8080819: [PATCH] fix Inet4AddressImpl.lookupAllHostAddr returning unroutable addresses

[Rob McKenna]

Adding bug id to subject for reference.

	-Rob

On 22/05/15 16:05, Rob McKenna wrote:
> 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);