Re: HAProxy and proxy protocol support

Sam Varshavchik <[email protected]> Wed, 12 Jun 2024 23:35:54 -0400

Newsgroups	gmane.mail.imap.courier.general
Message-ID	<[email protected]>

Andrew Athan writes:

> « HTML content follows
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> »Sam:
>
>
> I've googled but not been able to find a reference to this duplication of  
> initial bytes issue in TFO. Can you provide more information?

This is explicitly called out in RFC 7413 section 6.1.

I also found a layman's description at:

https://netty.io/wiki/tcp-fast-open.html

"TFO cannot always be used, however, because it changes how TCP behave: The  
receiving end might see this data duplicated due to retransmission of the  
SYN packet. For this reason, TFO must only be used when the data in the  
initial packet will be processed idempotently. Whether this is the case,  
depends on the protocol and the application."

> That seems like a catastrophic bug in the TCP contract. I'd like to make some  
> colleagues aware of the issue, ideally with a reference to some analysis of  
> it.

This seems like a well known, known issue with this.

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