Add address translation support for RTSP/RTP used by RealPlayer and

Quicktime streaming media applications.

Add a BUGS section to the man page.

Submitted by:	Erik Salander <erik@whistle.com>

8 files changed, 819 insertions, 3 deletions

diff --git a/lib/libalias/HISTORY b/lib/libalias/HISTORY
index 8760d92..c5bca59 100644
--- a/lib/libalias/HISTORY
+++ b/lib/libalias/HISTORY
@@ -139,3 +139,7 @@ Version 3.1: May, 2000 (Erik Salander, erik@whistle.com)
     - Added support to alias 227 replies, allows aliasing for
       FTP servers in passive mode.
     - Added support for PPTP aliasing.
+
+Version 3.2: July, 2000 (Erik Salander, erik@whistle.com and 
+      Junichi Satoh, junichi@junichi.org)
+    - Added support for streaming media (RTSP and PNA) aliasing.
diff --git a/lib/libalias/Makefile b/lib/libalias/Makefile
index 2ee0675..14ace0f 100644
--- a/lib/libalias/Makefile
+++ b/lib/libalias/Makefile
@@ -5,7 +5,8 @@ SHLIB_MAJOR=	4
 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_pptp.c alias_proxy.c alias_util.c
+		alias_nbt.c alias_pptp.c alias_proxy.c alias_smedia.c \
+		alias_util.c
 INCS=		alias.h
 MAN3=		libalias.3 
 
diff --git a/lib/libalias/alias.c b/lib/libalias/alias.c
index e4770fe..d70efb8 100644
--- a/lib/libalias/alias.c
+++ b/lib/libalias/alias.c
@@ -76,9 +76,13 @@
     Version 2.3 Dec 1998 (dillon)
 	- Major bounds checking additions, see FreeBSD/CVS
 
-    Version 3.1 May, 2000 (eds)
+    Version 3.1 May, 2000 (salander) 
 	- Added hooks to handle PPTP.
 
+    Version 3.2 July, 2000 (salander and satoh)
+	- Added PacketUnaliasOut routine.
+	- Added hooks to handle RTSP/RTP.
+
     See HISTORY file for additional revisions.
 
     $FreeBSD$
@@ -102,6 +106,8 @@
 #define IRC_CONTROL_PORT_NUMBER_1 6667
 #define IRC_CONTROL_PORT_NUMBER_2 6668
 #define CUSEEME_PORT_NUMBER 7648
+#define RTSP_CONTROL_PORT_NUMBER_1 554
+#define RTSP_CONTROL_PORT_NUMBER_2 7070
 #define PPTP_CONTROL_PORT_NUMBER 1723
 
 
@@ -1112,6 +1118,11 @@ TcpAliasOut(struct ip *pip, int maxpacketsize)
         else if (ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_1
          || ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_2)
             AliasHandleIrcOut(pip, link, maxpacketsize);
+        else if (ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_1
+         || ntohs(tc->th_sport) == RTSP_CONTROL_PORT_NUMBER_1
+         || ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_2
+         || ntohs(tc->th_sport) == RTSP_CONTROL_PORT_NUMBER_2) 
+            AliasHandleRtspOut(pip, link, maxpacketsize);
         else if (ntohs(tc->th_dport) == PPTP_CONTROL_PORT_NUMBER
          || ntohs(tc->th_sport) == PPTP_CONTROL_PORT_NUMBER)
             AliasHandlePptpOut(pip, link);
@@ -1236,6 +1247,7 @@ FragmentOut(struct ip *pip)
         PacketAliasFragmentIn()
         PacketAliasIn()
         PacketAliasOut()
+        PacketUnaliasOut()
 
