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<font color="#444444">// field.</font>

<strong>void</strong> <font color="#2040a0">init_ping_packet</font><font color="4444FF">(</font><font color="#2040a0">ICMPHeader</font><font color="4444FF">*</font> <font color="#2040a0">icmp_hdr</font>, <strong>int</strong> <font color="#2040a0">packet_size</font>, <strong>int</strong> <font color="#2040a0">seq_no</font><font color="4444FF">)</font>
<font color="4444FF"><strong>{</strong></font>
    <font color="#444444">// Set up the packet's fields</font>
    <font color="#2040a0">icmp_hdr</font><font color="4444FF">-</font><font color="4444FF">&gt;</font><font color="#2040a0">type</font> <font color="4444FF">=</font> <font color="#2040a0">ICMP_ECHO_REQUEST</font><font color="4444FF">;</font>
    <font color="#2040a0">icmp_hdr</font><font color="4444FF">-</font><font color="4444FF">&gt;</font><font color="#2040a0">code</font> <font color="4444FF">=</font> <font color="#FF0000">0</font><font color="4444FF">;</font>
    <font color="#2040a0">icmp_hdr</font><font color="4444FF">-</font><font color="4444FF">&gt;</font><font color="#2040a0">checksum</font> <font color="4444FF">=</font> <font color="#FF0000">0</font><font color="4444FF">;</font>
    <font color="#2040a0">icmp_hdr</font><font color="4444FF">-</font><font color="4444FF">&gt;</font><font color="#2040a0">id</font> <font color="4444FF">=</font> <font color="4444FF">(</font><font color="#2040a0">USHORT</font><font color="4444FF">)</font><font color="#2040a0">GetCurrentProcessId</font><font color="4444FF">(</font><font color="4444FF">)</font><font color="4444FF">;</font>
    <font color="#2040a0">icmp_hdr</font><font color="4444FF">-</font><font color="4444FF">&gt;</font><font color="#2040a0">seq</font> <font color="4444FF">=</font> <font color="#2040a0">seq_no</font><font color="4444FF">;</font>
    <font color="#2040a0">icmp_hdr</font><font color="4444FF">-</font><font color="4444FF">&gt;</font><font color="#2040a0">timestamp</font> <font color="4444FF">=</font> <font color="#2040a0">GetTickCount</font><font color="4444FF">(</font><font color="4444FF">)</font><font color="4444FF">;</font>

    <font color="#444444">// &quot;You're dead meat now, packet!&quot;</font>
    <strong>const</strong> <strong>unsigned</strong> <strong>long</strong> <strong>int</strong> <font color="#2040a0">deadmeat</font> <font color="4444FF">=</font> <font color="#FF0000">0xDEADBEEF</font><font color="4444FF">;</font>
    <strong>char</strong><font color="4444FF">*</font> <font color="#2040a0">datapart</font> <font color="4444FF">=</font> <font color="4444FF">(</font><strong>char</strong><font color="4444FF">*</font><font color="4444FF">)</font><font color="#2040a0">icmp_hdr</font> <font color="4444FF">+</font> <strong>sizeof</strong><font color="4444FF">(</font><font color="#2040a0">ICMPHeader</font><font color="4444FF">)</font><font color="4444FF">;</font>
    <strong>int</strong> <font color="#2040a0">bytes_left</font> <font color="4444FF">=</font> <font color="#2040a0">packet_size</font> <font color="4444FF">-</font> <strong>sizeof</strong><font color="4444FF">(</font><font color="#2040a0">ICMPHeader</font><font color="4444FF">)</font><font color="4444FF">;</font>
    <strong>while</strong> <font color="4444FF">(</font><font color="#2040a0">bytes_left</font> <font color="4444FF">&gt;</font> <font color="#FF0000">0</font><font color="4444FF">)</font> <font color="4444FF"><strong>{</strong></font>
        <font color="#2040a0">memcpy</font><font color="4444FF">(</font><font color="#2040a0">datapart</font>, <font color="4444FF">&amp;</font><font color="#2040a0">deadmeat</font>, <font color="#2040a0">min</font><font color="4444FF">(</font><strong>int</strong><font color="4444FF">(</font><strong>sizeof</strong><font color="4444FF">(</font><font color="#2040a0">deadmeat</font><font color="4444FF">)</font><font color="4444FF">)</font>, 
                <font color="#2040a0">bytes_left</font><font color="4444FF">)</font><font color="4444FF">)</font><font color="4444FF">;</font>
        <font color="#2040a0">bytes_left</font> <font color="4444FF">-</font><font color="4444FF">=</font> <strong>sizeof</strong><font color="4444FF">(</font><font color="#2040a0">deadmeat</font><font color="4444FF">)</font><font color="4444FF">;</font>
        <font color="#2040a0">datapart</font> <font color="4444FF">+</font><font color="4444FF">=</font> <strong>sizeof</strong><font color="4444FF">(</font><font color="#2040a0">deadmeat</font><font color="4444FF">)</font><font color="4444FF">;</font>
    <font color="4444FF"><strong>}</strong></font>

