Version 3.0: January 1, 1999

    - Transparent proxying support added.
    - PPTP redirecting support added based on patches
      contributed by Dru Nelson <dnelson@redwoodsoft.com>.

Submitted by: Charles Mott <cmott@srv.net>

14 files changed, 2352 insertions, 196 deletions

diff --git a/lib/libalias/HISTORY b/lib/libalias/HISTORY
index 3d97fd0803b1..575d1b4aa13d 100644
--- a/lib/libalias/HISTORY
+++ b/lib/libalias/HISTORY
@@ -127,3 +127,8 @@ Version 2.5: December, 1997 (ee)
 
 Version 2.6: May, 1998 (amurai)
     - Added supporting routine for NetBios over TCP/IP.
+
+Version 3.0: January 1, 1999
+    - Transparent proxying support added.
+    - PPTP redirecting support added based on patches
+      contributed by Dru Nelson <dnelson@redwoodsoft.com>.
diff --git a/lib/libalias/Makefile b/lib/libalias/Makefile
index 665d14e10b3d..ea6966449999 100644
--- a/lib/libalias/Makefile
+++ b/lib/libalias/Makefile
@@ -1,11 +1,11 @@
-#	$Id$
+#	$Id: Makefile,v 1.9 1998/08/31 12:14:30 brian Exp $
 
 LIB=		alias
-SHLIB_MAJOR=	2
-SHLIB_MINOR=	5
+SHLIB_MAJOR=	3
+SHLIB_MINOR=	0
 CFLAGS+=	-Wall -I${.CURDIR}
 SRCS=		alias.c alias_cuseeme.c alias_db.c alias_ftp.c alias_irc.c \
-		alias_nbt.c alias_old.c alias_util.c
+		alias_nbt.c alias_proxy.c alias_util.c
 MAN3=		libalias.3 
 
 beforeinstall:
diff --git a/lib/libalias/alias.c b/lib/libalias/alias.c
index 50e597f4364a..13d972c6ff8b 100644
--- a/lib/libalias/alias.c
+++ b/lib/libalias/alias.c
@@ -93,6 +93,10 @@
 #include <netinet/tcp.h>
 #include <netinet/udp.h>
 
+#ifndef IPPROTO_GRE
+#define IPPROTO_GRE 47
+#endif
+
 #include "alias_local.h"
 #include "alias.h"
 
@@ -104,38 +108,13 @@
 #define IRC_CONTROL_PORT_NUMBER_2 6668
 #define CUSEEME_PORT_NUMBER 7648
 
-/*
-   The following macro is used to update an
-   internet checksum.  "delta" is a 32-bit
-   accumulation of all the changes to the
-   checksum (adding in new 16-bit words and
-   subtracting out old words), and "cksum"
-   is the checksum value to be updated.
-*/
-#define ADJUST_CHECKSUM(acc, cksum) { \
-    acc += cksum; \
-    if (acc < 0) \
-    { \
-        acc = -acc; \
-        acc = (acc >> 16) + (acc & 0xffff); \
-        acc += acc >> 16; \
-        cksum = (u_short) ~acc; \
-    } \
-    else \
-    { \
-        acc = (acc >> 16) + (acc & 0xffff); \
-        acc += acc >> 16; \
-        cksum = (u_short) acc; \
-    } \
-}
-
 
 
 
 /* TCP Handling Routines
 
     TcpMonitorIn()  -- These routines monitor TCP connections, and
-    TcpMonitorOut() -- delete a link node when a connection is closed.
+    TcpMonitorOut()    delete a link when a connection is closed.
 
 These routines look for SYN, ACK and RST flags to determine when TCP
 connections open and close.  When a TCP connection closes, the data
@@ -406,7 +385,6 @@ fragment contained in ICMP data section */
     return(PKT_ALIAS_IGNORED);
 }
 
-
 static int
 IcmpAliasIn3(struct ip *pip)
 {
@@ -429,6 +407,10 @@ IcmpAliasIn(struct ip *pip)
     int iresult;
     struct icmp *ic;
 
+/* Return if proxy-only mode is enabled */
+    if (packetAliasMode & PKT_ALIAS_PROXY_ONLY)
+        return PKT_ALIAS_OK;
+
     ic = (struct icmp *) ((char *) pip + (pip->ip_hl << 2));
 
     iresult = PKT_ALIAS_IGNORED;
@@ -563,6 +545,10 @@ IcmpAliasOut(struct ip *pip)
     int iresult;
     struct icmp *ic;
 
+/* Return if proxy-only mode is enabled */
+    if (packetAliasMode & PKT_ALIAS_PROXY_ONLY)
+        return PKT_ALIAS_OK;
+
     ic = (struct icmp *) ((char *) pip + (pip->ip_hl << 2));
 
     iresult = PKT_ALIAS_IGNORED;
@@ -588,12 +574,73 @@ IcmpAliasOut(struct ip *pip)
     return(iresult);
 }
 
+
+
+static int
+PptpAliasIn(struct ip *pip)
+{
+/*
+  Handle incoming PPTP packets. The
+  only thing which is done in this case is to alias
+  the dest IP address of the packet to our inside
+  machine.
+*/
+    struct in_addr alias_addr;
+
+    if (!GetPptpAlias (&alias_addr))
+	return PKT_ALIAS_IGNORED;
+
+    if (pip->ip_src.s_addr != alias_addr.s_addr) {
+
+	    DifferentialChecksum(&pip->ip_sum,
+				 (u_short *) &alias_addr,
+				 (u_short *) &pip->ip_dst,
+				 2);
+	    pip->ip_dst = alias_addr;
+    }
+
+    return PKT_ALIAS_OK;
+}
+
+
+static int
+PptpAliasOut(struct ip *pip)
+{
+/*
+  Handle outgoing PPTP packets. The
+  only thing which is done in this case is to alias
+  the source IP address of the packet.
+*/
+    struct in_addr alias_addr;
+
+    if (!GetPptpAlias (&alias_addr))
+	return PKT_ALIAS_IGNORED;
+
+    if (pip->ip_src.s_addr == alias_addr.s_addr) {
+
+	    alias_addr = FindAliasAddress(pip->ip_src);
+	    DifferentialChecksum(&pip->ip_sum,
+				 (u_short *) &alias_addr,
+				 (u_short *) &pip->ip_src,
+				 2);
+	    pip->ip_src = alias_addr;
+    }
+
+    return PKT_ALIAS_OK;
+}
+
+
+
 static int
 UdpAliasIn(struct ip *pip)
 {
     struct udphdr *ud;
     struct alias_link *link;
 
+/* Return if proxy-only mode is enabled */
+    if (packetAliasMode & PKT_ALIAS_PROXY_ONLY)
+        return PKT_ALIAS_OK;
+
     ud = (struct udphdr *) ((char *) pip + (pip->ip_hl << 2));
 
     link = FindUdpTcpIn(pip->ip_src, pip->ip_dst,
@@ -670,6 +717,10 @@ UdpAliasOut(struct ip *pip)
     struct udphdr *ud;
     struct alias_link *link;
 
+/* Return if proxy-only mode is enabled */
+    if (packetAliasMode & PKT_ALIAS_PROXY_ONLY)
+        return PKT_ALIAS_OK;
+
     ud = (struct udphdr *) ((char *) pip + (pip->ip_hl << 2));
 
     link = FindUdpTcpOut(pip->ip_src, pip->ip_dst,
@@ -751,14 +802,18 @@ TcpAliasIn(struct ip *pip)
     {
         struct in_addr alias_address;
         struct in_addr original_address;
+        struct in_addr proxy_address;
         u_short alias_port;
+        u_short proxy_port;
         int accumulate;
         u_short *sptr;
 
         alias_address = GetAliasAddress(link);
         original_address = GetOriginalAddress(link);
+        proxy_address = GetProxyAddress(link);
         alias_port = tc->th_dport;
         tc->th_dport = GetOriginalPort(link);
+        proxy_port = GetProxyPort(link);
 
 /* Adjust TCP checksum since destination port is being unaliased */
 /* and destination port is being altered.                        */
@@ -771,6 +826,22 @@ TcpAliasIn(struct ip *pip)
         accumulate -= *sptr++;
         accumulate -= *sptr;
 
+/* If this is a proxy, then modify the tcp source port  and
+   checksum accumulation */
+        if (proxy_port != 0)
+        {
+            accumulate += tc->th_sport;
+            tc->th_sport = proxy_port;
+            accumulate -= tc->th_sport;
+
+            sptr = (u_short *) &pip->ip_src;
+            accumulate += *sptr++;
+            accumulate += *sptr;
+            sptr = (u_short *) &proxy_address;
+            accumulate -= *sptr++;
+            accumulate -= *sptr;
+        }
+
 /* See if ack number needs to be modified */
         if (GetAckModified(link) == 1)
         {
@@ -792,11 +863,28 @@ TcpAliasIn(struct ip *pip)
         ADJUST_CHECKSUM(accumulate, tc->th_sum);
 
 /* Restore original IP address */
-        DifferentialChecksum(&pip->ip_sum,
-                             (u_short *) &original_address,
-                             (u_short *) &pip->ip_dst,
-                             2);
+        sptr = (u_short *) &pip->ip_dst;
+        accumulate  = *sptr++;
+        accumulate += *sptr;
         pip->ip_dst = original_address;
+        sptr = (u_short *) &pip->ip_dst;
+        accumulate -= *sptr++;
+        accumulate -= *sptr;
+
+/* If this is a transparent proxy packet, then modify the source
+   address */
+        if (proxy_address.s_addr != 0)
+        {
+            sptr = (u_short *) &pip->ip_src;
+            accumulate += *sptr++;
+            accumulate += *sptr;
+            pip->ip_src = proxy_address;
+            sptr = (u_short *) &pip->ip_src;
+            accumulate -= *sptr++;
+            accumulate -= *sptr;
+        }
+
+        ADJUST_CHECKSUM(accumulate, pip->ip_sum);
 
 /* Monitor TCP connection state */
         TcpMonitorIn(pip, link);
@@ -809,39 +897,94 @@ TcpAliasIn(struct ip *pip)
 static int
 TcpAliasOut(struct ip *pip, int maxpacketsize)
 {
+    int proxy_type;
+    u_short dest_port;
+    u_short proxy_server_port;
+    struct in_addr dest_address;
+    struct in_addr proxy_server_address;
     struct tcphdr *tc;
     struct alias_link *link;
 
     tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
 
+    proxy_type = ProxyCheck(pip, &proxy_server_address, &proxy_server_port);
+
+    if (proxy_type == 0 && (packetAliasMode & PKT_ALIAS_PROXY_ONLY))
+        return PKT_ALIAS_OK;
+
+/* If this is a transparent proxy, save original destination,
+   then alter the destination and adust checksums */
+    dest_port = tc->th_dport;
+    dest_address = pip->ip_dst;
+    if (proxy_type != 0)
+    {
+        int accumulate;
+        u_short *sptr;
+
+        accumulate = tc->th_dport;
+        tc->th_dport = proxy_server_port;
+        accumulate -= tc->th_dport;
+
+        sptr = (u_short *) &(pip->ip_dst);
+        accumulate += *sptr++;
+        accumulate += *sptr;
+        sptr = (u_short *) &proxy_server_address;
+        accumulate -= *sptr++;
+        accumulate -= *sptr;
+
+        ADJUST_CHECKSUM(accumulate, tc->th_sum);
+
+        sptr = (u_short *) &(pip->ip_dst);
+        accumulate  = *sptr++;
+        accumulate += *sptr;
+        pip->ip_dst = proxy_server_address;
+        sptr = (u_short *) &(pip->ip_dst);
+        accumulate -= *sptr++;
+        accumulate -= *sptr;
+
+        ADJUST_CHECKSUM(accumulate, pip->ip_sum);
+    }
+
     link = FindUdpTcpOut(pip->ip_src, pip->ip_dst,
                          tc->th_sport, tc->th_dport,
                          IPPROTO_TCP);
     if (link !=NULL)
     {
-        struct in_addr alias_address;
         u_short alias_port;
+        struct in_addr alias_address;
         int accumulate;
         u_short *sptr;
 
+/* Save original destination address, if this is a proxy packet.
+   Also modify packet to include destination encoding. */
+        if (proxy_type != 0)
+        {
+            SetProxyPort(link, dest_port);
+            SetProxyAddress(link, dest_address);
+            ProxyModify(link, pip, maxpacketsize, proxy_type);
+        }
+
+/* Get alias address and port */
         alias_port = GetAliasPort(link);
         alias_address = GetAliasAddress(link);
 
 /* Monitor tcp connection state */
         TcpMonitorOut(pip, link);
 
-/* Special processing for ftp connection */
+/* Special processing for IP encoding protocols */
         if (ntohs(tc->th_dport) == FTP_CONTROL_PORT_NUMBER
          || ntohs(tc->th_sport) == FTP_CONTROL_PORT_NUMBER)
             AliasHandleFtpOut(pip, link, maxpacketsize);
         if (ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_1
-                        || ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_2)
+         || ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_2)
             AliasHandleIrcOut(pip, link, maxpacketsize);
 
