668 lines
18 KiB
HTML
668 lines
18 KiB
HTML
{% extends "_layout.html" %}
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{% block title %}I2NP Specification{% endblock %}
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{% block content %}
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<h1>I2P Network Protocol (I2NP) Specification</h1>
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<p>
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The I2P Network Protocol (I2NP),
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which is sandwiched between I2CP and the various I2P transport protocols, manages the
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routing and mixing of messages between routers, as well as the selection of what
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transports to use when communicating with a peer for which there are multiple
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common transports supported.
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</p>
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<h2 id="structures">Common structures</h2>
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<h3 id="struct_header">I2NP message header</h3>
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<h4>Description</h4>
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<p>
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Common header to all I2NP messages, which contains important information like an checksum, expiration date, etc.
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</p>
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<h4>Contents</h4>
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<p>
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1 byte <a href="common_structures_spec#type_Integer">Integer</a> specifying the type of this message, followed by an 4 byte <a href="common_structures_spec#type_Integer">Integer</a> specifying the message-id. After that there is an expiration <a href="common_structures_spec#type_Date">Date</a>, followed by an 2 byte <a href="common_structures_spec#type_Integer">Integer</a> specifying the length of the message payload, followed by an <a href="common_structures_spec#type_Hash">Hash</a>, which is truncated to the first byte. After that the actual message data follows.
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</p>
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<pre>
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{% filter escape %}
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+----+----+----+----+----+
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|type| msg-id |
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+----+----+----+----+----+----+----+----+
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| expiration |
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+----+----+----+----+----+----+----+----+
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| size |chks|
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+----+----+----+
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{% endfilter %}
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</pre>
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<h4>Definition</h4>
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<pre>
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{% filter escape %}
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type :: Integer
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length -> 1 byte
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purpose -> identifies the message type(see table below)
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msg-id :: Integer
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length -> 4 bytes
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purpose -> uniquely identifies this message(for some time at least)
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expiration :: Date
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8 bytes
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date this message will expire
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size :: Integer
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length -> 2 bytes
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purpose -> length of the payload
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chks :: Hash
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length -> 1 byte
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purpose -> checksum of the payload
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SHA256 hash truncated to the first byte
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data :: Data
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length -> $size bytes
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purpose -> actual message contents
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{% endfilter %}
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</pre>
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<h3 id="struct_BuildRequestRecord">BuildRequestRecord</h3>
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<h4>Description</h4>
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<p>
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One Record in a set of multiple records to request the creation of one hop in the tunnel. For more details see here.
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</p>
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<h4>Contents</h4>
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<p>
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<a href="common_structures_spec#type_TunnelId">TunnelId</a> to receive messages on, followed by the <a href="common_structures_spec#type_Hash">Hash</a> of our <a href="common_structures_spec#struct_RouterIdentity">RouterIdentity</a>. After that the <a href="common_structures_spec#type_TunnelId">TunnelId</a> and the <a href="common_structures_spec#type_Hash">Hash</a> of the next router's <a href="common_structures_spec#struct_RouterIdentity">RouterIdentity</a> follow.
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</p>
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<h4>Definition</h4>
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<pre>
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{% filter escape %}
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Cleartext:
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+----+----+----+----+----+----+----+----+
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| receive_tunnel | our_ident |
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+----+----+----+----+ +
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| |
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+ +
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+ +
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+ +----+----+----+----+
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| | next_tunnel |
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+----+----+----+----+----+----+----+----+
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| next_ident |
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+ +
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+ +
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+ +
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+----+----+----+----+----+----+----+----+
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| layer_key |
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+ +
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+ +
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+ +
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+----+----+----+----+----+----+----+----+
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| iv_key |
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+ +
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+ +
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+ +
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+----+----+----+----+----+----+----+----+
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| reply_key |
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+ +
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+ +
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+ +
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+----+----+----+----+----+----+----+----+
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| reply_iv |
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+ +
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+----+----+----+----+----+----+----+----+----+
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|flag| request_time | send_message_id |
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+----+----+----+----+----+----+----+----+----+
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| padding...
