[Vm-dev] Re: [Pharo-dev] strange difference between localhost and 127.0.0.1 with a Zinc server on mac

[Eliot Miranda]

Hi Sven,


On Sat, Jun 14, 2014 at 4:09 AM, Sven Van Caekenberghe <sven at stfx.eu> wrote:

>
> On 14 Jun 2014, at 12:18, Ben Coman <btc at openInWorld.com> wrote:
>
> > Sven Van Caekenberghe wrote:
> >> In any case, the server socket used is normally listening on all
> interfaces [0.0.0.0]
> >>
> >> Sven
> >>
> >>
> >
> > Maybe it matters that [0.0.0.0] is the IPv4-Unspecified-Address
> > and it might make a difference to use IPv6-Unspecified-Address
> [0:0:0:0:0:0:0:0] or [::]
> >
> > cheers -ben
>
> I guess it all depends on the Socket plugin. ZnServer has #bindingAddress:
> which eventually calls Socket>>#listenOn:backlogSize:interface: but the
> question is, what is acceptable as last argument. And how is the difference
> between v4 and v6 handled. There is a 'primitives-ipv6' category, but no
> #listenOn with an interface there.
>

I wonder whether this commit is relevant:

r2552 | eliot | 2012-05-02 16:13:02 -0700 (Wed, 02 May 2012) | 19 lines

CogVM source as per VMMakerr.oscog-eem.159
...

Fix limitation in platforms/unix/plugins/SocketPlugin/sqUnixSocket.c which
could
cause NetNameResolver localHostAddress to answer 0 (if host has a set
hostname
not being honoured by local DNS servers).  Fix falls back to localhost.
...

Here's the relevant part of the
platforms/unix/plugins/SocketPlugin/sqUnixSocket.c change:

-sqInt sqResolverLocalAddress(void)             { return
nameToAddr(localHostName); }
+sqInt sqResolverLocalAddress(void)
+{      sqInt localaddr = nameToAddr(localHostName);
+       if (!localaddr)
+               localaddr = nameToAddr("localhost");
+       return localaddr;
+}

This fixed several socket tests on my Mac OS box.  I think it affects
systems behind a broadband router, at least that's how it asffected me on
my laptop at home.  And here's what is probably the root cause in
platforms/unix/plugins/SocketPlugin/sqUnixSocket.c:

...
static char   localHostName[MAXHOSTNAMELEN];
static u_long localHostAddress; /* GROSS IPv4 ASSUMPTION! */
...
/* start a new network session */

sqInt sqNetworkInit(sqInt resolverSemaIndex)
{
  if (0 != thisNetSession)
    return 0;  /* already initialised */
  gethostname(localHostName, MAXHOSTNAMELEN);
  localHostAddress= nameToAddr(localHostName);
  thisNetSession= clock() + time(0);
  if (0 == thisNetSession)
    thisNetSession= 1;  /* 0 => uninitialised */
  resolverSema= resolverSemaIndex;
  return 0;
}
...
and so if gethostname answers something weird, attempts to access localHost
are screwed from initialization on.

HTH
--
best,
Eliot
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