    <font color="#444444">// Calculate a checksum on the result</font>
    <font color="#2040a0">icmp_hdr</font><font color="4444FF">-</font><font color="4444FF">&gt;</font><font color="#2040a0">checksum</font> <font color="4444FF">=</font> <font color="#2040a0">ip_checksum</font><font color="4444FF">(</font><font color="4444FF">(</font><font color="#2040a0">USHORT</font><font color="4444FF">*</font><font color="4444FF">)</font><font color="#2040a0">icmp_hdr</font>, <font color="#2040a0">packet_size</font><font color="4444FF">)</font><font color="4444FF">;</font>
<font color="4444FF"><strong>}</strong></font>


<font color="#444444">/////////////////////////////// send_ping //////////////////////////////</font>
<font color="#444444">// Send an ICMP echo (&quot;ping&quot;) packet to host dest by way of sd with</font>
<font color="#444444">// packet_size bytes.  packet_size is the total size of the ping packet</font>
<font color="#444444">// to send, including the ICMP header and the payload area; it is not</font>
<font color="#444444">// checked for sanity, so make sure that it's at least </font>
<font color="#444444">// sizeof(ICMPHeader) bytes, and that send_buf points to at least</font>
<font color="#444444">// packet_size bytes.  Returns &lt; 0 for failure.</font>

<strong>int</strong> <font color="#2040a0">send_ping</font><font color="4444FF">(</font><font color="#2040a0">SOCKET</font> <font color="#2040a0">sd</font>, <strong>const</strong> <font color="#2040a0">sockaddr_in</font><font color="4444FF">&amp;</font> <font color="#2040a0">dest</font>, <font color="#2040a0">ICMPHeader</font><font color="4444FF">*</font> <font color="#2040a0">send_buf</font>,
        <strong>int</strong> <font color="#2040a0">packet_size</font><font color="4444FF">)</font>
<font color="4444FF"><strong>{</strong></font>
    <font color="#444444">// Send the ping packet in send_buf as-is</font>
    <font color="#2040a0">cout</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#008000">&quot;Sending &quot;</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#2040a0">packet_size</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#008000">&quot; bytes to &quot;</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> 
            <font color="#2040a0">inet_ntoa</font><font color="4444FF">(</font><font color="#2040a0">dest</font>.<font color="#2040a0">sin_addr</font><font color="4444FF">)</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#008000">&quot;...&quot;</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#2040a0">flush</font><font color="4444FF">;</font>
    <strong>int</strong> <font color="#2040a0">bwrote</font> <font color="4444FF">=</font> <font color="#2040a0">sendto</font><font color="4444FF">(</font><font color="#2040a0">sd</font>, <font color="4444FF">(</font><strong>char</strong><font color="4444FF">*</font><font color="4444FF">)</font><font color="#2040a0">send_buf</font>, <font color="#2040a0">packet_size</font>, <font color="#FF0000">0</font>, 
            <font color="4444FF">(</font><font color="#2040a0">sockaddr</font><font color="4444FF">*</font><font color="4444FF">)</font><font color="4444FF">&amp;</font><font color="#2040a0">dest</font>, <strong>sizeof</strong><font color="4444FF">(</font><font color="#2040a0">dest</font><font color="4444FF">)</font><font color="4444FF">)</font><font color="4444FF">;</font>
    <strong>if</strong> <font color="4444FF">(</font><font color="#2040a0">bwrote</font> <font color="4444FF">=</font><font color="4444FF">=</font> <font color="#2040a0">SOCKET_ERROR</font><font color="4444FF">)</font> <font color="4444FF"><strong>{</strong></font>
        <font color="#2040a0">cerr</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#008000">&quot;send failed: &quot;</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#2040a0">WSAGetLastError</font><font color="4444FF">(</font><font color="4444FF">)</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#2040a0">endl</font><font color="4444FF">;</font>
        <strong>return</strong> <font color="4444FF">-</font><font color="#FF0000">1</font><font color="4444FF">;</font>
    <font color="4444FF"><strong>}</strong></font>
    <strong>else</strong> <strong>if</strong> <font color="4444FF">(</font><font color="#2040a0">bwrote</font> <font color="4444FF">&lt;</font> <font color="#2040a0">packet_size</font><font color="4444FF">)</font> <font color="4444FF"><strong>{</strong></font>
        <font color="#2040a0">cout</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#008000">&quot;sent &quot;</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#2040a0">bwrote</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#008000">&quot; bytes...&quot;</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#2040a0">flush</font><font color="4444FF">;</font>
    <font color="4444FF"><strong>}</strong></font>

