Date: Tue, 21 Feb 2006 16:12:40 -0800 From: Sean McNeil <sean@mcneil.com> To: Kurt Miller <kurt@intricatesoftware.com> Cc: Nate Williams <nate@yogotech.com>, "Arne H. Juul" <arnej@pvv.ntnu.no>, freebsd-java@freebsd.org Subject: Re: SO_REUSEADDR should not also mean SO_REUSEPORT Message-ID: <1140567160.87962.4.camel@triton.mcneil.com> In-Reply-To: <200602211011.39387.kurt@intricatesoftware.com> References: <43F4F22F.1060402@europe.yahoo-inc.com> <17399.20883.741021.688682@caddis.yogotech.com> <Pine.LNX.4.62.0602182107440.31913@decibel.pvv.ntnu.no> <200602211011.39387.kurt@intricatesoftware.com>
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On Tue, 2006-02-21 at 10:11 -0500, Kurt Miller wrote: > On Saturday 18 February 2006 3:45 pm, Arne H. Juul wrote: > > On Sat, 18 Feb 2006, Nate Williams wrote: > > >> Ok, thanks. I got that impression from reading some posts I found > > >> while googling. There was one in particular for NetBSD that > > >> discussed it in detail. Check out the Apr 2 portion of this > > >> http://www.tinyurl.com/b46gq by Jan Schaumann. Also this > > >> one http://tinyurl.com/9sa6a. From these posts it appears > > >> that SO_REUSEPORT is needed in some cases to be compatible > > >> with linux. > > > > > >> From the early days.... > > > > > > - In the Multicast constructor, the low level routine sets the > > > SO_REUSEADDR option by using JSO_REUSEADDR which corresponds to a call > > > to setsockopt(..SO_REUSEADDR). To make multicast sockets work in *all* > > > cases on FreeBSD, we should also set SO_REUSEPORT, else in many cases > > > the multicast bind will fail. > > > > I won't claim to know what's the best behaviour with multicast, but the > > problem is that SO_REUSEPORT is always used when SO_REUSEADDR was > > requested, meaning that: > > > > > SO_REUSEPORT allows completely duplicate bindings by multiple > > > processes if they all set SO_REUSEPORT before binding the port. > > > > so you can have two very different java servers listening on the same > > port, for example. Or the same java server started twice won't notice any > > problem because the second instance will bind its server port fine, while > > on all other OSes this would give a sensible error message. And so on. > > This is bad. > > > > The reason I found this problem in the first place was from a Java program > > that worked well on Linux, not at all on FreeBSD, and after much tracing > > we deduced that something was enabling SO_REUSEPORT on FreeBSD, after > > which finding the bad code was a simple matter of "grep", only leaving the > > question of why it was there in the first place. > > > > If anybody figures out what's best practice for supporting multicast > > applications, ask the BSD kernel people to change the kernel behaviour to > > match best practice, make it possible to control SO_REUSEPORT from the > > MulticastSocket class, or find some other solution that doesn't make > > *other* types of java application suffer. > > Thanks for the explanation and also to Nate for the Multicast > history. I've looked into this a bit more over the weekend and > found that the network stack promotes SO_REUSEADDR to include > SO_REUSEPORT for multicast addresses, so I believe that case is > covered already. I ran the network jck's on the 1.5 jvm with your > patch and found that SO_REUSEPORT is still needed to pass the jck's > but for datagram sockets only. > > Could you try this patch and test it with the program you referred > to above? > > --- ../../j2se/src/solaris/native/java/net/net_util_md.c.orig Tue Feb 21 09:56:11 2006 > +++ ../../j2se/src/solaris/native/java/net/net_util_md.c Tue Feb 21 10:06:31 2006 > @@ -1022,11 +1022,20 @@ > } > > /* > - * If SO_REUSEADDR option requested, unconditionally set SO_REUSEPORT. > + * If SO_REUSEADDR option requested for SOCK_DGRAM, set SO_REUSEPORT also. All UDP sockets? Why not just test the address to see if it is a multicast address? Shouldn't SO_REUSEPORT be set for TCP in that case as well? Sean
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