Mptcp: Moving laptop from GBit to wireless without applications noticing? • Hacker News Board

Re: Mptcp: Moving laptop from GBit to wireless without applications noticing?

#41

Post by globalc » Tue, Jun 14, 2022, 2:40 AM UTC

thrtythreeforty wrote: post #5

linsomniac wrote: post #2

MPTCP has been on my radar for a long while and seems very cool. I will say that for seamless wireless/wired switching, Linux bonding works very well. ~15+ years ago I had my laptop set up with eth and wifi bonded, with eth as the preferred, I believe using link-beat as the method. I could be running a big copy, plug in the ethernet and the transfer rate would almost instantly shoot up, and then when done I could unp…

Re: bonding, what a good idea! I may have to set this up on my laptop. Are there any downsides? (Besides being unable to connect to different networks of course)

You should pay attention to make the ethernet the preferred interface.

If aggregation of bandwidth over the various underlying media is important for you: depending on the exact mode, aggregation might not work. Even if working, via bonding you might only get aggregation if the traffic goes over multiple TCP channels, while MPTCP also aggregates for a single TCP channel.

Re: Mptcp: Moving laptop from GBit to wireless without applications noticing?

#42

Post by zootboy » Tue, Jun 14, 2022, 4:13 AM UTC

linsomniac wrote: post #38

zootboy wrote: post #37

Earlier quoted context omitted.

I've had a concept in mind for this exact scenario that I'm reasonably certain will work, I've just never taken the time to fully implement it. No need to bond interfaces or apply the same IP to both interfaces. Let them both acquire different IP addresses in the same subnet. Linux will start announcing its ARP replies on the ethernet path since it has a better path metric. Thus the return path for both the wifi IP a…

I guess you could do this by just sending gratuitous ARPs for the wifi IP with the eth MAC addr, over the eth interface. Probably have to turn off rp_filter as well?

You don't even need to do that. The ARP packets seem to be routed to the network through the normal route table, so replies for the wifi IP get sent via the ethernet link and the network switches seem to learn that as the return path.

As for rp_filter, it's set to "2" on my machines, which seems to allow return packets on the "wrong" port as long as it's an address that any other port owns.

Re: Mptcp: Moving laptop from GBit to wireless without applications noticing?

#43

Post by globalc » Sun, Jun 19, 2022, 10:56 PM UTC

I played through more scenarios with the "I have a laptop, and want seamless switching between ethernet and wireless".

shadowsocks proxy seems like the best choice, allowing transparent proxy for TCP applications, but also needs 2 helper systems for the setup.

Next best choice seems bonding, just needs helpers on the LAN.

Details: https://fluxcoil.net/wiki/software/mptcp