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+----+----+----+--//
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encrypted:
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+----+----+----+----+----+----+----+----+
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| toPeer |
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+ +
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+----+----+----+----+----+----+----+----+
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| encrypted data ... |
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+----+----+----+----+----+----+----+----+
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{% endfilter %}
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</pre>
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<h4>Definition</h4>
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<pre>
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{% filter escape %}
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unencrypted:
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receive_tunnel :: TunnelId
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length -> 4 bytes
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our_ident :: Hash
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length -> 32 bytes
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next_tunnel :: TunnelId
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length -> 4 bytes
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next_ident :: Hash
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length -> 32 bytes
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layer_key :: SessionKey
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length -> 32 bytes
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iv_key :: SessionKey
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length -> 32 bytes
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reply_key :: SessionKey
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length -> 32 bytes
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reply_iv :: Integer
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length -> 16 bytes
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flag :: Integer
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length -> 1 byte
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request_time :: Integer
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length -> 4 bytes
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send_message_id :: Integer
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length -> 4 bytes
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padding :: Data
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length -> 29 bytes
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source -> random
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encrypted:
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toPeer :: Hash
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length -> 16 bytes
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encrypted_data :: ElGamal-2048 encrypted data
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length -> 514
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{% endfilter %}
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</pre>
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<h3 id="struct_BuildResponseRecord">BuildResponseRecord</h3>
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<pre>
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{% filter escape %}
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unencrypted:
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+----+----+----+----+----+----+----+----+
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| random data... |
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+ +----+
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| |ret |
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+----+----+----+----+----+----+----+----+
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{% endfilter %}
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</pre>
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<h4>Definition</h4>
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<pre>
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{% filter escape %}
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unencrypted:
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bytes 0-526: random data
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byte 527 : reply
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encrypted:
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bytes 0-527: AES-encrypted record(note: same size as BuildRequestRecord!)
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{% endfilter %}
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</pre>
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<h2 id="messages">Messages</h2>
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<table border=1>
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<tr>
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<td>Message</td>
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<td>Type</td>
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</tr>
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<tr>
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<td><a href="#msg_DatabaseStore">DatabaseStore</a></td>
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<td align="right">1</td>
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</tr>
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<tr>
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<td><a href="#msg_DatabaseLookup">DatabaseLookup</a></td>
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<td align="right">2</td>
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</tr>
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<tr>
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<td><a href="#msg_DatabaseSearchReply">DatabaseSearchReply</a></td>
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<td align="right">3</td>
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</tr>
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<tr>
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<td><a href="#msg_DeliveryStatus">DeliveryStatus</a></td>
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<td align="right">10</td>
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</tr>
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<tr>
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<td><a href="#msg_Garlic">Garlic</a></td>
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<td align="right">11</td>
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</tr>
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<tr>
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<td><a href="#msg_TunnelData">TunnelData</a></td>
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<td align="right">18</td>
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</tr>
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<tr>
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<td><a href="#msg_TunnelGateway">TunnelGateway</a></td>
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<td align="right">19</td>
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</tr>
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<tr>
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<td><a href="#msg_Data">Data</a></td>
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<td align="right">20</td>
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</tr>
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<tr>
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<td><a href="#msg_TunnelBuild">TunnelBuild</a></td>
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<td align="right">21</td>
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</tr>
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<tr>
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<td><a href="#msg_TunnelBuildReply">TunnelBuildReply</a></td>
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<td align="right">22</td>
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</tr>
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<tr>
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<td><a href="#msg_VariableTunnelBuild">VariableTunnelBuild</a></td>
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<td align="right">23</td>
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</tr>
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<tr>
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<td><a href="#msg_VariableTunnelBuildReply">VariableTunnelBuildReply</a></td>
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<td align="right">24</td>
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</tr>
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</table>
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<h3 id="msg_DatabaseStore">DatabaseStore</h3>
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<pre>
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with reply token:
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+----+----+----+----+----+----+----+----+
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| SHA256 Hash as key |
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+ +
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+ +
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+ +
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+----+----+----+----+----+----+----+----+
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|type| reply token | reply tunnel-
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+----+----+----+----+----+----+----+----+
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Id | SHA256 of the gateway RouterInfo |
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+----+ +
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+ +
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+ +
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+ +----+----+----+----+----+----+----+
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| | data ...