 (prototypes in alias.h)
 */
@@ -1465,3 +1477,124 @@ PacketAliasOut(char *ptr,           /* valid IP packet */
     SetDefaultAliasAddress(addr_save);
     return(iresult);
 }
+
+int
+PacketUnaliasOut(char *ptr,           /* valid IP packet */
+                 int  maxpacketsize   /* for error checking */
+                )
+{
+    struct ip		*pip;
+    struct icmp 	*ic;
+    struct udphdr	*ud;
+    struct tcphdr 	*tc;
+    struct alias_link 	*link;
+    int 		iresult = PKT_ALIAS_IGNORED;
+
+    pip = (struct ip *) ptr;
+
+    /* Defense against mangled packets */
+    if (ntohs(pip->ip_len) > maxpacketsize
+     || (pip->ip_hl<<2) > maxpacketsize)
+        return(iresult);
+
+    ud = (struct udphdr *) ((char *) pip + (pip->ip_hl << 2));
+    tc = (struct tcphdr *) ud;
+    ic = (struct icmp *) ud;
+
+    /* Find a link */
+    if (pip->ip_p == IPPROTO_UDP)
+        link = QueryUdpTcpIn(pip->ip_dst, pip->ip_src,
+                            ud->uh_dport, ud->uh_sport,
+                            IPPROTO_UDP);
+    else if (pip->ip_p == IPPROTO_TCP)
+        link = QueryUdpTcpIn(pip->ip_dst, pip->ip_src,
+                            tc->th_dport, tc->th_sport,
+                            IPPROTO_TCP);
+    else if (pip->ip_p == IPPROTO_ICMP) 
+        link = FindIcmpIn(pip->ip_dst, pip->ip_src, ic->icmp_id);
+    else
+        link = NULL;
+
+    /* Change it from an aliased packet to an unaliased packet */
+    if (link != NULL)
+    {
+        if (pip->ip_p == IPPROTO_UDP || pip->ip_p == IPPROTO_TCP)
+        {
+            u_short        *sptr;
+            int 	   accumulate;
+            struct in_addr original_address;
+            u_short        original_port;
+
+            original_address = GetOriginalAddress(link);
+            original_port = GetOriginalPort(link);
+    
+            /* Adjust TCP/UDP checksum */
+            sptr = (u_short *) &(pip->ip_src);
+            accumulate  = *sptr++;
+            accumulate += *sptr;
+            sptr = (u_short *) &original_address;
+            accumulate -= *sptr++;
+            accumulate -= *sptr;
+
+            if (pip->ip_p == IPPROTO_UDP) {
+                accumulate += ud->uh_sport;
+                accumulate -= original_port;
+                ADJUST_CHECKSUM(accumulate, ud->uh_sum)
+	    } else { 
+                accumulate += tc->th_sport;
+                accumulate -= original_port;
+                ADJUST_CHECKSUM(accumulate, tc->th_sum)
+	    }
+
+            /* Adjust IP checksum */
+            DifferentialChecksum(&pip->ip_sum,
+                                 (u_short *) &original_address,
+                                 (u_short *) &pip->ip_src,
+                                 2);
+
+            /* Un-alias source address and port number */ 
+            pip->ip_src = original_address;
+            if (pip->ip_p == IPPROTO_UDP) 
+                ud->uh_sport = original_port; 
+	    else   
+                tc->th_sport = original_port; 
+            
+	    iresult = PKT_ALIAS_OK;
+
+        } else if (pip->ip_p == IPPROTO_ICMP) {
+
+            u_short        *sptr;
+            int            accumulate;
+            struct in_addr original_address;
+            u_short        original_id;
+
+            original_address = GetOriginalAddress(link);
+            original_id = GetOriginalPort(link);
+
+            /* Adjust ICMP checksum */
+            sptr = (u_short *) &(pip->ip_src);
+            accumulate  = *sptr++;
+            accumulate += *sptr;
+            sptr = (u_short *) &original_address;
+            accumulate -= *sptr++;
+            accumulate -= *sptr;
+            accumulate += ic->icmp_id;
+            accumulate -= original_id;
+            ADJUST_CHECKSUM(accumulate, ic->icmp_cksum)
+
+            /* Adjust IP checksum */
+            DifferentialChecksum(&pip->ip_sum,
+                                 (u_short *) &original_address,
+                                 (u_short *) &pip->ip_src,
+                                 2);
+
+            /* Un-alias source address and port number */
+            pip->ip_src = original_address;
+            ic->icmp_id = original_id;
+
+	    iresult = PKT_ALIAS_OK;
+        }
+    }
+    return(iresult);
+
+}
diff --git a/lib/libalias/alias.h b/lib/libalias/alias.h
index 61f759f..8785999 100644
--- a/lib/libalias/alias.h
+++ b/lib/libalias/alias.h
@@ -44,6 +44,9 @@ struct alias_link;
     extern int
     PacketAliasOut(char *, int maxpacketsize);
 