 /* Adjust TCP checksum since source port is being aliased */
 /* and source address is being altered                    */
         accumulate  = tc->th_sport;
-        accumulate -= alias_port;
+        tc->th_sport = alias_port;
+        accumulate -= tc->th_sport;
+
         sptr = (u_short *) &(pip->ip_src);
         accumulate += *sptr++;
         accumulate += *sptr;
@@ -869,15 +1012,16 @@ TcpAliasOut(struct ip *pip, int maxpacketsize)
 
         ADJUST_CHECKSUM(accumulate, tc->th_sum)
 
-/* Put alias address in TCP header */
-        tc->th_sport = alias_port;
-
 /* Change source address */
-        DifferentialChecksum(&pip->ip_sum,
-                             (u_short *) &alias_address,
-                             (u_short *) &pip->ip_src,
-                             2);
+        sptr = (u_short *) &(pip->ip_src);
+        accumulate  = *sptr++;
+        accumulate += *sptr;
         pip->ip_src = alias_address;
+        sptr = (u_short *) &(pip->ip_src);
+        accumulate -= *sptr++;
+        accumulate -= *sptr;
+
+        ADJUST_CHECKSUM(accumulate, pip->ip_sum)
 
         return(PKT_ALIAS_OK);
     }
@@ -1031,6 +1175,9 @@ PacketAliasIn(char *ptr, int maxpacketsize)
     struct ip *pip;
     int iresult;
 
+    if (packetAliasMode & PKT_ALIAS_REVERSE)
+        return PacketAliasOut(ptr, maxpacketsize);
+
     HouseKeeping();
     ClearCheckNewLink();
     pip = (struct ip *) ptr;
@@ -1055,6 +1202,9 @@ PacketAliasIn(char *ptr, int maxpacketsize)
             case IPPROTO_TCP:
                 iresult = TcpAliasIn(pip);
                 break;
+            case IPPROTO_GRE:
+		iresult = PptpAliasIn(pip);
+                break;
         }
 
         if (ntohs(pip->ip_off) & IP_MF)
@@ -1097,8 +1247,6 @@ PacketAliasIn(char *ptr, int maxpacketsize)
 #define UNREG_ADDR_C_LOWER 0xc0a80000
 #define UNREG_ADDR_C_UPPER 0xc0a8ffff
 
-
-
 int
 PacketAliasOut(char *ptr,           /* valid IP packet */
                int  maxpacketsize   /* How much the packet data may grow
@@ -1109,6 +1257,9 @@ PacketAliasOut(char *ptr,           /* valid IP packet */
     struct in_addr addr_save;
     struct ip *pip;
 
+    if (packetAliasMode & PKT_ALIAS_REVERSE)
+        return PacketAliasIn(ptr, maxpacketsize);
+
     HouseKeeping();
     ClearCheckNewLink();
     pip = (struct ip *) ptr;
@@ -1153,6 +1304,9 @@ PacketAliasOut(char *ptr,           /* valid IP packet */
             case IPPROTO_TCP:
                 iresult = TcpAliasOut(pip, maxpacketsize);
                 break;
+            case IPPROTO_GRE:
+		iresult = PptpAliasOut(pip);
+                break;
         }
     }
     else
diff --git a/lib/libalias/alias.h b/lib/libalias/alias.h
index 010db9885a5a..14325f4aa2e9 100644
--- a/lib/libalias/alias.h
+++ b/lib/libalias/alias.h
@@ -7,7 +7,7 @@
     This software is placed into the public domain with no restrictions
     on its distribution.
 
-    $Id: alias.h,v 1.7 1998/01/16 12:56:07 bde Exp $
+    $Id: alias.h,v 1.8 1998/04/19 21:42:05 brian Exp $
 */
 
 
@@ -55,6 +55,10 @@ struct alias_link;
                             struct in_addr, u_short,
                             u_char);
 
+    extern int
+    PacketAliasPptp(struct in_addr);
+
+
     extern struct alias_link *
     PacketAliasRedirectAddr(struct in_addr,
                             struct in_addr);
@@ -82,28 +86,10 @@ struct alias_link;
     extern u_short
     PacketAliasInternetChecksum(u_short *, int);
 
+/* Transparent Proxying */
+    extern int
+    PacketAliasProxyRule(char *);
 
-/*
-   In version 2.2, the function names were rationalized
-   to all be of the form PacketAlias...  These are the
-   old function names for backwards compatibility
-*/
-extern int SaveFragmentPtr(char *);
-extern char *GetNextFragmentPtr(char *);
-extern void FragmentAliasIn(char *, char *);
-extern void SetPacketAliasAddress(struct in_addr);
-extern void InitPacketAlias(void);
-extern unsigned int SetPacketAliasMode(unsigned int, unsigned int);
-extern int PacketAliasIn2(char *, struct in_addr, int maxpacketsize);
-extern int PacketAliasOut2(char *, struct in_addr, int maxpacketsize);
-extern int
-PacketAliasPermanentLink(struct in_addr, u_short, 
-                         struct in_addr, u_short,
-                         u_short, u_char);
-extern u_short InternetChecksum(u_short *, int);
-
-/* Obsolete constant */
-#define PKT_ALIAS_NEW_LINK 5
 
 /********************** Mode flags ********************/
 /* Set these flags using SetPacketAliasMode() */
@@ -138,7 +124,6 @@ extern u_short InternetChecksum(u_short *, int);
 	unregistered source addresses will be aliased (along with those
 	of the ppp host maching itself.  Private addresses are those
         in the following ranges:
-
 		10.0.0.0     ->   10.255.255.255
 		172.16.0.0   ->   172.31.255.255
 		192.168.0.0  ->   192.168.255.255  */
@@ -162,6 +147,14 @@ extern u_short InternetChecksum(u_short *, int);
 #define PKT_ALIAS_PUNCH_FW 0x40
 #endif
 
+/* If PKT_ALIAS_PROXY_ONLY is set, then NAT will be disabled and only
+      transparent proxying performed */
+#define PKT_ALIAS_PROXY_ONLY 0x40
+
+/* If PKT_ALIAS_REVERSE is set, the actions of PacketAliasIn()
+      and PacketAliasOut() are reversed */
+#define PKT_ALIAS_REVERSE 0x80
+
 /* Return Codes */
 #define PKT_ALIAS_ERROR -1
 #define PKT_ALIAS_OK 1
diff --git a/lib/libalias/alias_db.c b/lib/libalias/alias_db.c
index dc9d020bd858..c1d6985e5cf0 100644
--- a/lib/libalias/alias_db.c
+++ b/lib/libalias/alias_db.c
@@ -56,12 +56,12 @@
         Added ability to create an alias port without
         either destination address or port specified.
         port type = ALIAS_PORT_UNKNOWN_DEST_ALL (ee)
- 
+
         Removed K&R style function headers
         and general cleanup. (ee)
 
         Added packetAliasMode to replace compiler #defines's (ee)
- 
+
         Allocates sockets for partially specified
         ports if ALIAS_USE_SOCKETS defined. (cjm)
 
@@ -73,10 +73,10 @@
         links.  (J. Fortes suggested the need for this.)
         Examples:
 
-        (192.168.0.1, port 23)  <-> alias port 6002, unknown dest addr/port 
+        (192.168.0.1, port 23)  <-> alias port 6002, unknown dest addr/port
 
         (192.168.0.2, port 21)  <-> alias port 3604, known dest addr
-                                                     unknown dest port 
+                                                     unknown dest port
 
         These permament links allow for incoming connections to
         machines on the local network.  They can be given with a
@@ -111,7 +111,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <unistd.h>
- 
+
 #include <sys/errno.h>
 #include <sys/socket.h>
 #include <sys/time.h>
@@ -139,7 +139,7 @@
 #define LINK_TABLE_IN_SIZE         4001
 
 /* Parameters used for cleanup of expired links */
-#define ALIAS_CLEANUP_INTERVAL_SECS  60       
+#define ALIAS_CLEANUP_INTERVAL_SECS  60
 #define ALIAS_CLEANUP_MAX_SPOKES     30
 
 /* Timouts (in seconds) for different link types) */
@@ -174,14 +174,14 @@
 
 /* Dummy port number codes used for FindLinkIn/Out() and AddLink().
    These constants can be anything except zero, which indicates an
-   unknown port numbea. */
+   unknown port number. */
 
 #define NO_DEST_PORT     1
 #define NO_SRC_PORT      1
 
 
 
-/* Data Structures 
+/* Data Structures
 
     The fundamental data structure used in this program is
     "struct alias_link".  Whenever a TCP connection is made,
@@ -237,11 +237,13 @@ struct tcp_dat
 struct alias_link                /* Main data structure */
 {
     struct in_addr src_addr;     /* Address and port information        */
-    struct in_addr dst_addr;     /*  .                                  */
-    struct in_addr alias_addr;   /*  .                                  */
-    u_short src_port;            /*  .                                  */
-    u_short dst_port;            /*  .                                  */
-    u_short alias_port;          /*  .                                  */
+    struct in_addr dst_addr;
+    struct in_addr alias_addr;
+    struct in_addr proxy_addr;
+    u_short src_port;
+    u_short dst_port;
+    u_short alias_port;
+    u_short proxy_port;
 
     int link_type;               /* Type of link: tcp, udp, icmp, frag  */
 
@@ -348,6 +350,12 @@ static int fireWallFD = -1;          /* File descriptor to be able to   */
                                      /* flag.                           */
 #endif
 
+static int pptpAliasFlag; 	     /* Indicates if PPTP aliasing is   */
+                                     /* on or off                       */
+static struct in_addr pptpAliasAddr; /* Address of source of PPTP 	*/
+                                     /* packets.           		*/
+
+
 
 
 
@@ -853,15 +861,17 @@ AddLink(struct in_addr  src_addr,
             alias_addr.s_addr = 0;
 
     /* Basic initialization */
-        link->src_addr    = src_addr;
-        link->dst_addr    = dst_addr;
-        link->src_port    = src_port;
-        link->alias_addr  = alias_addr;
-        link->dst_port    = dst_port;
-        link->link_type   = link_type;
-        link->sockfd      = -1;
-        link->flags       = 0;
-        link->timestamp   = timeStamp;
+        link->src_addr          = src_addr;
+        link->dst_addr          = dst_addr;
+        link->alias_addr        = alias_addr;
+        link->proxy_addr.s_addr = 0;
+        link->src_port          = src_port;
+        link->dst_port          = dst_port;
+        link->proxy_port        = 0;
+        link->link_type         = link_type;
+        link->sockfd            = -1;
+        link->flags             = 0;
+        link->timestamp         = timeStamp;
 
     /* Expiration time */
         switch (link_type)
@@ -1304,7 +1314,9 @@ FindUdpTcpIn(struct in_addr dst_addr,
                       dst_port, alias_port,
                       link_type, 1);
 
-    if ( !(packetAliasMode & PKT_ALIAS_DENY_INCOMING) && link == NULL)
+    if (!(packetAliasMode & PKT_ALIAS_DENY_INCOMING)
+     && !(packetAliasMode & PKT_ALIAS_PROXY_ONLY)
+     && link == NULL)
     {
         struct in_addr target_addr;
 
@@ -1578,6 +1590,34 @@ SetAckModified(struct alias_link *link)
 }
 
 
+struct in_addr
+GetProxyAddress(struct alias_link *link)
+{
+    return link->proxy_addr;
+}
+
+
+void
+SetProxyAddress(struct alias_link *link, struct in_addr addr)
+{
+    link->proxy_addr = addr;
+}
+
+
+u_short
+GetProxyPort(struct alias_link *link)
+{
+    return link->proxy_port;
+}
+
+
+void
+SetProxyPort(struct alias_link *link, u_short port)
+{
+    link->proxy_port = port;
+}
+
+
 int
 GetAckModified(struct alias_link *link)
 {
@@ -1906,6 +1946,26 @@ PacketAliasRedirectPort(struct in_addr src_addr,   u_short src_port,
     return link;
 }
 
+/* Translate PPTP packets to a machine on the inside
+ */
+int
+PacketAliasPptp(struct in_addr src_addr)
+{
+
+    pptpAliasAddr = src_addr; 		/* Address of the inside PPTP machine */
+    pptpAliasFlag = 1;
+
+
+    return 1;
+}
+
+int GetPptpAlias (struct in_addr* alias_addr)
+{
+    if (pptpAliasFlag)
+	*alias_addr = pptpAliasAddr;
+
+    return pptpAliasFlag;
+}
 
 /* Static address translation */
 struct alias_link *
@@ -2007,6 +2067,8 @@ PacketAliasInit(void)
     packetAliasMode = PKT_ALIAS_SAME_PORTS
                     | PKT_ALIAS_USE_SOCKETS
                     | PKT_ALIAS_RESET_ON_ADDR_CHANGE;
+
+    pptpAliasFlag = 0;
 }
 
 void
diff --git a/lib/libalias/alias_local.h b/lib/libalias/alias_local.h
index 38462810733a..da451259cdf0 100644
--- a/lib/libalias/alias_local.h
+++ b/lib/libalias/alias_local.h
@@ -1,9 +1,11 @@
 /* -*- mode: c; tab-width: 3; c-basic-offset: 3; -*-
     Alias_local.h contains the function prototypes for alias.c,
     alias_db.c, alias_util.c and alias_ftp.c, alias_irc.c (as well
-    as any future add-ons).  It is intended to be used only within
-    the aliasing software.  Outside world interfaces are defined
-    in alias.h
+    as any future add-ons).  It also includes macros, globals and
+    struct definitions shared by more than one alias*.c file.
+
+    This include file is intended to be used only within the aliasing
+    software.  Outside world interfaces are defined in alias.h
 
