Hi Roel,
Thanks for your reply. My comments inline.
On Thursday, July 08, 2010 12:47:17 pm Roel van de Kraats wrote:
>
> On 07/08/2010 08:49 AM, Varun Chandramohan wrote:
> > Hi All,
> >
> > I have been looking into openslp code and i found a few changes that
> > might make things better in openslp. I dont have patches to share, but i
> > will create them if everyone here agrees.
> >
> Dear Varun,
>
> Thanks for putting this effort in improving Openslp and for discussing
> your ideas on the mailing list.
> > - Multiple Binding Issue: I observed that, when the list of interfaces is
> > not specified in the config file, the slpd daemon reads all interface
> > information and binds to all address of all interfaces. I feel this is a
> > overkill. When no specific interfaces are given, its much easier to bind to
> > :: or INADDR_ANY.
> >
> That sounds simpler indeed. However, by doing so a lot of responsibility
> is moved from slpd (which we can adapt to our needs) to the OS (for
> which this is much harder). Since handling multiple interfaces the
> correct way is quite delicate, I'd rather keep this responsibility on
> the slpd side. And although receiving messages may become simpler this
> way, for sending messages it is still necessary to specify the
> interface; otherwise the 'default' interface (chosen by the OS) is used.
> Finally, since the functionality for handling different interfaces is
> needed anyway (in case they are specified in the cfg), it is, in my
> opinion, better to have one mechanism (behavior) for the different
> situations.
ok to avoid the OS needing to do all the routing decisions, you think its
better to have control in openslp. Sounds ok to me.
How about others?
> > Proposal: In SLPDIncomingInit() function all the address are bound.
> >
> > if (G_SlpdProperty.interfaces != NULL)
> > SLPIfaceGetInfo(G_SlpdProperty.interfaces,&ifaces,&G_SLPDProcInfo,
> > AF_UNSPEC);
> > else
> > ifaces.iface_count = 0;
> > When the interfaces are found to be NULL, we can assume that slpd must bind
> > to all inetfaces. So depending on the config file we have 3 cases.
> > Case 1: Only IPv4 enabled. We can create TCP/UDP sockets with INADDR_ANY.
> > Case 2: Only IPv6 enabled. We can create TCP/UDP sockets with ::
> > Case 3: Both IPv6& IPv4 enabled. We can create sockets with :: but use
> > IPV6_V6ONLY option set.
> >
> > This way we will have only 1 or 2 sockets listening instead of all.
> > Improves performance as well. My only doubt is how this works with Windows.
> > Iam no expert in that.
> > If the interfaces are specified then we do exactly what is done now. Is
> > that ok with everyone?
> >
> > - Wrong Representation Of Interfaces In Config File: Although it looked at
> > first as a minor issue, this has caused multiple problems to basic
> > functionality. Openslp takes in ipaddress without the need for interface
> > information.
> > This leads to major issues. The function v6GetScope() is faulty function.
> >
> > There can be cases when interfaces can have same ips. Eg:
> > eth2 Link encap:Ethernet HWaddr 00:06:29:55:60:81
> > inet6 addr: fe80::206:29ff:fe55:6081/64 Scope:Link
> > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
> > RX packets:4037 errors:0 dropped:0 overruns:0 frame:0
> > TX packets:134395 errors:0 dropped:0 overruns:0 carrier:0
> > collisions:0 txqueuelen:1000
> > RX bytes:436006 (425.7 KiB) TX bytes:14655216 (13.9 MiB)
> > Interrupt:16 Base address:0x2200
> >
> > eth2.30 Link encap:Ethernet HWaddr 00:06:29:55:60:81
> > inet addr:192.168.1.2 Bcast:192.168.1.255 Mask:255.255.255.0
> > inet6 addr: 3001::1/128 Scope:Global
> > inet6 addr: fe80::206:29ff:fe55:6081/64 Scope:Link
> > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
> > RX packets:367 errors:0 dropped:0 overruns:0 frame:0
> > TX packets:15830 errors:0 dropped:0 overruns:0 carrier:0
> > collisions:0 txqueuelen:0
> > RX bytes:40872 (39.9 KiB) TX bytes:1650541 (1.5 MiB)
> >
> > The LL address of both interfaces are same, In which case it becomes clear
> > viewing the v6GetScope() code that the scope id returned will be same for
> > both interface but in reality it is different. This results in binding to
> > only one interface. This is wrong. This has to be changed. This also is the
> > case with ips specified in the config file.
> >
> > net.slp.interfaces = fe80::206:29ff:fe55:6081
> >
> > There is no way of saying which interface this must bind to.
> >
> > Proposal: The posix standard must be adopted to fix the issue. The
> > interface must be specified.
> > net.slp.interfaces =
> > fe80::206:29ff:fe55:6081%eth2.30,2001::1%eth1,10.0.0.1%eth0
> >
> > The<ip>%<iface> is standard posix method. This will greatly help in
> > getting the correct scopeid.
> >
> This is (probably) not described in the SLP RFC and I don't know if it
> creates an incompatibility, but when this extension is made optional, it
> sounds fine to me. I assume interface names never contain a ','
> otherwise that would clash with the list separator.
>
I have to revisit the RFC too, but i wonder how this was missed in RFC. I mean,
if a interface is given without the interface what assumption are we supposed
to make? To me it sounds wrong.
Making it optional might work, but that will make a code a little bit
complicated. I will start to work this way. If anyone has any idea on this do
let me know.
> BR,
> Roel
> > I have already looked into the code and made a temporary fix for the above
> > problem. But i want to rewrite that patch to make it better. If everyone is
> > ok with the above i will start working on it. Please reply back with any
> > issues. I have no windows programming knowledge, so if iam making a blunder
> > here, do let me know.
> >
> > Regards,
> > Varun
> >
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>
>
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