DNS Support code

diff --git a/common/dns.c b/common/dns.c
new file mode 100644 (file)
index 0000000..cf178ce
--- /dev/null
+++ b/common/dns.c
@@ -0,0 +1,332 @@
+/* dns.c
+
+   Domain Name Service subroutine. */
+
+/*
+ * Copyright (C) 1992 by Ted Lemon.
+ * Copyright (c) 1997 The Internet Software Consortium.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of The Internet Software Consortium nor the names
+ *    of its contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
+ * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * This file is based on software written in 1992 by Ted Lemon for
+ * a portable network boot loader.   That original code base has been
+ * substantially modified for use in the Internet Software Consortium
+ * DHCP suite.
+ *
+ * These later modifications were done on behalf of the Internet Software Consortium
+ * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
+ * Enterprises.  To learn more about the Internet Software Consortium,
+ * see ``http://www.vix.com/isc''.  To learn more about Vixie
+ * Enterprises, see ``http://www.vix.com''.
+ */
+
+#ifndef lint
+static char copyright[] =
+"$Id: dns.c,v 1.1 1997/03/08 02:24:16 mellon Exp $ Copyright (c) 1997 The Internet Software Consortium.  All rights reserved.\n";
+#endif /* not lint */
+
+#include "dhcpd.h"
+#include "arpa/nameser.h"
+
+/* Initialize the DNS protocol. */
+
+void dns_startup (handler)
+       void (*handler) PROTO ((struct iaddr, u_int8_t *, int));
+{
+       struct protoent *proto;
+       int protocol = 1;
+       struct sockaddr_in from;
+       int fd;
+
+       /* Only initialize icmp once. */
+       if (icmp_protocol_initialized)
+               error ("attempted to reinitialize icmp protocol");
+       icmp_protocol_initialized = 1;
+
+       /* Get the protocol number (should be 1). */
+       proto = getprotobyname ("icmp");
+       if (proto)
+               protocol = proto -> p_proto;
+
+       /* Get a raw socket for the ICMP protocol. */
+       icmp_protocol_fd = socket (AF_INET, SOCK_RAW, protocol);
+       if (!icmp_protocol_fd)
+               error ("unable to create icmp socket: %m");
+
+       if (setsockopt (icmp_protocol_fd, SOL_SOCKET, SO_DONTROUTE,
+                       (char *)&routep, sizeof routep))
+               error ("Can't set SO_DONTROUTE on ICMP socket: %m");
+
+       add_protocol ("icmp", icmp_protocol_fd, icmp_echoreply, handler);
+}
+
+/* Label manipulation stuff; see RFC1035, page 28 section 4.1.2 and
+   page 30, section 4.1.4. */
+
+/* addlabel copies a label into the specified buffer, putting the length of
+   the label in the first character, the contents of the label in subsequent
+   characters, and returning the length of the conglomeration. */
+
+addlabel (buf, label)
+     unsigned char *buf;
+     unsigned char *label;
+{
+  *buf = strlen (label);
+  strcpy (buf + 1, label);
+  return *buf + 1;
+}
+
+/* skipname skips over all of the labels in a single domain name,
+   returning the length of the domain name. */
+
+skipname (label)
+     unsigned char *label;
+{
+  if (*label & INDIR_MASK)
+    return 2;
+  if (*label == 0)
+    return 1;
+  return *label + 1 + skipname (label + *label + 1);
+}
+
+/* copy_out_name copies out the name appearing at the specified location
+   into a string, stored as fields seperated by dots rather than lengths
+   and labels.   The length of the label-formatted name is returned. */
+
+copy_out_name (base, name, buf)
+     unsigned char *base;
+     unsigned char *name;
+     unsigned char *buf;
+{
+  if (*name & INDIR_MASK)
+    {
+      int offset = (*name & ~INDIR_MASK) + (*name + 1);
+      return copy_out_name (base, base + offset, buf);
+    }
+  if (!*name)
+    {
+      *buf = 0;
+      return 1;
+    }
+  memcpy (buf, name + 1, *name);
+  *(buf + *name) = '.';
+  return *name + 1 + copy_out_name (base, name + *name + 1, buf + *name + 1);
+}
+
+/* ns_inaddr_lookup constructs a PTR lookup query for an internet address -
+   e.g., 1.200.9.192.in-addr.arpa.   If the specified timeout period passes
+   before the query is satisfied, or if the query fails, the callback is
+   called with a null pointer.   Otherwise, the callback is called with the
+   address of the string returned by the name server. */
+
