bpftool: Extend net dump with netkit progs

Add support to dump BPF programs on netkit via bpftool. This includes both
the BPF link and attach ops programs. Dumped information contain the attach
location, function entry name, program ID and link ID when applicable.

Example with tc BPF link:

# ./bpftool net
xdp:

tc:
nk1(22) netkit/peer tc1 prog_id 43 link_id 12

[...]

Example with json dump:

# ./bpftool net --json | jq
[
{
"xdp": [],
"tc": [
{
"devname": "nk1",
"ifindex": 18,
"kind": "netkit/primary",
"name": "tc1",
"prog_id": 29,
"prog_flags": [],
"link_id": 8,
"link_flags": []
}
],
"flow_dissector": [],
"netfilter": []
}
]

Signed-off-by: Daniel Borkmann <[e-mail]>
Reviewed-by: Quentin Monnet <[e-mail]>
Acked-by: Martin KaFai Lau <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Martin KaFai Lau <[e-mail]>

tools/bpf/bpftool/Documentation/bpftool-net.rst

···
 	**bpftool net { show | list }** [ **dev** *NAME* ]
 		  List bpf program attachments in the kernel networking subsystem.
 
-		  Currently, device driver xdp attachments, tcx and old-style tc
+		  Currently, device driver xdp attachments, tcx, netkit and old-style tc
 		  classifier/action attachments, flow_dissector as well as netfilter
 		  attachments are implemented, i.e., for
 		  program types **BPF_PROG_TYPE_XDP**, **BPF_PROG_TYPE_SCHED_CLS**,
···
 		  bpf programs, users should consult other tools, e.g., iproute2.
 
 		  The current output will start with all xdp program attachments, followed by
-		  all tcx, then tc class/qdisc bpf program attachments, then flow_dissector
-		  and finally netfilter programs. Both xdp programs and tcx/tc programs are
+		  all tcx, netkit, then tc class/qdisc bpf program attachments, then flow_dissector
+		  and finally netfilter programs. Both xdp programs and tcx/netkit/tc programs are
 		  ordered based on ifindex number. If multiple bpf programs attached
 		  to the same networking device through **tc**, the order will be first
-		  all bpf programs attached to tcx, then tc classes, then all bpf programs
+		  all bpf programs attached to tcx, netkit, then tc classes, then all bpf programs
 		  attached to non clsact qdiscs, and finally all bpf programs attached
 		  to root and clsact qdisc.
 

tools/bpf/bpftool/net.c

···
 static const char * const attach_loc_strings[] = {
 	[BPF_TCX_INGRESS]		= "tcx/ingress",
 	[BPF_TCX_EGRESS]		= "tcx/egress",
+	[BPF_NETKIT_PRIMARY]		= "netkit/primary",
+	[BPF_NETKIT_PEER]		= "netkit/peer",
 };
 
 const size_t net_attach_type_size = ARRAY_SIZE(attach_type_strings);
···
 {
 	__show_dev_tc_bpf(dev, BPF_TCX_INGRESS);
 	__show_dev_tc_bpf(dev, BPF_TCX_EGRESS);
+
+	__show_dev_tc_bpf(dev, BPF_NETKIT_PRIMARY);
+	__show_dev_tc_bpf(dev, BPF_NETKIT_PEER);
 }
 
 static int show_dev_tc_bpf_classic(int sock, unsigned int nl_pid,
···
 		"       ATTACH_TYPE := { xdp | xdpgeneric | xdpdrv | xdpoffload }\n"
 		"       " HELP_SPEC_OPTIONS " }\n"
 		"\n"
-		"Note: Only xdp, tcx, tc, flow_dissector and netfilter attachments\n"
+		"Note: Only xdp, tcx, tc, netkit, flow_dissector and netfilter attachments\n"
 		"      are currently supported.\n"
 		"      For progs attached to cgroups, use \"bpftool cgroup\"\n"
 		"      to dump program attachments. For program types\n"