Re: [Lksctp-developers] SCTP in Linux

[malc <mla...@gm...>]

Simply - an IPv6 LL address only makes sense in conjunction
with knowledge of  the link which is sending it, this is the 'scope'. In
order for the destination LL address to make sense on a machine with
multiple interfaces, you have to specify the scope - in this case, by
telling SCTP to bind to the relevant source (LL) address.

The IPv4 code will work as it picks the correct src address from the src/dst
addr pair, based on the configured subnet/routing table etc.

See [1] and [2] for further discussion of LL and SCTP in general.

Cheers,
malc.

[1] http://forums.sun.com/thread.jspa?threadID=5416971
[2] http://www.sctp.org/archive/0157.html


On Fri, Oct 29, 2010 at 6:06 PM, Greg Weeks <gre...@ne...>wrote:

> Vlad Yasevich wrote:
> > On 10/29/2010 01:31 PM, Greg Weeks wrote:
> >
> >> Is this the correct list to talk about the in-kernel parts of SCTP, or
> >> just the user space tools?
> >>
> >>
> >
> > this list is fine.  A slightly better list is lin...@vg...
> .
> > That list doesn't require subscription and contains a lot less spam.
> >
> >
> Good, I'll ask the question here then.
>
> I saw an oddity that surprised me. I've been using SCTP over IPv4 for a
> while. When I tried to get my code to work over IPv6 using link local
> addresses I found the INITs being sent with the wrong source address.
> The machine has two interfaces, both with just link local addresses for
> IPv6. One of the interfaces is a USB to a small ARM processor that runs
> the USB gadget ethernet device. The ARM is where I have a daemon
> listening. SSH worked fine, and then I tried my SCTP code. I got the
> code to work by doing an explicit bind of the SCTP socket to the link
> local address of the correct interface. When I didn't to the explicit
> bind or if I used in6addr_any for the address and did the sendto the
> INIT had the source address of the OTHER interface. The IP stack on the
> ARM processor then would have no way of replying to the INIT.
>
> IPV4 works fine across the same interface without the bind, so the IPv4
> code is getting the right address.
>
> Does this seem like correct behavior? Is it something weird about how
> I'm setting the sockets up? I'll post code if anyone wants to look at it.
>
> Greg Weeks
>
>
>
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