[quicwg/base-drafts] allow sending PADDING after receiving a non-ack-eliciting packet (#3135)

Marten Seemann <notifications@github.com> Wed, 23 October 2019 02:18 UTC

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Date: Tue, 22 Oct 2019 19:18:21 -0700
From: Marten Seemann <notifications@github.com>
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Subject: [quicwg/base-drafts] allow sending PADDING after receiving a non-ack-eliciting packet (#3135)
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#3104 changed the rules regarding what kind of packet an endpoint is allowed to send after receiving a non-ack-eliciting packet. The intention of that text used to be to prevent peers from getting stuck in an ACK-loop, but now the text says:

> An endpoint MUST NOT send a non-ack-eliciting packet in response to a non-ack-eliciting packet, even if there are packet gaps which precede the received packet.

Among others, this means that once an endpoint receives a non-ack-eliciting packet, it's not allowed to send a packet containing only PADDING. This would be valuable for defeating traffic analysis. While it would be possible to hack your way out of this by sending a PING + PADDING packet, I'm not sure if this was the intention of #3104.

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