Added "--server-bridge" (without parameters) to enable

DHCP proxy mode:  Configure server mode for ethernet
bridging using a DHCP-proxy, where clients talk to the
OpenVPN server-side DHCP server to receive their IP address
allocation and DNS server addresses.

Added "--route-gateway dhcp", to enable the extraction
of the gateway address from a DHCP negotiation with the
OpenVPN server-side LAN.

Modified client.conf and server.conf to reflect new option
modes.

Incremented version to 2.1_rc9a.


git-svn-id: http://svn.openvpn.net/projects/openvpn/branches/BETA21/openvpn@3164 e7ae566f-a301-0410-adde-c780ea21d3b5

1 files changed, 183 insertions, 0 deletions

diff --git a/dhcp.c b/dhcp.c
new file mode 100644
index 0000000..5f1694c
--- /dev/null
+++ b/dhcp.c
@@ -0,0 +1,183 @@
+/*
+ *  OpenVPN -- An application to securely tunnel IP networks
+ *             over a single TCP/UDP port, with support for SSL/TLS-based
+ *             session authentication and key exchange,
+ *             packet encryption, packet authentication, and
+ *             packet compression.
+ *
+ *  Copyright (C) 2002-2008 Telethra, Inc. <sales@openvpn.net>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2
+ *  as published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program (see the file COPYING included with this
+ *  distribution); if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include "syshead.h"
+
+#include "dhcp.h"
+#include "socket.h"
+#include "error.h"
+
+#include "memdbg.h"
+
+static int
+get_dhcp_message_type (const struct dhcp *dhcp, const int optlen)
+{
+  const uint8_t *p = (uint8_t *) (dhcp + 1);
+  int i;
+
+  for (i = 0; i < optlen; ++i)
+    {
+      const uint8_t type = p[i];
+      const int room = optlen - i;
+      if (type == DHCP_END)           /* didn't find what we were looking for */
+	return -1;
+      else if (type == DHCP_PAD)      /* no-operation */
+	;
+      else if (type == DHCP_MSG_TYPE) /* what we are looking for */
+	{
+	  if (room >= 3)
+	    {
+	      if (p[i+1] == 1)        /* option length should be 1 */
+		return p[i+2];        /* return message type */
+	    }
+	  return -1;
+	}
+      else                            /* some other option */
+	{
+	  if (room >= 2)
+	    {
+	      const int len = p[i+1]; /* get option length */
+	      i += (len + 1);         /* advance to next option */
+	    }
+	}
+    }
+  return -1;
+}
+
+static in_addr_t
+do_extract (struct dhcp *dhcp, const int optlen)
+{
+  uint8_t *p = (uint8_t *) (dhcp + 1);
+  int i;
+  in_addr_t ret = 0;
+
+  for (i = 0; i < optlen; ++i)
+    {
+      const uint8_t type = p[i];
+      const int room = optlen - i;
+      if (type == DHCP_END)
+	break;
+      else if (type == DHCP_PAD)
+	;
+      else if (type == DHCP_ROUTER)
+	{
+	  if (room >= 2)
+	    {
+	      const int len = p[i+1]; /* get option length */
+	      if (len <= (room-2))
+		{
+		  if (!ret && len >= 4 && (len & 3) == 0)
+		    {
+		      memcpy (&ret, p+i+2, 4);      /* get router IP address */
+		      ret = ntohl (ret);
+		    }
+		  memset (p+i, DHCP_PAD, len+2);    /* delete the router option by padding it out */
+		}
+	      i += (len + 1);         /* advance to next option */
+	    }
+	}
+      else                            /* some other option */
+	{
+	  if (room >= 2)
+	    {
+	      const int len = p[i+1]; /* get option length */
+	      i += (len + 1);         /* advance to next option */
+	    }
+	}
+    }
+  return ret;
+}
+
+static uint16_t
+udp_checksum (const uint8_t *buf,
+	      const int len_udp,
+	      const uint8_t *src_addr,
+	      const uint8_t *dest_addr)
+{
+  uint16_t word16;
+  uint32_t sum = 0;
+  int i;
+	
+  /* make 16 bit words out of every two adjacent 8 bit words and  */
+  /* calculate the sum of all 16 bit words */
+  for (i = 0; i < len_udp; i += 2){
+    word16 = ((buf[i] << 8) & 0xFF00) + ((i + 1 < len_udp) ? (buf[i+1] & 0xFF) : 0);
+    sum += word16;
+  }
+
+  /* add the UDP pseudo header which contains the IP source and destination addresses */
+  for (i = 0; i < 4; i += 2){
+    word16 =((src_addr[i] << 8) & 0xFF00) + (src_addr[i+1] & 0xFF);
+    sum += word16;
+  }
+  for (i = 0; i < 4; i += 2){
+    word16 =((dest_addr[i] << 8) & 0xFF00) + (dest_addr[i+1] & 0xFF);
+    sum += word16; 	
+  }
+
+  /* the protocol number and the length of the UDP packet */
+  sum += (uint16_t) OPENVPN_IPPROTO_UDP + (uint16_t) len_udp;
+
+  /* keep only the last 16 bits of the 32 bit calculated sum and add the carries */
+  while (sum >> 16)
+    sum = (sum & 0xFFFF) + (sum >> 16);
+		
+  /* Take the one's complement of sum */
+  return ((uint16_t) ~sum);
+}
+
+in_addr_t
+dhcp_extract_router_msg (struct buffer *ipbuf)
+{
+  struct dhcp_full *df = (struct dhcp_full *) BPTR (ipbuf);
+  const int optlen = BLEN (ipbuf) - (sizeof (struct openvpn_iphdr) + sizeof (struct openvpn_udphdr) + sizeof (struct dhcp));
+
+  if (optlen >= 0
+      && df->ip.protocol == OPENVPN_IPPROTO_UDP
+      && df->udp.source == htons (BOOTPS_PORT)
+      && df->udp.dest == htons (BOOTPC_PORT)
+      && df->dhcp.op == BOOTREPLY
+      && get_dhcp_message_type (&df->dhcp, optlen) == DHCPACK)
+    {
+      /* get the router IP address while padding out all DHCP router options */
+      const in_addr_t ret = do_extract (&df->dhcp, optlen);
+
+      /* recompute the UDP checksum */
+      df->udp.check = htons (udp_checksum ((uint8_t *) &df->udp, 
+					   sizeof (struct openvpn_udphdr) + sizeof (struct dhcp) + optlen,
+					   (uint8_t *)&df->ip.saddr,
+					   (uint8_t *)&df->ip.daddr));
+
+      if (ret)
+	{
+	  struct gc_arena gc = gc_new ();
+	  msg (D_ROUTE, "Extracted DHCP router address: %s", print_in_addr_t (ret, 0, &gc));
+	  gc_free (&gc);
+	}
+
+      return ret;
+    }
+  else
+    return 0;
+}