moving NAT client/server to NAT library

7 files changed, 4 insertions, 2416 deletions

diff --git a/src/transport/Makefile.am b/src/transport/Makefile.am
index e8ed46aad5..97c17d6151 100644
--- a/src/transport/Makefile.am
+++ b/src/transport/Makefile.am
@@ -2,15 +2,6 @@ INCLUDES = -I$(top_srcdir)/src/include
 
 plugindir = $(libdir)/gnunet
 
-if MINGW
-  WINFLAGS = -Wl,--no-undefined -Wl,--export-all-symbols
-  NATBIN = gnunet-nat-server gnunet-nat-client
-  NATSERVER = gnunet-nat-server-windows.c
-  NATCLIENT = gnunet-nat-client-windows.c
-else
-  NATSERVER = gnunet-nat-server.c
-  NATCLIENT = gnunet-nat-client.c
-endif
 
 if HAVE_MHD
 if HAVE_EXPERIMENTAL
@@ -53,15 +44,6 @@ UNIX_QUOTA_TEST = test_quota_compliance_unix \
      test_quota_compliance_unix_asymmetric_recv_constant
 endif
 
-if LINUX
-NATBIN = gnunet-nat-server gnunet-nat-client
-install-exec-hook:
-	chown root:root $(bindir)/gnunet-nat-server $(bindir)/gnunet-nat-client $(bindir)/gnunet-transport-wlan-helper || true
-	chmod u+s $(bindir)/gnunet-nat-server $(bindir)/gnunet-nat-client $(bindir)/gnunet-transport-wlan-helper || true
-else
-install-exec-hook:
-endif
-
 #noinst_PROGRAMS = ${check_PROGRAMS}
 
 lib_LTLIBRARIES = \
@@ -96,15 +78,12 @@ libgnunettransport_la_LDFLAGS = \
 bin_PROGRAMS = \
  gnunet-transport \
  $(WLAN_BIN) \
- gnunet-service-transport $(NATBIN) \
+ gnunet-service-transport \
  $(WLAN_BIN_DUMMY)
 
 bin_SCRIPTS = \
  gnunet-transport-certificate-creation
 
-gnunet_nat_server_SOURCES = \
- $(NATSERVER)
-
 
 gnunet_transport_wlan_helper_SOURCES = \
  wlan/byteorder.h \
@@ -127,9 +106,6 @@ gnunet_transport_wlan_helper_LDADD = \
 gnunet_transport_wlan_helper_dummy_LDADD = \
   $(top_builddir)/src/util/libgnunetutil.la 
 
-gnunet_nat_client_SOURCES = \
- $(NATCLIENT)         
-
 gnunet_transport_SOURCES = \
  gnunet-transport.c         
 gnunet_transport_LDADD = \
@@ -161,7 +137,6 @@ plugin_LTLIBRARIES = \
   $(HTTPS_PLUGIN_LA) \
   $(WLAN_PLUGIN_LA) \
   libgnunet_plugin_transport_template.la
-# TODO: add nat, etc.
 
 libgnunet_plugin_transport_tcp_la_SOURCES = \
   plugin_transport_tcp.c
@@ -197,6 +172,7 @@ libgnunet_plugin_transport_udp_la_LIBADD = \
   $(top_builddir)/src/hello/libgnunethello.la \
   $(top_builddir)/src/statistics/libgnunetstatistics.la \
   $(top_builddir)/src/peerinfo/libgnunetpeerinfo.la \
+  $(top_builddir)/src/nat/libgnunetnat.la \
   $(top_builddir)/src/util/libgnunetutil.la 
 libgnunet_plugin_transport_udp_la_LDFLAGS = \
  $(GN_PLUGIN_LDFLAGS)
@@ -218,6 +194,7 @@ libgnunet_plugin_transport_http_la_LIBADD = \
   $(top_builddir)/src/statistics/libgnunetstatistics.la \
   $(top_builddir)/src/peerinfo/libgnunetpeerinfo.la \
   @LIBCURL@ \
+  $(top_builddir)/src/nat/libgnunetnat.la \
   $(top_builddir)/src/util/libgnunetutil.la 
 libgnunet_plugin_transport_http_la_LDFLAGS = \
  $(GN_LIBMHD) \
@@ -234,6 +211,7 @@ libgnunet_plugin_transport_https_la_LIBADD = \
   $(top_builddir)/src/statistics/libgnunetstatistics.la \
   $(top_builddir)/src/peerinfo/libgnunetpeerinfo.la \
   @LIBCURL@ \
+  $(top_builddir)/src/nat/libgnunetnat.la \
   $(top_builddir)/src/util/libgnunetutil.la 
 libgnunet_plugin_transport_https_la_LDFLAGS = \
  $(GN_LIBMHD) \
@@ -277,7 +255,6 @@ check_PROGRAMS = \
  $(WLAN_API_TEST) \
  $(WLAN_REL_TEST) \
  $(WLAN_UREL_TEST)
-# TODO: add tests for nat, etc.
