bug#23606: 25.1.50; "localhost" vs. "127.0.0.1"

bug#23606: 25.1.50; "localhost" vs. "127.0.0.1"

[Ken Brown]

The test echo-server-nowait in test/lisp/net/network-stream-tests.el
fails on Cygwin, but it passes if I create the client process using
"127.0.0.1" instead of "localhost":

diff --git a/test/lisp/net/network-stream-tests.el b/test/lisp/net/network-stream-tests.el
index c9b7cc7..80f6b9c 100644
--- a/test/lisp/net/network-stream-tests.el
+++ b/test/lisp/net/network-stream-tests.el
@@ -143,7 +143,7 @@ server-process-filter
          (port (aref (process-contact server :local) 4))
          (proc (make-network-process :name "foo"
                                      :buffer (generate-new-buffer "*foo*")
-                                     :host "localhost"
+                                     :host "127.0.0.1"
                                      :nowait t
                                      :service port)))
     (should (eq (process-status proc) 'connect))



Further investigation shows that if "localhost" is used, then the
connection fails with ECONNREFUSED when the first addrinfo returned by
getaddrinfo is used, but it succeeds with the second.  Since the client
socket is nonblocking in the test under discussion, the loop through the
addrinfos never gets to try the second one.

I notice that there are a couple of places in process.c where the code
makes a point of using "127.0.0.1" instead of "localhost", so I wonder
if we should just patch the test to do the same.  Or do experts think
it's worth pursuing this further to find out why it makes a difference
on Cygwin?


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bug#23606: 25.1.50; "localhost" vs. "127.0.0.1"

[Glenn Morris]

Ken Brown wrote:

> The test echo-server-nowait in test/lisp/net/network-stream-tests.el
> fails on Cygwin, but it passes if I create the client process using
> "127.0.0.1" instead of "localhost":

I see the same thing on RHEL 7.2, so this isn't Cygwin-specific.

bug#23606: 25.1.50; "localhost" vs. "127.0.0.1"

[Lars Ingebrigtsen]

Ken Brown <kbrown@cornell.edu> writes:

> The test echo-server-nowait in test/lisp/net/network-stream-tests.el
> fails on Cygwin, but it passes if I create the client process using
> "127.0.0.1" instead of "localhost":

If it doesn't work on Cygwin, then perhaps the test should just be
disabled there.

> -                                     :host "localhost"
> +                                     :host "127.0.0.1"

There's one test for "localhost" and one for "127.0.0.1", and the point
of those tests are to test whether name resolution works, and to test
that connecting with an IP address works.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#23606: 25.1.50; "localhost" vs. "127.0.0.1"

[Glenn Morris]

Lars Ingebrigtsen wrote:

> If it doesn't work on Cygwin, then perhaps the test should just be
> disabled there.

It's not just Cygwin.

> There's one test for "localhost" and one for "127.0.0.1", and the point
> of those tests are to test whether name resolution works, and to test
> that connecting with an IP address works.

I think you mean echo-server-with-localhost and echo-server-with-ip?
Both those tests pass for me on RHEL 7.2.

This report is about echo-server-nowait, which fails if "localhost" is
used, for reasons that seem to be unrelated to what the test is actually
supposed to be for.

bug#23606: 25.1.50; "localhost" vs. "127.0.0.1"

[Lars Ingebrigtsen]

Glenn Morris <rgm@gnu.org> writes:

> I think you mean echo-server-with-localhost and echo-server-with-ip?
> Both those tests pass for me on RHEL 7.2.

Ah, then it's probably OK to use the IP address in this test:

> This report is about echo-server-nowait, which fails if "localhost" is
> used, for reasons that seem to be unrelated to what the test is actually
> supposed to be for.

It does sound like a bug that it doesn't work, though, but that should
perhaps be a separate bug report.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#23606: 25.1.50; "localhost" vs. "127.0.0.1"

[Achim Gratz]

Ken Brown writes:
> The test echo-server-nowait in test/lisp/net/network-stream-tests.el
> fails on Cygwin, but it passes if I create the client process using
> "127.0.0.1" instead of "localhost":

This could be a case where it makes a difference if the IPv6 (::1) or
IPv4 address is returned (first) for localhost.  IIRC, Windows and
up-to-date Linux prefer IPv6 by default.  If so, it would likely be
better to fix the parts of the code that assumes return of IPv4
addresses only.


Regards,
Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

Wavetables for the Waldorf Blofeld:
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bug#23606: 25.1.50; "localhost" vs. "127.0.0.1"

[Ken Brown]

On 5/24/2016 1:20 PM, Achim Gratz wrote:
> Ken Brown writes:
>> The test echo-server-nowait in test/lisp/net/network-stream-tests.el
>> fails on Cygwin, but it passes if I create the client process using
>> "127.0.0.1" instead of "localhost":
> 
> This could be a case where it makes a difference if the IPv6 (::1) or
> IPv4 address is returned (first) for localhost.  IIRC, Windows and
> up-to-date Linux prefer IPv6 by default.  If so, it would likely be
> better to fix the parts of the code that assumes return of IPv4
> addresses only.

You're right.  In the test in question, IPv4 is specified for the server but not for the client.  The test passes on Cygwin if I specify IPv4 for the client also:

diff --git a/test/lisp/net/network-stream-tests.el b/test/lisp/net/network-stream-tests.el
index c9b7cc7..f30c92a 100644
--- a/test/lisp/net/network-stream-tests.el
+++ b/test/lisp/net/network-stream-tests.el
@@ -145,6 +145,7 @@ server-process-filter
                                      :buffer (generate-new-buffer "*foo*")
                                      :host "localhost"
                                      :nowait t
+                                     :family 'ipv4
                                      :service port)))
     (should (eq (process-status proc) 'connect))
     (while (eq (process-status proc) 'connect)

Glenn, does this also fix the problem on RHEL 7.2?

Ken

bug#23606: 25.1.50; "localhost" vs. "127.0.0.1"

[Glenn Morris]

Ken Brown wrote:

> Glenn, does this also fix the problem on RHEL 7.2?

Yes, thanks.

bug#23606: 25.1.50; "localhost" vs. "127.0.0.1"

[Ken Brown]

On 5/24/2016 3:19 PM, Glenn Morris wrote:
> Ken Brown wrote:
>
>> Glenn, does this also fix the problem on RHEL 7.2?
>
> Yes, thanks.

I've installed this change and I'm closing the bug.

Ken