Patchwork [PATCHv2,net-next,3/3] xfrm: Add file to document IPsec corner case

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Submitter fan.du
Date Dec. 15, 2013, 9:19 a.m.
Message ID <1387099194-18540-4-git-send-email-fan.du@windriver.com>
Download mbox | patch
Permalink /patch/301334/
State Not Applicable
Delegated to: David Miller
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Comments

fan.du - Dec. 15, 2013, 9:19 a.m.
Create Documentation/networking/ipsec.txt to document IPsec
corner issues and other info, which will be useful when user
deploying IPsec.

Signed-off-by: Fan Du <fan.du@windriver.com>
---
 Documentation/networking/ipsec.txt |   40 ++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 Documentation/networking/ipsec.txt
Steffen Klassert - Dec. 16, 2013, 9:46 a.m.
On Sun, Dec 15, 2013 at 05:19:54PM +0800, Fan Du wrote:
> Create Documentation/networking/ipsec.txt to document IPsec
> corner issues and other info, which will be useful when user
> deploying IPsec.
> 
> Signed-off-by: Fan Du <fan.du@windriver.com>
> ---
>  Documentation/networking/ipsec.txt |   40 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
>  create mode 100644 Documentation/networking/ipsec.txt
> 
> diff --git a/Documentation/networking/ipsec.txt b/Documentation/networking/ipsec.txt
> new file mode 100644
> index 0000000..3b02806
> --- /dev/null
> +++ b/Documentation/networking/ipsec.txt
> @@ -0,0 +1,40 @@
> +
> +Here documents known IPsec corner cases which need to be keep in mind when
> +deploy various IPsec configuration in real world production environment.
> +
> +1. IPcomp: Small IP packet won't get compressed at sender, and failed on
> +	   policy check on receiver.
> +
> +Quote from RFC3173:
> +2.2. Non-Expansion Policy
> +
> +   If the total size of a compressed payload and the IPComp header, as
> +   defined in section 3, is not smaller than the size of the original
> +   payload, the IP datagram MUST be sent in the original non-compressed
> +   form.  To clarify: If an IP datagram is sent non-compressed, no
> +
> +   IPComp header is added to the datagram.  This policy ensures saving
> +   the decompression processing cycles and avoiding incurring IP
> +   datagram fragmentation when the expanded datagram is larger than the
> +   MTU.
> +
> +   Small IP datagrams are likely to expand as a result of compression.
> +   Therefore, a numeric threshold should be applied before compression,
> +   where IP datagrams of size smaller than the threshold are sent in the
> +   original form without attempting compression.  The numeric threshold
> +   is implementation dependent.
> +
> +Current IPComp implementation is indeed by the book, while as in practice
> +when sending non-compressed packet to the peer(whether or not packet len
> +is smaller than the threshold or the compressed len is large than original
> +packet len), the packet is dropped when checking the policy as this packet
> +matches the selector but not coming from any XFRM layer, i.e., with no
> +security path. Such naked packet will not eventually make it to upper layer.
> +The result is much more wired to the user when ping peer with different
> +payload length.
> +
> +One workaround is try to set "level use" for each policy if user observed
> +above scenario. The consequence of doing so is small packet(uncompressed)
> +will skip policy checking on receiver side.
> +
> +

Please remove the empty lines at the end of the file.