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+----+--------\\
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with reply token == 0:
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+----+----+----+----+----+----+----+----+
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| SHA256 Hash as key |
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+ +
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+ +
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+ +
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+----+----+----+----+----+----+----+----+
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|type| reply token | data ...
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+----+-------------------+---------\\
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</pre>
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<h4>Definition</h4>
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<pre>
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key:
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32 bytes
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SHA256 hash
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type:
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1 byte
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type identifier
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mapping:
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0 RouterInfo
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1 LeaseSet
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reply token:
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4 bytes
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TODO: find out what this does
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reply tunnelId:
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4 bytes
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only included if reply token > 0
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TODO: what this tunnel information is needed for
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reply gateway:
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32 bytes
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Hash of the routerInfo entry to reach the gateway
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only included if reply token > 0
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TODO: what this tunnel information is needed for
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data:
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rest of the message(could be anything)
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</pre>
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<h3 id="msg_DatabaseLookup">DatabaseLookup</h3>
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<pre>
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{% filter escape %}
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if flag==TRUE
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+----+----+----+----+----+----+----+----+
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| SHA256 hash as the key to look up |
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+ +
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+ +
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+ +
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+----+----+----+----+----+----+----+----+
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| SHA256 hash of the routerInfo |
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+ who is asking +
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+ +
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+ +
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+----+----+----+----+----+----+----+----+
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|flag| reply tunnelId |size | |
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+----+----+----+----+----+----+----+ +
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| SHA256 of $key1 to exclude |
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+ +
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+ +
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+ +----+
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+----+----+----+----+----+----+----+ +
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| SHA256 of $key2 to exclude |
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....
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{% endfilter %}
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</pre>
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<h4>Definition</h4>
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<pre>
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{% filter escape %}
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key:
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32 bytes
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SHA256 hash of the object to lookup
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from:
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32 bytes
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SHA256 hash of the routerInfo entry this request came from(and to which the reply should be sent)
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flag:
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1 byte
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mapping:
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0 FALSE => send reply directly
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1 TRUE => send reply to some tunnel
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reply tunnelId:
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2 bytes
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only included if flag==TRUE
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tunnelId of the tunnel to send the reply to
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size:
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2 bytes
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number of peers to exclude from the lookup(TODO: whatever this means)
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excludedPeers:
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rest of the message are $size SHA256 hashes of 32 bytes each(total $size*32 bytes)
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{% endfilter %}
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</pre>
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<h3 id="msg_DatabaseSearchReply">DatabaseSearchReply</h3>
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<pre>
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{% filter escape %}
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+----+----+----+----+----+----+----+----+
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| SHA256 hash as query key |
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+ +
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+ +
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+ +
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+----+----+----+----+----+----+----+----+
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|num | peer hash $1 |
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+----+ +
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+ +
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+ +
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+ +----+----+----+----+----+----+----+
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| | |
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+----+.... $num peer hashes
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+ +----+----+----+----+----+----+----+
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| | from |
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+----+ +
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+ +
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+ +
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+ +----+----+----+----+----+----+----+
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+----+
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{% endfilter %}
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<h4>Definition</h4>
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<pre>
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{% filter escape %}
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key:
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32 bytes
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SHA256 of the object being searched
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num:
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1 byte
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number of peer hashes that follow
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peer hash:
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32 bytes
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SHA256 of the RouterInfo that the other router thinks are close to the key
