</id>
<content type='text'>
Similar to IPv4, add fib metrics to the fib struct, which at the moment
is rt6_info. Will be moved to fib6_info in a later patch. Copy metrics
into dst by reference using refcount.

To make the transition:
- add dst_metrics to rt6_info. Default to dst_default_metrics if no
  metrics are passed during route add. No need for a separate pmtu
  entry; it can reference the MTU slot in fib6_metrics

- ip6_convert_metrics allocates memory in the FIB entry and uses
  ip_metrics_convert to copy from netlink attribute to metrics entry

- the convert metrics call is done in ip6_route_info_create simplifying
  the route add path
  + fib6_commit_metrics and fib6_copy_metrics and the temporary
    mx6_config are no longer needed

- add fib6_metric_set helper to change the value of a metric in the
  fib entry since dst_metric_set can no longer be used

- cow_metrics for IPv6 can drop to dst_cow_metrics_generic

- rt6_dst_from_metrics_check is no longer needed

- rt6_fill_node needs the FIB entry and dst as separate arguments to
  keep compatibility with existing output. Current dst address is
  renamed to dest.
  (to be consistent with IPv4 rt6_fill_node really should be split
  into 2 functions similar to fib_dump_info and rt_fill_info)

- rt6_fill_node no longer needs the temporary metrics variable

Signed-off-by: David Ahern &lt;dsahern@gmail.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>
Similar to IPv4, add fib metrics to the fib struct, which at the moment
is rt6_info. Will be moved to fib6_info in a later patch. Copy metrics
into dst by reference using refcount.

To make the transition:
- add dst_metrics to rt6_info. Default to dst_default_metrics if no
  metrics are passed during route add. No need for a separate pmtu
  entry; it can reference the MTU slot in fib6_metrics

- ip6_convert_metrics allocates memory in the FIB entry and uses
  ip_metrics_convert to copy from netlink attribute to metrics entry

- the convert metrics call is done in ip6_route_info_create simplifying
  the route add path
  + fib6_commit_metrics and fib6_copy_metrics and the temporary
    mx6_config are no longer needed

- add fib6_metric_set helper to change the value of a metric in the
  fib entry since dst_metric_set can no longer be used

- cow_metrics for IPv6 can drop to dst_cow_metrics_generic

- rt6_dst_from_metrics_check is no longer needed

- rt6_fill_node needs the FIB entry and dst as separate arguments to
  keep compatibility with existing output. Current dst address is
  renamed to dest.
  (to be consistent with IPv4 rt6_fill_node really should be split
  into 2 functions similar to fib_dump_info and rt_fill_info)

- rt6_fill_node no longer needs the temporary metrics variable

Signed-off-by: David Ahern &lt;dsahern@gmail.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: Remove dst-&gt;next</title>
<updated>2017-11-30T14:54:27+00:00</updated>
<author>
<name>David Miller</name>
<email>davem@davemloft.net</email>
</author>
<published>2017-11-28T20:41:07+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=7149f813d12d92ba9abcf49026f7cebc3d55c426'/>
<id>7149f813d12d92ba9abcf49026f7cebc3d55c426</id>
<content type='text'>
There are no more users.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
There are no more users.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>xfrm: Move dst-&gt;path into struct xfrm_dst</title>
<updated>2017-11-30T14:54:26+00:00</updated>
<author>
<name>David Miller</name>
<email>davem@davemloft.net</email>
</author>
<published>2017-11-28T20:40:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=0f6c480f23f49b53644b383c5554e579498347f3'/>
<id>0f6c480f23f49b53644b383c5554e579498347f3</id>
<content type='text'>
The first member of an IPSEC route bundle chain sets it's dst-&gt;path to
the underlying ipv4/ipv6 route that carries the bundle.

Stated another way, if one were to follow the xfrm_dst-&gt;child chain of
the bundle, the final non-NULL pointer would be the path and point to
either an ipv4 or an ipv6 route.

This is largely used to make sure that PMTU events propagate down to
the correct ipv4 or ipv6 route.

When we don't have the top of an IPSEC bundle 'dst-&gt;path == dst'.

Move it down into xfrm_dst and key off of dst-&gt;xfrm.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The first member of an IPSEC route bundle chain sets it's dst-&gt;path to
the underlying ipv4/ipv6 route that carries the bundle.

Stated another way, if one were to follow the xfrm_dst-&gt;child chain of
the bundle, the final non-NULL pointer would be the path and point to
either an ipv4 or an ipv6 route.

