example resolution using several recursive servers

1 files changed, 121 insertions, 0 deletions

diff --git a/src/0tDNS.c b/src/0tDNS.c
new file mode 100644
index 0000000..838cae6
--- /dev/null
+++ b/src/0tDNS.c
@@ -0,0 +1,121 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.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);
+
+        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 *ztdns_create_context_with_resolver(const char *resolver_addr) {
+	int rc;
+	struct ub_ctx* ctx;
+        ctx = ub_ctx_create();
+        if (!ctx) {
+		fprintf(stderr, "Couldn't create libunbound context.\n");
+		return NULL;
+	}
+	rc = ub_ctx_set_fwd(ctx, resolver_addr);
+	if (rc) {
+                fprintf(stderr, "Couldn't set forward server: %s\n",
+			ub_strerror(rc));
+		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_google1 = NULL,
+		*ctx_google2 = NULL,
+		*ctx_cloudflare = NULL;
+        int rc = EXIT_SUCCESS;
+
+        if(argc != 2) {
+                printf("usage: <hostname>\n");
+                return EXIT_FAILURE;
+        }
+
+	ctx_google1 = ztdns_create_context_with_resolver("8.8.8.8");
+	ctx_google2 = ztdns_create_context_with_resolver("8.8.4.4");
+	ctx_cloudflare = ztdns_create_context_with_resolver("1.1.1.1");
+
+	if (!ctx_google1 || !ctx_google2 || !ctx_cloudflare) {
+		rc = EXIT_FAILURE;
+		goto abort;
+	}
+
+	printf("* VIA GOOGLE (8.8.8.8)\n");
+	ztdns_try_resolve(ctx_google1, argv[1]);
+	printf("* VIA GOOGLE (8.8.4.4)\n");
+	ztdns_try_resolve(ctx_google2, argv[1]);
+	printf("* VIA CLOUDFLARE (1.1.1.1)\n");
+	ztdns_try_resolve(ctx_cloudflare, argv[1]);
+
+abort:
+        if (ctx_google1)
+		ub_ctx_delete(ctx_google1);
+        if (ctx_google2)
+		ub_ctx_delete(ctx_google2);
+        if (ctx_cloudflare)
+		ub_ctx_delete(ctx_cloudflare);
+
+	return rc;
+}