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net, net/http: adjust time-in-past constant even earlier

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The aLongTimeAgo time value in net and net/http is used to cancel
in-flight read and writes. It was set to time.Unix(233431200, 0)
which seemed like far enough in the past.

But Raspberry Pis, lacking a real time clock, had to spoil the fun and
boot in 1970 at the Unix epoch time, breaking assumptions in net and
net/http.

So change aLongTimeAgo to time.Unix(1, 0), which seems like the
earliest safe value. I don't trust subsecond values on all operating
systems, and I don't trust the Unix zero time. The Raspberry Pis do
advance their clock at least. And the reported problem was that Hijack
on a ResponseWriter hung forever, waiting for the connection read
operation to finish. So now, even if kernel + userspace boots in under
a second (unlikely), the Hijack will just have to wait for up to a
second.

Fixes #19747

Change-Id: Id59430de2e7b5b5117d4903a788863e9d344e53a
Reviewed-on: https://go-review.googlesource.com/38785
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
This commit is contained in:
Brad Fitzpatrick 2017-03-29 16:55:58 +00:00
parent 041ecb697f
commit 6983b9a579
2 changed files with 2 additions and 2 deletions
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2
src/net/http/http.go
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@ -20,7 +20,7 @@ const maxInt64 = 1<<63 - 1
// aLongTimeAgo is a non-zero time, far in the past, used for
// immediate cancelation of network operations.
var aLongTimeAgo = time.Unix(233431200, 0)
var aLongTimeAgo = time.Unix(1, 0)
// TODO(bradfitz): move common stuff here. The other files have accumulated
// generic http stuff in random places.

2
src/net/net.go
View File

@ -467,7 +467,7 @@ func (e *OpError) Error() string {
var (
// aLongTimeAgo is a non-zero time, far in the past, used for
// immediate cancelation of dials.
aLongTimeAgo = time.Unix(233431200, 0)
aLongTimeAgo = time.Unix(1, 0)
// nonDeadline and noCancel are just zero values for
// readability with functions taking too many parameters.