 
 if ENABLE_TEST_RUN
 TESTS = \
diff --git a/src/transport/gnunet-nat-client-script.sh b/src/transport/gnunet-nat-client-script.sh
deleted file mode 100755
index 4e4ccafadc..0000000000
--- a/src/transport/gnunet-nat-client-script.sh
+++ /dev/null
@@ -1,4 +0,0 @@
-#!/bin/sh
-IP=`ifconfig | grep inet | head -n1 | awk '{print $2}' | sed -e "s/addr://"`
-echo "Using IP $IP, trying to connect to $1"
-./gnunet-nat-client-udp $IP $1
diff --git a/src/transport/gnunet-nat-client-windows.c b/src/transport/gnunet-nat-client-windows.c
deleted file mode 100644
index 2e7c8a86e4..0000000000
--- a/src/transport/gnunet-nat-client-windows.c
+++ /dev/null
@@ -1,550 +0,0 @@
-/*
-     This file is part of GNUnet.
-     (C) 2010 Christian Grothoff (and other contributing authors)
-
-     GNUnet is free software; you can redistribute it and/or modify
-     it under the terms of the GNU General Public License as published
-     by the Free Software Foundation; either version 3, or (at your
-     option) any later version.
-
-     GNUnet is distributed in the hope that it will be useful, but
-     WITHOUT ANY WARRANTY; without even the implied warranty of
-     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-     General Public License for more details.
-
-     You should have received a copy of the GNU General Public License
-     along with GNUnet; see the file COPYING.  If not, write to the
-     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
-     Boston, MA 02111-1307, USA.
-*/
-
-/**
- * @file src/transport/gnunet-nat-client-windows.c
- * @brief Tool to help bypass NATs using ICMP method; must run as
- *        root (SUID will do) or administrator on W32
- *        This code will work under GNU/Linux or W32.
- * @author Nathan Evans
- *
- * This program will send ONE ICMP message using RAW sockets
- * to the IP address specified as the second argument.  Since
- * it uses RAW sockets, it must be installed SUID or run as 'root'.
- * In order to keep the security risk of the resulting SUID binary
- * minimal, the program ONLY opens the RAW socket with root
- * privileges, then drops them and only then starts to process
- * command line arguments.  The code also does not link against
- * any shared libraries (except libc) and is strictly minimal
- * (except for checking for errors).  The following list of people
- * have reviewed this code and considered it safe since the last
- * modification (if you reviewed it, please have your name added
- * to the list):
- *
- * - Christian Grothoff
- * - Nathan Evans
- */
-#define _GNU_SOURCE
-
-#include <winsock2.h>
-#include <ws2tcpip.h>
-#include <sys/time.h>
-#include <sys/types.h>
-#include <unistd.h>
-#include <stdio.h>
-#include <string.h>
-#include <errno.h>
-#include <stdlib.h>
-#include <stdint.h>
-#include <time.h>
-
-
-#define ICMP_ECHO 8
-#define IPDEFTTL 64
-#define ICMP_TIME_EXCEEDED 11
-
-/**
- * Must match IP given in the server.
- */
-#define DUMMY_IP "192.0.2.86"
-
-#define NAT_TRAV_PORT 22225
-
-/**
- * IPv4 header.
- */
-struct ip_header
-{
-
-  /**
-   * Version (4 bits) + Internet header length (4 bits)
-   */
-  uint8_t vers_ihl;
-
-  /**
-   * Type of service
-   */
-  uint8_t tos;
-
-  /**
-   * Total length
-   */
-  uint16_t pkt_len;
-
-  /**
-   * Identification
-   */
-  uint16_t id;
-
-  /**
-   * Flags (3 bits) + Fragment offset (13 bits)
-   */
-  uint16_t flags_frag_offset;
-
-  /**
-   * Time to live
-   */
-  uint8_t ttl;
-
-  /**
-   * Protocol
-   */
-  uint8_t proto;
-
-  /**
-   * Header checksum
-   */
-  uint16_t checksum;
-
-  /**
-   * Source address
-   */
-  uint32_t src_ip;
-
-  /**
-   * Destination address
-   */
-  uint32_t dst_ip;
-};
-
-
-/**
- * Format of ICMP packet.
- */
-struct icmp_ttl_exceeded_header
-{
-  uint8_t type;
-
-  uint8_t code;
-
-  uint16_t checksum;
-
-  uint32_t unused;
-
-  /* followed by original payload */
-};
-
-struct icmp_echo_header
-{
-  uint8_t type;
-
-  uint8_t code;
-
-  uint16_t checksum;
-
-  uint32_t reserved;
-};
-
-/**
- * Beginning of UDP packet.