+    extern int
+    PacketUnaliasOut(char *, int maxpacketsize);
+
 /* Port and Address Redirection */
     extern struct alias_link *
     PacketAliasRedirectPort(struct in_addr, u_short, 
diff --git a/lib/libalias/alias_db.c b/lib/libalias/alias_db.c
index f8baa71..8cf7da5 100644
--- a/lib/libalias/alias_db.c
+++ b/lib/libalias/alias_db.c
@@ -103,6 +103,16 @@
         version of PacketAliasPermanentLink().  The second function
         implements static network address translation.
 
+    Version 3.2: July, 2000 (salander and satoh)
+        Added FindNewPortGroup to get contiguous range of port values.  
+
+        Added QueryUdpTcpIn and QueryUdpTcpOut to look for an aliasing
+	link but not actually add one.
+
+        Added FindRtspOut, which is closely derived from FindUdpTcpOut, 
+	except that the alias port (from FindNewPortGroup) is provided
+	as input.
+
     See HISTORY file for additional revisions.
 
     $FreeBSD$
@@ -500,6 +510,9 @@ Link creation and deletion:
 Link search:
     FindLinkOut()           - find link for outgoing packets
     FindLinkIn()            - find link for incoming packets
+
+Port search:
+    FindNewPortGroup()      - find an available group of ports 
 */
 
 /* Local prototypes */
@@ -531,11 +544,14 @@ FindLinkIn(struct in_addr, struct in_addr, u_short, u_short, int, int);
 
 #define ALIAS_PORT_BASE            0x08000
 #define ALIAS_PORT_MASK            0x07fff
+#define ALIAS_PORT_MASK_EVEN       0x07ffe
 #define GET_NEW_PORT_MAX_ATTEMPTS       20
 
 #define GET_ALIAS_PORT                  -1
 #define GET_ALIAS_ID        GET_ALIAS_PORT
 
+#define FIND_EVEN_ALIAS_BASE             1
+
 /* GetNewPort() allocates port numbers.  Note that if a port number
    is already in use, that does not mean that it cannot be used by
    another link concurrently.  This is because GetNewPort() looks for
@@ -704,6 +720,102 @@ GetSocket(u_short port_net, int *sockfd, int link_type)
 }
 
 
+/* FindNewPortGroup() returns a base port number for an available        
+   range of contiguous port numbers. Note that if a port number
+   is already in use, that does not mean that it cannot be used by
+   another link concurrently.  This is because FindNewPortGroup()
+   looks for unused triplets: (dest addr, dest port, alias port). */
+
+int
+FindNewPortGroup(struct in_addr  dst_addr,
+                 struct in_addr  alias_addr,
+                 u_short         src_port,
+                 u_short         dst_port,
+                 u_short         port_count, 
+		 u_char          proto, 
+		 u_char          align)
+{
+    int     i, j;
+    int     max_trials;
+    u_short port_sys;
+    int     link_type;
+
+    /*
+     * Get link_type from protocol
+     */
+
+    switch (proto)
+    {
+    case IPPROTO_UDP:
+        link_type = LINK_UDP;
+        break;
+    case IPPROTO_TCP:
+        link_type = LINK_TCP;
+        break;
+    default:
+        return (0);
+        break;
+    }
+
+    /*
+     * The aliasing port is automatically selected
+     * by one of two methods below:
+     */
+    max_trials = GET_NEW_PORT_MAX_ATTEMPTS;
+
+    if (packetAliasMode & PKT_ALIAS_SAME_PORTS) {
+      /*
+       * When the ALIAS_SAME_PORTS option is
+       * chosen, the first try will be the
+       * actual source port. If this is already
+       * in use, the remainder of the trials
+       * will be random.
+       */
+      port_sys = ntohs(src_port);
+
+    } else {
+
+      /* First trial and all subsequent are random. */
+      if (align == FIND_EVEN_ALIAS_BASE)
+        port_sys = random() & ALIAS_PORT_MASK_EVEN;
+      else
+        port_sys = random() & ALIAS_PORT_MASK;
+
+      port_sys += ALIAS_PORT_BASE;
+    }
+
+/* Port number search */
+    for (i = 0; i < max_trials; i++) {
+
+      struct alias_link *search_result;
+
+      for (j = 0; j < port_count; j++)  
+        if (0 != (search_result = FindLinkIn(dst_addr, alias_addr,
+                                        dst_port, htons(port_sys + j),
+                                        link_type, 0)))
+	  break;
+
+      /* Found a good range, return base */
+      if (j == port_count)
+	return (htons(port_sys));
+
+      /* Find a new base to try */
+      if (align == FIND_EVEN_ALIAS_BASE)
+        port_sys = random() & ALIAS_PORT_MASK_EVEN;
+      else
+        port_sys = random() & ALIAS_PORT_MASK;
+
+      port_sys += ALIAS_PORT_BASE;
+    }
+
+#ifdef DEBUG
+    fprintf(stderr, "PacketAlias/FindNewPortGroup(): ");
+    fprintf(stderr, "could not find free port(s)\n");
+#endif
+
+    return(0);
+}
+
 static void
 CleanupAliasData(void)
 {
@@ -1600,6 +1712,107 @@ FindPptpOut(struct in_addr  src_addr,
 }
 
