loading multiple, separate instances of an BPF_MAP_TYPE_XSKMAP?

[thediveo]

I have an XDP socket dispatcher ebpf program that declares an XSK map as follows:

struct {
	__uint(type, BPF_MAP_TYPE_XSKMAP);
	__uint(key_size, sizeof(__u32));
	__uint(value_size, sizeof(__u32));
	__uint(max_entries, MAX_QUEUE_IDS);
} xsks_map SEC(".maps");

And an dispatcher:

SEC("xdp")
int xsk_dispatcher(struct xdp_md *ctx) {
	return bpf_redirect_map(&xsks_map, ctx->rx_queue_index, XDP_PASS);
}

Now, in my Go code when I do this...

objs := bpfObjects{}
loadBpfObjects(&objs, nil)

...and when doing the loadBpfObjects call multiple times, each time passing in a new freshly zeroed bpfObjects{}, do I then get multiple, independent XSK map instances?

[binw666]

Yes, that's right, descriptors to programs and Maps are saved in objs. In addition, you can redefine bpfObjects{} to decide which programs and Maps to load.

[ti-mo]

Also, if you need to share a map across multiple Collections (so, multiple calls to loadBpfObjects()) you can pin that map to bpffs to make subsequent loads use the same instance of the map.

If you prefer to keep everything in process space (no bpffs pinning), use CollectionOptions.MapReplacements for the second (re)load of your Collection after it loaded correctly once before:

loadBpfObjects(&objs,
	&ebpf.CollectionOptions{
		MapReplacements: map[string]*Map{
			"xsks_map": old_objs.XsksMap,
		},
	})