Hi, I have ported kernel XDP synproxy selftest https://elixir.bootlin.com/linux/v6.11.6/source/tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c to https://github.com/vincentmli/xdp-tools/tree/master/xdp-synproxy, barely make any changes functionally. one user reported to me after attaching the XDP synproxy to their server hosting website, they observed slow website page loading. I somehow could reproduce the issue by testing a simple one page website https://check-host.net/check-http?host=https://www.bpfire.net, some random country locations would report 5 - 6 seconds delay. I have capture screenshot here https://github.com/vincentmli/xdp-tools/issues/7#issuecomment-2465554843, it looks to me for some reason server split the SSL server hello with small packet size according to client's advertised receive window, tcp window scaling is not in effect for some reason, I suspect the small packet size sent from server caused the delay, the strange part is this does not alway happen since majority of other country locations seems fine. with XDP detached, no such problem. Any clue to troubleshooting this issue? Thanks Vincent
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