JDK-8200719: Cannot connect to IPv6 host when exists any active network interface without IPv6 address

[Joel Peláez Jorge]

Hi Christoph,

OS X has a issue that needs "always" add a sin6_scope_id a multicast packet, I check that exists a old issue that logged it and add that piece of code: https://bugs.openjdk.java.net/browse/JDK-7144274

The DefaultInterface class in OS X is a plain Java class that list all interfaces and discards loopback and ppp interfaces, and prefers multistack interfaces than ones with only IPv4. I think that this class must use the network interface order defined in System Configuration but I don't find a way to use it.

I already signed the OCA, then I would like to have your help.

El 11/04/2018 a las 04:42, Langer, Christoph escribió:
> Hi Joel,
> 
> your fix sounds reasonable. In fact, I'm not even sure if the sin6_scope_id should be set for multicast. Maybe it should be done only for link local addresses.
> 
> Additionally, I guess the selection of the default interface (for IPv6) should be improved because I still can imagine a scenario where the first interface only has IPv4 but you want to do an IPv6 link local connect where you need a scope.
> 
> Do you have signed an OCA as per [1], section "0. Become a Contributor"? Then I can help you with sponsoring this...
> 
> Best regards
> Christoph
> 
> [1] http://openjdk.java.net/contribute/
> 
>> -----Original Message-----
>> From: net-dev [mailto:net-dev-bounces at openjdk.java.net] On Behalf Of
>> Joel Peláez Jorge
>> Sent: Dienstag, 10. April 2018 00:37
>> To: net-dev at openjdk.java.net
>> Subject: JDK-8200719: Cannot connect to IPv6 host when exists any active
>> network interface without IPv6 address
>>
>> Hi,
>>
>> I am new in the OpenJDK Community and I contribute with a fix for the bug
>> 8200719 related to networking in macOS system.
>>
>> I wrote a minimal patch that only set the scope id when the address is link-
>> local or multicast. This change avoid send IPv6 packets on a wrong interface.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8200719
>>
>> Patch:
>>
>> diff -r f088ec60bed5 src/java.base/unix/native/libnet/net_util_md.c
>> --- a/src/java.base/unix/native/libnet/net_util_md.c Mon Apr 09 10:39:29
>> 2018 -0700
>> +++ b/src/java.base/unix/native/libnet/net_util_md.c Mon Apr 09 16:50:18
>> 2018 -0500
>> @@ -89,7 +89,8 @@
>>        }
>>        int defaultIndex;
>>        struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)him;
>> -    if (sin6->sin6_family == AF_INET6 && (sin6->sin6_scope_id == 0)) {
>> +    if (sin6->sin6_family == AF_INET6 && (sin6->sin6_scope_id == 0) &&
>> +        (IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr) ||
>> IN6_IS_ADDR_MULTICAST(&sin6->sin6_addr))) {
>>            defaultIndex = (*env)->GetStaticIntField(env, ni_class,
>>                                                     ni_defaultIndexID);
>>            sin6->sin6_scope_id = defaultIndex;
>>
>>
>> Thanks,
>> Joel