     This software is placed into the public domain with no restrictions
     on its distribution.
@@ -15,9 +17,54 @@
 #ifndef ALIAS_LOCAL_H
 #define ALIAS_LOCAL_H
 
+
+/*
+    Macros
+ */
+
+/*
+   The following macro is used to update an
+   internet checksum.  "delta" is a 32-bit
+   accumulation of all the changes to the
+   checksum (adding in new 16-bit words and
+   subtracting out old words), and "cksum"
+   is the checksum value to be updated.
+*/
+#define ADJUST_CHECKSUM(acc, cksum) { \
+    acc += cksum; \
+    if (acc < 0) \
+    { \
+        acc = -acc; \
+        acc = (acc >> 16) + (acc & 0xffff); \
+        acc += acc >> 16; \
+        cksum = (u_short) ~acc; \
+    } \
+    else \
+    { \
+        acc = (acc >> 16) + (acc & 0xffff); \
+        acc += acc >> 16; \
+        cksum = (u_short) acc; \
+    } \
+}
+
+
+/*
+    Globals
+*/
+
 extern int packetAliasMode;
 
-struct alias_link;
+
+/*
+    Structs
+*/
+
+struct alias_link;    /* Incomplete structure */
+
+
+/*
+    Prototypes
+*/
 
 /* General utilities */
 u_short IpChecksum(struct ip *);
@@ -71,6 +118,10 @@ struct in_addr GetDefaultAliasAddress(void);
 void SetDefaultAliasAddress(struct in_addr);
 u_short GetOriginalPort(struct alias_link *);
 u_short GetAliasPort(struct alias_link *);
+struct in_addr GetProxyAddress(struct alias_link *);
+void SetProxyAddress(struct alias_link *, struct in_addr);
+u_short GetProxyPort(struct alias_link *);
+void SetProxyPort(struct alias_link *, u_short);
 void SetAckModified(struct alias_link *);
 int GetAckModified(struct alias_link *);
 int GetDeltaAckIn(struct ip *, struct alias_link *);
@@ -88,13 +139,24 @@ void HouseKeeping(void);
 
 /* Tcp specfic routines */
 /*lint -save -library Suppress flexelint warnings */
+
+/* FTP routines */
 void AliasHandleFtpOut(struct ip *, struct alias_link *, int);
+
+/* IRC routines */
 void AliasHandleIrcOut(struct ip *pip, struct alias_link *link, int maxsize );
+
+/* NetBIOS routines */
 int AliasHandleUdpNbt(struct ip *, struct alias_link *, struct in_addr *, u_short);
 int AliasHandleUdpNbtNS(struct ip *, struct alias_link *, struct in_addr *, u_short *, struct in_addr *, u_short *);
+
+/* CUSeeMe routines */
 void AliasHandleCUSeeMeOut(struct ip *, struct alias_link *);
 void AliasHandleCUSeeMeIn(struct ip *, struct in_addr);
 
+/* Transparent proxy routines */
+int ProxyCheck(struct ip *, struct in_addr *, u_short *);
+void ProxyModify(struct alias_link *, struct ip *, int, int);
 
 
 enum alias_tcp_state {
@@ -103,5 +165,6 @@ enum alias_tcp_state {
     ALIAS_TCP_STATE_DISCONNECTED
 };
 
