feat(dns): Support TXT query type (#1679)

Allows monitoring of things like spf records and others.

Co-authored-by: TwiN <twin@linux.com>

client/client.go

@@ -499,6 +499,13 @@ func QueryDNS(queryType, queryName, url string) (connected bool, dnsRcode string
 			if srv, ok := rr.(*dns.SRV); ok {
 				body = []byte(fmt.Sprintf("%s:%d", srv.Target, srv.Port))
 			}
+		case dns.TypeTXT:
+			if txt, ok := rr.(*dns.TXT); ok {
+				if len(body) > 0 {
+					body = append(body, '\n')
+				}
+				body = append(body, []byte(strings.Join(txt.Txt, ""))...)
+			}
 		default:
 			body = []byte("query type is not supported yet")
 		}

client/client_test.go

@@ -507,6 +507,16 @@ func TestQueryDNS(t *testing.T) {
 			expectedDNSCode: "NOERROR",
 			expectedBody:    "one.one.one.one.",
 		},
+		{
+			name: "test Config with type TXT",
+			inputDNS: dns.Config{
+				QueryType: "TXT",
+				QueryName: "example.com.",
+			},
+			inputURL:        "1.1.1.1",
+			expectedDNSCode: "NOERROR",
+			expectedBody:    "*v=spf1*",
+		},
 		{
 			name: "test Config with fake type and retrieve error",
 			inputDNS: dns.Config{
@@ -526,8 +536,8 @@ func TestQueryDNS(t *testing.T) {
 			if dnsRCode != scenario.expectedDNSCode {
 				t.Errorf("expected DNSRCode to be %s, got %s", scenario.expectedDNSCode, dnsRCode)
 			}
-			if scenario.inputDNS.QueryType == "NS" {
-				// Because there are often multiple nameservers backing a single domain, we'll only look at the suffix
+			if scenario.inputDNS.QueryType == "NS" || scenario.inputDNS.QueryType == "TXT" {
+				// Some record types can have multiple valid answers, so wildcard matching is used in those scenarios
 				if !pattern.Match(scenario.expectedBody, string(body)) {
 					t.Errorf("got %s, expected result %s,", string(body), scenario.expectedBody)
 				}