refactor(netx): start moving tls-specific code inside the tlsx pkg (#363)

* refactor(netx): move cert pool code inside tlsx

* refactor(netx): move more tls code inside tlsx

internal/engine/netx/tlsx/tlsx_test.go

@@ -2,6 +2,7 @@ package tlsx
 
 import (
 	"crypto/tls"
+	"errors"
 	"testing"
 )
 
@@ -28,3 +29,77 @@ func TestCipherSuite(t *testing.T) {
 		t.Fatal("not working for zero cipher suite")
 	}
 }
+
+func TestNewDefaultCertPoolWorks(t *testing.T) {
+	pool := NewDefaultCertPool()
+	if pool == nil {
+		t.Fatal("expected non-nil value here")
+	}
+}
+
+func TestConfigureTLSVersion(t *testing.T) {
+	tests := []struct {
+		name       string
+		version    string
+		wantErr    error
+		versionMin int
+		versionMax int
+	}{{
+		name:       "with TLSv1.3",
+		version:    "TLSv1.3",
+		wantErr:    nil,
+		versionMin: tls.VersionTLS13,
+		versionMax: tls.VersionTLS13,
+	}, {
+		name:       "with TLSv1.2",
+		version:    "TLSv1.2",
+		wantErr:    nil,
+		versionMin: tls.VersionTLS12,
+		versionMax: tls.VersionTLS12,
+	}, {
+		name:       "with TLSv1.1",
+		version:    "TLSv1.1",
+		wantErr:    nil,
+		versionMin: tls.VersionTLS11,
+		versionMax: tls.VersionTLS11,
+	}, {
+		name:       "with TLSv1.0",
+		version:    "TLSv1.0",
+		wantErr:    nil,
+		versionMin: tls.VersionTLS10,
+		versionMax: tls.VersionTLS10,
+	}, {
+		name:       "with TLSv1",
+		version:    "TLSv1",
+		wantErr:    nil,
+		versionMin: tls.VersionTLS10,
+		versionMax: tls.VersionTLS10,
+	}, {
+		name:       "with default",
+		version:    "",
+		wantErr:    nil,
+		versionMin: 0,
+		versionMax: 0,
+	}, {
+		name:       "with invalid version",
+		version:    "TLSv999",
+		wantErr:    ErrInvalidTLSVersion,
+		versionMin: 0,
+		versionMax: 0,
+	}}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			conf := new(tls.Config)
+			err := ConfigureTLSVersion(conf, tt.version)
+			if !errors.Is(err, tt.wantErr) {
+				t.Fatalf("not the error we expected: %+v", err)
+			}
+			if conf.MinVersion != uint16(tt.versionMin) {
+				t.Fatalf("not the min version we expected: %+v", conf.MinVersion)
+			}
+			if conf.MaxVersion != uint16(tt.versionMax) {
+				t.Fatalf("not the max version we expected: %+v", conf.MaxVersion)
+			}
+		})
+	}
+}