+int GetPptpAlias (struct in_addr*);
 /*lint -restore */
 #endif /* defined(ALIAS_LOCAL_H) */
diff --git a/lib/libalias/alias_proxy.c b/lib/libalias/alias_proxy.c
new file mode 100644
index 000000000000..27a56c25daed
--- /dev/null
+++ b/lib/libalias/alias_proxy.c
@@ -0,0 +1,801 @@
+/* file: alias_proxy.c
+
+    This file encapsulates special operations related to transparent
+    proxy redirection.  This is where packets with a particular destination,
+    usually tcp port 80, are redirected to a proxy server.
+
+    When packets are proxied, the destination address and port are
+    modified.  In certain cases, it is necessary to somehow encode
+    the original address/port info into the packet.  Two methods are
+    presently supported: addition of a [DEST addr port] string at the
+    beginning a of tcp stream, or inclusion of an optional field
+    in the IP header.
+    
+    There is one public API function:
+
+        PacketAliasProxyRule()    -- Adds and deletes proxy
+                                     rules.
+
+    Rules are stored in a linear linked list, so lookup efficiency
+    won't be too good for large lists.
+
+
+    Initial development: April, 1998 (cjm)
+*/
+
+
+/* System includes */
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <netdb.h>
+
+#include <sys/types.h>
+#include <sys/socket.h>
+
+/* BSD IPV4 includes */
+#include <netinet/in_systm.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/tcp.h>
+
+#include <arpa/inet.h>
+
+#include "alias_local.h"  /* Functions used by alias*.c */
+#include "alias.h"        /* Public API functions for libalias */
+
+
+
+/*
+    Data structures
+ */
+
+/*
+ * A linked list of arbitrary length, based on struct proxy_entry is
+ * used to store proxy rules.
+ */
+struct proxy_entry
+{
+#define PROXY_TYPE_ENCODE_NONE      1
+#define PROXY_TYPE_ENCODE_TCPSTREAM 2
+#define PROXY_TYPE_ENCODE_IPHDR     3
+    int rule_index;
+    int proxy_type;
+    u_char proto;
+    u_short proxy_port;
+    u_short server_port;
+
+    struct in_addr server_addr;
+
+    struct in_addr src_addr;
+    struct in_addr src_mask;
+
+    struct in_addr dst_addr;
+    struct in_addr dst_mask;
+
+    struct proxy_entry *next;
+    struct proxy_entry *last;
+};
+
+
+
+/*
+    File scope variables
+*/
+
+static struct proxy_entry *proxyList;
+
+
+
+/* Local (static) functions:
+
+    IpMask()                 -- Utility function for creating IP
+                                masks from integer (1-32) specification.
+    IpAddr()                 -- Utility function for converting string
+                                to IP address
+    IpPort()                 -- Utility function for converting string
+                                to port number
+    RuleAdd()                -- Adds an element to the rule list.
+    RuleDelete()             -- Removes an element from the rule list.
+    RuleNumberDelete()       -- Removes all elements from the rule list
+                                having a certain rule number.
+    ProxyEncodeTcpStream()   -- Adds [DEST x.x.x.x xxxx] to the beginning
+                                of a TCP stream.
+    ProxyEncodeIpHeader()    -- Adds an IP option indicating the true
+                                destination of a proxied IP packet
+*/
+
+static int IpMask(int, struct in_addr *);
+static int IpAddr(char *, struct in_addr *);
+static int IpPort(char *, int, int *);
+static void RuleAdd(struct proxy_entry *);
+static void RuleDelete(struct proxy_entry *);
+static int RuleNumberDelete(int);
+static void ProxyEncodeTcpStream(struct alias_link *, struct ip *, int);
+static void ProxyEncodeIpHeader(struct ip *, int);
+
+static int
+IpMask(int nbits, struct in_addr *mask)
+{
+    int i;
+    u_int imask;
+
+    if (nbits < 0 || nbits > 32)
+        return -1;
+
+    imask = 0;
+    for (i=0; i<nbits; i++)
+        imask = (imask >> 1) + 0x80000000;
+    mask->s_addr = htonl(imask);
+
+    return 0;
+}
+
+static int
+IpAddr(char *s, struct in_addr *addr)
+{
+    if (inet_aton(s, addr) == 0)
+        return -1;
+    else
+        return 0;
+}
+
+static int
+IpPort(char *s, int proto, int *port)
+{
+    int n;
+
+    n = sscanf(s, "%d", port);
+    if (n != 1)
+    {
+        struct servent *se;
+
+        if (proto == IPPROTO_TCP)
+            se = getservbyname(s, "tcp");
+        else if (proto == IPPROTO_UDP)
+            se = getservbyname(s, "udp");
+        else
+            return -1;
+
+        if (se == NULL)
+                return -1;
+
+        *port = (u_int) ntohs(se->s_port);
+    }
+
+    return 0;
+}
+
+void
+RuleAdd(struct proxy_entry *entry)
+{
+    int rule_index;
+    struct proxy_entry *ptr;
+    struct proxy_entry *ptr_last;
+
+    if (proxyList == NULL)
+    {
+        proxyList = entry;
+        entry->last = NULL;
+        entry->next = NULL;
+        return;
+    }
+
+    rule_index = entry->rule_index;
+    ptr = proxyList;
+    ptr_last = NULL;
+    while (ptr != NULL)
+    {
+        if (ptr->rule_index >= rule_index)
+        {
+            if (ptr_last == NULL)
+            {
+                entry->next = proxyList;
+                entry->last = NULL;
+                proxyList->last = entry;
+                proxyList = entry;
+                return;
+            }
+
+            ptr_last->next = entry;
+            ptr->last = entry;
+            entry->last = ptr->last;
+            entry->next = ptr;
+            return;
+        }
+        ptr_last = ptr;
+        ptr = ptr->next;
+    }
+
+    ptr_last->next = entry;
+    entry->last = ptr_last;
+    entry->next = NULL;
+}
+
+static void
+RuleDelete(struct proxy_entry *entry)
+{
+    if (entry->last != NULL)
+        entry->last->next = entry->next;
+    else
+        proxyList = entry->next;
+
+    if (entry->next != NULL)
+        entry->next->last = entry->last;
+
+    free(entry);
+}
+
+static int
+RuleNumberDelete(int rule_index)
+{
+    int err;
+    struct proxy_entry *ptr;
+
+    err = -1;
+    ptr = proxyList;
+    while (ptr != NULL)
+    {
+        struct proxy_entry *ptr_next;
+
+        ptr_next = ptr->next;
+        if (ptr->rule_index == rule_index)
+        {
+            err = 0;
+            RuleDelete(ptr);
+        }
+
+        ptr = ptr_next;
+    }
+
+    return err;
+}
+
+static void
+ProxyEncodeTcpStream(struct alias_link *link,
+                     struct ip *pip,
+                     int maxpacketsize)
+{
+    int slen;
+    char buffer[40];
+    struct tcphdr *tc;
+
+/* Compute pointer to tcp header */
+    tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
+
+/* Don't modify if once already modified */
+
+    if (GetAckModified (link))
+	return;
+
+/* Translate destination address and port to string form */
+    snprintf(buffer, sizeof(buffer) - 2, "[DEST %s %d]",
+        inet_ntoa(GetProxyAddress (link)), (u_int) ntohs(GetProxyPort (link)));
+    
+/* Pad string out to a multiple of two in length */
+    slen = strlen(buffer);
+    switch (slen % 2)
+    {
+    case 0:
+        strcat(buffer, " \n");
+	slen += 2;
+        break;
+    case 1:
+        strcat(buffer, "\n");
+	slen += 1;
+    }
+
+/* Check for packet overflow */
+    if ((ntohs(pip->ip_len) + strlen(buffer)) > maxpacketsize)
+        return;
+
+/* Shift existing TCP data and insert destination string */
+    {
+        int dlen;
+        int hlen;
+        u_char *p;
+
+        hlen = (pip->ip_hl + tc->th_off) << 2;
+        dlen = ntohs (pip->ip_len) - hlen;
+
+/* Modify first packet that has data in it */
+
+	if (dlen == 0)
+		return;
+
+        p = (char *) pip;
+        p += hlen;
+
+        memmove(p + slen, p, dlen);
+        memcpy(p, buffer, slen);
+    }
+
+/* Save information about modfied sequence number */
+    {
+        int delta;
+
+        SetAckModified(link);
+        delta = GetDeltaSeqOut(pip, link);
+        AddSeq(pip, link, delta+slen);
+    }
+
+/* Update IP header packet length and checksum */
+    {
+        int accumulate;
+
+        accumulate  = pip->ip_len;
+        pip->ip_len = htons(ntohs(pip->ip_len) + slen);
+        accumulate -= pip->ip_len;
+
+        ADJUST_CHECKSUM(accumulate, pip->ip_sum);
+    }
+
+/* Update TCP checksum, Use TcpChecksum since so many things have
+   already changed. */
+
+    tc->th_sum = 0;
+    tc->th_sum = TcpChecksum (pip);
+}
+
+static void
+ProxyEncodeIpHeader(struct ip *pip,
+                    int maxpacketsize)
+{
+#define OPTION_LEN_BYTES  8
+#define OPTION_LEN_INT16  4
+#define OPTION_LEN_INT32  2
+    u_char option[OPTION_LEN_BYTES];
+
+fprintf(stdout, " ip cksum 1 = %x\n", (u_int) IpChecksum(pip));
+fprintf(stdout, "tcp cksum 1 = %x\n", (u_int) TcpChecksum(pip));
+
+/* Check to see that there is room to add an IP option */
+    if (pip->ip_hl > (0x0f - OPTION_LEN_INT32))
+        return;
+
+/* Build option and copy into packet */
+    {
+        u_char *ptr;
+        struct tcphdr *tc;
+
+        ptr = (u_char *) pip;
+        ptr += 20;
+        memcpy(ptr + OPTION_LEN_BYTES, ptr, ntohs(pip->ip_len) - 20);
+
+        option[0] = 0x64; /* class: 3 (reserved), option 4 */
+        option[1] = OPTION_LEN_BYTES;
+
+        memcpy(&option[2], (u_char *) &pip->ip_dst, 4);
+
+        tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
+        memcpy(&option[6], (u_char *) &tc->th_sport, 2);
+
+        memcpy(ptr, option, 8);
+    }
+
+/* Update checksum, header length and packet length */
+    {
+        int i;
+        int accumulate;
+        u_short *sptr;
+
+        sptr = (u_short *) option;
+        accumulate = 0;
+        for (i=0; i<OPTION_LEN_INT16; i++)
+            accumulate -= *(sptr++);
+
+        sptr = (u_short *) pip;
+        accumulate += *sptr;
+        pip->ip_hl += OPTION_LEN_INT32;
+        accumulate -= *sptr;
+
+        accumulate += pip->ip_len;
+        pip->ip_len = htons(ntohs(pip->ip_len) + OPTION_LEN_BYTES);
+        accumulate -= pip->ip_len;
+
+        ADJUST_CHECKSUM(accumulate, pip->ip_sum);
+    }
+#undef OPTION_LEN_BYTES
+#undef OPTION_LEN_INT16
+#undef OPTION_LEN_INT32
+fprintf(stdout, " ip cksum 2 = %x\n", (u_int) IpChecksum(pip));
+fprintf(stdout, "tcp cksum 2 = %x\n", (u_int) TcpChecksum(pip));
+}
+
+
+/* Functions by other packet alias source files
+
+    ProxyCheck()         -- Checks whether an outgoing packet should
+                            be proxied.
+    ProxyModify()        -- Encodes the original destination address/port
+                            for a packet which is to be redirected to
+                            a proxy server.
+*/
+
+int
+ProxyCheck(struct ip *pip,
+           struct in_addr *proxy_server_addr,
+           u_short *proxy_server_port)
+{
+    u_short dst_port;
+    struct in_addr src_addr;
+    struct in_addr dst_addr;
+    struct proxy_entry *ptr;
+
+    src_addr = pip->ip_src;
+    dst_addr = pip->ip_dst;
+    dst_port = ((struct tcphdr *) ((char *) pip + (pip->ip_hl << 2)))
+        ->th_dport;
+
+    ptr = proxyList;
+    while (ptr != NULL)
+    {
+        u_short proxy_port;
+
+        proxy_port = ptr->proxy_port;
+        if ((dst_port == proxy_port || proxy_port == 0)
+         && pip->ip_p == ptr->proto
+         && src_addr.s_addr != ptr->server_addr.s_addr)
+        {
+            struct in_addr src_addr_masked;
+            struct in_addr dst_addr_masked;
+
+            src_addr_masked.s_addr = src_addr.s_addr & ptr->src_mask.s_addr;
+            dst_addr_masked.s_addr = dst_addr.s_addr & ptr->dst_mask.s_addr;
+
+            if ((src_addr_masked.s_addr == ptr->src_addr.s_addr)
+             && (dst_addr_masked.s_addr == ptr->dst_addr.s_addr))
+            {
+                if ((*proxy_server_port = ptr->server_port) == 0)
+                    *proxy_server_port = dst_port;
+                *proxy_server_addr = ptr->server_addr;
+                return ptr->proxy_type;
+            }
+        }
+        ptr = ptr->next;
+    }
+
+    return 0;
+}
+
+void
+ProxyModify(struct alias_link *link,
+            struct ip *pip,
+            int maxpacketsize,
+            int proxy_type)
+{
+    switch (proxy_type)
+    {
+    case PROXY_TYPE_ENCODE_IPHDR:
+        ProxyEncodeIpHeader(pip, maxpacketsize);
+        break;
+
+    case PROXY_TYPE_ENCODE_TCPSTREAM:
+        ProxyEncodeTcpStream(link, pip, maxpacketsize);
+        break;
+    }
+}
+
+
+/*
+    Public API functions
+*/
+
+int
+PacketAliasProxyRule(char *cmd)
+{
+/*
+ * This function takes command strings of the form:
+ *
+ *   server <addr>[:<port>]
+ *   [port <port>]
+ *   [rule n]
+ *   [proto tcp|udp]
+ *   [src <addr>[/n]]
+ *   [dst <addr>[/n]]
+ *   [type encode_tcp_stream|encode_ip_hdr|no_encode]
+ *
+ *   delete <rule number>
+ *
+ * Subfields can be in arbitrary order.  Port numbers and addresses
+ * must be in either numeric or symbolic form. An optional rule number
+ * is used to control the order in which rules are searched.  If two
+ * rules have the same number, then search order cannot be guaranteed,
+ * and the rules should be disjoint.  If no rule number is specified,
+ * then 0 is used, and group 0 rules are always checked before any
+ * others.
+ */
+    int i, n, len;
+    int cmd_len;
+    int token_count;
+    int state;
+    char *token;
+    char buffer[256];
+    char str_port[sizeof(buffer)];
+    char str_server_port[sizeof(buffer)];
+
+    int rule_index;
+    int proto;
+    int proxy_type;
+    int proxy_port;
+    int server_port;
+    struct in_addr server_addr;
+    struct in_addr src_addr, src_mask;
+    struct in_addr dst_addr, dst_mask;
+    struct proxy_entry *proxy_entry;
+
+/* Copy command line into a buffer */
+    cmd_len = strlen(cmd);
+    if (cmd_len > (sizeof(buffer) - 1))
+        return -1;
+    strcpy(buffer, cmd);
+
+/* Convert to lower case */
+    len = strlen(buffer);
+    for (i=0; i<len; i++)
+        buffer[i] = tolower(buffer[i]);
+
+/* Set default proxy type */
+
+/* Set up default values */
+    rule_index = 0;
+    proxy_type = PROXY_TYPE_ENCODE_NONE;
+    proto = IPPROTO_TCP;
+    proxy_port = 0;
+    server_addr.s_addr = 0;
+    server_port = 0;
+    src_addr.s_addr = 0;
+    IpMask(0, &src_mask);
+    dst_addr.s_addr = 0;
+    IpMask(0, &dst_mask);
+
+    str_port[0] = 0;
+    str_server_port[0] = 0;
+
+/* Parse command string with state machine */
+#define STATE_READ_KEYWORD    0
+#define STATE_READ_TYPE       1
+#define STATE_READ_PORT       2
+#define STATE_READ_SERVER     3
+#define STATE_READ_RULE       4
+#define STATE_READ_DELETE     5
+#define STATE_READ_PROTO      6
+#define STATE_READ_SRC        7
+#define STATE_READ_DST        8
+    state = STATE_READ_KEYWORD;
+    token = strtok(buffer, " \t");
+    token_count = 0;
+    while (token != NULL)
+    {
+        token_count++;
+        switch (state)
+        {
+        case STATE_READ_KEYWORD:
+            if (strcmp(token, "type") == 0)
+                state = STATE_READ_TYPE;
+            else if (strcmp(token, "port") == 0)
+                state = STATE_READ_PORT;
+            else if (strcmp(token, "server") == 0)
+                state = STATE_READ_SERVER;
+            else if (strcmp(token, "rule") == 0)
+                state = STATE_READ_RULE;
+            else if (strcmp(token, "delete") == 0)
+                state = STATE_READ_DELETE;
+            else if (strcmp(token, "proto") == 0)
+                state = STATE_READ_PROTO;
+            else if (strcmp(token, "src") == 0)
+                state = STATE_READ_SRC;
+            else if (strcmp(token, "dst") == 0)
+                state = STATE_READ_DST;
+            else
+                return -1;
+            break;
+
+        case STATE_READ_TYPE:
+            if (strcmp(token, "encode_ip_hdr") == 0)
+                proxy_type = PROXY_TYPE_ENCODE_IPHDR;
+            else if (strcmp(token, "encode_tcp_stream") == 0)
+                proxy_type = PROXY_TYPE_ENCODE_TCPSTREAM;
+            else if (strcmp(token, "no_encode") == 0)
+                proxy_type = PROXY_TYPE_ENCODE_NONE;
+            else
+                return -1;
+            state = STATE_READ_KEYWORD;
+            break;
+
+        case STATE_READ_PORT:
+            strcpy(str_port, token);
+            state = STATE_READ_KEYWORD;
+            break;
+
+        case STATE_READ_SERVER:
+            {
+                int err;
+                char *p;
+                char s[sizeof(buffer)];
+
+                p = token;
+                while (*p != ':' && *p != 0)
+                    p++;
+
+                if (*p != ':')
+                {
+                    err = IpAddr(token, &server_addr);
+                    if (err)
+                        return -1;
+                }
+                else
+                {
+                    *p = ' ';
+                
+                    n = sscanf(token, "%s %s", s, str_server_port);
+                    if (n != 2)
+                        return -1;
+
+                    err = IpAddr(s, &server_addr);
+                    if (err)
+                        return -1;
+                }
+            }
+            state = STATE_READ_KEYWORD;
+            break;
+
+        case STATE_READ_RULE:
+            n = sscanf(token, "%d", &rule_index);
+            if (n != 1 || rule_index < 0)
+                return -1;
+            state = STATE_READ_KEYWORD;
+            break;
+
+        case STATE_READ_DELETE:
+            {
+                int err;
+                int rule_to_delete;
+
+                if (token_count != 2)
+                    return -1;
+
+                n = sscanf(token, "%d", &rule_to_delete);
+                if (n != 1)
+                    return -1;
+                err = RuleNumberDelete(rule_to_delete);
+                if (err)
+                    return -1;
+                return 0;
+            }
+
+        case STATE_READ_PROTO:
+            if (strcmp(token, "tcp") == 0)
+                proto = IPPROTO_TCP;
+            else if (strcmp(token, "udp") == 0)
+                proto = IPPROTO_UDP;
+            else
+                return -1;
+            state = STATE_READ_KEYWORD;
+            break;
+
+        case STATE_READ_SRC:
+        case STATE_READ_DST:
+            {
+                int err;
+                char *p;
+                struct in_addr mask;
+                struct in_addr addr;
+
+                p = token;
+                while (*p != '/' && *p != 0)
+                    p++;
+
+                if (*p != '/')
+                {
+                     IpMask(32, &mask);
+                     err = IpAddr(token, &addr);
+                     if (err)
+                         return -1;
+                }
+                else
+                {
+                    int n;
+                    int nbits;
+                    char s[sizeof(buffer)];
+
+                    *p = ' ';
+                    n = sscanf(token, "%s %d", s, &nbits);
+                    if (n != 2)
+                        return -1;
+
+                    err = IpAddr(s, &addr);
+                    if (err)
+                        return -1;
+
+                    err = IpMask(nbits, &mask);
+                    if (err)
+                        return -1;
+                }
+
+                if (state == STATE_READ_SRC)
+                {
+                    src_addr = addr;
+                    src_mask = mask;
+                }
+                else 
+                {
+                    dst_addr = addr;
+                    dst_mask = mask;
+                }
+            }
+            state = STATE_READ_KEYWORD;
+            break;
+
+        default:
+            return -1;
+            break;
+        }
+
+        token = strtok(NULL, " \t");
+    }
+#undef STATE_READ_KEYWORD
+#undef STATE_READ_TYPE
+#undef STATE_READ_PORT
+#undef STATE_READ_SERVER
+#undef STATE_READ_RULE
+#undef STATE_READ_DELETE
+#undef STATE_READ_PROTO
+#undef STATE_READ_SRC
+#undef STATE_READ_DST
+
+/* Convert port strings to numbers.  This needs to be done after
+   the string is parsed, because the prototype might not be designated
+   before the ports (which might be symbolic entries in /etc/services) */
+
+    if (strlen(str_port) != 0)
+    {
+        int err;
+
+        err = IpPort(str_port, proto, &proxy_port);
+        if (err)
+            return -1;
+    }
+    else
+    {
+        proxy_port = 0;
+    }
+
+    if (strlen(str_server_port) != 0)
+    { 
+        int err;
+
+        err = IpPort(str_server_port, proto, &server_port);
+        if (err)
+            return -1;
+    }
+    else
+    {
+        server_port = 0;
+    }
+
+/* Check that at least the server address has been defined */
+    if (server_addr.s_addr == 0)
+        return -1;
+
+/* Add to linked list */
+    proxy_entry = malloc(sizeof(struct proxy_entry));
+    if (proxy_entry == NULL)
+        return -1;
+
+    proxy_entry->proxy_type = proxy_type;
+    proxy_entry->rule_index = rule_index;
+    proxy_entry->proto = proto;
+    proxy_entry->proxy_port = htons(proxy_port);
+    proxy_entry->server_port = htons(server_port);
+    proxy_entry->server_addr = server_addr;
+    proxy_entry->src_addr.s_addr = src_addr.s_addr & src_mask.s_addr;
+    proxy_entry->dst_addr.s_addr = dst_addr.s_addr & dst_mask.s_addr;
+    proxy_entry->src_mask = src_mask;
+    proxy_entry->dst_mask = dst_mask;
+
+    RuleAdd(proxy_entry);
+
+    return 0;
+}
diff --git a/sys/netinet/libalias/HISTORY b/sys/netinet/libalias/HISTORY
index 3d97fd0803b1..575d1b4aa13d 100644
--- a/sys/netinet/libalias/HISTORY
+++ b/sys/netinet/libalias/HISTORY
@@ -127,3 +127,8 @@ Version 2.5: December, 1997 (ee)
 
