[PATCH] fix Inet4AddressImpl.lookupAllHostAddr returning unroutable addresses

[Rob McKenna]

Hi Brian,

By coincidence I just started looking at this today myself.

We have an existing bug filed for this issue: 
https://bugs.openjdk.java.net/browse/JDK-8080819

The diagnosis looks good.

	-Rob

On 22/05/15 07:56, Brian Toal wrote:
> The fix for https://bugs.openjdk.java.net/browse/JDK-7180557 causes a
> regression for Mac OSX hosts connected to a VPN (or otherwise with more
> than network
> interface associated with the hostname).
>
> For example, when on Cisco VPN, the ifconfig is as follows:
>
> lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
>      options=3<RXCSUM,TXCSUM>
>      inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
>      inet 127.0.0.1 netmask 0xff000000
>      inet6 ::1 prefixlen 128
> gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
> stf0: flags=0<> mtu 1280
> en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>      ether 28:cf:e9:1a:eb:6b
>      inet6 fe80::2acf:e9ff:fe1a:eb6b%en0 prefixlen 64 scopeid 0x4
>      inet 192.168.0.106 netmask 0xffffff00 broadcast 192.168.0.255
>      media: autoselect
>      status: active
> p2p0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 2304
>      ether 0a:cf:e9:1a:eb:6b
>      media: autoselect
>      status: inactive
> utun0: flags=80d1<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1320
>      inet 10.3.23.199 --> 10.3.23.199 netmask 0xffffc000
>      inet6 fe80::2acf:e9ff:fe1a:eb6b%utun0 prefixlen 64 scopeid 0x6
>      inet6 fe80::49cd:21e1:4c11:721d%utun0 prefixlen 128 scopeid 0x6
>
> The hostname entry in DNS is associated with the utun0 interface, and
> 10.3.23.199 and all routes go through that interface. The 192.168.0.106
> IP is my local wifi address, and is not used (other than to tunnel the
> VPN traffic when VPN is connected). Any connections to the 192.168
> address, even from localhost, will fail (hang indefinitely, as all
> packets are dropped).
>
> The OS getaddrinfo calls, when passed the FQDN hostname only return the
> 10.3 address (getaddrinfo.c attached).
>
> Prior to the fix for JDK-7180557, getaddrinfo was being used and
> everything worked fine. As part of the fix, the following block was
> added for OSX only in the IPv4 path:
>
> + #ifdef MACOSX
> +     /* If we're looking up the local machine, bypass DNS lookups and get
> +      * address from getifaddrs.
> +      */
> +     ret = lookupIfLocalhost(env, hostname, JNI_FALSE);
> +     if (ret != NULL) {
> +         JNU_ReleaseStringPlatformChars(env, host, hostname);
> +         return ret;
> +     }
> + #endif
>
> This code, which occurs before the usual path and applies only to
> localhost lookups, tries to "guess" the localaddress by interface
> enumeration. In the case of a VPN configuration, both en0 (192.168) and
> utun0 will match as they are active. So, for example,
> InetAddress.getAllByName("localhost FQDN"), will return both addresses.
> However, the getByName() call and most other code which implicitly uses
> the localhost will return only the first entry, which is the unroutable
> en0 address.
>
> The host is configured correctly and other processes all resolve the
> hostname correctly. The issue is specific to this OSX workaround.
>
> On the IPv6 path for the same fix, the lookupIfLocalhost workaround was
> only applied *if* the original lookup via the usual routines failed. The
> attached patch follows the same approach in the IPv4 path, if the
> orginal lookup fails then call lookupIfLocalhost If this was applied to
> the IPv4 path.  The patch fixes the issue without regressing the hosts
> that triggered this fix.
>
> # HG changeset patch
> # User btoal
> # Date 1432276472 25200
> #      Thu May 21 23:34:32 2015 -0700
> # Node ID 24cf7a8a8bf4f489da6b2506bcb57cb329a93593
> # Parent  20e6cadfac43717a81d99daff5e769de695992cd
> Only call lookupIfLocalhost if getaddrinfo call errors to avoid
> resolving to a incorrect address.
>
> diff -r 20e6cadfac43 -r 24cf7a8a8bf4
> src/solaris/native/java/net/Inet4AddressImpl.c
> --- a/src/solaris/native/java/net/Inet4AddressImpl.c    Thu Feb 05
> 13:00:26 2015 +0100
> +++ b/src/solaris/native/java/net/Inet4AddressImpl.c    Thu May 21
> 23:34:32 2015 -0700
> @@ -172,20 +172,19 @@
>           return NULL;
>       }
>
> -#ifdef MACOSX
> -    /* If we're looking up the local machine, bypass DNS lookups and get
> -     * address from getifaddrs.
> -     */
> -    ret = lookupIfLocalhost(env, hostname, JNI_FALSE);
> -    if (ret != NULL || (*env)->ExceptionCheck(env)) {
> -        JNU_ReleaseStringPlatformChars(env, host, hostname);
> -        return ret;
> -    }
> -#endif
> -
>       error = getaddrinfo(hostname, NULL, &hints, &res);
>
>       if (error) {
> +#ifdef MACOSX
> +        /* If we're looking up the local machine, bypass DNS lookups
> and get
> +         * address from getifaddrs.
> +         */
> +        ret = lookupIfLocalhost(env, hostname, JNI_FALSE);
> +        if (ret != NULL || (*env)->ExceptionCheck(env)) {
> +            JNU_ReleaseStringPlatformChars(env, host, hostname);
> +            return ret;
> +        }
> +#endif
>           /* report error */
>           ThrowUnknownHostExceptionWithGaiError(env, hostname, error);
>           JNU_ReleaseStringPlatformChars(env, host, hostname);