    <strong>return</strong> <font color="#FF0000">0</font><font color="4444FF">;</font>
<font color="4444FF"><strong>}</strong></font>


<font color="#444444">/////////////////////////////// recv_ping //////////////////////////////</font>
<font color="#444444">// Receive a ping reply on sd into recv_buf, and stores address info</font>
<font color="#444444">// for sender in source.  On failure, returns &lt; 0, 0 otherwise.  </font>
<font color="#444444">// </font>
<font color="#444444">// Note that recv_buf must be larger than send_buf (passed to send_ping)</font>
<font color="#444444">// because the incoming packet has the IP header attached.  It can also </font>
<font color="#444444">// have IP options set, so it is not sufficient to make it </font>
<font color="#444444">// sizeof(send_buf) + sizeof(IPHeader).  We suggest just making it</font>
<font color="#444444">// fairly large and not worrying about wasting space.</font>

<strong>int</strong> <font color="#2040a0">recv_ping</font><font color="4444FF">(</font><font color="#2040a0">SOCKET</font> <font color="#2040a0">sd</font>, <font color="#2040a0">sockaddr_in</font><font color="4444FF">&amp;</font> <font color="#2040a0">source</font>, <font color="#2040a0">IPHeader</font><font color="4444FF">*</font> <font color="#2040a0">recv_buf</font>, 
        <strong>int</strong> <font color="#2040a0">packet_size</font><font color="4444FF">)</font>
<font color="4444FF"><strong>{</strong></font>
    <font color="#444444">// Wait for the ping reply</font>
    <strong>int</strong> <font color="#2040a0">fromlen</font> <font color="4444FF">=</font> <strong>sizeof</strong><font color="4444FF">(</font><font color="#2040a0">source</font><font color="4444FF">)</font><font color="4444FF">;</font>
    <strong>int</strong> <font color="#2040a0">bread</font> <font color="4444FF">=</font> <font color="#2040a0">recvfrom</font><font color="4444FF">(</font><font color="#2040a0">sd</font>, <font color="4444FF">(</font><strong>char</strong><font color="4444FF">*</font><font color="4444FF">)</font><font color="#2040a0">recv_buf</font>, 
            <font color="#2040a0">packet_size</font> <font color="4444FF">+</font> <strong>sizeof</strong><font color="4444FF">(</font><font color="#2040a0">IPHeader</font><font color="4444FF">)</font>, <font color="#FF0000">0</font>,
            <font color="4444FF">(</font><font color="#2040a0">sockaddr</font><font color="4444FF">*</font><font color="4444FF">)</font><font color="4444FF">&amp;</font><font color="#2040a0">source</font>, <font color="4444FF">&amp;</font><font color="#2040a0">fromlen</font><font color="4444FF">)</font><font color="4444FF">;</font>
    <strong>if</strong> <font color="4444FF">(</font><font color="#2040a0">bread</font> <font color="4444FF">=</font><font color="4444FF">=</font> <font color="#2040a0">SOCKET_ERROR</font><font color="4444FF">)</font> <font color="4444FF"><strong>{</strong></font>
        <font color="#2040a0">cerr</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#008000">&quot;read failed: &quot;</font><font color="4444FF">;</font>
        <strong>if</strong> <font color="4444FF">(</font><font color="#2040a0">WSAGetLastError</font><font color="4444FF">(</font><font color="4444FF">)</font> <font color="4444FF">=</font><font color="4444FF">=</font> <font color="#2040a0">WSAEMSGSIZE</font><font color="4444FF">)</font> <font color="4444FF"><strong>{</strong></font>
            <font color="#2040a0">cerr</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#008000">&quot;buffer too small&quot;</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#2040a0">endl</font><font color="4444FF">;</font>
        <font color="4444FF"><strong>}</strong></font>
        <strong>else</strong> <font color="4444FF"><strong>{</strong></font>
            <font color="#2040a0">cerr</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#008000">&quot;error #&quot;</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#2040a0">WSAGetLastError</font><font color="4444FF">(</font><font color="4444FF">)</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#2040a0">endl</font><font color="4444FF">;</font>
        <font color="4444FF"><strong>}</strong></font>
        <strong>return</strong> <font color="4444FF">-</font><font color="#FF0000">1</font><font color="4444FF">;</font>
    <font color="4444FF"><strong>}</strong></font>

