DNS plugin

SRC/plugins/Makefile.in

@@ -1,9 +1,9 @@
 CCFLAGS=-DHAVE_CONFIG_H -Wall -O0 -g 
 CCDYNAMICFLAGS=${CCFLAGS} -fPIC 
 LDFLAGS=
-LDDYNAMICFLAGS=${LDFLAGS} -shared -lpq # TODO: add the flags only when necessary
+LDDYNAMICFLAGS=${LDFLAGS} -shared -lpq -lresolv # TODO: add the flags only when necessary
 
-PLUGINS=random.so whois.so postgres
+PLUGINS=random.so whois.so postgres dns.so
 
 all: $(PLUGINS)
 

SRC/plugins/dns.c

@@ -0,0 +1,133 @@
+/*
+ * DNS plugin. 
+ *
+ * $Id$
+ */
+
+#define IN_PLUGIN
+#include "../echoping.h"
+
+#include <netinet/in.h>
+#include <arpa/nameser.h>
+#include <resolv.h>
+
+struct addrinfo name_server;
+poptContext dns_poptcon;
+char *request;
+int type;
+
+/* nsError stolen from Liu & Albitz check_soa (in their book "DNS and BIND") */
+
+/****************************************************************
+ * nsError -- Print an error message from h_errno for a failure *
+ *     looking up NS records.  res_query() converts the DNS     *
+ *     packet return code to a smaller list of errors and       *
+ *     places the error value in h_errno.  There is a routine   *
+ *     called herror() for printing out strings from h_errno    *
+ *     like perror() does for errno.  Unfortunately, the        *
+ *     herror() messages assume you are looking up address      *
+ *     records for hosts.  In this program, we are looking up   *
+ *     NS records for domains, so we need our own list of error *
+ *     strings.                                                 *
+ ****************************************************************/
+void
+nsError (error, domain)
+     int error;
+     char *domain;
+{
+  switch (error)
+    {
+    case HOST_NOT_FOUND:
+      (void) fprintf (stderr, "Unknown domain: %s\n", domain);
+      break;
+    case NO_DATA:
+      (void) fprintf (stderr, "No NS records for %s\n", domain);
+      break;
+    case TRY_AGAIN:
+      (void) fprintf (stderr, "No response for NS query\n");
+      break;
+    default:
+      (void) fprintf (stderr, "Unexpected error\n");
+      break;
+    }
+}
+
+void
+dns_usage (const char *msg)
+{
+  if (msg)
+    {
+      printf ("Error: %s\n", msg);
+    }
+  poptPrintUsage (dns_poptcon, stdout, 0);
+  exit (1);
+}
+
+char *
+init (const int argc, const char **argv)
+{
+  int value;
+  char *msg = malloc (256);
+  char *type_name;
+  /* popt variables */
+  struct poptOption options[] = {
+    {"request", 'r', POPT_ARG_STRING, &request, 0,
+     "Request (a domain name) to send to the name server",
+     "request"},
+    {"type", 't', POPT_ARG_STRING, &type_name, 0,
+     "Type of resources queried (A, MX, SOA, etc)",
+     "type"},
+    POPT_AUTOHELP POPT_TABLEEND
+  };
+  dns_poptcon = poptGetContext (NULL, argc,
+				argv, options, POPT_CONTEXT_KEEP_FIRST);
+  while ((value = poptGetNextOpt (dns_poptcon)) > 0)
+    {
+      if (value < -1)
+	{
+	  sprintf (msg, "%s: %s",
+		   poptBadOption (dns_poptcon, POPT_BADOPTION_NOALIAS),
+		   poptStrerror (value));
+	  dns_usage (msg);
+	}
+    }
+  if (request == NULL)
+    dns_usage ("Mandatory request missing");
+
+  return "domain";
+}
+
+void
+start (struct addrinfo *res)
+{
+  name_server = *res;
+  if (res_init () < 0)
+    err_sys ("res_init");
+}
+
+int
+execute ()
+{
+  union
+  {
+    HEADER hdr;			/* defined in resolv.h */
+    u_char buf[PACKETSZ];	/* defined in arpa/nameser.h */
+  } response;			/* response buffers */
+  int response_length;		/* buffer length */
+  if ((response_length = res_query (request,	/* the domain we care about   */
+				    C_IN,	/* Internet class records     */
+				    T_NS,	/* Look up name server records */
+				    (u_char *) & response,	/*response buffer */
+				    sizeof (response)))	/*buffer size    */
+      < 0)
+    {				/*If negative    */
+      nsError (h_errno, request);	/* report the error           */
+      return -1;		/* and quit                   */
+    }
+  return 0;
+}
+
+void
+terminate ()
+{
+}