[tcpm] Comments to draft-ietf-tcpm-tcp-edo-13

["D. Wythe" <[e-mail]>]

Hi all,

I am D. Wythe from Alibaba, currently conducting research on EDO. I 
would like to report an issue
involving certain middleboxes that may have an impact on EDO.

We have observed that some middleboxes incorrectly copy unknown TCP 
options from SYN packets into the SYN-ACK packets.
We believe this behavior is entirely incorrect, although we are 
uncertain of the reasons behind it.

Here is an example of a TCP SYN packet I constructed with an unknown SYN 
TCP option:

local.32218 > remote.http: Flags [S], seq 4026107292, win 8192, options 
[unknown-100 0x01020304,nop,nop], length 0
remote.http > local.32218: Flags [S.], seq 3220955308, ack 4026107293, 
win 8192, options [unknown-100 0x01020304,nop,nop], length 0

Unfortunately, this is not an isolated incident. We have observed 
several publicly available services on the internet
exhibiting the same incorrect behavior.

We would like to know if anyone else has encountered similar issues and 
how you perceive the impact of EDO in this scenario
(we believe it may result in the server interpreting the TCP options as 
application data).

Additionally, is there any possibility of adding an explicit 
notification when one side detects a violation of the EDO protocol.
This could potentially prevent all segments from being discarded by 
restricting the peer from further extending the TCP header.


Best regards,
D. Wythe