This is largely used to make sure that PMTU events propagate down to
the correct ipv4 or ipv6 route.

When we don't have the top of an IPSEC bundle 'dst-&gt;path == dst'.

Move it down into xfrm_dst and key off of dst-&gt;xfrm.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ipv6: Move dst-&gt;from into struct rt6_info.</title>
<updated>2017-11-30T14:54:26+00:00</updated>
<author>
<name>David Miller</name>
<email>davem@davemloft.net</email>
</author>
<published>2017-11-28T20:40:40+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=3a2232e92e87166a8a5113e918b8c7b7bdce4d83'/>
<id>3a2232e92e87166a8a5113e918b8c7b7bdce4d83</id>
<content type='text'>
The dst-&gt;from value is only used by ipv6 routes to track where
a route "came from".

Any time we clone or copy a core ipv6 route in the ipv6 routing
tables, we have the copy/clone's -&gt;from point to the base route.

This is used to handle route expiration properly.

Only ipv6 uses this mechanism, and only ipv6 code references
it.  So it is safe to move it into rt6_info.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The dst-&gt;from value is only used by ipv6 routes to track where
a route "came from".

Any time we clone or copy a core ipv6 route in the ipv6 routing
tables, we have the copy/clone's -&gt;from point to the base route.

This is used to handle route expiration properly.

Only ipv6 uses this mechanism, and only ipv6 code references
it.  So it is safe to move it into rt6_info.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>xfrm: Move child route linkage into xfrm_dst.</title>
<updated>2017-11-30T14:54:26+00:00</updated>
<author>
<name>David Miller</name>
<email>davem@davemloft.net</email>
</author>
<published>2017-11-28T20:45:44+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=b6ca8bd5a9198c70c48297390723e4e56bd6e879'/>
<id>b6ca8bd5a9198c70c48297390723e4e56bd6e879</id>
<content type='text'>
XFRM bundle child chains look like this:

	xdst1 --&gt; xdst2 --&gt; xdst3 --&gt; path_dst

All of xdstN are xfrm_dst objects and xdst-&gt;u.dst.xfrm is non-NULL.
The final child pointer in the chain, here called 'path_dst', is some
other kind of route such as an ipv4 or ipv6 one.

The xfrm output path pops routes, one at a time, via the child
pointer, until we hit one which has a dst-&gt;xfrm pointer which
is NULL.

We can easily preserve the above mechanisms with child sitting
only in the xfrm_dst structure.  All children in the chain
before we break out of the xfrm_output() loop have dst-&gt;xfrm
non-NULL and are therefore xfrm_dst objects.

Since we break out of the loop when we find dst-&gt;xfrm NULL, we
will not try to dereference 'dst' as if it were an xfrm_dst.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
XFRM bundle child chains look like this:

	xdst1 --&gt; xdst2 --&gt; xdst3 --&gt; path_dst

All of xdstN are xfrm_dst objects and xdst-&gt;u.dst.xfrm is non-NULL.
The final child pointer in the chain, here called 'path_dst', is some
other kind of route such as an ipv4 or ipv6 one.

The xfrm output path pops routes, one at a time, via the child
pointer, until we hit one which has a dst-&gt;xfrm pointer which
is NULL.

We can easily preserve the above mechanisms with child sitting
only in the xfrm_dst structure.  All children in the chain
before we break out of the xfrm_output() loop have dst-&gt;xfrm
non-NULL and are therefore xfrm_dst objects.

Since we break out of the loop when we find dst-&gt;xfrm NULL, we
will not try to dereference 'dst' as if it were an xfrm_dst.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: Create and use new helper xfrm_dst_child().</title>
<updated>2017-11-30T14:54:25+00:00</updated>
<author>
<name>David Miller</name>
<email>davem@davemloft.net</email>
</author>
<published>2017-11-28T20:40:22+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=b92cf4aab8e688b1bd501ac2ac4f1b5c99601e3b'/>
<id>b92cf4aab8e688b1bd501ac2ac4f1b5c99601e3b</id>
<content type='text'>
Only IPSEC routes have a non-NULL dst-&gt;child pointer.  And IPSEC
routes are identified by a non-NULL dst-&gt;xfrm pointer.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Only IPSEC routes have a non-NULL dst-&gt;child pointer.  And IPSEC
routes are identified by a non-NULL dst-&gt;xfrm pointer.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
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