getting a callback ip address for nfsv4 client

[Rick Macklem]

On Mon, 6 Apr 2009, Robert Watson wrote:

> On Sun, 5 Apr 2009, Julian Elischer wrote:
>
>>> One possibility is to connect() a socket to the server address, then call 
>>> getsockaddr() to query what address the network stack is using.  If the 
>>> connection completed, then the address could at least send packets to the 
>>> server, even if it isn't reachable from the server.
>>> 
>>> (Obviously, kernel versions of the above...)
>> 
>> we ended up with him doing "whatever the connect code would have done" 
>> since as he is in fact inside the kernel, he can just do the same..
>
> I figured that if the RPC layer was going to make a connection anyway, we 
> could just query the RPC layer and ask it what address it had used.  However, 
> if the decision needs to be made earlier than that, then that doesn't make as 
> much sense.  This would mean NFS could avoid knowing about routes and 
> interfaces, and just know about sockets and addresses.
>

I just took a quick look at Doug's RPC code and the socket doesn't seem to 
be exposed to the client side by the rpc layer, so I think that rtalloc1() 
is probably easier? I'd also be worried about knowing when the socket
pointer is valid and in a connected state. (The rtalloc1() code only uses the
one path rt->rt_ifa->ifa_addr after sanity checking that the pointers 
aren't null, so I don't think it will be difficult to maintain. It does imply
that the code knows the route locking rules, but that just means it
uses RTFREE_LOCKED(rt), so as long as that macro keeps working, it should
be ok, I think.)

rick