RFR 8153674: Expected SocketException not thrown when calling bind() with setReuseAddress(false)

Lu, Yingqi yingqi.lu at intel.com
Wed Sep 28 19:02:05 UTC 2016

Hi Vyom,

Thank you very much checking with us.

We agree that SO_RESUEADDR and SO_REUSEPORT behave the same way for MulticastSocket. There is no need to check and enable SO_REUSEPORT for this particular type of socket. SO_REUSEADDR is sufficient.


From: Vyom Tewari [mailto:vyom.tewari at oracle.com]
Sent: Wednesday, September 28, 2016 1:26 AM
To: Chris Hegarty <chris.hegarty at oracle.com>; Mark Sheppard <mark.sheppard at oracle.com>; net-dev <net-dev at openjdk.java.net>; Kaczmarek, Eric <eric.kaczmarek at intel.com>; Viswanathan, Sandhya <sandhya.viswanathan at intel.com>; Kharbas, Kishor <kishor.kharbas at intel.com>; Aundhe, Shirish <shirish.aundhe at intel.com>; Lu, Yingqi <yingqi.lu at intel.com>
Subject: Re: RFR 8153674: Expected SocketException not thrown when calling bind() with setReuseAddress(false)

Hi All,

I had off line discussion here at Oracle and we decided  not to override getReuseAddr/setReuseAddr for MulticastSocket. If user wants, he can set the SO_REUSEPORT with "setOption" before bind.

For MulticastSocket SO_REUSEADDR&SO_REUSEPORT are semantically equivalent which means either option will be sufficient to indicate that the address&port is reusable. So setting SO_REUSEPORT in constructor is really necessary/required ?

I am looking some comments on this from Intel people(they are in mail chain) who did this original change, before we decide how we wants to proceed on this issue.



On Wednesday 14 September 2016 08:47 PM, Chris Hegarty wrote:
On 14/09/16 15:53, Mark Sheppard wrote:

that's true wrt SO_REUSEPORT in MulticastSocket constructor. But the
same could have been argued for the original
invocation of setReuseAddress, by default , in the constructors, which
is encapsulating, what pereceived as, common or defacto
practice wrt applying SO_REUSEADDR on mcast sockets at the system level.
As I understand it, it is generally perceived that SO_REUSEADDR and
SO_REUSEPORT are semantically equivalent for multicast sockets.
As such, I think in the case of MulticastSocket, the fact that the
setRuseAddress() is called in the constructor, it is appropriate
to set SO_REUSEPORT also when it exists in the OS.

I take your point on the semantics of setReuseAddress in DatagramSocket
as per its spec. The spec does allude to MulticastSocket.
As such, the current proposal's changes just lack the appropriate
javadoc to describe its behavior, and its additional functionality of
It is not necessary that overridden method should mirror the semantics
of the base class method.
If it is accepted that it is generally perceived that SO_REUSEADDR and
SO_REUSEPORT are semantically equivalent for multicast sockets,
then it seems appropriate that an overriding setReuseAddress(..) method
in MulticastSocket can reflect this.

That sounds reasonable.



On 14/09/2016 14:58, Chris Hegarty wrote:

One additional remark.

Was it appropriate to update the legacy MC constructors
to set the new JDK 9 SO_REUSEPORT in the first place?
This can be achievable, opt-in from new code, by creating
an unbound MS, setting the option, then binding.


On 14/09/16 14:47, Chris Hegarty wrote:


On 14/09/16 14:22, Mark Sheppard wrote:

Hi Chris,
     I don't fully understand your objections to the approach taken.
Is there a compatibility issue with the addition of the additional
methods to MulticastSocket?

The concern is with setReuseAddress performing an operation that
is not clear from the method specification, e.g. from setReuseAddress()

     * Enable/disable the SO_REUSEADDR socket option.

