kdig: parse dnstap generate ("-G") command-line option

This adds support for parsing the "-G" flag and opens the dnstap input
file, but does not yet actually generate the dnstap message trace
output.

man/kdig.1.in

@@ -85,6 +85,9 @@ the shared secret encoded in Base64.
 Export a dnstap trace of the response messages received to the file
 \fItapfile\fR. If \fB+qr\fR is specified, also export query messages.
 .TP
+.BI \-G \ tapfile
+Generate message output from a previously saved dnstap file \fItapfile\fR.
+.TP
 .BR + [ no ] multiline
 Wrap long records to more lines and improve human readability.
 .TP

src/utils/dig/dig_params.c

@@ -903,6 +903,7 @@ void dig_clean(dig_params_t *params)
 
 #if USE_DNSTAP
 	// Cleanup dnstap.
+	dt_reader_free(params->config->dt_reader);
 	dt_writer_free(params->config->dt_writer);
 #endif
 
@@ -1098,6 +1099,22 @@ static int parse_dnstap_export(const char *value, query_t *query)
 
 	return KNOT_EOK;
 }
+
+static int parse_dnstap_generate(const char *value, query_t *query)
+{
+	DBG("Generating message output from dnstap input file %s\n", value);
+
+	if (query->dt_reader != NULL) {
+		dt_reader_free(query->dt_reader);
+	}
+
+	query->dt_reader = dt_reader_create(value);
+	if (query->dt_reader == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	return KNOT_EOK;
+}
 #endif
 
 static void complete_servers(query_t *query, const query_t *conf)
@@ -1223,6 +1240,7 @@ static void dig_help(void)
 	printf("Usage: kdig [-4] [-6] [-dh] [-b address] [-c class] [-p port]\n"
 	       "            [-q name] [-t type] [-x address] [-k keyfile]\n"
 	       "            [-y [algo:]keyname:key] [-E tapfile] name @server\n"
+	       "       kdig [-G tapfile]\n"
 	       "\n"
 	       "       +[no]multiline  Wrap long records to more lines.\n"
 	       "       +[no]short      Show record data only.\n"
@@ -1433,6 +1451,23 @@ static int parse_opt1(const char *opt, const char *value, dig_params_t *params,
 #else
 		ERR("no dnstap support but -E specified\n");
 		return KNOT_EINVAL;
+#endif
+		break;
+	case 'G':
+#if USE_DNSTAP
+		if (val == NULL) {
+			ERR("missing filename\n");
+			return KNOT_EINVAL;
+		}
+
+		if (parse_dnstap_generate(val, query) != KNOT_EOK) {
+			ERR("unable to open dnstap input file %s\n", val);
+			return KNOT_EINVAL;
+		}
+		*index += add;
+#else
+		ERR("no dnstap support but -G specified\n");
+		return KNOT_EINVAL;
 #endif
 		break;
 	case '-':

src/utils/dig/dig_params.h

@@ -33,6 +33,7 @@
 #include "utils/common/exec.h"		// sign_context_t
 
 #if USE_DNSTAP
+# include "dnstap/reader.h"
 # include "dnstap/writer.h"
 #endif
 
@@ -117,6 +118,8 @@ typedef struct {
 	/*!< Context for operations with signatures. */
 	sign_context_t	sign_ctx;
 #if USE_DNSTAP
+	/*!< Context for dnstap reader input. */
+	dt_reader_t	*dt_reader;
 	/*!< Context for dnstap writer output. */
 	dt_writer_t	*dt_writer;
 #endif