 
+struct alias_link *
+QueryUdpTcpIn(struct in_addr dst_addr,
+              struct in_addr alias_addr,
+              u_short        dst_port,
+              u_short        alias_port,
+              u_char         proto)
+{
+    int link_type;
+    struct alias_link *link;
+
+    switch (proto)
+    {
+    case IPPROTO_UDP:
+        link_type = LINK_UDP;
+        break;
+    case IPPROTO_TCP:
+        link_type = LINK_TCP;
+        break;
+    default:
+        return NULL;
+        break;
+    }
+
+    link = FindLinkIn(dst_addr, alias_addr,
+                      dst_port, alias_port,
+                      link_type, 0);
+
+    return(link);
+}
+
+
+struct alias_link * 
+QueryUdpTcpOut(struct in_addr  src_addr,
+               struct in_addr  dst_addr,
+               u_short         src_port,
+               u_short         dst_port,
+               u_char          proto)
+{
+    int link_type;
+    struct alias_link *link;
+
+    switch (proto)
+    {
+    case IPPROTO_UDP:
+        link_type = LINK_UDP;
+        break;
+    case IPPROTO_TCP:
+        link_type = LINK_TCP;
+        break;
+    default:
+        return NULL;
+        break;
+    }
+
+    link = FindLinkOut(src_addr, dst_addr,
+                       src_port, dst_port,
+		       link_type, 0);
+
+    return(link);
+}
+
+
+struct alias_link * 
+FindRtspOut(struct in_addr  src_addr,
+            struct in_addr  dst_addr,
+            u_short         src_port,
+            u_short         alias_port,
+            u_char          proto)
+{
+    int link_type;
+    struct alias_link *link;
+
+    switch (proto)
+    {
+    case IPPROTO_UDP:
+        link_type = LINK_UDP;
+        break;
+    case IPPROTO_TCP:
+        link_type = LINK_TCP;
+        break;
+    default:
+        return NULL;
+        break;
+    }
+
+    link = FindLinkOut(src_addr, dst_addr, src_port, 0, link_type, 1);
+
+    if (link == NULL)
+    {
+        struct in_addr alias_addr;
+
+        alias_addr = FindAliasAddress(src_addr);
+        link = AddLink(src_addr, dst_addr, alias_addr,
+                       src_port, 0, alias_port,
+                       link_type);
+    }
+
+    return(link);
+}
+
+
 struct in_addr
 FindOriginalAddress(struct in_addr alias_addr)
 {
diff --git a/lib/libalias/alias_local.h b/lib/libalias/alias_local.h
index 439c9ea..f916d21 100644
--- a/lib/libalias/alias_local.h
+++ b/lib/libalias/alias_local.h
@@ -113,6 +113,15 @@ FindPptpIn(struct in_addr, struct in_addr, u_short);
 struct alias_link *
 FindPptpOut(struct in_addr, struct in_addr, u_short);
 
