How about the following for the apidoc in j.n.StandardSocketOptions?
We can then reference this text from everywhere else rather than
repeating it.
(just noticed Lucy was not included in the last few mails)
- Michael
/**
* Re-use port.
*
* <p> The value of this socket option is a {@code Boolean} that
represents
* whether the option is enabled or disabled. The exact semantics
of this
* socket option are socket type and system dependent.
*
* SO_REUSEPORT can be used with both TCP and UDP sockets.
*
* <p> In the case of stream-oriented sockets, this socket option
allows
* multiple listening sockets to be bound to both the same address
* and same port.
*
* <p> For datagram-oriented sockets the socket option is used to allow
* multiple UDP sockets to be bound to the same address and port.
*
* @implNote Generally, this option must be set before the
* socket is bound or connected. Changing the value of this socket
option
* after the socket is bound has no effect. There may be further
* restrictions imposed by implementations such as the requirement that
* all sockets bound to the same port, must have set the option.
*/
On 23/11/15 10:54, Michael McMahon wrote:
I agree we should enable the option on all platforms.
We can add the code to do that and run the tests.
On the existing use of SO_REUSEPORT on AIX and Mac
it appears that is set to emulate expected behavior on
other platforms when SO_REUSEADDR is set for datagram sockets.
The expectation is that ports can be reused for datagram sockets
and the JCK tests this. So, I guess we have to leave this behavior by
default,
except if SO_REUSEPORT is explicitly disabled maybe. Though
this code hasn't been forward ported to JDK 9 yet.
For reference, SO_REUSEPORT on Linux is documented here
http://man7.org/linux/man-pages/man7/socket.7.html
- Michael
On 23/11/15 09:13, Volker Simonis wrote:
Hi Lucy,
in general I support the addition of SO_REUSEPORT to the set of
standard socket options. However for me the problem is not that this
new option is not supported on all platforms, but instead that it has
such different semantics on different platforms. If you look at the
code, you'll see that we already implicitly set SO_REUSEPORT on Mac
and AIX for datagram sockets for which we set SO_REUSEADDR. So maybe
we have to rethink this, once SO_REUSEPORT becomes available as a
standard socket option.
I like the new wording you've posted for JavaDoc of SO_REUSEPORT, but
I think the sentence:
* Although SO_REUSEADDR option already enables similar
* functionality, SO_REUSEPORT prevents port hijacking and
* distributes the involving datagrams evenly across all of the
* receiving threads.
refers to a Linux-specific implementation detail which shouldn't be
mentioned in the general documentation. You already have the sentence
"The exact semantics of this socket option are socket type and system
dependent" which should let everybody think twice before using this
option. I'm also not sure about the link to the Linux article but I
again think it is inappropriate in a general API documentation
(otherwise we would have to add links for every platform which
supports SO_REUSEPORT).
As far as I can see (and please correct me if I'm wrong) you actually
only add the new option for Linux platforms. But this socket option is
also supported on Solaris (>= 11), MacOS X, AIX. So could you please
enable it on the other platforms as well.
Finally I want to mention the good stackoverflow article at
http://stackoverflow.com/questions/14388706/socket-options-so-reuseaddr-and-so-reuseport-how-do-they-differ-do-they-mean-t
which covers the topic SO_REUSEADDR vs. SO_REUSEPORT quite well. And
I've collected the man-page entries for SO_REUSEADDR and SO_REUSEPORT
for the systems I have (unfortunately, I couldn't find an updated
Linux man-page which mentions SO_REUSEPORT):
Linux
=====
SO_REUSEADDR
Indicates that the rules used in validating addresses
supplied in a bind(2) call should allow reuse of local
addresses. For AF_INET sockets this means that a socket
may bind, except when there is an active listening
socket bound to the address. When the listening socket
is bound to INADDR_ANY with a specific port then it is
not possi- ble to bind to this port for any local
address. Argument is an integer boolean flag.
