Hi Hannes, On 11/29/16 at 03:15pm, Hannes Frederic Sowa wrote: > Did you look at the cgroup based hooks which were added recently in > ip_finish_output for cgroup ebpf support and in general the cgroup bpf > subsystem. Does some of this solve the problem for you already? Would be > interesting to hear your opinion on that.
What I'm looking for is the ability to collect statistics and generate samples for a subset of the traffic, e.g. all intra data center traffic, all packets hitting the default route in a network namespace, all packets which use a dst tying a certain endpoint to particular TCP metrics. For the examples above, LWT provides a very intuitive and natural way to do so while amortizing the cost of the route lookup which is required anyway. The cgroup hook provides similar semantics but if the application context is of interest. Obviously, tasks in a cgroup may be sharing routes so I can't use it as a replacement. However, using the two in combination will become highly useful as it allows to gather statistics individually for both application context and routing context and then aggregate them to see how applications are using different network segments. Aside from the different context matching, the cgroup hook will not allow to modify the packet as the lwtunnel_xmit() post ip_finish_output does.