+struct alias_link *
+QueryUdpTcpIn (struct in_addr, struct in_addr, u_short, u_short, u_char);
+
+struct alias_link *
+QueryUdpTcpOut(struct in_addr, struct in_addr, u_short, u_short, u_char);
+
+struct alias_link *
+FindRtspOut(struct in_addr, struct in_addr, u_short, u_short, u_char);
+
 struct in_addr
 FindOriginalAddress(struct in_addr);
 
@@ -120,6 +129,8 @@ struct in_addr
 FindAliasAddress(struct in_addr);
 
 /* External data access/modification */
+int FindNewPortGroup(struct in_addr, struct in_addr,
+                     u_short, u_short, u_short, u_char, u_char);
 void GetFragmentAddr(struct alias_link *, struct in_addr *);
 void SetFragmentAddr(struct alias_link *, struct in_addr);
 void GetFragmentPtr(struct alias_link *, char **);
@@ -165,6 +176,9 @@ void AliasHandleFtpOut(struct ip *, struct alias_link *, int);
 /* IRC routines */
 void AliasHandleIrcOut(struct ip *, struct alias_link *, int);
 
+/* RTSP routines */
+void AliasHandleRtspOut(struct ip *, struct alias_link *, int);
+
 /* PPTP routines */
 int  PptpGetCallID(struct ip *, u_short *);
 void PptpSetCallID(struct ip *, u_short);
diff --git a/lib/libalias/alias_smedia.c b/lib/libalias/alias_smedia.c
new file mode 100644
index 0000000..2b9ca5f
--- /dev/null
+++ b/lib/libalias/alias_smedia.c
@@ -0,0 +1,427 @@
+/*
+ * alias_smedia.c
+ *
+ * Copyright (c) 2000 Whistle Communications, Inc.
+ * All rights reserved.
+ *
+ * Subject to the following obligations and disclaimer of warranty, use and
+ * redistribution of this software, in source or object code forms, with or
+ * without modifications are expressly permitted by Whistle Communications;
+ * provided, however, that:
+ * 1. Any and all reproductions of the source or object code must include the
+ *    copyright notice above and the following disclaimer of warranties; and
+ * 2. No rights are granted, in any manner or form, to use Whistle
+ *    Communications, Inc. trademarks, including the mark "WHISTLE
+ *    COMMUNICATIONS" on advertising, endorsements, or otherwise except as
+ *    such appears in the above copyright notice or in the software.
+ *
+ * THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
+ * TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
+ * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
+ * INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
+ * WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
+ * REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
+ * SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
+ * IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
+ * RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
+ * WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
+ * PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
+ * OF SUCH DAMAGE.
+ *
+ * Copyright (c) 2000  Junichi SATOH <junichi@astec.co.jp>
+ *                                   <junichi@junichi.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * Authors: Erik Salander <erik@whistle.com>
+ *          Junichi SATOH <junichi@astec.co.jp>
+ *                        <junichi@junichi.org>
+ *
+ * $FreeBSD$
+ */
+
+/*
+   Alias_smedia.c is meant to contain the aliasing code for streaming media
+   protocols.  It performs special processing for RSTP sessions under TCP.
+   Specifically, when a SETUP request is sent by a client, or a 200 reply
+   is sent by a server, it is intercepted and modified.  The address is  
+   changed to the gateway machine and an aliasing port is used.
+
+   More specifically, the "client_port" configuration parameter is 
+   parsed for SETUP requests.  The "server_port" configuration parameter is 
