Add HTTPBandwidth/HTTPBandwidthWithDialAddr probe classes that download a
fixed number of bytes and record transfer time and bytes transferred as
Prometheus counters for bandwidth measurement, plus HTTPWithDialAddr and
the shared NewProbeTransport and HTTPBandwidthMetrics helpers.
The dial-address override lets a probe target a specific backend (e.g. a
single Funnel ingress node) while SNI, the Host header, and TLS cert
validation continue to derive from the URL host. HTTPBandwidthMetrics is
exported so other bandwidth probes (e.g. a receiver-reported upload probe)
emit an identical metric set and compare under a shared direction label.
Updates tailscale/corp#41587
Signed-off-by: Mike O'Driscoll <mikeo@tailscale.com>
Mike O'DriscollandGitHub
59159d9180