Install gethostbyaddr

dns/GNUmakefile

@@ -1,9 +1,10 @@
 include GNUmakevars
 
-all: gethostbyname fqdn query
+all: gethostbyaddr gethostbyname fqdn query check
 install: \
 	$(BINDIR)/axfr \
 	$(BINDIR)/fqdn \
+	$(BINDIR)/gethostbyaddr \
 	$(BINDIR)/gethostbyname \
 	$(BINDIR)/minnet \
 	$(BINDIR)/query \

dns/gethostbyaddr.c

@@ -0,0 +1,57 @@
+#include <netdb.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "hstrerror.h"
+
+char *cmnd;
+
+void usage(void) {
+    fprintf(stderr, "Usage: %s [hostname ...]\n", cmnd);
+    exit(1);
+}
+
+int main(int argc, char **argv) {
+    int i;
+    int rc = 0;
+
+    cmnd = argv[0];
+
+    if (argc < 2) {
+	usage();
+    }
+
+    for (i = 1; i < argc; i++) {
+        struct in_addr ia;
+        if (!inet_aton(argv[i], &ia)) {
+            fprintf(stderr, "%s: cannot parse %s\n",
+                    argv[0], argv[i]);
+            continue;
+        }
+	struct hostent *he = gethostbyaddr(&ia, sizeof(ia), AF_INET);
+	char **a;
+
+	if (!he) {
+	    fprintf(stderr, "%s: cannot resolve %s: %s\n",
+	    	    argv[0], argv[i], hstrerror(h_errno));
+	    rc++;
+	    continue;
+	}
+
+	printf("%s\n", argv[i]);
+	printf("\tCanonical:  %s\n", he->h_name);
+	for (a = he->h_aliases; *a; a++) {
+	    printf("\tAlias:      %s\n", *a);
+	}
+	for (a = he->h_addr_list; *a; a++) {
+	    int j;
+	    printf("\tAddress:    ");
+	    for (j = 0; j < he->h_length; j++) {
+		printf("%s%d", j ? "." : "", (unsigned char)(*a)[j]);
+	    }
+	    printf("\n");
+	}
+	printf("\n");
+    }
+    return rc;
+}