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Analysis of the GFW's Unconditional Port 443 Block on August 20, 2025

3 points| Welteneroberer | 6 months ago |github.com

1 comment

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NitpickLawyer|6 months ago

> It appears that the SYN packet triggered three forged RST+ACK packets, each with a relative sequence number 0, as well as incremental TCP window sizes of 1980, 1981, and 1982.

Ah, there's a joke there, if only they used 10 packets :D

> I observed that existing cross-border Internet connections were not affected, while both new IPv4 and IPv6 connections were reset.

Interesting, that would suggest it wasn't an intentional kill-switch (as rumoured initially, testing the capability), but rather likely a misbehaving device / service.

There's also a comment about Pakistan having issues in the same window (tho larger outage for them) so it might be an update / config for some of the same equipment family?