- */
-struct udp_header
-{
-  uint16_t src_port;
-
-  uint16_t dst_port;
-
-  uint16_t length;
-
-  uint16_t crc;
-};
-
-
-/**
- * Socket we use to send our ICMP packets.
- */
-static SOCKET rawsock;
-
-/**
- * Target "dummy" address.
- */
-static struct in_addr dummy;
-
-/**
- * Port we are listening on (communicated to the server).
- */
-static uint16_t port;
-
-
-
-/**
- * Convert IPv4 address from text to binary form.
- *
- * @param af address family
- * @param cp the address to print
- * @param buf where to write the address result
- * @return 1 on success
- */
-static int
-inet_pton (int af,
-	   const char *cp,
-	   struct in_addr *buf)
-{
-  buf->s_addr = inet_addr(cp);
-  if (buf->s_addr == INADDR_NONE)
-    {
-      fprintf(stderr,
-	      "Error %d handling address %s",
-	      WSAGetLastError(),
-	      cp);
-      return 0;
-    }
-  return 1;
-}
-
-
-/**
- * CRC-16 for IP/ICMP headers.
- *
- * @param data what to calculate the CRC over
- * @param bytes number of bytes in data (must be multiple of 2)
- * @return the CRC 16.
- */
-static uint16_t
-calc_checksum(const uint16_t *data,
-	      unsigned int bytes)
-{
-  uint32_t sum;
-  unsigned int i;
-
-  sum = 0;
-  for (i=0;i<bytes/2;i++)
-    sum += data[i];
-  sum = (sum & 0xffff) + (sum >> 16);
-  sum = htons(0xffff - sum);
-  return sum;
-}
-
-
-/**
- * Send an ICMP message to the target.
- *
- * @param my_ip source address
- * @param other target address
- */
-static void
-send_icmp_udp (const struct in_addr *my_ip,
-               const struct in_addr *other)
-{
-  char packet[sizeof(struct ip_header) * 2 +
-	      sizeof(struct icmp_ttl_exceeded_header) +
-	      sizeof(struct udp_header)];
-  struct ip_header ip_pkt;
-  struct icmp_ttl_exceeded_header icmp_pkt;
-  struct udp_header udp_pkt;
-  struct sockaddr_in dst;
-  size_t off;
-  int err;
-
-  /* ip header: send to (known) ip address */
-  off = 0;
-  ip_pkt.vers_ihl = 0x45;
-  ip_pkt.tos = 0;
-  ip_pkt.pkt_len = htons(sizeof (packet));
-  ip_pkt.id = htons(256);
-  ip_pkt.flags_frag_offset = 0;
-  ip_pkt.ttl = 128;
-  ip_pkt.proto = IPPROTO_ICMP;
-  ip_pkt.checksum = 0;
-  ip_pkt.src_ip = my_ip->s_addr;
-  ip_pkt.dst_ip = other->s_addr;
-  ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt,
-					sizeof (struct ip_header)));
-  memcpy(&packet[off],
-	 &ip_pkt,
-	 sizeof(struct ip_header));
-  off += sizeof(struct ip_header);
-
-  icmp_pkt.type = ICMP_TIME_EXCEEDED;
-  icmp_pkt.code = 0;
-  icmp_pkt.checksum = 0;
-  icmp_pkt.unused = 0;
-  memcpy(&packet[off],
-	 &icmp_pkt,
-	 sizeof(struct icmp_ttl_exceeded_header));
-  off += sizeof(struct icmp_ttl_exceeded_header);
-
-  /* ip header of the presumably 'lost' udp packet */
-  ip_pkt.vers_ihl = 0x45;
-  ip_pkt.tos = 0;
-  ip_pkt.pkt_len = htons(sizeof (struct ip_header) +
-			 sizeof (struct udp_header));
-  ip_pkt.id = htons(0);
-  ip_pkt.flags_frag_offset = 0;
-  ip_pkt.ttl = 128;
-  ip_pkt.proto = IPPROTO_UDP;
-  ip_pkt.checksum = 0;
-  ip_pkt.src_ip = other->s_addr;
-  ip_pkt.dst_ip = dummy.s_addr;
-  ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt,
-					sizeof (struct ip_header)));
-  memcpy(&packet[off],
-	 &ip_pkt,
-	 sizeof(struct ip_header));
-  off += sizeof(struct ip_header);
-
-  /* build UDP header */
-  udp_pkt.src_port = htons(NAT_TRAV_PORT);
-  udp_pkt.dst_port = htons(NAT_TRAV_PORT);
-  udp_pkt.length = htons (port);
-  udp_pkt.crc = 0;
-  memcpy(&packet[off],
-	 &udp_pkt,
-	 sizeof(struct udp_header));
-  off += sizeof(struct udp_header);
-
-  /* no go back to calculate ICMP packet checksum */
-  icmp_pkt.checksum = htons(calc_checksum((uint16_t*)&packet[off],
-					  sizeof (struct icmp_ttl_exceeded_header) +
-					  sizeof (struct ip_header) +
-					  sizeof (struct udp_header)));
-  memcpy (&packet[sizeof (struct ip_header)],
-	  &icmp_pkt,
-	  sizeof (struct icmp_ttl_exceeded_header));
-
-  memset (&dst, 0, sizeof (dst));
-  dst.sin_family = AF_INET;
-  dst.sin_addr = *other;
-  err = sendto(rawsock,
-               packet,
-               sizeof (packet), 0,
-               (struct sockaddr*)&dst,
-               sizeof(dst));
-  if (err < 0)
-    {
-      fprintf(stderr,
-              "sendto failed: %s\n", strerror(errno));
-    }
-  else if (sizeof (packet) != (size_t) err)
-    {
-      fprintf(stderr,
-              "Error: partial send of ICMP message\n");
-    }
-}
-
-
-/**
- * Send an ICMP message to the target.
