EHOSTUNREACH should not be considered as an exception when send on a loopback network interface.

[Charles Lee]

On 12/07/2011 09:39 PM, Chris Hegarty wrote:
>
>
> On 07/12/2011 11:12, Alan Bateman wrote:
>> On 07/12/2011 08:11, Charles Lee wrote:
>>> :
>>>
>>> I'd like to raise this issue again. The patch is on the [1]:
>>>
>>> When a loopback network interface is bound to sendto and connect, in
>>> some linuxes it will throw an EINVAL errno, in other linuxes (AIX,
>>> iSeries) it will throw an EHOSTUNREACH errno. The man page of sendto
>>> on Aix and solaris is [2][3].
>>> In such situation, EHOSTUNREACH should treat as the same as EINVAL:
>>> not throw an exception but return false.
>>>
>>> Below is the simple test case can test this situation in specific
>>> platforms:
>>>
>>> /public class IsReachableTest {
>>> public static void main(String[] args) throws Exception{
>>> InetAddress testHost1 = InetAddress.getByName("openjdk.java.net");
>>> NetworkInterface loopbackNi = null;
>>> Enumeration<NetworkInterface> list =
>>> NetworkInterface.getNetworkInterfaces();
>>> boolean loopbackFound = false;
>>> while (list.hasMoreElements() && !loopbackFound){
>>> loopbackNi = list.nextElement();
>>> if (loopbackNi.isLoopback() && loopbackNi.isUp()) {
>>> loopbackFound = true;
>>> }
>>> }
>>>
>>> if (!loopbackFound)
>>> return;
>>> if (testHost1.isReachable(loopbackNi, 64, 1000))
>>> System.out.println(String.format("Fail: external host '%s' is
>>> reachable via loopback '%s'!",
>>> testHost1, loopbackNi));
>>> }
>>> }/
>>>
>>> Any thoughts, guys?
>> APIs that return a boolean to indicate success/failure and can also
>> throw IOException when there is a failure can be awkward as there will
>> be cases where IOException is thrown when false might seem to be more
>> correct. In this case, if sendto can fail with EHOSTUNREACH on Linux
>> then the proposed patch looks okay to me. I'm kinda surprised that
>> EINVAL is returned in some cases, that seems misleading to me.
>
> Ugh, I remember this one. Not pretty, but we found not better 
> alternative, see
>   http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6947677
>
> I filed a new CR for this issue:
>   7118907: "InetAddress.isReachable() should return false if sendto 
> fails with EHOSTUNREACH"
>
> I approved the proposed changes.
>
> Trivially can you put a new line in the comment after EHOSTUNREACH.
>
>   /*
>   * On some Linuxes, when bound to the loopback interface, sendto
>   * will fail and errno will be set to EINVAL or EHOSTUNREACH.
>   * When that happens, don't throw an exception, just return false.
>   */
>
> I assume Neil can push this for you? If not, I can help with the push.
>
> -Chris.
>
>>
>> -Alan
>>
>>
>>
>
Hi Alan, hi Chris,

Thank you for reviewing this and creating a bug id for me. I have put a 
revised webrev at http://cr.openjdk.java.net/~littlee/7118907/webrev.00/ 
<http://cr.openjdk.java.net/%7Elittlee/7118907/webrev.00/> .
If it is ok for you guys, maybe Neil can help :-)

-- 
Yours Charles