    <strong>return</strong> <font color="#FF0000">0</font><font color="4444FF">;</font>
<font color="4444FF"><strong>}</strong></font>


<font color="#444444">///////////////////////////// decode_reply /////////////////////////////</font>
<font color="#444444">// Decode and output details about an ICMP reply packet.  Returns -1</font>
<font color="#444444">// on failure, -2 on &quot;try again&quot; and 0 on success.</font>

<strong>int</strong> <font color="#2040a0">decode_reply</font><font color="4444FF">(</font><font color="#2040a0">IPHeader</font><font color="4444FF">*</font> <font color="#2040a0">reply</font>, <strong>int</strong> <font color="#2040a0">bytes</font>, <font color="#2040a0">sockaddr_in</font><font color="4444FF">*</font> <font color="#2040a0">from</font><font color="4444FF">)</font> 
<font color="4444FF"><strong>{</strong></font>
    <font color="#444444">// Skip ahead to the ICMP header within the IP packet</font>
    <strong>unsigned</strong> <strong>short</strong> <font color="#2040a0">header_len</font> <font color="4444FF">=</font> <font color="#2040a0">reply</font><font color="4444FF">-</font><font color="4444FF">&gt;</font><font color="#2040a0">h_len</font> <font color="4444FF">*</font> <font color="#FF0000">4</font><font color="4444FF">;</font>
    <font color="#2040a0">ICMPHeader</font><font color="4444FF">*</font> <font color="#2040a0">icmphdr</font> <font color="4444FF">=</font> <font color="4444FF">(</font><font color="#2040a0">ICMPHeader</font><font color="4444FF">*</font><font color="4444FF">)</font><font color="4444FF">(</font><font color="4444FF">(</font><strong>char</strong><font color="4444FF">*</font><font color="4444FF">)</font><font color="#2040a0">reply</font> <font color="4444FF">+</font> <font color="#2040a0">header_len</font><font color="4444FF">)</font><font color="4444FF">;</font>

    <font color="#444444">// Make sure the reply is sane</font>
    <strong>if</strong> <font color="4444FF">(</font><font color="#2040a0">bytes</font> <font color="4444FF">&lt;</font> <font color="#2040a0">header_len</font> <font color="4444FF">+</font> <font color="#2040a0">ICMP_MIN</font><font color="4444FF">)</font> <font color="4444FF"><strong>{</strong></font>
        <font color="#2040a0">cerr</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#008000">&quot;too few bytes from &quot;</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#2040a0">inet_ntoa</font><font color="4444FF">(</font><font color="#2040a0">from</font><font color="4444FF">-</font><font color="4444FF">&gt;</font><font color="#2040a0">sin_addr</font><font color="4444FF">)</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> 
                <font color="#2040a0">endl</font><font color="4444FF">;</font>
        <strong>return</strong> <font color="4444FF">-</font><font color="#FF0000">1</font><font color="4444FF">;</font>
    <font color="4444FF"><strong>}</strong></font>
    <strong>else</strong> <strong>if</strong> <font color="4444FF">(</font><font color="#2040a0">icmphdr</font><font color="4444FF">-</font><font color="4444FF">&gt;</font><font color="#2040a0">type</font> <font color="4444FF">!</font><font color="4444FF">=</font> <font color="#2040a0">ICMP_ECHO_REPLY</font><font color="4444FF">)</font> <font color="4444FF"><strong>{</strong></font>
        <strong>if</strong> <font color="4444FF">(</font><font color="#2040a0">icmphdr</font><font color="4444FF">-</font><font color="4444FF">&gt;</font><font color="#2040a0">type</font> <font color="4444FF">!</font><font color="4444FF">=</font> <font color="#2040a0">ICMP_TTL_EXPIRE</font><font color="4444FF">)</font> <font color="4444FF"><strong>{</strong></font>
            <strong>if</strong> <font color="4444FF">(</font><font color="#2040a0">icmphdr</font><font color="4444FF">-</font><font color="4444FF">&gt;</font><font color="#2040a0">type</font> <font color="4444FF">=</font><font color="4444FF">=</font> <font color="#2040a0">ICMP_DEST_UNREACH</font><font color="4444FF">)</font> <font color="4444FF"><strong>{</strong></font>
                <font color="#2040a0">cerr</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#008000">&quot;Destination unreachable&quot;</font> <font color="4444FF">&lt;</font><font color="4444FF">&lt;</font> <font color="#2040a0">endl</font><font color="4444FF">;</font>
            <font color="4444FF"><strong>}</strong></font>
            <strong>else</strong> <font color="4444FF"><strong>{</strong></font>