 Version 2.6: May, 1998 (amurai)
     - Added supporting routine for NetBios over TCP/IP.
+
+Version 3.0: January 1, 1999
+    - Transparent proxying support added.
+    - PPTP redirecting support added based on patches
+      contributed by Dru Nelson <dnelson@redwoodsoft.com>.
diff --git a/sys/netinet/libalias/Makefile b/sys/netinet/libalias/Makefile
index 665d14e10b3d..ea6966449999 100644
--- a/sys/netinet/libalias/Makefile
+++ b/sys/netinet/libalias/Makefile
@@ -1,11 +1,11 @@
-#	$Id$
+#	$Id: Makefile,v 1.9 1998/08/31 12:14:30 brian Exp $
 
 LIB=		alias
-SHLIB_MAJOR=	2
-SHLIB_MINOR=	5
+SHLIB_MAJOR=	3
+SHLIB_MINOR=	0
 CFLAGS+=	-Wall -I${.CURDIR}
 SRCS=		alias.c alias_cuseeme.c alias_db.c alias_ftp.c alias_irc.c \
-		alias_nbt.c alias_old.c alias_util.c
+		alias_nbt.c alias_proxy.c alias_util.c
 MAN3=		libalias.3 
 
 beforeinstall:
diff --git a/sys/netinet/libalias/alias.c b/sys/netinet/libalias/alias.c
index 50e597f4364a..13d972c6ff8b 100644
--- a/sys/netinet/libalias/alias.c
+++ b/sys/netinet/libalias/alias.c
@@ -93,6 +93,10 @@
 #include <netinet/tcp.h>
 #include <netinet/udp.h>
 
+#ifndef IPPROTO_GRE
+#define IPPROTO_GRE 47
+#endif
+
 #include "alias_local.h"
 #include "alias.h"
 
@@ -104,38 +108,13 @@
 #define IRC_CONTROL_PORT_NUMBER_2 6668
 #define CUSEEME_PORT_NUMBER 7648
 
-/*
-   The following macro is used to update an
-   internet checksum.  "delta" is a 32-bit
-   accumulation of all the changes to the
-   checksum (adding in new 16-bit words and
-   subtracting out old words), and "cksum"
-   is the checksum value to be updated.
-*/
-#define ADJUST_CHECKSUM(acc, cksum) { \
-    acc += cksum; \
-    if (acc < 0) \
-    { \
-        acc = -acc; \
-        acc = (acc >> 16) + (acc & 0xffff); \
-        acc += acc >> 16; \
-        cksum = (u_short) ~acc; \
-    } \
-    else \
-    { \
-        acc = (acc >> 16) + (acc & 0xffff); \
-        acc += acc >> 16; \
-        cksum = (u_short) acc; \
-    } \
-}
-
 
 
 
 /* TCP Handling Routines
 
     TcpMonitorIn()  -- These routines monitor TCP connections, and
-    TcpMonitorOut() -- delete a link node when a connection is closed.
+    TcpMonitorOut()    delete a link when a connection is closed.
 
 These routines look for SYN, ACK and RST flags to determine when TCP
 connections open and close.  When a TCP connection closes, the data
@@ -406,7 +385,6 @@ fragment contained in ICMP data section */
     return(PKT_ALIAS_IGNORED);
 }
 
-
 static int
 IcmpAliasIn3(struct ip *pip)
 {
@@ -429,6 +407,10 @@ IcmpAliasIn(struct ip *pip)
     int iresult;
     struct icmp *ic;
 
+/* Return if proxy-only mode is enabled */
+    if (packetAliasMode & PKT_ALIAS_PROXY_ONLY)
+        return PKT_ALIAS_OK;
+
     ic = (struct icmp *) ((char *) pip + (pip->ip_hl << 2));
 
     iresult = PKT_ALIAS_IGNORED;
@@ -563,6 +545,10 @@ IcmpAliasOut(struct ip *pip)
     int iresult;
     struct icmp *ic;
 
+/* Return if proxy-only mode is enabled */
+    if (packetAliasMode & PKT_ALIAS_PROXY_ONLY)
+        return PKT_ALIAS_OK;
+
     ic = (struct icmp *) ((char *) pip + (pip->ip_hl << 2));
 
     iresult = PKT_ALIAS_IGNORED;
@@ -588,12 +574,73 @@ IcmpAliasOut(struct ip *pip)
     return(iresult);
 }
 
+
+
+static int
+PptpAliasIn(struct ip *pip)
+{
+/*
+  Handle incoming PPTP packets. The
+  only thing which is done in this case is to alias
+  the dest IP address of the packet to our inside
+  machine.
+*/
+    struct in_addr alias_addr;
+
+    if (!GetPptpAlias (&alias_addr))
+	return PKT_ALIAS_IGNORED;
+
+    if (pip->ip_src.s_addr != alias_addr.s_addr) {
+
+	    DifferentialChecksum(&pip->ip_sum,
+				 (u_short *) &alias_addr,
+				 (u_short *) &pip->ip_dst,
+				 2);
+	    pip->ip_dst = alias_addr;
+    }
+
+    return PKT_ALIAS_OK;
+}
+
+
+static int
+PptpAliasOut(struct ip *pip)
+{
+/*
+  Handle outgoing PPTP packets. The
+  only thing which is done in this case is to alias
+  the source IP address of the packet.
+*/
+    struct in_addr alias_addr;
+
+    if (!GetPptpAlias (&alias_addr))
+	return PKT_ALIAS_IGNORED;
+
+    if (pip->ip_src.s_addr == alias_addr.s_addr) {
+
+	    alias_addr = FindAliasAddress(pip->ip_src);
+	    DifferentialChecksum(&pip->ip_sum,
+				 (u_short *) &alias_addr,
+				 (u_short *) &pip->ip_src,
+				 2);
+	    pip->ip_src = alias_addr;
+    }
+
+    return PKT_ALIAS_OK;
+}
+
+
+
 static int
 UdpAliasIn(struct ip *pip)
 {
     struct udphdr *ud;
     struct alias_link *link;
 
+/* Return if proxy-only mode is enabled */
+    if (packetAliasMode & PKT_ALIAS_PROXY_ONLY)
+        return PKT_ALIAS_OK;
+
     ud = (struct udphdr *) ((char *) pip + (pip->ip_hl << 2));
 
     link = FindUdpTcpIn(pip->ip_src, pip->ip_dst,
@@ -670,6 +717,10 @@ UdpAliasOut(struct ip *pip)
     struct udphdr *ud;
     struct alias_link *link;
 
+/* Return if proxy-only mode is enabled */
+    if (packetAliasMode & PKT_ALIAS_PROXY_ONLY)
+        return PKT_ALIAS_OK;
+
     ud = (struct udphdr *) ((char *) pip + (pip->ip_hl << 2));
 
     link = FindUdpTcpOut(pip->ip_src, pip->ip_dst,
@@ -751,14 +802,18 @@ TcpAliasIn(struct ip *pip)
     {
         struct in_addr alias_address;
         struct in_addr original_address;
+        struct in_addr proxy_address;
         u_short alias_port;
+        u_short proxy_port;
         int accumulate;
         u_short *sptr;
 
         alias_address = GetAliasAddress(link);
         original_address = GetOriginalAddress(link);
+        proxy_address = GetProxyAddress(link);
         alias_port = tc->th_dport;
         tc->th_dport = GetOriginalPort(link);
+        proxy_port = GetProxyPort(link);
 
 /* Adjust TCP checksum since destination port is being unaliased */
 /* and destination port is being altered.                        */
@@ -771,6 +826,22 @@ TcpAliasIn(struct ip *pip)
         accumulate -= *sptr++;
         accumulate -= *sptr;
 
+/* If this is a proxy, then modify the tcp source port  and
+   checksum accumulation */
+        if (proxy_port != 0)
+        {
+            accumulate += tc->th_sport;
+            tc->th_sport = proxy_port;
+            accumulate -= tc->th_sport;
+
+            sptr = (u_short *) &pip->ip_src;
+            accumulate += *sptr++;
+            accumulate += *sptr;
+            sptr = (u_short *) &proxy_address;
+            accumulate -= *sptr++;
+            accumulate -= *sptr;
+        }
+
 /* See if ack number needs to be modified */
         if (GetAckModified(link) == 1)
         {
@@ -792,11 +863,28 @@ TcpAliasIn(struct ip *pip)
         ADJUST_CHECKSUM(accumulate, tc->th_sum);
 
 /* Restore original IP address */
-        DifferentialChecksum(&pip->ip_sum,
-                             (u_short *) &original_address,
-                             (u_short *) &pip->ip_dst,
-                             2);
+        sptr = (u_short *) &pip->ip_dst;
+        accumulate  = *sptr++;
+        accumulate += *sptr;
         pip->ip_dst = original_address;
+        sptr = (u_short *) &pip->ip_dst;
+        accumulate -= *sptr++;
+        accumulate -= *sptr;
+
+/* If this is a transparent proxy packet, then modify the source
+   address */
+        if (proxy_address.s_addr != 0)
+        {
+            sptr = (u_short *) &pip->ip_src;
+            accumulate += *sptr++;
+            accumulate += *sptr;
+            pip->ip_src = proxy_address;
+            sptr = (u_short *) &pip->ip_src;
+            accumulate -= *sptr++;
+            accumulate -= *sptr;
+        }
+
+        ADJUST_CHECKSUM(accumulate, pip->ip_sum);
 
 /* Monitor TCP connection state */
         TcpMonitorIn(pip, link);
@@ -809,39 +897,94 @@ TcpAliasIn(struct ip *pip)
 static int
 TcpAliasOut(struct ip *pip, int maxpacketsize)
 {
+    int proxy_type;
+    u_short dest_port;
+    u_short proxy_server_port;
+    struct in_addr dest_address;
+    struct in_addr proxy_server_address;
     struct tcphdr *tc;
     struct alias_link *link;
 
     tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
 
+    proxy_type = ProxyCheck(pip, &proxy_server_address, &proxy_server_port);
+
+    if (proxy_type == 0 && (packetAliasMode & PKT_ALIAS_PROXY_ONLY))
+        return PKT_ALIAS_OK;
+
+/* If this is a transparent proxy, save original destination,
+   then alter the destination and adust checksums */
+    dest_port = tc->th_dport;
+    dest_address = pip->ip_dst;
+    if (proxy_type != 0)
+    {
+        int accumulate;
+        u_short *sptr;
+
+        accumulate = tc->th_dport;
+        tc->th_dport = proxy_server_port;
+        accumulate -= tc->th_dport;
+
+        sptr = (u_short *) &(pip->ip_dst);
+        accumulate += *sptr++;
+        accumulate += *sptr;
+        sptr = (u_short *) &proxy_server_address;
+        accumulate -= *sptr++;
+        accumulate -= *sptr;
+
+        ADJUST_CHECKSUM(accumulate, tc->th_sum);
+
+        sptr = (u_short *) &(pip->ip_dst);
+        accumulate  = *sptr++;
+        accumulate += *sptr;
+        pip->ip_dst = proxy_server_address;
+        sptr = (u_short *) &(pip->ip_dst);
+        accumulate -= *sptr++;
+        accumulate -= *sptr;
+
+        ADJUST_CHECKSUM(accumulate, pip->ip_sum);
+    }
+
     link = FindUdpTcpOut(pip->ip_src, pip->ip_dst,
                          tc->th_sport, tc->th_dport,
                          IPPROTO_TCP);
     if (link !=NULL)
     {
-        struct in_addr alias_address;
         u_short alias_port;
+        struct in_addr alias_address;
         int accumulate;
         u_short *sptr;
 
+/* Save original destination address, if this is a proxy packet.
+   Also modify packet to include destination encoding. */
+        if (proxy_type != 0)
+        {
+            SetProxyPort(link, dest_port);
+            SetProxyAddress(link, dest_address);
+            ProxyModify(link, pip, maxpacketsize, proxy_type);
+        }
+
+/* Get alias address and port */
         alias_port = GetAliasPort(link);
         alias_address = GetAliasAddress(link);
 
 /* Monitor tcp connection state */
         TcpMonitorOut(pip, link);
 
-/* Special processing for ftp connection */
+/* Special processing for IP encoding protocols */
         if (ntohs(tc->th_dport) == FTP_CONTROL_PORT_NUMBER
          || ntohs(tc->th_sport) == FTP_CONTROL_PORT_NUMBER)
             AliasHandleFtpOut(pip, link, maxpacketsize);
         if (ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_1
-                        || ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_2)
+         || ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_2)
             AliasHandleIrcOut(pip, link, maxpacketsize);
 
 /* Adjust TCP checksum since source port is being aliased */
 /* and source address is being altered                    */
         accumulate  = tc->th_sport;
-        accumulate -= alias_port;
+        tc->th_sport = alias_port;
+        accumulate -= tc->th_sport;
+
         sptr = (u_short *) &(pip->ip_src);
         accumulate += *sptr++;
         accumulate += *sptr;
@@ -869,15 +1012,16 @@ TcpAliasOut(struct ip *pip, int maxpacketsize)
 
