plugin/hosts: add wildcard support (#8185)

* plugin/hosts: add wildcard support for owner names

Signed-off-by: youknowforsearch <amirhebrahimzader@gmail.com>

* plugin/hosts: document wildcard owner name support

Signed-off-by: youknowforsearch <amirhebrahimzader@gmail.com>

* plugin/hosts: remove unused lookupStaticHost

Signed-off-by: Amirhossein Ebrahimzade <amirhossein.e@smartech.ir>

---------

Signed-off-by: youknowforsearch <amirhebrahimzader@gmail.com>
Signed-off-by: Amirhossein Ebrahimzade <amirhossein.e@smartech.ir>
Co-authored-by: Amirhossein Ebrahimzade <amirhossein.e@smartech.ir>

plugin/hosts/wildcard_test.go

@@ -0,0 +1,58 @@
+package hosts
+
+import (
+	"testing"
+)
+
+func TestReplaceWithAsteriskLabel(t *testing.T) {
+	tests := []struct {
+		in, out string
+	}{
+		{".", ""},
+		{"example.com.", "*.com."},
+		{"foo.example.com.", "*.example.com."},
+		{"bar.intern.example.com.", "*.intern.example.com."},
+	}
+
+	for _, tc := range tests {
+		got := replaceWithAsteriskLabel(tc.in)
+		if got != tc.out {
+			t.Errorf("replaceWithAsteriskLabel(%q) = %q, want %q", tc.in, got, tc.out)
+		}
+	}
+}
+
+func TestReplaceWithAsteriskLabelApex(t *testing.T) {
+	// Apex names produce a *.parent pattern but must not match *.zone wildcards.
+	if got := replaceWithAsteriskLabel("example.com."); got != "*.com." {
+		t.Fatalf("replaceWithAsteriskLabel(example.com.) = %q, want *.com.", got)
+	}
+}
+
+func TestLookupWildcardHost(t *testing.T) {
+	const hosts = `
+127.0.0.53 *.example.org
+127.0.1.52 *.intern.example.org
+127.0.0.54 foo.example.org
+192.168.33.10 *.example.com
+192.168.33.11 a.example.com
+192.168.33.12 b.example.com
+`
+
+	h := testHostsfile(hosts)
+
+	tests := []staticHostEntry{
+		{"foo.example.org.", []string{"127.0.0.54"}, []string{}},
+		{"bar.example.org.", []string{"127.0.0.53"}, []string{}},
+		{"bar.intern.example.org.", []string{"127.0.1.52"}, []string{}},
+		{"a.example.com.", []string{"192.168.33.11"}, []string{}},
+		{"b.example.com.", []string{"192.168.33.12"}, []string{}},
+		{"c.example.com.", []string{"192.168.33.10"}, []string{}},
+		{"example.com.", []string{}, []string{}},
+		{"deep.foo.example.org.", []string{}, []string{}},
+	}
+
+	for _, ent := range tests {
+		testStaticHost(t, ent, h)
+	}
+}