Also, it might be good to mention what the user exactly
has configure do to get a workaround.
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fan.du - Dec. 16, 2013, 9:58 a.m.
On 2013年12月16日 17:46, Steffen Klassert wrote:
> On Sun, Dec 15, 2013 at 05:19:54PM +0800, Fan Du wrote:
>> Create Documentation/networking/ipsec.txt to document IPsec
>> corner issues and other info, which will be useful when user
>> deploying IPsec.
>>
>> Signed-off-by: Fan Du<fan.du@windriver.com>
>> ---
>>   Documentation/networking/ipsec.txt |   40 ++++++++++++++++++++++++++++++++++++
>>   1 file changed, 40 insertions(+)
>>   create mode 100644 Documentation/networking/ipsec.txt
>>
>> diff --git a/Documentation/networking/ipsec.txt b/Documentation/networking/ipsec.txt
>> new file mode 100644
>> index 0000000..3b02806
>> --- /dev/null
>> +++ b/Documentation/networking/ipsec.txt
>> @@ -0,0 +1,40 @@
>> +
>> +Here documents known IPsec corner cases which need to be keep in mind when
>> +deploy various IPsec configuration in real world production environment.
>> +
>> +1. IPcomp: Small IP packet won't get compressed at sender, and failed on
>> +	   policy check on receiver.
>> +
>> +Quote from RFC3173:
>> +2.2. Non-Expansion Policy
>> +
>> +   If the total size of a compressed payload and the IPComp header, as
>> +   defined in section 3, is not smaller than the size of the original
>> +   payload, the IP datagram MUST be sent in the original non-compressed
>> +   form.  To clarify: If an IP datagram is sent non-compressed, no
>> +
>> +   IPComp header is added to the datagram.  This policy ensures saving
>> +   the decompression processing cycles and avoiding incurring IP
>> +   datagram fragmentation when the expanded datagram is larger than the
>> +   MTU.
>> +
>> +   Small IP datagrams are likely to expand as a result of compression.
>> +   Therefore, a numeric threshold should be applied before compression,
>> +   where IP datagrams of size smaller than the threshold are sent in the
>> +   original form without attempting compression.  The numeric threshold
>> +   is implementation dependent.
>> +
>> +Current IPComp implementation is indeed by the book, while as in practice
>> +when sending non-compressed packet to the peer(whether or not packet len
>> +is smaller than the threshold or the compressed len is large than original
>> +packet len), the packet is dropped when checking the policy as this packet
>> +matches the selector but not coming from any XFRM layer, i.e., with no
>> +security path. Such naked packet will not eventually make it to upper layer.
>> +The result is much more wired to the user when ping peer with different
>> +payload length.
>> +
>> +One workaround is try to set "level use" for each policy if user observed
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ here

>> +above scenario. The consequence of doing so is small packet(uncompressed)
>> +will skip policy checking on receiver side.
>> +
>> +
>
> Please remove the empty lines at the end of the file.
>
> Also, it might be good to mention what the user exactly
> has configure do to get a workaround.
     It's in above here..

Will fix while space error, sorry for such mistakes.
Steffen Klassert - Dec. 16, 2013, 10:06 a.m.
On Mon, Dec 16, 2013 at 05:58:50PM +0800, Fan Du wrote:
> 
> 
> On 2013年12月16日 17:46, Steffen Klassert wrote:
> >On Sun, Dec 15, 2013 at 05:19:54PM +0800, Fan Du wrote:
> >>+
> >>+One workaround is try to set "level use" for each policy if user observed
>                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ here
> 
> >>+above scenario. The consequence of doing so is small packet(uncompressed)
> >>+will skip policy checking on receiver side.
> >>+
> >>+
> >
> >Please remove the empty lines at the end of the file.
> >
> >Also, it might be good to mention what the user exactly
> >has configure do to get a workaround.
>     It's in above here..
> 

Ok.
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Patch

diff --git a/Documentation/networking/ipsec.txt b/Documentation/networking/ipsec.txt
new file mode 100644
index 0000000..3b02806
--- /dev/null
+++ b/Documentation/networking/ipsec.txt
@@ -0,0 +1,40 @@ 
+
+Here documents known IPsec corner cases which need to be keep in mind when
+deploy various IPsec configuration in real world production environment.
+
+1. IPcomp: Small IP packet won't get compressed at sender, and failed on
+	   policy check on receiver.
+
+Quote from RFC3173:
+2.2. Non-Expansion Policy
+
+   If the total size of a compressed payload and the IPComp header, as
+   defined in section 3, is not smaller than the size of the original
+   payload, the IP datagram MUST be sent in the original non-compressed
+   form.  To clarify: If an IP datagram is sent non-compressed, no
+
+   IPComp header is added to the datagram.  This policy ensures saving
+   the decompression processing cycles and avoiding incurring IP
+   datagram fragmentation when the expanded datagram is larger than the
+   MTU.
+
+   Small IP datagrams are likely to expand as a result of compression.
+   Therefore, a numeric threshold should be applied before compression,
+   where IP datagrams of size smaller than the threshold are sent in the
+   original form without attempting compression.  The numeric threshold
+   is implementation dependent.
+
+Current IPComp implementation is indeed by the book, while as in practice
+when sending non-compressed packet to the peer(whether or not packet len
+is smaller than the threshold or the compressed len is large than original
+packet len), the packet is dropped when checking the policy as this packet
+matches the selector but not coming from any XFRM layer, i.e., with no
+security path. Such naked packet will not eventually make it to upper layer.
+The result is much more wired to the user when ping peer with different
+payload length.
+
+One workaround is try to set "level use" for each policy if user observed
+above scenario. The consequence of doing so is small packet(uncompressed)
+will skip policy checking on receiver side.
+
+