         ADJUST_CHECKSUM(accumulate, tc->th_sum)
 
-/* Put alias address in TCP header */
-        tc->th_sport = alias_port;
-
 /* Change source address */
-        DifferentialChecksum(&pip->ip_sum,
-                             (u_short *) &alias_address,
-                             (u_short *) &pip->ip_src,
-                             2);
+        sptr = (u_short *) &(pip->ip_src);
+        accumulate  = *sptr++;
+        accumulate += *sptr;
         pip->ip_src = alias_address;
+        sptr = (u_short *) &(pip->ip_src);
+        accumulate -= *sptr++;
+        accumulate -= *sptr;
+
+        ADJUST_CHECKSUM(accumulate, pip->ip_sum)
 
         return(PKT_ALIAS_OK);
     }
@@ -1031,6 +1175,9 @@ PacketAliasIn(char *ptr, int maxpacketsize)
     struct ip *pip;
     int iresult;
 
+    if (packetAliasMode & PKT_ALIAS_REVERSE)
+        return PacketAliasOut(ptr, maxpacketsize);
+
     HouseKeeping();
     ClearCheckNewLink();
     pip = (struct ip *) ptr;
@@ -1055,6 +1202,9 @@ PacketAliasIn(char *ptr, int maxpacketsize)
             case IPPROTO_TCP:
                 iresult = TcpAliasIn(pip);
                 break;
+            case IPPROTO_GRE:
+		iresult = PptpAliasIn(pip);
+                break;
         }
 
         if (ntohs(pip->ip_off) & IP_MF)
@@ -1097,8 +1247,6 @@ PacketAliasIn(char *ptr, int maxpacketsize)
 #define UNREG_ADDR_C_LOWER 0xc0a80000
 #define UNREG_ADDR_C_UPPER 0xc0a8ffff
 
-
-
 int
 PacketAliasOut(char *ptr,           /* valid IP packet */
                int  maxpacketsize   /* How much the packet data may grow
@@ -1109,6 +1257,9 @@ PacketAliasOut(char *ptr,           /* valid IP packet */
     struct in_addr addr_save;
     struct ip *pip;
 
+    if (packetAliasMode & PKT_ALIAS_REVERSE)
+        return PacketAliasIn(ptr, maxpacketsize);
+
     HouseKeeping();
     ClearCheckNewLink();
     pip = (struct ip *) ptr;
@@ -1153,6 +1304,9 @@ PacketAliasOut(char *ptr,           /* valid IP packet */
             case IPPROTO_TCP:
                 iresult = TcpAliasOut(pip, maxpacketsize);
                 break;
+            case IPPROTO_GRE:
+		iresult = PptpAliasOut(pip);
+                break;
         }
     }
     else
diff --git a/sys/netinet/libalias/alias.h b/sys/netinet/libalias/alias.h
index 010db9885a5a..14325f4aa2e9 100644
--- a/sys/netinet/libalias/alias.h
+++ b/sys/netinet/libalias/alias.h
@@ -7,7 +7,7 @@
     This software is placed into the public domain with no restrictions
     on its distribution.
 
-    $Id: alias.h,v 1.7 1998/01/16 12:56:07 bde Exp $
+    $Id: alias.h,v 1.8 1998/04/19 21:42:05 brian Exp $
 */
 
 
@@ -55,6 +55,10 @@ struct alias_link;
                             struct in_addr, u_short,
                             u_char);
 
+    extern int
+    PacketAliasPptp(struct in_addr);
+
+
     extern struct alias_link *
     PacketAliasRedirectAddr(struct in_addr,
                             struct in_addr);
@@ -82,28 +86,10 @@ struct alias_link;
     extern u_short
     PacketAliasInternetChecksum(u_short *, int);
 
+/* Transparent Proxying */
+    extern int
+    PacketAliasProxyRule(char *);
 
-/*
-   In version 2.2, the function names were rationalized
-   to all be of the form PacketAlias...  These are the
-   old function names for backwards compatibility
-*/
-extern int SaveFragmentPtr(char *);
-extern char *GetNextFragmentPtr(char *);
-extern void FragmentAliasIn(char *, char *);
-extern void SetPacketAliasAddress(struct in_addr);
-extern void InitPacketAlias(void);
-extern unsigned int SetPacketAliasMode(unsigned int, unsigned int);
-extern int PacketAliasIn2(char *, struct in_addr, int maxpacketsize);
-extern int PacketAliasOut2(char *, struct in_addr, int maxpacketsize);
-extern int
-PacketAliasPermanentLink(struct in_addr, u_short, 
-                         struct in_addr, u_short,
-                         u_short, u_char);
-extern u_short InternetChecksum(u_short *, int);
-
-/* Obsolete constant */
-#define PKT_ALIAS_NEW_LINK 5
 
 /********************** Mode flags ********************/
 /* Set these flags using SetPacketAliasMode() */
@@ -138,7 +124,6 @@ extern u_short InternetChecksum(u_short *, int);
 	unregistered source addresses will be aliased (along with those
 	of the ppp host maching itself.  Private addresses are those
         in the following ranges:
-
 		10.0.0.0     ->   10.255.255.255
 		172.16.0.0   ->   172.31.255.255
 		192.168.0.0  ->   192.168.255.255  */
@@ -162,6 +147,14 @@ extern u_short InternetChecksum(u_short *, int);
 #define PKT_ALIAS_PUNCH_FW 0x40
 #endif
 
+/* If PKT_ALIAS_PROXY_ONLY is set, then NAT will be disabled and only
+      transparent proxying performed */
+#define PKT_ALIAS_PROXY_ONLY 0x40
+
+/* If PKT_ALIAS_REVERSE is set, the actions of PacketAliasIn()
+      and PacketAliasOut() are reversed */
+#define PKT_ALIAS_REVERSE 0x80
+
 /* Return Codes */
 #define PKT_ALIAS_ERROR -1
 #define PKT_ALIAS_OK 1
diff --git a/sys/netinet/libalias/alias_db.c b/sys/netinet/libalias/alias_db.c
index dc9d020bd858..c1d6985e5cf0 100644
--- a/sys/netinet/libalias/alias_db.c
+++ b/sys/netinet/libalias/alias_db.c
@@ -56,12 +56,12 @@
         Added ability to create an alias port without
         either destination address or port specified.
         port type = ALIAS_PORT_UNKNOWN_DEST_ALL (ee)
- 
+
         Removed K&R style function headers
         and general cleanup. (ee)
 
         Added packetAliasMode to replace compiler #defines's (ee)
- 
+
         Allocates sockets for partially specified
         ports if ALIAS_USE_SOCKETS defined. (cjm)
 
@@ -73,10 +73,10 @@
         links.  (J. Fortes suggested the need for this.)
         Examples:
 
-        (192.168.0.1, port 23)  <-> alias port 6002, unknown dest addr/port 
+        (192.168.0.1, port 23)  <-> alias port 6002, unknown dest addr/port
 
         (192.168.0.2, port 21)  <-> alias port 3604, known dest addr
-                                                     unknown dest port 
+                                                     unknown dest port
 
         These permament links allow for incoming connections to
         machines on the local network.  They can be given with a
@@ -111,7 +111,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <unistd.h>
- 
+
 #include <sys/errno.h>
 #include <sys/socket.h>
 #include <sys/time.h>
@@ -139,7 +139,7 @@
 #define LINK_TABLE_IN_SIZE         4001
 
 /* Parameters used for cleanup of expired links */
-#define ALIAS_CLEANUP_INTERVAL_SECS  60       
+#define ALIAS_CLEANUP_INTERVAL_SECS  60
 #define ALIAS_CLEANUP_MAX_SPOKES     30
 
 /* Timouts (in seconds) for different link types) */
@@ -174,14 +174,14 @@
 
 /* Dummy port number codes used for FindLinkIn/Out() and AddLink().
    These constants can be anything except zero, which indicates an
-   unknown port numbea. */
+   unknown port number. */
 
 #define NO_DEST_PORT     1
 #define NO_SRC_PORT      1
 
 
 
-/* Data Structures 
+/* Data Structures
 
     The fundamental data structure used in this program is
     "struct alias_link".  Whenever a TCP connection is made,
@@ -237,11 +237,13 @@ struct tcp_dat
 struct alias_link                /* Main data structure */
 {
     struct in_addr src_addr;     /* Address and port information        */
-    struct in_addr dst_addr;     /*  .                                  */
-    struct in_addr alias_addr;   /*  .                                  */
-    u_short src_port;            /*  .                                  */
-    u_short dst_port;            /*  .                                  */
-    u_short alias_port;          /*  .                                  */
+    struct in_addr dst_addr;
+    struct in_addr alias_addr;
+    struct in_addr proxy_addr;
+    u_short src_port;
+    u_short dst_port;
+    u_short alias_port;
+    u_short proxy_port;
 
     int link_type;               /* Type of link: tcp, udp, icmp, frag  */
 
@@ -348,6 +350,12 @@ static int fireWallFD = -1;          /* File descriptor to be able to   */
                                      /* flag.                           */
 #endif
 
+static int pptpAliasFlag; 	     /* Indicates if PPTP aliasing is   */
+                                     /* on or off                       */
+static struct in_addr pptpAliasAddr; /* Address of source of PPTP 	*/
+                                     /* packets.           		*/
+
+
 
 
 
@@ -853,15 +861,17 @@ AddLink(struct in_addr  src_addr,
             alias_addr.s_addr = 0;
 
     /* Basic initialization */
-        link->src_addr    = src_addr;
-        link->dst_addr    = dst_addr;
-        link->src_port    = src_port;
-        link->alias_addr  = alias_addr;
-        link->dst_port    = dst_port;
-        link->link_type   = link_type;
-        link->sockfd      = -1;
-        link->flags       = 0;
-        link->timestamp   = timeStamp;
+        link->src_addr          = src_addr;
+        link->dst_addr          = dst_addr;
+        link->alias_addr        = alias_addr;
+        link->proxy_addr.s_addr = 0;
+        link->src_port          = src_port;
+        link->dst_port          = dst_port;
+        link->proxy_port        = 0;
+        link->link_type         = link_type;
+        link->sockfd            = -1;
+        link->flags             = 0;
+        link->timestamp         = timeStamp;
 
     /* Expiration time */
         switch (link_type)
@@ -1304,7 +1314,9 @@ FindUdpTcpIn(struct in_addr dst_addr,
                       dst_port, alias_port,
                       link_type, 1);
 
-    if ( !(packetAliasMode & PKT_ALIAS_DENY_INCOMING) && link == NULL)
+    if (!(packetAliasMode & PKT_ALIAS_DENY_INCOMING)
+     && !(packetAliasMode & PKT_ALIAS_PROXY_ONLY)
+     && link == NULL)
     {
         struct in_addr target_addr;
 
@@ -1578,6 +1590,34 @@ SetAckModified(struct alias_link *link)
 }
 
 
+struct in_addr
+GetProxyAddress(struct alias_link *link)
+{
+    return link->proxy_addr;
+}
+
+
+void
+SetProxyAddress(struct alias_link *link, struct in_addr addr)
+{
+    link->proxy_addr = addr;
+}
+
+
+u_short
+GetProxyPort(struct alias_link *link)
+{
+    return link->proxy_port;
+}
+
+
+void
+SetProxyPort(struct alias_link *link, u_short port)
+{
+    link->proxy_port = port;
+}
+
+
 int
 GetAckModified(struct alias_link *link)
 {
@@ -1906,6 +1946,26 @@ PacketAliasRedirectPort(struct in_addr src_addr,   u_short src_port,
     return link;
 }
 
+/* Translate PPTP packets to a machine on the inside
+ */
+int
+PacketAliasPptp(struct in_addr src_addr)
+{
+
+    pptpAliasAddr = src_addr; 		/* Address of the inside PPTP machine */
+    pptpAliasFlag = 1;
+
+
+    return 1;
+}
+
+int GetPptpAlias (struct in_addr* alias_addr)
+{
+    if (pptpAliasFlag)
+	*alias_addr = pptpAliasAddr;
+
+    return pptpAliasFlag;
+}
 
 /* Static address translation */
 struct alias_link *
@@ -2007,6 +2067,8 @@ PacketAliasInit(void)
     packetAliasMode = PKT_ALIAS_SAME_PORTS
                     | PKT_ALIAS_USE_SOCKETS
                     | PKT_ALIAS_RESET_ON_ADDR_CHANGE;
+
+    pptpAliasFlag = 0;
 }
 
 void
diff --git a/sys/netinet/libalias/alias_local.h b/sys/netinet/libalias/alias_local.h
index 38462810733a..da451259cdf0 100644
--- a/sys/netinet/libalias/alias_local.h
+++ b/sys/netinet/libalias/alias_local.h
@@ -1,9 +1,11 @@
 /* -*- mode: c; tab-width: 3; c-basic-offset: 3; -*-
     Alias_local.h contains the function prototypes for alias.c,
     alias_db.c, alias_util.c and alias_ftp.c, alias_irc.c (as well
-    as any future add-ons).  It is intended to be used only within
-    the aliasing software.  Outside world interfaces are defined
-    in alias.h
+    as any future add-ons).  It also includes macros, globals and
+    struct definitions shared by more than one alias*.c file.
+
+    This include file is intended to be used only within the aliasing
+    software.  Outside world interfaces are defined in alias.h
 