This is no longer accurate. The proposed changes would affect

I don't see Datagram.setReuseAddress(...) handling the SO_REUSEPORT
option, this has to be done explicitly via setOption at this level of

Yes, it is a bit odd, but these are legacy classes. I am not opposed
to adding a new method for this, or something else. I just want to
avoid future issues and confusion when setReuseAddress is called and
then it is noticed that, the somewhat orthogonal option, SO_REUSEPORT's
value has changed. setReuseAddress's spec is very clear about what it

MulticastSocket is a subclass of DatagramSocket (that in itself is a
questionable structuring), and as such
has specialized behaviour, and part  of that specialization is the
setting of  the setting SO_REUSEADDR and SO_REUSEPORT
in its constructors, to enable address reuse semantics, prior to
an address.

Understood. Of course, the setting of SO_REUSEPORT is new in 9,
hence the problem.

As part of that specialization, it would seem appropriate that
MulticastSocket manipulate the SO_REUSEPORT
option in a consistent way. Adding an overridden setReuseAddress(...)
method provides that consistency and
encapsulates the specialized behaviour.

I agree with the abstraction, just not that setReuseAddress should
be used to achieve it. The name and spec of this method is so

Is alternatively proposal to NOT do anything to MulticastSocket, BUT
document clearly how to handle the failing scenario, that an
requires both setReuseAddress() and a setOption call to disable
reuseaddress semantics on an unbound MulticastSocket ?

That is one option, and the option that I was suggesting as a possible

This then raises the question of why have a convenience method, such as
setReuseAddress() in the first place, when it can be handled
adequately via the setOption

We are moving away from these option specific getter and setter
methods, in favor of the more general get/setOption methods, as
the latter are more adaptable.

If setReuseAddress is to operate on more than SO_REUSEADDR, then
its spec should be very clear about this.



On 14/09/2016 13:34, Chris Hegarty wrote:


On 14/09/16 13:23, Mark Sheppard wrote:

Hi Chris,
    so are you accepting that it is correct to add the overridden
methods in MulticastSocket and that these need
appropriate javadoc ?

I think we need these, but they should just call their super
equivalents, i.e. no implicit setting of SO_REUSEPORT. They would
exist solely as a place to locate guidance, or a note, that one
will likely want to set SO_REUSEPORT too.

or are you advocating pushing the handing of the SO_REUSEPORT into
base DatagramSocket class ?

It is already there. I am not proposing to change this.

It is not clear how your code changes fit in the proposed fix i.e.
explicit setting of the option to false?

My proposal is an alternative. It is not related to the current

With the current proposed changes then I think it would be
sufficient to
invoke setReuseAddress(true) in MulticastSocket constructors
rather than

        // Enable SO_REUSEADDR before binding

        // Enable SO_REUSEPORT if supported before binding
        *if* (supportedOptions








as the overridden setReuseAddress takes care of SO_REUSEPORT

Yes, this is what Vyom has proposed, in the webrev.

I would like to explore an alternative, so see what it would look



On 14/09/2016 11:43, Chris Hegarty wrote:


On 11/09/16 08:01, Vyom Tewari wrote:

Hi All,

Please review the below code change.

Bug        : https://bugs.openjdk.java.net/browse/JDK-8153674

Webrev  :

This change override the "get/setReuseAddress"  for MulticaseSocket
will abstract with both reuse attributes(SO_REUSEADDR &

This issue arises since the changes for 6432031 "Add support for
SO_REUSEPORT" [1], which sets SO_REUSEPORT on MulticastSocket, if
the available. So setting setReuseAddress(false) alone is no longer
sufficient to disable address/port reuse, one must also set
SO_REUSEPORT to false.

I would be really nervous about changing set/getReuseAddress,
at least updating the javadoc to indicate that it is now, for MS,
operating on two socket options.  Although, I do have sympathy
here since SO_REUSEPORT and SO_REUSEADDR are almost identical when
dealing with multicasting.

An alternative, maybe; Since the MS constructors document that
SO_REUSEPORT will be set, where available, maybe a javadoc note
on the set/getReuseAddress methods would be sufficient, that
indicates that StandardSocketOptions#SO_REUSEPORT may also need
to be set to have the desired effect?

If so, then code would have to:


this.setOption(StandardSocketOptions.SO_REUSEPORT, false);

  , but at least it is explicit.

Q: not all MS constructors document that SO_REUSEPORT is set, but
they should, right? This seems to have slipped past during 6432031


[1] https://bugs.openjdk.java.net/browse/JDK-6432031

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