Previously the DERP handler served each connection for its lifetime
on its hijacked connection's net/http handler goroutine. That
goroutine's conn.serve stack frame kept the dead HTTP/1 server state
reachable for the whole DERP connection: the http.conn and its 4KB
bufio.Writer (hijack hands over c.bufw but conn.serve still references
it, so derpserver returning it to its flush pool never made it
collectable), the 4KB bufio.Reader, the upgrade *http.Request with its
parsed headers, and the request context chain. The goroutine also kept
the stack growth from the TLS handshake and HTTP request parsing.
Instead, hand the connection off to a new goroutine and return from
the handler (ala tailscale/corp@dc09e27aef), letting all the HTTP
upgrade state be collected. Give Accept a smaller 1KB frame reader,
draining and releasing the hijacked reader if it contains buffered
bytes from a fast-start client, and a nil bufio.Writer so writes go
through pooled buffers held only for the duration of a write instead
of a per-connection buffer.
Because the handler now returns at handoff time, cmd/derper's
gauge_derper_tls_active_version decrement can no longer be deferred
to handler return: intercept Hijack in the TLS metrics wrapper and,
for hijacked connections (DERP, its WebSocket flavor, and CONNECT),
decrement the gauge once when the hijacked connection closes,
restoring the gauge's connection-lifetime semantics. Teach
derpserver's TCP RTT stats to unwrap the close-hook conn so they
still find the underlying *net.TCPConn.
Also soften the UntypedHexString deprecation notices in types/key to
warnings: the untyped hex string format is the DERP wire protocol's
key encoding, so these call sites are legitimate and permanent, and
a Deprecated marker just makes them light up in editors and linters.
The cautionary text about the format's risks remains.
Measured with 100,000 idle TLS DERP connections on linux/amd64:
standing memory drops from 55.6KB to 32.6KB per connection (-41%).
Updates #21064
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Change-Id: If05a0c6ea79134807e9e8872861db216
This file was never truly necessary and has never actually been used in
the history of Tailscale's open source releases.
A Brief History of AUTHORS files
---
The AUTHORS file was a pattern developed at Google, originally for
Chromium, then adopted by Go and a bunch of other projects. The problem
was that Chromium originally had a copyright line only recognizing
Google as the copyright holder. Because Google (and most open source
projects) do not require copyright assignemnt for contributions, each
contributor maintains their copyright. Some large corporate contributors
then tried to add their own name to the copyright line in the LICENSE
file or in file headers. This quickly becomes unwieldy, and puts a
tremendous burden on anyone building on top of Chromium, since the
license requires that they keep all copyright lines intact.
The compromise was to create an AUTHORS file that would list all of the
copyright holders. The LICENSE file and source file headers would then
include that list by reference, listing the copyright holder as "The
Chromium Authors".
This also become cumbersome to simply keep the file up to date with a
high rate of new contributors. Plus it's not always obvious who the
copyright holder is. Sometimes it is the individual making the
contribution, but many times it may be their employer. There is no way
for the proejct maintainer to know.
Eventually, Google changed their policy to no longer recommend trying to
keep the AUTHORS file up to date proactively, and instead to only add to
it when requested: https://opensource.google/docs/releasing/authors.
They are also clear that:
> Adding contributors to the AUTHORS file is entirely within the
> project's discretion and has no implications for copyright ownership.
It was primarily added to appease a small number of large contributors
that insisted that they be recognized as copyright holders (which was
entirely their right to do). But it's not truly necessary, and not even
the most accurate way of identifying contributors and/or copyright
holders.
In practice, we've never added anyone to our AUTHORS file. It only lists
Tailscale, so it's not really serving any purpose. It also causes
confusion because Tailscalars put the "Tailscale Inc & AUTHORS" header
in other open source repos which don't actually have an AUTHORS file, so
it's ambiguous what that means.
Instead, we just acknowledge that the contributors to Tailscale (whoever
they are) are copyright holders for their individual contributions. We
also have the benefit of using the DCO (developercertificate.org) which
provides some additional certification of their right to make the
contribution.
The source file changes were purely mechanical with:
git ls-files | xargs sed -i -e 's/\(Tailscale Inc &\) AUTHORS/\1 contributors/g'
Updates #cleanup
Change-Id: Ia101a4a3005adb9118051b3416f5a64a4a45987d
Signed-off-by: Will Norris <will@tailscale.com>
This exports a number of things from the derp (generic + client) package
to be used by the new derpserver package, as now used by cmd/derper.
And then enough other misc changes to lock in that cmd/tailscaled can
be configured to not bring in tailscale.com/client/local. (The webclient
in particular, even when disabled, was bringing it in, so that's now fixed)
Fixes#17257
Change-Id: I88b6c7958643fb54f386dd900bddf73d2d4d96d5
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Brad Fitzpatrick