- *
- * @param my_ip source address
- * @param other target address
- */
-static void
-send_icmp (const struct in_addr *my_ip,
-	   const struct in_addr *other)
-{
-  struct ip_header ip_pkt;
-  struct icmp_ttl_exceeded_header icmp_ttl;
-  struct icmp_echo_header icmp_echo;
-  struct sockaddr_in dst;
-  char packet[sizeof (struct ip_header) * 2 +
-	      sizeof (struct icmp_ttl_exceeded_header) +
-	      sizeof(struct icmp_echo_header)];
-  size_t off;
-  int err;
-
-  /* ip header: send to (known) ip address */
-  off = 0;
-  ip_pkt.vers_ihl = 0x45;
-  ip_pkt.tos = 0;
-  ip_pkt.pkt_len = htons (sizeof (packet));
-  ip_pkt.id = htons(256);
-  ip_pkt.flags_frag_offset = 0;
-  ip_pkt.ttl = IPDEFTTL;
-  ip_pkt.proto = IPPROTO_ICMP;
-  ip_pkt.checksum = 0;
-  ip_pkt.src_ip = my_ip->s_addr;
-  ip_pkt.dst_ip = other->s_addr;
-  ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt,
-					sizeof (struct ip_header)));
-  memcpy (&packet[off],
-	  &ip_pkt,
-	  sizeof (struct ip_header));
-  off += sizeof (ip_pkt);
-
-  /* icmp reply: time exceeded */
-  icmp_ttl.type = ICMP_TIME_EXCEEDED;
-  icmp_ttl.code = 0;
-  icmp_ttl.checksum = 0;
-  icmp_ttl.unused = 0; 
-  memcpy (&packet[off],
-	  &icmp_ttl,
-	  sizeof (struct icmp_ttl_exceeded_header));
-  off += sizeof (struct icmp_ttl_exceeded_header);
-
-  /* ip header of the presumably 'lost' udp packet */
-  ip_pkt.vers_ihl = 0x45;
-  ip_pkt.tos = 0;
-  ip_pkt.pkt_len = htons(sizeof (struct ip_header) + sizeof (struct icmp_echo_header));
-  ip_pkt.id = htons (256);
-  ip_pkt.flags_frag_offset = 0;
-  ip_pkt.ttl = 1; /* real TTL would be 1 on a time exceeded packet */
-  ip_pkt.proto = IPPROTO_ICMP;
-  ip_pkt.src_ip = other->s_addr;
-  ip_pkt.dst_ip = dummy.s_addr;
-  ip_pkt.checksum = 0;
-  ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt,
-					sizeof (struct ip_header)));
-  memcpy (&packet[off],
-	  &ip_pkt,
-	  sizeof (struct ip_header));
-  off += sizeof (struct ip_header);
-
-  icmp_echo.type = ICMP_ECHO;
-  icmp_echo.code = 0;
-  icmp_echo.reserved = htonl(port);
-  icmp_echo.checksum = 0;
-  icmp_echo.checksum = htons(calc_checksum((uint16_t*) &icmp_echo,
-					   sizeof (struct icmp_echo_header)));
-  memcpy (&packet[off],
-	  &icmp_echo,
-	  sizeof(struct icmp_echo_header));
-
-  /* no go back to calculate ICMP packet checksum */
-  off = sizeof (struct ip_header);
-  icmp_ttl.checksum = htons(calc_checksum((uint16_t*) &packet[off],
-					  sizeof (struct icmp_ttl_exceeded_header) +
-					  sizeof (struct ip_header) +
-					  sizeof (struct icmp_echo_header)));
-  memcpy (&packet[off],
-	  &icmp_ttl,
-	  sizeof (struct icmp_ttl_exceeded_header));
-
-  memset (&dst, 0, sizeof (dst));
-  dst.sin_family = AF_INET;
-  dst.sin_addr = *other;
-
-  err = sendto(rawsock,
-	       packet,
-	       sizeof (packet), 0,
-	       (struct sockaddr*)&dst,
-	       sizeof(dst));
-
-  if (err < 0)
-    {
-      fprintf(stderr,
-	      "sendto failed: %s\n", strerror(errno));
-    }
-  else if (sizeof (packet) != (size_t) err)
-    {
-      fprintf(stderr,
-	      "Error: partial send of ICMP message\n");
-    }
-}
-
-
-/**
- * Create an ICMP raw socket.
