feat: Add support for reverse DNS lookups

Closes https://github.com/mr-karan/doggo/issues/25

internal/app/questions.go

@@ -33,3 +33,23 @@ func (app *App) PrepareQuestions() {
 		}
 	}
 }
+
+// ReverseLookup is used to perform a reverse DNS Lookup
+// using an IPv4 or IPv6 address.
+// Query Type is set to PTR, Query Class is set to IN.
+// Query Names must be formatted in in-addr.arpa. or ip6.arpa format.
+func (app *App) ReverseLookup() {
+	app.QueryFlags.QTypes = []string{"PTR"}
+	app.QueryFlags.QClasses = []string{"IN"}
+	formattedNames := make([]string, 0, len(app.QueryFlags.QNames))
+
+	for _, n := range app.QueryFlags.QNames {
+		addr, err := dns.ReverseAddr(n)
+		if err != nil {
+			app.Logger.WithError(err).Error("error formatting address")
+			app.Logger.Exit(2)
+		}
+		formattedNames = append(formattedNames, addr)
+	}
+	app.QueryFlags.QNames = formattedNames
+}