On Fri, 15 May 2020 at 15:24, David Ahern <dsahern@xxxxxxxxx> wrote: > > On 5/15/20 3:59 AM, Lorenz Bauer wrote: > > > > Yes, but that doesn't play well with changing the source address to > > the local machine's, since the upper part of the stack will drop the > > packet due to accept_local=0. > > Can you defer the source address swap to the Tx path? Let the packet go > up the stack and do the fib lookup again as an skb. neighbor entry does > not exist, so the packet is stashed, neighbor resolution done, once > resolved the packet goes out. tc program on the egress device can flip > the source address, and then subsequent packets take the XDP fast path. Hm, that's an interesting idea! I guess this means I have to mark the packet somehow, to make sure I can identify it on the TX path. Plus, in theory the packet could exit via any interface, so I'd have to attach classifiers to a bunch of places if I want to be on the safe side. Upside: this seems doable in current kernels. Downside: seems more fragile than I'd like. Thanks for the thought, I'll play around with it :) > > If the next host is on the same LAN I believe the stack will want to > generate an ICMP redirect, but that can be squashed. -- Lorenz Bauer | Systems Engineer 6th Floor, County Hall/The Riverside Building, SE1 7PB, UK www.cloudflare.com