Linux will only allow port reuse with the SO_REUSEADDR option
when this option was set both in the previous program that
performed a bind(2) to the port and in the program that wants
to reuse the port. This differs from some implementations
(e.g., FreeBSD) where only the later program needs to set the
SO_REUSEADDR option. Typically this difference is invisi- ble,
since, for example, a server program is designed to always set
this option.
MacOS X
=======
SO_REUSEADDR enables local address reuse
SO_REUSEPORT enables duplicate address and port bindings
SO_REUSEADDR indicates that the rules used in validating
addresses supplied in a bind(2) call should allow reuse of local
addresses.
SO_REUSEPORT allows completely duplicate bindings by multiple
processes if they all set SO_REUSEPORT before bind- ing the port.
This option permits multiple instances of a program to each
receive UDP/IP multicast or broadcast datagrams destined for the
bound port.
Solaris
=======
SO_REUSEADDR enable/disable local address reuse
SO_REUSEPORT enable/disable local port reuse for
PF_INET/PF_INET6 socket
The SO_REUSEADDR/SO_REUSEPORT options indi- cate that the rules
used in validating addresses and ports supplied in a
bind(3SOCKET) call should allow reuse of local addresses or
ports.
AIX
===
SO_REUSEADDR
Specifies that the rules used in validating
addresses supplied by a bind subroutine should
allow reuse of a local port. A particular IP
address can only be bound once to the same
port. This option enables or disables reuse of
local ports.
SO_REUSEADDR allows an application to explicitly
deny subsequent bind subroutine to the port/address
of the socket with SO_REUSEADDR set. This allows an
application to block other applications from
binding with the bind subroutine.
SO_REUSEPORT
Specifies that the rules used in validating
addresses supplied by a bind subroutine should
allow reuse of a local port/address
combination. Each binding of the port/address
combination must specify the SO_REUSEPORT socket
option. This option enables or disables the reuse
of local port/address combinations.
HPUX
====
SO_REUSEADDR
(int; boolean; AF_INET sockets only) If enabled, allows
a local address to be reused in subsequent calls to
bind(). Default: disallowed.
SO_REUSEPORT
(int; boolean; AF_INET sockets only) If enabled, allows
a local address and port to be reused in subsequent
calls to bind(). Default: disallowed.
Setting the SO_REUSEADDR option allows the local socket address
to be reused in subsequent calls to bind(). This permits
multiple SOCK_STREAM sockets to be bound to the same local
address, as long as all existing sockets with the desired local
address are in a connected state before bind() is called for a
new socket. For SOCK_DGRAM sockets, SO_REUSEADDR allows
multiple sockets to receive UDP multicast datagrams addressed to
the bound port number. For all SOCK_DGRAM sockets bound to the
same local address, SO_REUSEADDR must be set before calling
bind().
Setting the SO_REUSEPORT option allows multiple SOCK_DGRAM
sockets to share the same address and port. Each one of those
sockets, including the first one to use that port, must specify
this option before calling bind().
Regards,
Volker
On Mon, Nov 23, 2015 at 9:00 AM, Alan Bateman
<alan.bate...@oracle.com> wrote:
On 23/11/2015 04:12, Lu, Yingqi wrote:
Hi Alan,
One more question please J I want to make sure I understand
correctly on
your following suggestion. In order to use supportedOptions method
to test
SO_REUSEPORT, I will need to first write a native function to check if
SO_REUSEPORT is supported. Then, in the defaultOptions method, I do a
conditional add for StandardSocketOptions.SO_REUSEPORT if it is
supported on
the platform? Is this a preferred way to implement? Please let me know!
Yes as supportedOptions() shouldn't return SO_REUSEPORT in the set
when it's
not supported. It might be simplest to put that code in sun.nio.ch.Net,
maybe isReusePortSupported or some such method. In the implementation
(Net.c) then you can return true or false depending on the platform and
maybe kernel version.
-Alan
