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feat: report the negotiated TLS version and cipher under --debug - #127

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BKPepe:feat/report-negotiated-tls
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feat: report the negotiated TLS version and cipher under --debug#127
BKPepe wants to merge 1 commit into
librespeed:masterfrom
BKPepe:feat/report-negotiated-tls

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@BKPepe

@BKPepe BKPepe commented Aug 9, 2026

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On hardware without AES acceleration the cipher, not the link, bounds an
HTTPS result — and under TLS 1.3 the server picks it. The client offers a
set and has no say in the choice, and Go does not allow that set to be
configured at all (CipherSuites covers TLS 1.0–1.2 only). Two runs can
then differ several-fold for a reason the numbers do not show.

Measured on a CZ.NIC Turris 1.x, whose e500v2 core has no crypto
instructions:

throughput
AES-256-GCM ~150 Mbps
ChaCha20-Poly1305 ~390 Mbps

Same core, same link. A server that picks the first looks like a slow link
next to one that picks the second, and nothing in the report says which
happened.

$ librespeed-cli --server 85 --debug
Negotiated TLS 1.3 with TLS_AES_256_GCM_SHA384

$ librespeed-cli --server 85 --insecure --debug
Connection is not encrypted

Printed once, from the backend check that already runs before every test.
Nothing changes without --debug, and the JSON and CSV schemas are
untouched.

On hardware without AES acceleration the cipher, not the link, is what
bounds an HTTPS result, and the server chooses it. Two runs can differ
several-fold for a reason the numbers alone do not show.

Measured on a CZ.NIC Turris 1.x, whose e500v2 core has no crypto
instructions: AES-256-GCM tops out around 150 Mbps while ChaCha20-Poly1305
reaches about 390 Mbps on the same core. A server that picks the first will
look like a slow link next to one that picks the second.

Print it once, from the backend check that already runs before every test.
Copilot AI lite review requested due to automatic review settings August 9, 2026 21:29

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2 participants