Date: Wed, 14 Aug 1996 10:16:22 -0700 (PDT) From: Jon Inouye <jinouye@cse.ogi.edu> To: Nate Williams <nate@mt.sri.com> Cc: mobile@freebsd.org Subject: Re: 2.1.5 vs. 2.2-SNAP Message-ID: <Pine.HPP.3.95.960814095732.15198A-100000@indurain.cse.ogi.edu> In-Reply-To: <199608141650.KAA27565@rocky.mt.sri.com>
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On Wed, 14 Aug 1996, Nate Williams wrote: > They should be almost *exactly* the same. > Okay, I'll spend some time investigating why the PC card ioctl PIOCSDRV fails for my modem card in 2.1.5 but not 2.2. > > If so, I may try to migrate some > > 2.1 kernel modifications to 2.2-SNAP rather than to 2.1.5. > > What kernel modifications? The code in -current (therefore any of the > recent SNAPS) is mostly functional already, although some of the Nomad > 'features' don't yet exist in the -current code. And, given the lack of > interest and help I've received it's not obvious when/if the code will > ever make it into -current. (Yes, I'm a bit frustrated!) > I have some kernel modifications to support physical media independence, something folks at Intel call "media switching". It adjusts the network stack to survive changes in network interfaces --- enabled through PC card technology. Some of this can be accomplished using a modified arp (to filter out invalid ARP entries) and route flush but doing so at user level has some synchronization problems --- the kernel is a better place for atomic operations. I also reset TCP retransmission timers to avoid the backoff when no interface is available. Resetting retransmission timers on correspondent hosts is on the todo list; I plan on using Ramon Caceres' triple ack hack. Other dependencies on ifnet pointers include multicast groups and tunnels, the BPF, and routed/gated. Migrating tunnels is impossible with most implementations of mrouted (fixed endpoints) and breaks the concept of efficient multicasting. Migrating mcast groups and BPF filters to different interfaces may not be a good idea. Opinions? Then there's Jim Binkley's Mobile IP modifications, which allow survival across IP address changes (assuming you have connectivity to your home agent). Otherwise, long-term TCP/UDP connections like telnet, X11, and a certain distributed real-time MPEG player break when the new interface has a different IP address. -JI
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