Re: [tor-relays] Dropping packets with TCP MSS=1400 to foil GFW active probing

On Sun, Aug 19, 2018 at 07:41:26PM -0400, Nathaniel Suchy wrote:

Is China successfully probing OBFS4 bridges? Or does this apply more to non obfs bridges?

China doesn't dynamically probe obfs4 bridges. (More precisely: they may try to probe, but the probes don't result in blocks for obfs4.) They only block obfs4 bridges whose addresses they learn in other ways. The MSS=1400 trick works, the authors report, even for non-obfuscated bridges.