+   parsed for 200 replies eminating from a server.  This is intended to handle
+   the unicast case.
+
+   RTSP also allows a redirection of a stream to another client by using the
+   "destination" configuration parameter.  The destination config parm would
+   indicate a different IP address.  This function is NOT supported by the 
+   RTSP translation code below.
+
+   The RTSP multicast functions without any address translation intervention.
+
+   For this routine to work, the SETUP/200 must fit entirely
+   into a single TCP packet.  This is typically the case, but exceptions
+   can easily be envisioned under the actual specifications.
+
+   Probably the most troubling aspect of the approach taken here is
+   that the new SETUP/200 will typically be a different length, and
+   this causes a certain amount of bookkeeping to keep track of the
+   changes of sequence and acknowledgment numbers, since the client
+   machine is totally unaware of the modification to the TCP stream.
+
+   Initial version:  May, 2000 (eds)  
+*/
+
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <netinet/in_systm.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/tcp.h>
+#include <netinet/udp.h>
+
+#include "alias_local.h"
+
+#define RTSP_CONTROL_PORT_NUMBER_1 554 
+#define RTSP_CONTROL_PORT_NUMBER_2 7070 
+#define RTSP_PORT_GROUP            2
+
+#define ISDIGIT(a) (((a) >= '0') && ((a) <= '9'))
+
+int search_string(char *data, int dlen, char *search_str)
+{
+    int i, j, k;
+    int search_str_len;
+
+    search_str_len = strlen(search_str);
+    for (i = 0; i < dlen - search_str_len; i++) {
+	for (j = i, k = 0; j < dlen - search_str_len; j++, k++) {
+	    if (data[j] != search_str[k] &&
+		data[j] != search_str[k] - ('a' - 'A')) {
+		break;
+	    }
+	    if (k == search_str_len - 1) {
+		return j + 1;
+	    }
+	}
+    }
+    return -1;
+}
+
+int alias_rtsp_out(struct ip *pip,
+		   struct alias_link *link,
+		   char *data,
+		   char *port_str)
+{
+    int     hlen, tlen, dlen;
+    struct tcphdr *tc;
+    int     i, j, pos, state, port_dlen, new_dlen, delta;
+    u_short p[2], new_len;
+    u_short sport, eport, base_port;
+    u_short salias = 0, ealias = 0, base_alias = 0;
+    char    *transport_str = "transport:";
+    char    newdata[2048], *port_data, *port_newdata, stemp[80];
+    int     links_created = 0, pkt_updated = 0;
+    struct alias_link *rtsp_link = NULL;
+    struct in_addr null_addr; 
+
+    /* Calculate data length of TCP packet */
+    tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
+    hlen = (pip->ip_hl + tc->th_off) << 2;
+    tlen = ntohs(pip->ip_len);
+    dlen = tlen - hlen;
+
+    /* Find keyword, "Transport: " */
+    pos = search_string(data, dlen, transport_str);
+    if (pos < 0) {
+	return -1;
+    }
+    port_data = data + pos;
+    port_dlen = dlen - pos;
+
+    memcpy(newdata, data, pos);
+    port_newdata = newdata + pos;
+
+    while (port_dlen > strlen(port_str)) {
+	/* Find keyword, appropriate port string */
+	pos = search_string(port_data, port_dlen, port_str);
+	if (pos < 0) {
+	    break;
+	}
+
+	memcpy (port_newdata, port_data, pos + 1);
+	port_newdata += (pos + 1);
+
+	p[0] = p[1] = 0;
+	sport = eport = 0;
+	state = 0;
+	for (i = pos; i < port_dlen; i++) {
+	    switch(state) {
+	    case 0:
+		if (port_data[i] == '=') {
+		    state++;
+		}
+		break;
+	    case 1:
+		if (ISDIGIT(port_data[i])) {
+		    p[0] = p[0] * 10 + port_data[i] - '0';
+		} else {
+		    if (port_data[i] == ';') {
+			state = 3;
+		    }
+		    if (port_data[i] == '-') {
+			state++;
+		    }
+		}
+		break;
+	    case 2:
+		if (ISDIGIT(port_data[i])) {
