With #60078 accepted, we expect Go 1.22 will have different
for loop semantics than Go 1.19 did.
Go 1.19 is already unsupported, but add a check anyway, just to
help catch some mistakes and usage of old Go toolchains
beyond their end-of-support.

Note that Go 1.19 can keep being used indefinitely with pre-Go 1.22 code.
This change only makes it refuse to build code that says it needs
Go 1.22 semantics, because Go 1.19 does not provide those.

Cherry-pick of the change from the Go 1.20 branch.

For #60078.

Change-Id: I75118d6fbd0cc08a6bc309aca54c389a255ba7dc
Reviewed-on: https://go-review.googlesource.com/c/go/+/518675
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-on: https://go-review.googlesource.com/c/go/+/518815
Auto-Submit: Russ Cox <rsc@golang.org>
TryBot-Bypass: Russ Cox <rsc@golang.org>

…eaders

Historically, the Transport has silently truncated invalid
Host headers at the first '/' or ' ' character. CL 506996 changed
this behavior to reject invalid Host headers entirely.
Unfortunately, Docker appears to rely on the previous behavior.

When sending a HTTP/1 request with an invalid Host, send an empty
Host header. This is safer than truncation: If you care about the
Host, then you should get the one you set; if you don't care,
then an empty Host should be fine.

Continue to fully validate Host headers sent to a proxy,
since proxies generally can't productively forward requests
without a Host.

For #60374
Fixes #61431
Fixes #61825

Change-Id: If170c7dd860aa20eb58fe32990fc93af832742b6
Reviewed-on: https://go-review.googlesource.com/c/go/+/511155
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Run-TryBot: Damien Neil <dneil@google.com>
(cherry picked from commit b9153f6)
Reviewed-on: https://go-review.googlesource.com/c/go/+/518855
Auto-Submit: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Roland Shoemaker <roland@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

…y size

Add a new GODEBUG setting, tlsmaxrsasize, which allows controlling the
maximum RSA key size we will accept during TLS handshakes.

Fixes #61968

Change-Id: I52f060be132014d219f4cd438f59990011a35c96
Reviewed-on: https://go-review.googlesource.com/c/go/+/517495
Auto-Submit: Roland Shoemaker <roland@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Roland Shoemaker <roland@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-on: https://go-review.googlesource.com/c/go/+/518536
Auto-Submit: Dmitri Shuralyov <dmitshur@google.com>

Change-Id: I2536f540cb7271f1edfcfb3a126e62ebf0c24261
Reviewed-on: https://go-review.googlesource.com/c/go/+/526138
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>