feat(p2p): add ICMP backend support

gold/p2p/icmp/init.go

@@ -0,0 +1,26 @@
+// Package icmp for non-privileged datagram-oriented ICMP endpoints,
+// currently only Darwin and Linux support this.
+package icmp
+
+import (
+	"net/netip"
+
+	"github.com/fumiama/WireGold/gold/p2p"
+	"github.com/fumiama/WireGold/internal/file"
+)
+
+func NewEndpoint(endpoint string, _ ...any) (p2p.EndPoint, error) {
+	addr, err := netip.ParseAddr(endpoint)
+	if err != nil {
+		return nil, err
+	}
+	return (*EndPoint)(&addr), nil
+}
+
+func init() {
+	name := file.FolderName()
+	_, hasexist := p2p.Register(name, NewEndpoint)
+	if hasexist {
+		panic("network " + name + " has been registered")
+	}
+}