     This software is placed into the public domain with no restrictions
     on its distribution.
@@ -15,9 +17,54 @@
 #ifndef ALIAS_LOCAL_H
 #define ALIAS_LOCAL_H
 
+
+/*
+    Macros
+ */
+
+/*
+   The following macro is used to update an
+   internet checksum.  "delta" is a 32-bit
+   accumulation of all the changes to the
+   checksum (adding in new 16-bit words and
+   subtracting out old words), and "cksum"
+   is the checksum value to be updated.
+*/
+#define ADJUST_CHECKSUM(acc, cksum) { \
+    acc += cksum; \
+    if (acc < 0) \
+    { \
+        acc = -acc; \
+        acc = (acc >> 16) + (acc & 0xffff); \
+        acc += acc >> 16; \
+        cksum = (u_short) ~acc; \
+    } \
+    else \
+    { \
+        acc = (acc >> 16) + (acc & 0xffff); \
+        acc += acc >> 16; \
+        cksum = (u_short) acc; \
+    } \
+}
+
+
+/*
+    Globals
+*/
+
 extern int packetAliasMode;
 
-struct alias_link;
+
+/*
+    Structs
+*/
+
+struct alias_link;    /* Incomplete structure */
+
+
+/*
+    Prototypes
+*/
 
 /* General utilities */
 u_short IpChecksum(struct ip *);
@@ -71,6 +118,10 @@ struct in_addr GetDefaultAliasAddress(void);
 void SetDefaultAliasAddress(struct in_addr);
 u_short GetOriginalPort(struct alias_link *);
 u_short GetAliasPort(struct alias_link *);
+struct in_addr GetProxyAddress(struct alias_link *);
+void SetProxyAddress(struct alias_link *, struct in_addr);
+u_short GetProxyPort(struct alias_link *);
+void SetProxyPort(struct alias_link *, u_short);
 void SetAckModified(struct alias_link *);
 int GetAckModified(struct alias_link *);
 int GetDeltaAckIn(struct ip *, struct alias_link *);
@@ -88,13 +139,24 @@ void HouseKeeping(void);
 
 /* Tcp specfic routines */
 /*lint -save -library Suppress flexelint warnings */
+
+/* FTP routines */
 void AliasHandleFtpOut(struct ip *, struct alias_link *, int);
+
+/* IRC routines */
 void AliasHandleIrcOut(struct ip *pip, struct alias_link *link, int maxsize );
+
+/* NetBIOS routines */
 int AliasHandleUdpNbt(struct ip *, struct alias_link *, struct in_addr *, u_short);
 int AliasHandleUdpNbtNS(struct ip *, struct alias_link *, struct in_addr *, u_short *, struct in_addr *, u_short *);
+
+/* CUSeeMe routines */
 void AliasHandleCUSeeMeOut(struct ip *, struct alias_link *);
 void AliasHandleCUSeeMeIn(struct ip *, struct in_addr);
 
+/* Transparent proxy routines */
+int ProxyCheck(struct ip *, struct in_addr *, u_short *);
+void ProxyModify(struct alias_link *, struct ip *, int, int);
 
 
 enum alias_tcp_state {
@@ -103,5 +165,6 @@ enum alias_tcp_state {
     ALIAS_TCP_STATE_DISCONNECTED
 };
 