- *
- * @return INVALID_SOCKET on error
- */
-static SOCKET
-make_raw_socket ()
-{
-  DWORD bOptVal = TRUE;
-  int bOptLen = sizeof(bOptVal);
-  SOCKET ret;
-
-  ret = socket (AF_INET, SOCK_RAW, IPPROTO_RAW);
-  if (INVALID_SOCKET == ret)
-    {
-      fprintf (stderr,
-	       "Error opening RAW socket: %s\n",
-	       strerror (errno));
-      return INVALID_SOCKET;
-    }
-  if (0 != setsockopt(ret, SOL_SOCKET, SO_BROADCAST, (char*)&bOptVal, bOptLen))
-    {
-      fprintf(stderr,
-	      "Error setting SO_BROADCAST to ON: %s\n",
-	      strerror (errno));
-      closesocket(rawsock);
-      return INVALID_SOCKET;
-    }
-
-  if (0 != setsockopt(ret, IPPROTO_IP, IP_HDRINCL, (char*)&bOptVal, bOptLen))
-    {
-      fprintf(stderr,
-	      "Error setting IP_HDRINCL to ON: %s\n",
-	      strerror (errno));
-      closesocket(rawsock);
-      return INVALID_SOCKET;
-    }
-  return ret;
-}
-
-
-int
-main (int argc, char *const *argv)
-{
-  struct in_addr external;
-  struct in_addr target;
-  WSADATA wsaData;
-
-  unsigned int p;
-
-  if (argc != 4)
-    {
-      fprintf (stderr,
-	       "This program must be started with our IP, the targets external IP, and our port as arguments.\n");
-      return 1;
-    }
-  if ( (1 != inet_pton (AF_INET, argv[1], &external)) ||
-       (1 != inet_pton (AF_INET, argv[2], &target)) )
-    {
-      fprintf (stderr,
-	       "Error parsing IPv4 address: %s\n",
-	       strerror (errno));
-      return 1;
-    }
-  if ( (1 != sscanf (argv[3], "%u", &p) ) ||
-       (0 == p) ||
-       (0xFFFF < p) )
-    {
-      fprintf (stderr,
-	       "Error parsing port value `%s'\n",
-	       argv[3]);
-      return 1;
-    }
-  port = (uint16_t) p;
-
-  if (0 != WSAStartup (MAKEWORD (2, 1), &wsaData))
-    {
-      fprintf (stderr, "Failed to find Winsock 2.1 or better.\n");
-      return 2;
-    }
-  if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy))
-    {
-      fprintf (stderr,
-	       "Internal error converting dummy IP to binary.\n");
-      return 2;
-    }
-  if (-1 == (rawsock = make_raw_socket()))
-    return 3;
-  send_icmp (&external,
-	     &target);
-  send_icmp_udp (&external,
-                 &target);
-  closesocket (rawsock);
-  WSACleanup ();
-  return 0;
-}
-
-/* end of gnunet-nat-client-windows.c */
diff --git a/src/transport/gnunet-nat-client.c b/src/transport/gnunet-nat-client.c
deleted file mode 100644
index 3e35aa8f4f..0000000000
--- a/src/transport/gnunet-nat-client.c
+++ /dev/null
@@ -1,527 +0,0 @@
-/*
-     This file is part of GNUnet.
-     (C) 2010 Christian Grothoff (and other contributing authors)
-
-     GNUnet is free software; you can redistribute it and/or modify
-     it under the terms of the GNU General Public License as published
-     by the Free Software Foundation; either version 3, or (at your
-     option) any later version.
-
-     GNUnet is distributed in the hope that it will be useful, but
-     WITHOUT ANY WARRANTY; without even the implied warranty of
-     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-     General Public License for more details.
-
-     You should have received a copy of the GNU General Public License
-     along with GNUnet; see the file COPYING.  If not, write to the
-     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
-     Boston, MA 02111-1307, USA.
-*/
-
-/**
- * @file src/transport/gnunet-nat-client.c
- * @brief Tool to help bypass NATs using ICMP method; must run as root (SUID will do)
- *        This code will work under GNU/Linux only.
- * @author Christian Grothoff
- *
- * This program will send ONE ICMP message using RAW sockets
- * to the IP address specified as the second argument.  Since
- * it uses RAW sockets, it must be installed SUID or run as 'root'.