+		    p[1] = p[1] * 10 + port_data[i] - '0';
+		} else {
+		    state++;
+		}
+		break;
+	    case 3:
+		base_port = p[0];
+		sport = htons(p[0]);
+		eport = htons(p[1]);
+
+		if (!links_created) {
+
+	  	  links_created = 1; 
+		  /* Find an even numbered port number base that
+		     satisfies the contiguous number of ports we need  */
+		  null_addr.s_addr = 0;
+		  if (0 == (salias = FindNewPortGroup(null_addr,
+	       			    FindAliasAddress(pip->ip_src),
+				    sport, 0, 
+				    RTSP_PORT_GROUP, 
+				    IPPROTO_UDP, 1))) {  
+#ifdef DEBUG
+		    fprintf(stderr,
+		    "PacketAlias/RTSP: Cannot find contiguous RTSP data ports\n");
+#endif
+		  } else {
+
+  		    base_alias = ntohs(salias);
+		    for (j = 0; j < RTSP_PORT_GROUP; j++) {
+		      /* Establish link to port found in RTSP packet */
+		      rtsp_link = FindRtspOut(GetOriginalAddress(link), null_addr,
+                                htons(base_port + j), htons(base_alias + j),
+                                IPPROTO_UDP);
+		      if (rtsp_link != NULL) {
+#ifndef NO_FW_PUNCH
+		        /* Punch hole in firewall */
+		        PunchFWHole(rtsp_link);
+#endif
+		      } else {
+#ifdef DEBUG
+		        fprintf(stderr,
+		        "PacketAlias/RTSP: Cannot allocate RTSP data ports\n");
+#endif
+		        break;
+		      }
+		    }
+		  }
+                  ealias = htons(base_alias + (RTSP_PORT_GROUP - 1));
+		}
+
+		if (salias && rtsp_link) {
+
+		  pkt_updated = 1;
+
+	          /* Copy into IP packet */
+		  sprintf(stemp, "%d", ntohs(salias));
+		  memcpy(port_newdata, stemp, strlen(stemp));
+		  port_newdata += strlen(stemp);
+
+		  if (eport != 0) {
+		    *port_newdata = '-';
+		    port_newdata++;
+
+		    /* Copy into IP packet */
+		    sprintf(stemp, "%d", ntohs(ealias));
+		    memcpy(port_newdata, stemp, strlen(stemp));
+		    port_newdata += strlen(stemp);
+		  }
+
+	          *port_newdata = ';';
+		  port_newdata++;
+		}
+		state++;
+		break;
+	    }
+	    if (state > 3) {
+		break;
+	    }
+	}
+	port_data += i;
+	port_dlen -= i;
+    }
+
+    if (!pkt_updated)
+      return -1;
+
+    memcpy (port_newdata, port_data, port_dlen);
+    port_newdata += port_dlen;
+    *port_newdata = '\0';
+
+    /* Create new packet */
+    new_dlen = port_newdata - newdata;
+    memcpy (data, newdata, new_dlen);
+
+    SetAckModified(link);
+    delta = GetDeltaSeqOut(pip, link);
+    AddSeq(pip, link, delta + new_dlen - dlen);
+
+    new_len = htons(hlen + new_dlen);
+    DifferentialChecksum(&pip->ip_sum,
+			 &new_len,
+			 &pip->ip_len,
+			 1);
+    pip->ip_len = new_len;
+
+    tc->th_sum = 0;
+    tc->th_sum = TcpChecksum(pip);
+
+    return 0;
+}
+
+/* Support the protocol used by early versions of RealPlayer */
+
+int alias_pna_out(struct ip *pip,
+		  struct alias_link *link,
+		  char *data,
+		  int dlen)
+{
+    struct alias_link *pna_links;
+    u_short msg_id, msg_len;
+    char    *work;
+    u_short alias_port, port;
+    struct  tcphdr *tc;
+
+    work = data;
+    work += 5;
+    while (work + 4 < data + dlen) {
+	memcpy(&msg_id, work, 2);
+	work += 2;
+	memcpy(&msg_len, work, 2);
+	work += 2;
+	if (ntohs(msg_id) == 0) {
+	    /* end of options */
+	    return 0;
+	}
+	if ((ntohs(msg_id) == 1) || (ntohs(msg_id) == 7)) {
+	    memcpy((char*)&port, (char*)work, 2);
+	    pna_links = FindUdpTcpOut(pip->ip_src, GetDestAddress(link),
+				      port, 0, IPPROTO_UDP);
+	    if (pna_links != NULL) {
+#ifndef NO_FW_PUNCH
+		/* Punch hole in firewall */
+		PunchFWHole(pna_links);
+#endif
+		tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
+		alias_port = GetAliasPort(pna_links);
+		memcpy((char*)work, (char*)&alias_port, 2);
