Missing support for iterating over per-CPU maps about ebpf

[lmb]

You're not checking srcTrafficIter.Err(). Otherwise you'd see the following error:

look up next key: per-cpu value requires a slice or a pointer to slice

Here is a diff to one of the examples which shows how to use it:

diff --git a/examples/xdp/bpf_bpfeb.o b/examples/xdp/bpf_bpfeb.o
index f90c8b99..9ab3a59f 100644
Binary files a/examples/xdp/bpf_bpfeb.o and b/examples/xdp/bpf_bpfeb.o differ
diff --git a/examples/xdp/bpf_bpfel.o b/examples/xdp/bpf_bpfel.o
index 35dba4b8..e708d827 100644
Binary files a/examples/xdp/bpf_bpfel.o and b/examples/xdp/bpf_bpfel.o differ
diff --git a/examples/xdp/main.go b/examples/xdp/main.go
index 123513b1..99796157 100644
--- a/examples/xdp/main.go
+++ b/examples/xdp/main.go
@@ -72,10 +72,10 @@ func formatMapContents(m *ebpf.Map) (string, error) {
 	var (
 		sb  strings.Builder
 		key netip.Addr
-		val uint32
+		val = make([]uint32, ebpf.MustPossibleCPU())
 	)
 	iter := m.Iterate()
-	for iter.Next(&key, &val) {
+	for iter.Next(&key, val) {
 		sourceIP := key // IPv4 source address in network byte order.
 		packetCount := val
 		sb.WriteString(fmt.Sprintf("\t%s => %d\n", sourceIP, packetCount))
diff --git a/examples/xdp/xdp.c b/examples/xdp/xdp.c
index 2f36c161..ac414b66 100644
--- a/examples/xdp/xdp.c
+++ b/examples/xdp/xdp.c
@@ -9,7 +9,7 @@ char __license[] SEC("license") = "Dual MIT/GPL";
 
 /* Define an LRU hash map for storing packet count by source IPv4 address */
 struct {
-	__uint(type, BPF_MAP_TYPE_LRU_HASH);
+	__uint(type, BPF_MAP_TYPE_LRU_PERCPU_HASH);
 	__uint(max_entries, MAX_MAP_ENTRIES);
 	__type(key, __u32); // source IPv4 address
 	__type(value, __u32); // packet count

Output:

2024/01/08 12:15:10 Attached XDP program to iface "lo" (index 1)
2024/01/08 12:15:10 Press Ctrl-C to exit and remove the program
2024/01/08 12:15:11 Map contents:
2024/01/08 12:15:12 Map contents:
2024/01/08 12:15:13 Map contents:
	127.0.0.1 => [0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0]
2024/01/08 12:15:14 Map contents:
	127.0.0.1 => [2 2 4 0 5 0 0 0 0 0 0 0 0 2 0 0]
2024/01/08 12:15:15 Map contents:
	127.0.0.1 => [2 2 4 0 5 0 0 0 0 0 0 0 0 2 0 0]

[HouzuoGuo]

That's very cool, thank you!