+ns_inaddr_lookup (inaddr, timeout, callback)
+     Address *inaddr;
+     int timeout;
+     void (*callback) (char *);
+{
+  unsigned char namebuf [MAXDNAME];
+  unsigned char *s = namebuf;
+  unsigned char *label;
+  int i;
+  unsigned char c;
+
+  for (i = 3; i >= 0; --i)
+    {
+      label = s++;
+      *label = 1;
+      c = inaddr -> addr [i];
+      if (c > 100)
+       {
+         ++*label;
+         *s++ = '0' + c / 100;
+       }
+      if (c > 10)
+       {
+         ++*label;
+         *s++ = '0' + ((c / 10) % 10);
+       }
+      *s++ = '0' + (c % 10);
+    }
+  s += addlabel (s, "in-addr");
+  s += addlabel (s, "arpa");
+  *s = 0;
+  nslookup (namebuf, T_PTR, C_IN, timeout, callback);
+}
+
+nslookup (qname, qtype, qclass, timeout, callback)
+     char *qname;
+     int qtype;
+     int qclass;
+     int timeout;
+     void (*callback) (char *);
+{
+  HEADER hdr;
+  unsigned char buf [MTUSIZE];
+  unsigned char query [PACKETSZ];
+  unsigned char *s;
+  int len;
+  void ns_timeout ();
+  int i;
+
+       /* Construct a query ID... */
+  do
+    ns_query_id = random ();
+  while (ns_query_id < 2048);
+
+  memset (&hdr, 0, sizeof hdr);
+  hdr.id = ns_query_id;
+  hdr.rd = 1;
+  hdr.opcode = QUERY;
+  hdr.qdcount = 1;
+  nsswap (&hdr);
+
+  memcpy (query, &hdr, sizeof hdr);
+  len = sizeof hdr;
+
+  strcpy (&query [len], qname);
+  len += strlen (qname) + 1;
+
+  s = &query [len];
+  PUTSHORT (qtype, s);
+  len += sizeof (short);
+  PUTSHORT (qclass, s);
+  len += sizeof (short);
+       /* Tack on an extra zero for the checksummer... */
+  *s++ = 0;
+
+       /* Create the packet header... */
+  len = build_udp_packet (buf, sizeof buf, query, len,
+                         ns_query_id, NAMESERVER_PORT,
+                         &myiaddr, &nsiaddr);
+
+       /* Save the callback vector... */
+  ns_callback = callback;
+
+       /* Push a packet out, retrying in an exponential decay starting
+          with one second, and time out when the user specifies... */
+  pushpacket (buf, len, (void (*) (char *, int))0, ns_timeout, timeout, 1);
+}
+
+void ns_timeout ()
+{
+  void (*callback) (char *) = ns_callback;
+  ns_callback = (void (*) (char *))0;
+  ns_query_id = 0;
+  (*callback) ((char *)0);
+}
+
+ns_packet (ns_header, udp, ip, machine_header)
+     HEADER *ns_header;
+     struct udphdr *udp;
+     struct ip *ip;
+     unsigned char *machine_header;
+{
+  unsigned char *base = (unsigned char *)(ns_header + 1);
+  unsigned char *dptr;
+  void (*callback) (char *) = ns_callback;
+  int type;
+  int class;
+  int ttl;
+  int rdlength;
+  char nbuf [MAXDNAME];
+
+  nsswap (ns_header);
+
+       /* Ignore invalid packets... */
+  if (ns_header -> id != ns_query_id)
+    {
+      printf ("Unexpected NS message; id = %d\n", ns_header -> id);
+      return;
+    }
+
+       /* We have our response, so shut down the protocol... */
+  ns_callback = (void (*) (char *))0;
+  ns_query_id = 0;
+  stop_pushing ();
+
+       /* Parse the response... */
+  dptr = base;
+
+       /* Skip over the query name... */
+  dptr += skipname (dptr);
+       /* Skip over the query type and the query class. */
+  dptr += 2 * sizeof (short);
+
+       /* Skip over the reply name... */
+  dptr += skipname (dptr);
+       /* Extract the numeric fields: */
+  GETSHORT (type, dptr);
+  GETSHORT (class, dptr);
+  GETLONG (ttl, dptr);
+  GETSHORT (rdlength, dptr);
+
+  switch (type)
+    {
+    case T_A:
+      printf ("A record; value is ");
+      printiaddr (dptr);
+      if (callback)
+       (*callback) (dptr);
+      break;
+
+    case T_CNAME:
+    case T_PTR:
+      copy_out_name (base, dptr, nbuf);
+      printf ("Domain name; value is %s\n", nbuf);
+      if (callback)
+       (*callback) (nbuf);
+      return;
+
+#ifdef T_TXT
+    case T_TXT:
+      printf ("Text string; value is %s\n", dptr);
+      if (callback)
+       (*callback) (dptr);
+      break;
+#endif /* T_TXT */
+
+    default:
+      printf ("unhandled type: %x\n", type);
+    }
+
+  if (callback)
+    (*callback) ((char *)1);
+}
+
+#if BYTE_ORDER == LITTLE_ENDIAN
+nsswap (hdr)
+     HEADER *hdr;
+{
+  shortswap (hdr -> opcode);
+  shortswap (hdr -> qdcount);
+  shortswap (hdr -> ancount);
+  shortswap (hdr -> nscount);
+  shortswap (hdr -> arcount);
+}
+#endif