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net: avoid opening an external port in TestDialListenerAddr

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The behavior in #18806 can be tested with a localhost-only port,
provided that we're willing to assume what format the listener would
report for an external dual-stack port.

Fixes #59497.

Change-Id: I171fb03eb46aee8e85480e04626a23f4f3b923e9
Reviewed-on: https://go-review.googlesource.com/c/go/+/482163
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>
This commit is contained in:
Bryan C. Mills 2023-04-10 13:59:12 +00:00 committed by Gopher Robot
parent 313d965393
commit f00c54146c
1 changed files with 36 additions and 4 deletions
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40
src/net/dial_test.go
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@ -884,17 +884,49 @@ func TestCancelAfterDial(t *testing.T) {
// "::" not connect back to that same address.
func TestDialListenerAddr(t *testing.T) {
mustHaveExternalNetwork(t)
ln, err := Listen("tcp", ":0")
if !testableNetwork("tcp4") {
t.Skipf("skipping: can't listen on tcp4")
}
// The original issue report was for listening on just ":0" on a system that
// supports both tcp4 and tcp6 for external traffic but only tcp4 for loopback
// traffic. However, the port opened by ":0" is externally-accessible, and may
// trigger firewall alerts or otherwise be mistaken for malicious activity
// (see https://go.dev/issue/59497). Moreover, it often does not reproduce
// the scenario in the issue, in which the port *cannot* be dialed as tcp6.
//
// To address both of those problems, we open a tcp4-only localhost port, but
// then dial the address string that the listener would have reported for a
// dual-stack port.
ln, err := Listen("tcp4", "localhost:0")
if err != nil {
t.Fatal(err)
}
defer ln.Close()
addr := ln.Addr().String()
c, err := Dial("tcp", addr)
t.Logf("listening on %q", ln.Addr())
_, port, err := SplitHostPort(ln.Addr().String())
if err != nil {
t.Fatalf("for addr %q, dial error: %v", addr, err)
t.Fatal(err)
}
// If we had opened a dual-stack port without an explicit "localhost" address,
// the Listener would arbitrarily report an empty tcp6 address in its Addr
// string.
//
// The documentation for Dial says ‘if the host is empty or a literal
// unspecified IP address, as in ":80", "0.0.0.0:80" or "[::]:80" for TCP and
// UDP, "", "0.0.0.0" or "::" for IP, the local system is assumed.’
// In #18806, it was decided that that should include the local tcp4 host
// even if the string is in the tcp6 format.
dialAddr := "[::]:" + port
c, err := Dial("tcp4", dialAddr)
if err != nil {
t.Fatalf(`Dial("tcp4", %q): %v`, dialAddr, err)
}
c.Close()
t.Logf(`Dial("tcp4", %q) succeeded`, dialAddr)
}
func TestDialerControl(t *testing.T) {