Thinking about UDP and tunneling
Randall Stewart
rrs at lakerest.net
Thu Nov 20 09:37:53 PST 2008
On Nov 20, 2008, at 8:50 AM, Max Laier wrote:
> On Thursday 20 November 2008 14:00:11 Randall Stewart wrote:
>> On Nov 19, 2008, at 5:33 PM, Julian Elischer wrote:
>>>> Its not new, its the same ip header..
>>>> Its just you go into the mbuf chain and take out
>>>> the udp header...
>>>
>>> well you can't do that at the socket buffer becasue you've discarded
>>> the IP header. It may not even be in the mbufs you have. (though
>>> it's
>>> unlikely). After you've processed the UDP part the IP part is gone
>>> so
>>> you'd need to intercept the packet way earlier and then do your
>>> own UDP processing, (or maybe attach the IP header onto it with a
>>> tag).
>>
>> One would definitely have to do some work in udp_input() not a lot
>> from
>> what I can tell... but it would take some work.
>>
>> Maybe good course is to use the socket(9) stuff, but add an option
>> that can set a "by-pass function" if the socket is udp... right
>> after you establish the INP the packet goes to, if the function is
>> set, you engage the bypass...
>
> This sounds reasonable. One would only have to replace calls to
> udp_append in
> udp_input with the by-pass function et voila. Should be clean
> enough. There
> might be some problems with holding the socket lock, though.
>
> For the record, I don't like all the UDP-tunneling madness either,
> but it
> seems that we are stuck with it ... so we should at least try to
> come up with
> a somewhat reasonable implementation for this hackery.
Max:
This was along the lines of what I was thinking exactly.. one side
note. I am told by my colleague in SCTP crime (Michael Tüxen) that Apple
has this functional by-pass interface. He has already got the UDP
tunneling
code working in the MAC version of our stack :-)
I will start working on this when I get back from the IETF. I need to
finish
up the NAT support stuff (almost done) and then I will start looking at
the locking issues that this may bring...
R
>
>
> --
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Randall Stewart
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