On Mon, Nov 18, 2019 at 5:20 PM Ben Pfaff <[email protected]> wrote: > > On Tue, Nov 12, 2019 at 04:46:12PM +0100, Matteo Croce wrote: > > On Tue, Nov 12, 2019 at 4:00 PM Simon Horman <[email protected]> > > wrote: > > > > > > On Tue, Nov 12, 2019 at 11:25:18AM +0100, Matteo Croce wrote: > > > > New action to decrement TTL instead of setting it to a fixed value. > > > > This action will decrement the TTL and, in case of expired TTL, send the > > > > packet to userspace via output_userspace() to take care of it. > > > > > > > > Supports both IPv4 and IPv6 via the ttl and hop_limit fields, > > > > respectively. > > > > > > > > > > Usually OVS achieves this behaviour by matching on the TTL and > > > setting it to the desired value, pre-calculated as TTL -1. > > > With that in mind could you explain the motivation for this > > > change? > > > > > > > Hi, > > > > the problem is that OVS creates a flow for each ttl it see. I can let > > vswitchd create 255 flows with like this: > > > > $ for i in {2..255}; do ping 192.168.0.2 -t $i -c1 -w1 &>/dev/null & done > > $ ovs-dpctl dump-flows |fgrep -c 'set(ipv4(ttl' > > 255 > > Sure, you can easily invent a situation. In real traffic there's not > usually such a variety of TTLs for a flow that matches on the number of > fields that OVS usually needs to match. Do you see a real problem given > actual traffic in practice? >
Hi Ben, yes, my situation was a bit artificious, but you can get a similar situation in practice. Imagine a router with some subnetworks behind it on N levels, with some nodes hosting virtual machines. Windows and Linux have different default TTL values, 128 and 64 respectively, so you could see N*2 different TTL values. Bye, -- Matteo Croce per aspera ad upstream _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