+int GetPptpAlias (struct in_addr*);
 /*lint -restore */
 #endif /* defined(ALIAS_LOCAL_H) */
diff --git a/sys/netinet/libalias/alias_proxy.c b/sys/netinet/libalias/alias_proxy.c
new file mode 100644
index 000000000000..27a56c25daed
--- /dev/null
+++ b/sys/netinet/libalias/alias_proxy.c
@@ -0,0 +1,801 @@
+/* file: alias_proxy.c
+
+    This file encapsulates special operations related to transparent
+    proxy redirection.  This is where packets with a particular destination,
+    usually tcp port 80, are redirected to a proxy server.
+
+    When packets are proxied, the destination address and port are
+    modified.  In certain cases, it is necessary to somehow encode
+    the original address/port info into the packet.  Two methods are
+    presently supported: addition of a [DEST addr port] string at the
+    beginning a of tcp stream, or inclusion of an optional field
+    in the IP header.
+    
+    There is one public API function:
+
+        PacketAliasProxyRule()    -- Adds and deletes proxy
+                                     rules.
+
+    Rules are stored in a linear linked list, so lookup efficiency
+    won't be too good for large lists.
+
+
+    Initial development: April, 1998 (cjm)
+*/
+
+
+/* System includes */
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <netdb.h>
+
+#include <sys/types.h>
+#include <sys/socket.h>
+
+/* BSD IPV4 includes */
+#include <netinet/in_systm.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/tcp.h>
+
+#include <arpa/inet.h>
+
+#include "alias_local.h"  /* Functions used by alias*.c */
+#include "alias.h"        /* Public API functions for libalias */
+
+
+
+/*
+    Data structures
+ */
+
+/*
+ * A linked list of arbitrary length, based on struct proxy_entry is
+ * used to store proxy rules.
+ */
+struct proxy_entry
+{
+#define PROXY_TYPE_ENCODE_NONE      1
+#define PROXY_TYPE_ENCODE_TCPSTREAM 2
+#define PROXY_TYPE_ENCODE_IPHDR     3
+    int rule_index;
+    int proxy_type;
+    u_char proto;
+    u_short proxy_port;
+    u_short server_port;
+
+    struct in_addr server_addr;
+
+    struct in_addr src_addr;
+    struct in_addr src_mask;
+
+    struct in_addr dst_addr;
+    struct in_addr dst_mask;
+
+    struct proxy_entry *next;
+    struct proxy_entry *last;
+};
+
+
+
+/*
+    File scope variables
+*/
+
+static struct proxy_entry *proxyList;
+
+
+
+/* Local (static) functions:
+
+    IpMask()                 -- Utility function for creating IP
+                                masks from integer (1-32) specification.
+    IpAddr()                 -- Utility function for converting string
+                                to IP address
+    IpPort()                 -- Utility function for converting string
+                                to port number
+    RuleAdd()                -- Adds an element to the rule list.
+    RuleDelete()             -- Removes an element from the rule list.
+    RuleNumberDelete()       -- Removes all elements from the rule list
+                                having a certain rule number.
+    ProxyEncodeTcpStream()   -- Adds [DEST x.x.x.x xxxx] to the beginning
+                                of a TCP stream.
+    ProxyEncodeIpHeader()    -- Adds an IP option indicating the true
+                                destination of a proxied IP packet
+*/
+
+static int IpMask(int, struct in_addr *);
+static int IpAddr(char *, struct in_addr *);
+static int IpPort(char *, int, int *);
+static void RuleAdd(struct proxy_entry *);
+static void RuleDelete(struct proxy_entry *);
+static int RuleNumberDelete(int);
+static void ProxyEncodeTcpStream(struct alias_link *, struct ip *, int);
+static void ProxyEncodeIpHeader(struct ip *, int);
+
+static int
+IpMask(int nbits, struct in_addr *mask)
+{
+    int i;
+    u_int imask;
+
+    if (nbits < 0 || nbits > 32)
+        return -1;
+
+    imask = 0;
+    for (i=0; i<nbits; i++)
+        imask = (imask >> 1) + 0x80000000;
+    mask->s_addr = htonl(imask);
+
+    return 0;
+}
+
+static int
+IpAddr(char *s, struct in_addr *addr)
+{
+    if (inet_aton(s, addr) == 0)
+        return -1;
+    else
+        return 0;
+}
+
+static int
+IpPort(char *s, int proto, int *port)
+{
+    int n;
+
+    n = sscanf(s, "%d", port);
+    if (n != 1)
+    {
+        struct servent *se;
+
+        if (proto == IPPROTO_TCP)
+            se = getservbyname(s, "tcp");
+        else if (proto == IPPROTO_UDP)
+            se = getservbyname(s, "udp");
+        else
+            return -1;
+
+        if (se == NULL)
+                return -1;
+
+        *port = (u_int) ntohs(se->s_port);
+    }
+
+    return 0;
+}
+
+void
+RuleAdd(struct proxy_entry *entry)
+{
+    int rule_index;
+    struct proxy_entry *ptr;
+    struct proxy_entry *ptr_last;
+
+    if (proxyList == NULL)
+    {
+        proxyList = entry;
+        entry->last = NULL;
+        entry->next = NULL;
+        return;
+    }
+
+    rule_index = entry->rule_index;
+    ptr = proxyList;
+    ptr_last = NULL;
+    while (ptr != NULL)
+    {
+        if (ptr->rule_index >= rule_index)
+        {
+            if (ptr_last == NULL)
+            {
+                entry->next = proxyList;
+                entry->last = NULL;
+                proxyList->last = entry;
+                proxyList = entry;
+                return;
+            }
+
+            ptr_last->next = entry;
+            ptr->last = entry;
+            entry->last = ptr->last;
+            entry->next = ptr;
+            return;
+        }
+        ptr_last = ptr;
+        ptr = ptr->next;
+    }
+
+    ptr_last->next = entry;
+    entry->last = ptr_last;
+    entry->next = NULL;
+}
+
+static void
+RuleDelete(struct proxy_entry *entry)
+{
+    if (entry->last != NULL)
+        entry->last->next = entry->next;
+    else
+        proxyList = entry->next;
+
+    if (entry->next != NULL)
+        entry->next->last = entry->last;
+
+    free(entry);
+}
+
+static int
+RuleNumberDelete(int rule_index)
+{
+    int err;
+    struct proxy_entry *ptr;
+
+    err = -1;
+    ptr = proxyList;
+    while (ptr != NULL)
+    {
+        struct proxy_entry *ptr_next;
+
+        ptr_next = ptr->next;
+        if (ptr->rule_index == rule_index)
+        {
+            err = 0;
+            RuleDelete(ptr);
+        }
+
+        ptr = ptr_next;
+    }
+
+    return err;
+}
+
+static void
+ProxyEncodeTcpStream(struct alias_link *link,
+                     struct ip *pip,
+                     int maxpacketsize)
+{
+    int slen;
+    char buffer[40];
+    struct tcphdr *tc;
+
+/* Compute pointer to tcp header */
+    tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
+
+/* Don't modify if once already modified */
+
+    if (GetAckModified (link))
+	return;
+
+/* Translate destination address and port to string form */
+    snprintf(buffer, sizeof(buffer) - 2, "[DEST %s %d]",
+        inet_ntoa(GetProxyAddress (link)), (u_int) ntohs(GetProxyPort (link)));
+    
+/* Pad string out to a multiple of two in length */
+    slen = strlen(buffer);
+    switch (slen % 2)
+    {
+    case 0:
+        strcat(buffer, " \n");
+	slen += 2;
+        break;
+    case 1:
+        strcat(buffer, "\n");
+	slen += 1;
+    }
+
+/* Check for packet overflow */
+    if ((ntohs(pip->ip_len) + strlen(buffer)) > maxpacketsize)
+        return;
+
+/* Shift existing TCP data and insert destination string */
+    {
+        int dlen;
+        int hlen;
+        u_char *p;
+
+        hlen = (pip->ip_hl + tc->th_off) << 2;
+        dlen = ntohs (pip->ip_len) - hlen;
+
+/* Modify first packet that has data in it */
+
+	if (dlen == 0)
+		return;
+
+        p = (char *) pip;
+        p += hlen;
+
+        memmove(p + slen, p, dlen);
+        memcpy(p, buffer, slen);
+    }
+
+/* Save information about modfied sequence number */
+    {
+        int delta;
+
+        SetAckModified(link);
+        delta = GetDeltaSeqOut(pip, link);
+        AddSeq(pip, link, delta+slen);
+    }
+
+/* Update IP header packet length and checksum */
+    {
+        int accumulate;
+
+        accumulate  = pip->ip_len;
+        pip->ip_len = htons(ntohs(pip->ip_len) + slen);
+        accumulate -= pip->ip_len;
+
+        ADJUST_CHECKSUM(accumulate, pip->ip_sum);
+    }
+
+/* Update TCP checksum, Use TcpChecksum since so many things have
+   already changed. */
+
+    tc->th_sum = 0;
+    tc->th_sum = TcpChecksum (pip);
+}
+
+static void
+ProxyEncodeIpHeader(struct ip *pip,
+                    int maxpacketsize)
+{
+#define OPTION_LEN_BYTES  8
+#define OPTION_LEN_INT16  4
+#define OPTION_LEN_INT32  2
+    u_char option[OPTION_LEN_BYTES];
+
+fprintf(stdout, " ip cksum 1 = %x\n", (u_int) IpChecksum(pip));
+fprintf(stdout, "tcp cksum 1 = %x\n", (u_int) TcpChecksum(pip));
+
+/* Check to see that there is room to add an IP option */
+    if (pip->ip_hl > (0x0f - OPTION_LEN_INT32))
+        return;
+
+/* Build option and copy into packet */
+    {
+        u_char *ptr;
+        struct tcphdr *tc;
+
+        ptr = (u_char *) pip;
+        ptr += 20;
+        memcpy(ptr + OPTION_LEN_BYTES, ptr, ntohs(pip->ip_len) - 20);
+
+        option[0] = 0x64; /* class: 3 (reserved), option 4 */
+        option[1] = OPTION_LEN_BYTES;
+
+        memcpy(&option[2], (u_char *) &pip->ip_dst, 4);
+
+        tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
+        memcpy(&option[6], (u_char *) &tc->th_sport, 2);
+
+        memcpy(ptr, option, 8);
+    }
+
+/* Update checksum, header length and packet length */
+    {
+        int i;
+        int accumulate;
+        u_short *sptr;
+
+        sptr = (u_short *) option;
+        accumulate = 0;
+        for (i=0; i<OPTION_LEN_INT16; i++)
+            accumulate -= *(sptr++);
+
+        sptr = (u_short *) pip;
+        accumulate += *sptr;
+        pip->ip_hl += OPTION_LEN_INT32;
+        accumulate -= *sptr;
+
+        accumulate += pip->ip_len;
+        pip->ip_len = htons(ntohs(pip->ip_len) + OPTION_LEN_BYTES);
+        accumulate -= pip->ip_len;
+
+        ADJUST_CHECKSUM(accumulate, pip->ip_sum);
+    }
+#undef OPTION_LEN_BYTES
+#undef OPTION_LEN_INT16
+#undef OPTION_LEN_INT32
+fprintf(stdout, " ip cksum 2 = %x\n", (u_int) IpChecksum(pip));
+fprintf(stdout, "tcp cksum 2 = %x\n", (u_int) TcpChecksum(pip));
+}
+
+
+/* Functions by other packet alias source files
+
+    ProxyCheck()         -- Checks whether an outgoing packet should
+                            be proxied.
+    ProxyModify()        -- Encodes the original destination address/port
+                            for a packet which is to be redirected to
+                            a proxy server.
+*/
+
+int
+ProxyCheck(struct ip *pip,
+           struct in_addr *proxy_server_addr,
+           u_short *proxy_server_port)
+{
+    u_short dst_port;
+    struct in_addr src_addr;
+    struct in_addr dst_addr;
+    struct proxy_entry *ptr;
+
+    src_addr = pip->ip_src;
+    dst_addr = pip->ip_dst;
+    dst_port = ((struct tcphdr *) ((char *) pip + (pip->ip_hl << 2)))
+        ->th_dport;
+
+    ptr = proxyList;
+    while (ptr != NULL)
+    {
+        u_short proxy_port;
+
+        proxy_port = ptr->proxy_port;
+        if ((dst_port == proxy_port || proxy_port == 0)
+         && pip->ip_p == ptr->proto
+         && src_addr.s_addr != ptr->server_addr.s_addr)
+        {
+            struct in_addr src_addr_masked;
+            struct in_addr dst_addr_masked;
+
+            src_addr_masked.s_addr = src_addr.s_addr & ptr->src_mask.s_addr;
+            dst_addr_masked.s_addr = dst_addr.s_addr & ptr->dst_mask.s_addr;
+
+            if ((src_addr_masked.s_addr == ptr->src_addr.s_addr)
+             && (dst_addr_masked.s_addr == ptr->dst_addr.s_addr))
+            {
+                if ((*proxy_server_port = ptr->server_port) == 0)
+                    *proxy_server_port = dst_port;
+                *proxy_server_addr = ptr->server_addr;
+                return ptr->proxy_type;
+            }
+        }
+        ptr = ptr->next;
+    }
+
+    return 0;
+}
+
+void
+ProxyModify(struct alias_link *link,
+            struct ip *pip,
+            int maxpacketsize,
+            int proxy_type)
+{
+    switch (proxy_type)
+    {
+    case PROXY_TYPE_ENCODE_IPHDR:
+        ProxyEncodeIpHeader(pip, maxpacketsize);
+        break;
+
+    case PROXY_TYPE_ENCODE_TCPSTREAM:
+        ProxyEncodeTcpStream(link, pip, maxpacketsize);
+        break;
+    }
+}
+
+
+/*
+    Public API functions
+*/
+
+int
+PacketAliasProxyRule(char *cmd)
+{
+/*
+ * This function takes command strings of the form:
+ *
+ *   server <addr>[:<port>]
+ *   [port <port>]
+ *   [rule n]
+ *   [proto tcp|udp]
+ *   [src <addr>[/n]]
+ *   [dst <addr>[/n]]
+ *   [type encode_tcp_stream|encode_ip_hdr|no_encode]
+ *
+ *   delete <rule number>
+ *
+ * Subfields can be in arbitrary order.  Port numbers and addresses
+ * must be in either numeric or symbolic form. An optional rule number
+ * is used to control the order in which rules are searched.  If two
+ * rules have the same number, then search order cannot be guaranteed,
+ * and the rules should be disjoint.  If no rule number is specified,
+ * then 0 is used, and group 0 rules are always checked before any
+ * others.
+ */
+    int i, n, len;
+    int cmd_len;
+    int token_count;
+    int state;
+    char *token;
+    char buffer[256];
+    char str_port[sizeof(buffer)];
+    char str_server_port[sizeof(buffer)];
+
+    int rule_index;
+    int proto;
+    int proxy_type;
+    int proxy_port;
+    int server_port;
+    struct in_addr server_addr;
+    struct in_addr src_addr, src_mask;
+    struct in_addr dst_addr, dst_mask;
+    struct proxy_entry *proxy_entry;
+
+/* Copy command line into a buffer */
+    cmd_len = strlen(cmd);
+    if (cmd_len > (sizeof(buffer) - 1))
+        return -1;
+    strcpy(buffer, cmd);
+
+/* Convert to lower case */
+    len = strlen(buffer);
+    for (i=0; i<len; i++)
+        buffer[i] = tolower(buffer[i]);
+
+/* Set default proxy type */
+
+/* Set up default values */
+    rule_index = 0;
+    proxy_type = PROXY_TYPE_ENCODE_NONE;
+    proto = IPPROTO_TCP;
+    proxy_port = 0;
+    server_addr.s_addr = 0;
+    server_port = 0;
+    src_addr.s_addr = 0;
+    IpMask(0, &src_mask);
+    dst_addr.s_addr = 0;
+    IpMask(0, &dst_mask);
+
+    str_port[0] = 0;
+    str_server_port[0] = 0;
+
+/* Parse command string with state machine */
+#define STATE_READ_KEYWORD    0
+#define STATE_READ_TYPE       1
+#define STATE_READ_PORT       2
+#define STATE_READ_SERVER     3
+#define STATE_READ_RULE       4
+#define STATE_READ_DELETE     5
+#define STATE_READ_PROTO      6
+#define STATE_READ_SRC        7
+#define STATE_READ_DST        8
+    state = STATE_READ_KEYWORD;
+    token = strtok(buffer, " \t");
+    token_count = 0;
+    while (token != NULL)
+    {
+        token_count++;
+        switch (state)
+        {
+        case STATE_READ_KEYWORD:
+            if (strcmp(token, "type") == 0)
+                state = STATE_READ_TYPE;
+            else if (strcmp(token, "port") == 0)
+                state = STATE_READ_PORT;
+            else if (strcmp(token, "server") == 0)
+                state = STATE_READ_SERVER;
+            else if (strcmp(token, "rule") == 0)
+                state = STATE_READ_RULE;
+            else if (strcmp(token, "delete") == 0)
+                state = STATE_READ_DELETE;
+            else if (strcmp(token, "proto") == 0)
+                state = STATE_READ_PROTO;
+            else if (strcmp(token, "src") == 0)
+                state = STATE_READ_SRC;
+            else if (strcmp(token, "dst") == 0)
+                state = STATE_READ_DST;
+            else
+                return -1;
+            break;
+
+        case STATE_READ_TYPE:
+            if (strcmp(token, "encode_ip_hdr") == 0)
+                proxy_type = PROXY_TYPE_ENCODE_IPHDR;
+            else if (strcmp(token, "encode_tcp_stream") == 0)
+                proxy_type = PROXY_TYPE_ENCODE_TCPSTREAM;
+            else if (strcmp(token, "no_encode") == 0)
+                proxy_type = PROXY_TYPE_ENCODE_NONE;
+            else
+                return -1;
+            state = STATE_READ_KEYWORD;
+            break;
+
+        case STATE_READ_PORT:
+            strcpy(str_port, token);
+            state = STATE_READ_KEYWORD;
+            break;
+
+        case STATE_READ_SERVER:
+            {
+                int err;
+                char *p;
+                char s[sizeof(buffer)];
+
+                p = token;
+                while (*p != ':' && *p != 0)
+                    p++;
+
+                if (*p != ':')
+                {
+                    err = IpAddr(token, &server_addr);
+                    if (err)
+                        return -1;
+                }
+                else
+                {
+                    *p = ' ';
+                
+                    n = sscanf(token, "%s %s", s, str_server_port);
+                    if (n != 2)
+                        return -1;
+
+                    err = IpAddr(s, &server_addr);
+                    if (err)
+                        return -1;
+                }
+            }
+            state = STATE_READ_KEYWORD;
+            break;
+
+        case STATE_READ_RULE:
+            n = sscanf(token, "%d", &rule_index);
+            if (n != 1 || rule_index < 0)
+                return -1;
+            state = STATE_READ_KEYWORD;
+            break;
+
+        case STATE_READ_DELETE:
+            {
+                int err;
+                int rule_to_delete;
+
+                if (token_count != 2)
+                    return -1;
+
+                n = sscanf(token, "%d", &rule_to_delete);
+                if (n != 1)
+                    return -1;
+                err = RuleNumberDelete(rule_to_delete);
+                if (err)
+                    return -1;
+                return 0;
+            }
+
+        case STATE_READ_PROTO:
+            if (strcmp(token, "tcp") == 0)
+                proto = IPPROTO_TCP;
+            else if (strcmp(token, "udp") == 0)
+                proto = IPPROTO_UDP;
+            else
+                return -1;
+            state = STATE_READ_KEYWORD;
+            break;
+
+        case STATE_READ_SRC:
+        case STATE_READ_DST:
+            {
+                int err;
+                char *p;
+                struct in_addr mask;
+                struct in_addr addr;
+
+                p = token;
+                while (*p != '/' && *p != 0)
+                    p++;
+
+                if (*p != '/')
+                {
+                     IpMask(32, &mask);
+                     err = IpAddr(token, &addr);
+                     if (err)
+                         return -1;
+                }
+                else
+                {
+                    int n;
+                    int nbits;
+                    char s[sizeof(buffer)];
+
+                    *p = ' ';
+                    n = sscanf(token, "%s %d", s, &nbits);
+                    if (n != 2)
+                        return -1;
+
+                    err = IpAddr(s, &addr);
+                    if (err)
+                        return -1;
+
+                    err = IpMask(nbits, &mask);
+                    if (err)
+                        return -1;
+                }
+
+                if (state == STATE_READ_SRC)
+                {
+                    src_addr = addr;
+                    src_mask = mask;
+                }
+                else 
+                {
+                    dst_addr = addr;
+                    dst_mask = mask;
+                }
+            }
+            state = STATE_READ_KEYWORD;
+            break;
+
+        default:
+            return -1;
+            break;
+        }
+
+        token = strtok(NULL, " \t");
+    }
+#undef STATE_READ_KEYWORD
+#undef STATE_READ_TYPE
+#undef STATE_READ_PORT
+#undef STATE_READ_SERVER
+#undef STATE_READ_RULE
+#undef STATE_READ_DELETE
+#undef STATE_READ_PROTO
+#undef STATE_READ_SRC
+#undef STATE_READ_DST
+
+/* Convert port strings to numbers.  This needs to be done after
+   the string is parsed, because the prototype might not be designated
+   before the ports (which might be symbolic entries in /etc/services) */
+
+    if (strlen(str_port) != 0)
+    {
+        int err;
+
+        err = IpPort(str_port, proto, &proxy_port);
+        if (err)
+            return -1;
+    }
+    else
+    {
+        proxy_port = 0;
+    }
+
+    if (strlen(str_server_port) != 0)
+    { 
+        int err;
+
+        err = IpPort(str_server_port, proto, &server_port);
+        if (err)
+            return -1;
+    }
+    else
+    {
+        server_port = 0;
+    }
+
+/* Check that at least the server address has been defined */
+    if (server_addr.s_addr == 0)
+        return -1;
+
+/* Add to linked list */
+    proxy_entry = malloc(sizeof(struct proxy_entry));
+    if (proxy_entry == NULL)
+        return -1;
+
+    proxy_entry->proxy_type = proxy_type;
+    proxy_entry->rule_index = rule_index;
+    proxy_entry->proto = proto;
+    proxy_entry->proxy_port = htons(proxy_port);
+    proxy_entry->server_port = htons(server_port);
+    proxy_entry->server_addr = server_addr;
+    proxy_entry->src_addr.s_addr = src_addr.s_addr & src_mask.s_addr;
+    proxy_entry->dst_addr.s_addr = dst_addr.s_addr & dst_mask.s_addr;
+    proxy_entry->src_mask = src_mask;
+    proxy_entry->dst_mask = dst_mask;
+
+    RuleAdd(proxy_entry);
+
+    return 0;
+}