Subject: Re: (Revisiting) Using airport- doesn't anyone know?
From: Brice D Ruth (brice@webprojkt.com)
Date: Tue Jun 19 2001 - 15:46:23 MDT
Wow, you have certainly run the gamut on configurations! I'm not sure
what's going on or what's wrong, but I'll try my darndest to help you
out. I've been running MacOS exclusively on the iMac DV I have LinuxPPC
installed on (I was doing 100% of my work in the MacOS, didn't see why I
should be booting into Linux just to start MOL :)).
I'm a bit behind, though - so maybe what I'll do is grab the YDL 2.0
isos, install the latest & greatest kernel, then rsync the latest mol
and start trying to get things to work. Just to refresh my memory, what
hardware are you running and what distribution are you running? As many
details (however insignificant they may seem) as you can provide will help.
To answer your question about masquerading - here's how that works.
When you enable IP forwarding in the linux kernel (echo 1 >
/proc/sys/net/ipv4/ip_forward) the kernel will forward IP packets
according to its routing table - so if it receives a packet destined for
say www.apple.com from the tap0 interface, it will automagically forward
that to its default interface (assuming you're not on the subnet of
www.apple.com :)). However, a response (ack) packet from www.apple.com
will encounter some difficulty in getting back to your tap0 interface,
since the return address of the packet you sent is a private network
address, the routers on the Internet won't know what to do with it.
Enter masquerading - by setting up eth1 to masquerade, you're telling
the kernel that it should modify the outgoing packets for eth1 so that
they can safely get back - the kernel's forwarding takes care of getting
packets from tap0 to eth1, the masquerading takes care of everything
thereafter. Does that make sense?
OK - let me get started on my iMac, we'll see how things go :)
-Brice
William K. Gibson wrote:
>on 6/7/01 7:15 PM, Brice D Ruth at brice@webprojkt.com wrote:
>
>>I have MOL setup on an iMac DV w/ AirPort and it works fine. I have done as
>>Sam suggested - tap device + masquerading since this how I'm used to setting up
>>shared networking from my PC experience w/ VMware.
>>
>
>>With kernel 2.4.x, you'll use iptables, so you'll want something to the
>>following effect:
>>
>
>I really wish to thank Brice, Samuel, Derrik, Tom, and Reto for their kind
>and intelligent responses. However, I must regretfully say that after ten
>days of trying various things, I am still exactly where I was. I have tried
>just about everything and the internet access is still deathly slow. I set
>up a tap0 interface and tried to use it and it is still slow.
>
>First: I don't understand why my compile of the benh 2.4.5 kernel decides to
>set up airport as eth1. I have no idea what I did wrong there.
>
>Second: I tried to set up a tap0 device and follow directions on various
>sites (like the MOL FAQ). It was extremely difficult to understand and
>repeated persusal of various HOWTOs, man pages, and web pages did not make
>it any easier. Each source seemed to leave out important details. Putting
>them all together I attempted many many different scenarios.
>
>I tried setting up masquerades for the various interfaces. I tried to make
>various changes in /proc/sys/net/ipv4/conf/tap0/... I tried to use the route
>command to set up a route from MOL to the gateway address of my base station
>using tap0. I tried using route to set up a route from MOL to my linux box
>using tap0. I tried using route to set up a route from MOL using eth1. Etc.
>etc. Nothing seemed to work.
>
>Third: What should be the gateway address on the Macintosh side? Should it
>be the linux box or the base station? Both seemed to work- but did nothing
>to improve the speed. And what should be the gateway address on the routing
>table side for tap0? Should it be the linux box or the base station?
>
>Fourth: I tried setting my own arp entries which was recommended by one
>site. But they seemed to get set automatically. Anyway it didn't help.
>
>Fifth:
>
>>iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE (assuming eth1 is your
>>AirPort card)
>>
>
>This I don't understand. Why set up a masquerade on eth1? Shouldn't I set up
>a masquerade on tap0? And supposing I did this correctly, what would be the
>effect of a masquerade on a packet from MOL that was sent to the base
>station, which does it's own masquerade? This seems like it would screw up
>the packet. I just don't get it.
>
>Anyway, masquerading on both tap0 and eth1 did not help or hinder the
>transmission of packets. The only thing that worked was the routing table
>entry for tap0. And of course it was still slow.
>
>Sixth: Should eth0, eth1, and tap0 all have the same internal ip address or
>should they be different? I tried giving them all 10.0.1.5. It worked but
>again no help on speed. I tried giving them the range 10.0.1.3-5. It worked
>but no help on the speed.
>
>I'm at my wits end here, and ready to give up. I really wanted to use MOL
>wirelessly but unless I can figure this out, it looks like I'm going to have
>to run wires where ever I use my machine or reboot. I can only think I
>missed something on the Linux side- like DNS problems, or forgetting to
>compile something into the kernel that Airport needs (although there was no
>blurb for it to tell me what), or maybe I set up my tap0 interface poorly.
>
>If anyone can point me toward a comprehensive and definitive source for
>using MOL with airport or even with a tap interface, I would really
>appreciate it.
>
>--William K. Gibson
>1stDesk Systems
>firstdesk@columbus.rr.com
>
-- WebProjkt, Inc. (ph) 773.562.1008 (fax) 608.204.7004 http://www.webprojkt.com/
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