On Wed, 19 Dec 2018 16:46:05 +0100 Daniel Borkmann <borkm...@iogearbox.net> wrote:
> Hmm, why not just doing something as in your example below with napi_poll() > where you pass in the napi pointer, and then use bpf_probe_read_str() on > ctx->dev for fetching the name? At least there this should work and should > be okay given it's rather slow-path event. > > > [1] > > https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/samples/bpf/napi_monitor_kern.c#L34-L130 I didn't try to use bpf_probe_read_str() in [1], but that is also not what I want in my use-case. I don't want the name, but the ifindex to filter on, as it will be faster. My use-case is allowing my napi_monitor program to filter on a specific net_device, inside the kernel via BPF. E.g. this didn't work: bpf_probe_read(&ifindex, 4, &ctx->napi->dev->ifindex); Perhaps you know how I can do this deref correctly? My napi_monitor use-case is not a slow-path event, even-though in optimal cases we should handle 64 packets per tracepoint invocation, but I'm using this for 100G NICs with >20Mpps. And I mostly use the tool when something looks wrong and I don't see 64 packet bulks, which is also why I detect when this gets invoked from idle task or from ksoftirqd. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