+
+		/* Compute TCP checksum for revised packet */
+		tc->th_sum = 0;
+		tc->th_sum = TcpChecksum(pip);
+	    }
+	}
+	work += ntohs(msg_len);
+    }
+    
+    return 0;
+}
+
+void
+AliasHandleRtspOut(struct ip *pip, struct alias_link *link, int maxpacketsize)
+{
+    int    hlen, tlen, dlen;
+    struct tcphdr *tc;
+    char   *data, *setup = "SETUP", *pna = "PNA", *str200 = "200", *okstr = "OK";
+    char   *client_port_str = "client_port", *server_port_str = "server_port";
+    int    i, parseOk;
+
+    tc = (struct tcphdr *)((char *)pip + (pip->ip_hl << 2));
+    hlen = (pip->ip_hl + tc->th_off) << 2;
+    tlen = ntohs(pip->ip_len);
+    dlen = tlen - hlen;
+
+    data = (char*)pip;
+    data += hlen;
+
+    /* When aliasing a client, check for the SETUP request */
+    if ((ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_1) || 
+      (ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_2)) { 
+
+      if (dlen >= strlen(setup)) {
+        if (memcmp(data, setup, strlen(setup)) == 0) {
+	    alias_rtsp_out(pip, link, data, client_port_str);
+	    return;
+	}
+      }
+      if (dlen >= strlen(pna)) {
+	if (memcmp(data, pna, strlen(pna)) == 0) {
+	    alias_pna_out(pip, link, data, dlen);
+	}
+      }
+
+    } else {
+
+      /* When aliasing a server, check for the 200 reply
+         Accomodate varying number of blanks between 200 & OK */
+
+      if (dlen >= strlen(str200)) {
+
+        for (parseOk = 0, i = 0;         
+             i <= dlen - strlen(str200);          
+             i++) {
+          if (memcmp(&data[i], str200, strlen(str200)) == 0) { 
+            parseOk = 1; 
+            break;
+          }
+        }
+        if (parseOk) { 
+
+          i += strlen(str200);        /* skip string found */ 
+          while(data[i] == ' ')       /* skip blank(s) */
+	    i++;
+	
+          if ((dlen - i) >= strlen(okstr)) {
+
+            if (memcmp(&data[i], okstr, strlen(okstr)) == 0) 
+              alias_rtsp_out(pip, link, data, server_port_str);
+
+          }
+        }
+      }
+    }
+}
diff --git a/lib/libalias/libalias.3 b/lib/libalias/libalias.3
index 4c06d98..0090387 100644
--- a/lib/libalias/libalias.3
+++ b/lib/libalias/libalias.3
@@ -808,6 +808,25 @@ If the checksum is valid,
 .Fn PacketAliasInternetChecksum
 will return zero.
 .Ed
+.Pp
+.Ft int
+.Fn PacketUnaliasOut "char *buffer" "int maxpacketsize"
+.Bd -ragged -offset indent
+An outgoing packet, which has already been aliased, has its private address/port 
+information restored by this function.
+The IP packet is pointed to by
+.Fa buffer ,
+and
+.Fa maxpacketsize
+is provided for error checking purposes.          
+This function can be used if an already-aliased packet needs to have its 
+original IP header restored for further processing (eg. logging).
+.Ed
+.Sh BUGS
+PPTP aliasing does not work when more than one internal client
+connects to the same external server at the same time, because
+PPTP requires a single TCP control connection to be established
+between any two IP addresses.
 .Sh AUTHORS
 .An Charles Mott Aq cmott@scientech.com ,
 versions 1.0 - 1.8, 2.0 - 2.4.
@@ -816,7 +835,9 @@ versions 1.8b, 1.9 and 2.5.
 Added IRC DCC support as well as contributing a number of architectural
 improvements; added the firewall bypass for FTP/IRC DCC.
 .An Erik Salander Aq erik@whistle.com
-added support for PPTP.
+added support for PPTP and RTSP.
+.An Junichi Satoh Aq junichi@junichi.org
+added support for RTSP/PNA.
 .Sh ACKNOWLEDGMENTS
 Listed below, in approximate chronological order, are individuals who
 have provided valuable comments and/or debugging assistance.