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net: Forget lookups for canceled contexts

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A sequential lookup using any non-canceled context has a risk of
returning the result of the previous lookup for a canceled context (i.e.
an error).

This is already prevented for timed out context by forgetting the host
immediately and extending this to also compare the error to
`context.Canceled` resolves this issue.

Fixes #22724

Change-Id: I7aafa1459a0de4dc5c4332988fbea23cbf4dba07
Reviewed-on: https://go-review.googlesource.com/77670
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Troels Thomsen 2017-11-14 23:22:19 +01:00 committed by Brad Fitzpatrick
parent 3a181dc7bc
commit 6a3d4be3b8
2 changed files with 23 additions and 1 deletions
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2
src/net/lookup.go
View File

@ -200,7 +200,7 @@ func (r *Resolver) LookupIPAddr(ctx context.Context, host string) ([]IPAddr, err
// rather than waiting for the current lookup to
// complete. See issue 8602.
ctxErr := ctx.Err()
if ctxErr == context.DeadlineExceeded {
if ctxErr == context.Canceled || ctxErr == context.DeadlineExceeded {
lookupGroup.Forget(host)
}
err := mapErr(ctxErr)

22
src/net/lookup_test.go
View File

@ -739,3 +739,25 @@ func TestLookupNonLDH(t *testing.T) {
t.Fatalf("lookup error = %v, want %v", err, errNoSuchHost)
}
}
func TestLookupContextCancel(t *testing.T) {
if runtime.GOOS == "nacl" {
t.Skip("skip on NaCl")
}
ctx, ctxCancel := context.WithCancel(context.Background())
ctxCancel()
_, err := DefaultResolver.LookupIPAddr(ctx, "google.com")
if err != errCanceled {
testenv.SkipFlakyNet(t)
t.Fatalf("unexpected error: %q", err)
}
ctx = context.Background()
_, err = DefaultResolver.LookupIPAddr(ctx, "google.com")
if err != nil {
t.Fatalf("unexpected error: %q", err)
}
}