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159 lines
4.6 KiB
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159 lines
4.6 KiB
Plaintext
<pre>
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BIP: 61
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Layer: Peer Services
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Title: Reject P2P message
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Author: Gavin Andresen <gavinandresen@gmail.com>
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Comments-Summary: Controversial; some recommendation, and some discouragement
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Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0061
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Status: Final
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Type: Standards Track
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Created: 2014-06-18
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</pre>
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==Abstract==
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This BIP describes a new message type for the Bitcoin peer-to-peer network.
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==Motivation==
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Giving peers feedback about why their blocks or transactions are rejected, or
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why they are being banned for not following the protocol helps
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interoperability between different implementations.
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It also gives SPV (simplified payment verification) clients a hint that something
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may be wrong when their transactions are rejected due to insufficient priority
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or fees.
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==Specification==
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Data types in this specification are as described at https://en.bitcoin.it/wiki/Protocol_specification
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===reject===
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One new message type "reject" is introduced. It is sent directly to a peer in response to a "version", "tx" or "block" message.
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For example, the message flow between two peers for a relayed transaction that is rejected for some reason would be:
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--> inv
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<-- getdata
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--> tx
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<-- reject
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All implementations of the P2P protocol version 70,002 and later should support the reject message.
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====common payload====
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Every reject message begins with the following fields. Some messages append extra, message-specific data.
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{|
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| Field Size || Name || Data type || Comments
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|-
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| variable || response-to-msg || var_str || Message that triggered the reject
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| 1 || reject-code || uint8_t || 0x01 through 0x4f (see below)
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| variable || reason || var_string || Human-readable message for debugging
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|}
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The human-readable string is intended only for debugging purposes; in particular, different implementations may
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use different strings. The string should not be shown to users or used for anthing besides diagnosing
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interoperability problems.
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The following reject code categories are used; in the descriptions below, "server" is the peer generating
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the reject message, "client" is the peer that will receive the message.
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{|
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| Range || Category
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|-
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| 0x01-0x0f || Protocol syntax errors
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|-
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| 0x10-0x1f || Protocol semantic errors
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|-
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| 0x40-0x4f || Server policy rule
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|}
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==== rejection codes common to all message types ====
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{|
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| Code || Description
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| 0x01 || Message could not be decoded
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|}
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==== reject version codes ====
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Codes generated during the initial connection process in response to a "version" message:
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{|
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| Code || Description
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| 0x11 || Client is an obsolete, unsupported version
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| 0x12 || Duplicate version message received
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|}
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==== reject tx payload, codes ====
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Transaction rejection messages extend the basic message with the transaction id hash:
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{|
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| Field Size || Name || Data type || Comments
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| 32 || hash || char[32] || transaction that is rejected
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|}
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The following codes are used:
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{|
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| Code || Description
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| 0x10 || Transaction is invalid for some reason (invalid signature, output value greater than input, etc.)
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|-
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| 0x12 || An input is already spent
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|-
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| 0x40 || Not mined/relayed because it is "non-standard" (type or version unknown by the server)
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| 0x41 || One or more output amounts are below the 'dust' threshold
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| 0x42 || Transaction does not have enough fee/priority to be relayed or mined
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|}
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==== payload, reject block ====
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Block rejection messages extend the basic message with the block header hash:
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{|
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| Field Size || Name || Data type || Comments
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| 32 || hash || char[32] || block (hash of block header) that is rejected
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|}
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Rejection codes:
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{|
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| code || description
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| 0x10 || Block is invalid for some reason (invalid proof-of-work, invalid signature, etc)
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| 0x11 || Block's version is no longer supported
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| 0x43 || Inconsistent with a compiled-in checkpoint
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|}
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Note: blocks that are not part of the server's idea of the current best chain, but are otherwise valid, should not trigger reject messages.
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== Compatibility ==
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The reject message is backwards-compatible; older peers that do not recognize the reject message will ignore it.
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== Implementation notes ==
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Implementors must consider what happens if an attacker either sends them
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reject messages for valid transactions/blocks or sends them random
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reject messages, and should beware of possible denial-of-service attacks.
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For example, notifying the user of every reject message received
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would make it trivial for an attacker to mount an annoy-the-user attack.
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Even merely writing every reject message to a debugging log could make
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an implementation vulnerable to a fill-up-the-users-disk attack.
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