- * In order to keep the security risk of the resulting SUID binary
- * minimal, the program ONLY opens the RAW socket with root
- * privileges, then drops them and only then starts to process
- * command line arguments.  The code also does not link against
- * any shared libraries (except libc) and is strictly minimal
- * (except for checking for errors).  The following list of people
- * have reviewed this code and considered it safe since the last
- * modification (if you reviewed it, please have your name added
- * to the list):
- *
- * - Christian Grothoff
- * - Nathan Evans
- * - Benjamin Kuperman (22 Aug 2010)
- */
-#if HAVE_CONFIG_H
-/* Just needed for HAVE_SOCKADDR_IN_SIN_LEN test macro! */
-#include "gnunet_config.h"
-#else
-#define _GNU_SOURCE
-#endif
-#include <sys/types.h>
-#include <sys/socket.h>
-#include <arpa/inet.h>
-#include <sys/types.h>
-#include <unistd.h>
-#include <stdio.h>
-#include <string.h>
-#include <errno.h>
-#include <stdlib.h>
-#include <stdint.h>
-#include <netinet/ip.h>
-#include <netinet/ip_icmp.h>
-#include <netinet/in.h>
-
-/**
- * Must match IP given in the server.
- */
-#define DUMMY_IP "192.0.2.86"
-
-#define NAT_TRAV_PORT 22225
-
-/**
- * IPv4 header.
- */
-struct ip_header
-{
-
-  /**
-   * Version (4 bits) + Internet header length (4 bits)
-   */
-  uint8_t vers_ihl;
-
-  /**
-   * Type of service
-   */
-  uint8_t tos;
-
-  /**
-   * Total length
-   */
-  uint16_t pkt_len;
-
-  /**
-   * Identification
-   */
-  uint16_t id;
-
-  /**
-   * Flags (3 bits) + Fragment offset (13 bits)
-   */
-  uint16_t flags_frag_offset;
-
-  /**
-   * Time to live
-   */
-  uint8_t ttl;
-
-  /**
-   * Protocol
-   */
-  uint8_t proto;
-
-  /**
-   * Header checksum
-   */
-  uint16_t checksum;
-
-  /**
-   * Source address
-   */
-  uint32_t src_ip;
-
-  /**
-   * Destination address
-   */
-  uint32_t dst_ip;
-};
-
-/**
- * Format of ICMP packet.
- */
-struct icmp_ttl_exceeded_header
-{
-  uint8_t type;
-
-  uint8_t code;
-
-  uint16_t checksum;
-
-  uint32_t unused;
-
-  /* followed by original payload */
-};
-
-struct icmp_echo_header
-{
-  uint8_t type;
-
-  uint8_t code;
-
-  uint16_t checksum;
-
-  uint32_t reserved;
-};
-
-/**
- * Beginning of UDP packet.
- */
-struct udp_header
-{
-  uint16_t src_port;
-
-  uint16_t dst_port;
-
-  uint16_t length;
-
-  uint16_t crc;
-};
-
-/**
- * Socket we use to send our fake ICMP replies.
- */
-static int rawsock;
-
-/**
- * Target "dummy" address of the packet we pretend to respond to.
- */
-static struct in_addr dummy;
-
-/**
- * Our "source" port.
- */
-static uint16_t port;
-
-
-/**
- * CRC-16 for IP/ICMP headers.
- *
- * @param data what to calculate the CRC over
- * @param bytes number of bytes in data (must be multiple of 2)
- * @return the CRC 16.
- */
-static uint16_t
-calc_checksum (const uint16_t *data,
-	       unsigned int bytes)
-{
-  uint32_t sum;
-  unsigned int i;
-
-  sum = 0;
-  for (i=0;i<bytes/2;i++)
-    sum += data[i];
-  sum = (sum & 0xffff) + (sum >> 16);
-  sum = htons(0xffff - sum);
-  return sum;
-}
-
-
-/**
- * Send an ICMP message to the target.