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$num entries
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from:
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32 bytes
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SHA256 of the RouterInfo of the router this reply was sent from
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{% endfilter %}
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</pre>
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<h3 id="msg_DeliveryStatus">DeliveryStatus</h3>
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<pre>
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{% filter escape %}
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+----+----+----+----+----+----+----+----+----+----+----+----+
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|msg-id | arrival-time |
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+----+----+----+----+----+----+----+----+----+----+----+----+
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{% endfilter %}
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</pre>
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<h4>Definition</h4>
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<pre>
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{% filter escape %}
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msg-id:
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4 bytes
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unique ID of the message we deliver the DeliveryStatus for(see common I2NP header for details)
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arrival-time:
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8 bytes
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time the message was successfully delivered
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{% endfilter %}
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</pre>
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<h3 id="msg_Garlic">Garlic</h3>
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<pre>
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{% filter escape %}
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encrypted:
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+----+----+----+----+----+----+----+----+
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|length | tag |
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+----+----+----+----+ +
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| |
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+ +
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+ +
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+ +----+----+----+----+
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{% endfilter %}
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</pre>
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<h4>Definition</h4>
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<pre>
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{% filter escape %}
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length:
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4 bytes
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number of bytes that follow
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data:
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$length bytes
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elgamal en
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{% endfilter %}
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</pre>
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<h3 id="msg_TunnelData">TunnelData</h3>
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<pre>
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{% filter escape %}
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+----+----+----+----+----+----+----+----+
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| tunnelId | data |
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+----+----+----+----+ |
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| |
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+----+----+----+----+----+----+----+----+
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{% endfilter %}
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</pre>
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<h4>Definition</h4>
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<pre>
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{% filter escape %}
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tunnelId:
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4 bytes
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identifies the tunnel this message is directed at
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data:
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1024 bytes
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payload data.. fixed to 1024 bytes
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{% endfilter %}
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</pre>
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<h3 id="msg_TunnelGateway">TunnelGateway</h3>
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<pre>
|
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{% filter escape %}
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+----+----+----+----+----+----+--\\----+
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| tunnelId | length | data...|
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+----+----+----+----+----+----+--\\----+
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{% endfilter %}
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</pre>
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|
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<h4>Definition</h4>
|
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<pre>
|
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{% filter escape %}
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tunnelId:
|
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4 bytes
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identifies the tunnel this message is directed at
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length:
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2 bytes
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length of the payload
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data:
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$length bytes
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actual payload of this message
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{% endfilter %}
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</pre>
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{% endblock %}
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<h3 id="msg_Data">Data</h3>
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<pre>
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{% filter escape %}
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+----+----+----+----+----+---//--+
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| length | data... |
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+----+----+----+----+----+---//--+
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{% endfilter %}
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</pre>
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<h4>Definition</h4>
|
|
<pre>
|
|
{% filter escape %}
|
|
length:
|
|
4 bytes
|
|
length of the payload
|
|
|
|
data:
|
|
$length bytes
|
|
actual payload of this message
|
|
{% endfilter %}
|
|
</pre>
|
|
|
|
<h3 id="msg_TunnelBuild">TunnelBuild</h3>
|
|
<pre>
|
|
{% filter escape %}
|
|
+----+----+----+----+----+----+----+----+
|
|
| Record 0 ... |
|
|
|
|
| |
|
|
+----+----+----+----+----+----+----+----+
|
|
| Record 1 ... |
|
|
|
|
.....
|
|
+----+----+----+----+----+----+----+----+
|
|
| Record 7 ... |
|
|
|
|
| |
|
|
+----+----+----+----+----+----+----+----+
|
|
{% endfilter %}
|
|
</pre>
|
|
|
|
<h4>Definition</h4>
|
|
<pre>
|
|
{% filter escape %}
|
|
Just 8 records attached together
|
|
Record size: 528 bytes
|
|
Total size: 8*528 = 4224 bytes
|
|
{% endfilter %}
|
|
</pre>
|
|
|
|
|
|
<h3 id="msg_TunnelBuildReply">TunnelBuildReply</h3>
|
|
<pre>
|
|
{% filter escape %}
|
|
same format as TunnelBuild message
|
|
{% endfilter %}
|
|
</pre>
|
|
|
|
<h3 id="msg_VariableTunnelBuild">VariableTunnelBuild</h3>
|
|
<pre>
|
|
{% filter escape %}
|
|
+----+----+----+----+----+----+----+----+
|
|
|num | ....
|
|
{% endfilter %}
|
|
</pre>
|
|
|
|
<h4>Definition</h4>
|
|
<pre>
|
|
{% filter escape %}
|
|
same format as TunnelBuildMessage, except for the addition of an "num" field in front and $num number of records instead of 8
|
|
{% endfilter %}
|
|
</pre>
|
|
|
|
<h3 id="msg_VariableTunnelBuildReply">VariableTunnelBuildReply</h3>
|
|
<pre>
|
|
{% filter escape %}
|
|
same format as VariableTunnelBuild message
|
|
{% endfilter %}
|
|
</pre>
|