add ask_localhost helper program

2 files changed, 145 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 11152b9..30a9d27 100644
--- a/Makefile
+++ b/Makefile
@@ -13,12 +13,18 @@ receive_respond : build/receive_respond.o
 build/receive_respond.o : src/receive_respond.c | build
 	gcc $(CFLAGS) $^ -c -o $@
 
+ask_localhost : build/ask_localhost.o
+	$(CC) $^ -lunbound -o $@
+
+build/ask_localhost.o : src/ask_localhost.c | build
+	gcc $(CFLAGS) $^ -c -o $@
+
 build :
 	mkdir build
 
 all : 0tDNS receive_respond
 
 clean :
-	-rm -r build 0tDNS receive_respond
+	-rm -r build 0tDNS receive_respond ask_localhost
 
 .PHONY : clean
diff --git a/src/ask_localhost.c b/src/ask_localhost.c
new file mode 100644
index 0000000..49845c3
--- /dev/null
+++ b/src/ask_localhost.c
@@ -0,0 +1,138 @@
+/*
+ * Code in examine_result() is taken from official libunbound examples:
+ * https://nlnetlabs.nl/documentation/unbound/libunbound-tutorial-3/
+ * The rest of this file is
+ * Copyright (C) 2020 by Wojtek Kosior <echo a3dvanR1c0Bwcm90b25tYWlsLmNvbQo= | base64 --decode>
+
+ * Permission to use, copy, modify, and/or distribute this software
+ * for any purpose with or without fee is hereby granted.
+
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+ * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * This is a simple helper program for testing our resolver.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <arpa/inet.h>
+
+#include <unbound.h>
+
+/* examine the result structure in detail */
+void examine_result(const char *query, struct ub_result *result)
+{
+        int i;
+        int num;
+
+        printf("The query is for: %s\n", query);
+        printf("The result has:\n");
+        printf("qname: %s\n", result->qname);
+        printf("qtype: %d\n", result->qtype);
+        printf("qclass: %d\n", result->qclass);
+        if(result->canonname)
+                printf("canonical name: %s\n",
+		       result->canonname);
+        else    printf("canonical name: <none>\n");
+
+        if(result->havedata)
+                printf("has data\n");
+        else    printf("has no data\n");
+
+        if(result->nxdomain)
+                printf("nxdomain (name does not exist)\n");
+        else    printf("not an nxdomain (name exists)\n");
+
+        if(result->secure)
+                printf("validated to be secure\n");
+        else    printf("not validated as secure\n");
+
+        if(result->bogus)
+                printf("a security failure! (bogus)\n");
+        else    printf("not a security failure (not bogus)\n");
+
+        printf("DNS rcode: %d\n", result->rcode);
+
+        if(!result->havedata)
+		return;
+
+        num = 0;
+        for(i=0; result->data[i]; i++) {
+                printf("result data element %d has length %d\n",
+		       i, result->len[i]);
+                printf("result data element %d is: %s\n",
+		       i, inet_ntoa(*(struct in_addr*)result->data[i]));
+                num++;
+        }
+        printf("result has %d data element(s)\n", num);
+}
+
+struct ub_ctx *create_ub_context(int debuglevel) {
+	int rc;
+	struct ub_ctx* ctx;
+	char *error_message_format;
+
+        ctx = ub_ctx_create();
+        if (!ctx) {
+		fprintf(stderr, "Couldn't create libunbound context.\n");
+		return NULL;
+	}
+
+	error_message_format = "Couldn't set forwarder: %s\n";
+	rc = ub_ctx_set_fwd(ctx, "127.0.0.1");
+	if (rc)
+		goto out;
+
+	error_message_format = "Couldn't set debuglevel: %s\n";
+	rc = ub_ctx_debuglevel(ctx, debuglevel);
+
+out:
+	if (rc) {
+		fprintf(stderr, error_message_format, ub_strerror(rc));
+		ub_ctx_delete(ctx);
+		return NULL;
+	}
+
+	return ctx;
+}
+
+void ztdns_try_resolve(struct ub_ctx *ctx, const char *name) {
+	struct ub_result* result;
+	int rc;
+        rc = ub_resolve(ctx, name,
+			1 /* TYPE A (IPv4 address) */,
+			1 /* CLASS IN (internet) */, &result);
+        if(rc)
+                printf("resolve error: %s\n", ub_strerror(rc));
+	else {
+		examine_result(name, result);
+		ub_resolve_free(result);
+	}
+}
+
+int main(int argc, char** argv)
+{
+	struct ub_ctx *ctx;
+	
+	if (argc < 2) {
+		printf("Usage: %s DOMAINNAME\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	ctx = create_ub_context(3);
+	if (!ctx)
+		return EXIT_FAILURE;
+
+	ztdns_try_resolve(ctx, argv[1]);
+
+	ub_ctx_delete(ctx);
+
+	return EXIT_SUCCESS;
+}