- *
- * @param my_ip source address
- * @param other target address
- */
-static void
-send_icmp_udp (const struct in_addr *my_ip,
-               const struct in_addr *other)
-{
-  char packet[sizeof(struct ip_header) * 2 +
-	      sizeof(struct icmp_ttl_exceeded_header) +
-	      sizeof(struct udp_header)];
-  struct ip_header ip_pkt;
-  struct icmp_ttl_exceeded_header icmp_pkt;
-  struct udp_header udp_pkt;
-  struct sockaddr_in dst;
-  size_t off;
-  int err;
-
-  /* ip header: send to (known) ip address */
-  off = 0;
-  ip_pkt.vers_ihl = 0x45;
-  ip_pkt.tos = 0;
-  ip_pkt.pkt_len = htons (sizeof (packet));
-  ip_pkt.id = htons(256);
-  ip_pkt.flags_frag_offset = 0;
-  ip_pkt.ttl = 128;
-  ip_pkt.proto = IPPROTO_ICMP;
-  ip_pkt.checksum = 0;
-  ip_pkt.src_ip = my_ip->s_addr;
-  ip_pkt.dst_ip = other->s_addr;
-  ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt,
-					sizeof (struct ip_header)));
-  memcpy(&packet[off],
-	 &ip_pkt,
-	 sizeof(struct ip_header));
-  off += sizeof(struct ip_header);
-
-  icmp_pkt.type = ICMP_TIME_EXCEEDED;
-  icmp_pkt.code = 0;
-  icmp_pkt.checksum = 0;
-  icmp_pkt.unused = 0;
-  memcpy(&packet[off],
-	 &icmp_pkt,
-	 sizeof(struct icmp_ttl_exceeded_header));
-  off += sizeof(struct icmp_ttl_exceeded_header);
-
-  /* ip header of the presumably 'lost' udp packet */
-  ip_pkt.vers_ihl = 0x45;
-  ip_pkt.tos = 0;
-  ip_pkt.pkt_len = htons(sizeof (struct ip_header) +
-			 sizeof (struct udp_header));
-  ip_pkt.id = htons(0);
-  ip_pkt.flags_frag_offset = 0;
-  ip_pkt.ttl = 128;
-  ip_pkt.proto = IPPROTO_UDP;
-  ip_pkt.checksum = 0;
-  ip_pkt.src_ip = other->s_addr;
-  ip_pkt.dst_ip = dummy.s_addr;
-  ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt,
-					sizeof (struct ip_header)));
-  memcpy(&packet[off],
-	 &ip_pkt,
-	 sizeof(struct ip_header));
-  off += sizeof(struct ip_header);
-
-  /* build UDP header */
-  udp_pkt.src_port = htons(NAT_TRAV_PORT);
-  udp_pkt.dst_port = htons(NAT_TRAV_PORT);
-  udp_pkt.length = htons (port);
-  udp_pkt.crc = 0;
-  memcpy(&packet[off],
-	 &udp_pkt,
-	 sizeof(struct udp_header));
-  off += sizeof(struct udp_header);
-
-  /* set ICMP checksum */
-  icmp_pkt.checksum = htons(calc_checksum((uint16_t*)&packet[sizeof(struct ip_header)],
-					  sizeof (struct icmp_ttl_exceeded_header) +
-					  sizeof (struct ip_header) +
-					  sizeof (struct udp_header)));
-  memcpy (&packet[sizeof(struct ip_header)],
-	  &icmp_pkt,
-	  sizeof (struct icmp_ttl_exceeded_header));
-
-  memset (&dst, 0, sizeof (dst));
-  dst.sin_family = AF_INET;
-#if HAVE_SOCKADDR_IN_SIN_LEN
-  dst.sin_len = sizeof (struct sockaddr_in);
-#endif
-  dst.sin_addr = *other;
-  err = sendto(rawsock,
-               packet,
-               sizeof (packet), 0,
-               (struct sockaddr*)&dst,
-               sizeof(dst));
-  if (err < 0)
-    {
-      fprintf(stderr,
-              "sendto failed: %s\n", strerror(errno));
-    }
-  else if (sizeof (packet) != (size_t) err)
-    {
-      fprintf(stderr,
-              "Error: partial send of ICMP message\n");
-    }
-}
-
-
-/**
- * Send an ICMP message to the target.
- *
- * @param my_ip source address
- * @param other target address
- */
-static void
-send_icmp (const struct in_addr *my_ip,
-	   const struct in_addr *other)
-{
-  struct ip_header ip_pkt;
-  struct icmp_ttl_exceeded_header icmp_ttl;
-  struct icmp_echo_header icmp_echo;
-  struct sockaddr_in dst;
-  char packet[sizeof (struct ip_header) * 2 +
-	      sizeof (struct icmp_ttl_exceeded_header) +
-	      sizeof (struct icmp_echo_header)];
-  size_t off;
-  int err;
-
-  /* ip header: send to (known) ip address */
-  off = 0;
-  ip_pkt.vers_ihl = 0x45;
-  ip_pkt.tos = 0;
-  ip_pkt.pkt_len = htons (sizeof (packet));
-  ip_pkt.id = htons (256);
-  ip_pkt.flags_frag_offset = 0;
-  ip_pkt.ttl = IPDEFTTL;
-  ip_pkt.proto = IPPROTO_ICMP;
-  ip_pkt.checksum = 0;
-  ip_pkt.src_ip = my_ip->s_addr;
-  ip_pkt.dst_ip = other->s_addr;
-  ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt,
-					sizeof (struct ip_header)));
-  memcpy (&packet[off],
-	  &ip_pkt,
-	  sizeof (struct ip_header));
-  off = sizeof (ip_pkt);
-
-  /* icmp reply: time exceeded */
-  icmp_ttl.type = ICMP_TIME_EXCEEDED;
-  icmp_ttl.code = 0;
-  icmp_ttl.checksum = 0;
-  icmp_ttl.unused = 0;
-  memcpy (&packet[off],
-	  &icmp_ttl,
-	  sizeof (struct icmp_ttl_exceeded_header));
-  off += sizeof (struct icmp_ttl_exceeded_header);
-
-  /* ip header of the presumably 'lost' udp packet */
-  ip_pkt.vers_ihl = 0x45;
-  ip_pkt.tos = 0;
-  ip_pkt.pkt_len = htons (sizeof (struct ip_header) + sizeof (struct icmp_echo_header));
-  ip_pkt.id = htons (256);
-  ip_pkt.flags_frag_offset = 0;
-  ip_pkt.ttl = 1; /* real TTL would be 1 on a time exceeded packet */
-  ip_pkt.proto = IPPROTO_ICMP;
-  ip_pkt.src_ip = other->s_addr;
-  ip_pkt.dst_ip = dummy.s_addr;
-  ip_pkt.checksum = 0;
-  ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt,
-					sizeof (struct ip_header)));
-  memcpy (&packet[off],
-	  &ip_pkt,
-	  sizeof (struct ip_header));
-  off += sizeof (struct ip_header);
-
-  icmp_echo.type = ICMP_ECHO;
-  icmp_echo.code = 0;
-  icmp_echo.reserved = htonl (port);
-  icmp_echo.checksum = 0;
-  icmp_echo.checksum = htons(calc_checksum((uint16_t*) &icmp_echo,
-					   sizeof (struct icmp_echo_header)));
-  memcpy (&packet[off],
-	  &icmp_echo,
-	  sizeof(struct icmp_echo_header));
-
-  /* no go back to calculate ICMP packet checksum */
-  off = sizeof (struct ip_header);
-  icmp_ttl.checksum = htons(calc_checksum((uint16_t*) &packet[off],
-					  sizeof (struct icmp_ttl_exceeded_header) +
-					  sizeof (struct ip_header) +
-					  sizeof (struct icmp_echo_header)));
-  memcpy (&packet[off],
-	  &icmp_ttl,
-	  sizeof (struct icmp_ttl_exceeded_header));
-
-  /* prepare for transmission */
-  memset (&dst, 0, sizeof (dst));
-  dst.sin_family = AF_INET;
-#if HAVE_SOCKADDR_IN_SIN_LEN
-  dst.sin_len = sizeof (struct sockaddr_in);
-#endif
-  dst.sin_addr = *other;
-  err = sendto(rawsock,
-	       packet,
-	       sizeof (packet), 0,
-	       (struct sockaddr*)&dst,
-	       sizeof(dst));
-  if (err < 0)
-    {
-      fprintf(stderr,
-	      "sendto failed: %s\n", strerror(errno));
-    }
-  else if (sizeof (packet) != (size_t) err)
-    {
-      fprintf(stderr,
-	      "Error: partial send of ICMP message\n");
-    }
-}
-
-
-/**
- * Create an ICMP raw socket for writing.
- *
- * @return -1 on error
- */
-static int
-make_raw_socket ()
-{
-  const int one = 1;
-  int ret;
-
-  ret = socket (AF_INET, SOCK_RAW, IPPROTO_RAW);
-  if (-1 == ret)
-    {
-      fprintf (stderr,
-	       "Error opening RAW socket: %s\n",
-	       strerror (errno));
-      return -1;
-    }
-  if (0 != setsockopt(ret, SOL_SOCKET, SO_BROADCAST,
-		      (char *)&one, sizeof(one)))
-    {
-      fprintf(stderr,
-	      "setsockopt failed: %s\n",
-	      strerror (errno));
-      close (ret);
-      return -1;
-    }
-  if (0 != setsockopt(ret, IPPROTO_IP, IP_HDRINCL,
-		      (char *)&one, sizeof(one)))
-    {
-      fprintf(stderr,
-	      "setsockopt failed: %s\n",
-	      strerror (errno));
-      close (ret);
-      return -1;
-    }
-  return ret;
-}
-
-
-int
-main (int argc, char *const *argv)
-{
-  struct in_addr external;
-  struct in_addr target;
-  uid_t uid;
-  unsigned int p;
-
-  if (4 != argc)
-    {
-      fprintf (stderr,
-	       "This program must be started with our IP, the targets external IP, and our port as arguments.\n");
-      return 1;
-    }
-  if ( (1 != inet_pton (AF_INET, argv[1], &external)) ||
-       (1 != inet_pton (AF_INET, argv[2], &target)) )
-    {
-      fprintf (stderr,
-	       "Error parsing IPv4 address: %s\n",
-	       strerror (errno));
-      return 1;
-    }
-  if ( (1 != sscanf (argv[3], "%u", &p) ) ||
-       (0 == p) ||
-       (0xFFFF < p) )
-    {
-      fprintf (stderr,
-	       "Error parsing port value `%s'\n",
-	       argv[3]);
-      return 1;
-    }
-  port = (uint16_t)