github.com/xfond/eth-implementation@v1.8.9-0.20180514135602-f6bc65fc6811/whisper/whisperv6/doc.go (about)

     1  // Copyright 2016 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  /*
    18  Package whisper implements the Whisper protocol (version 6).
    19  
    20  Whisper combines aspects of both DHTs and datagram messaging systems (e.g. UDP).
    21  As such it may be likened and compared to both, not dissimilar to the
    22  matter/energy duality (apologies to physicists for the blatant abuse of a
    23  fundamental and beautiful natural principle).
    24  
    25  Whisper is a pure identity-based messaging system. Whisper provides a low-level
    26  (non-application-specific) but easily-accessible API without being based upon
    27  or prejudiced by the low-level hardware attributes and characteristics,
    28  particularly the notion of singular endpoints.
    29  */
    30  
    31  // Contains the Whisper protocol constant definitions
    32  
    33  package whisperv6
    34  
    35  import (
    36  	"fmt"
    37  	"time"
    38  )
    39  
    40  // Whisper protocol parameters
    41  const (
    42  	ProtocolVersion    = uint64(6) // Protocol version number
    43  	ProtocolVersionStr = "6.0"     // The same, as a string
    44  	ProtocolName       = "shh"     // Nickname of the protocol in geth
    45  
    46  	// whisper protocol message codes, according to EIP-627
    47  	statusCode           = 0   // used by whisper protocol
    48  	messagesCode         = 1   // normal whisper message
    49  	powRequirementCode   = 2   // PoW requirement
    50  	bloomFilterExCode    = 3   // bloom filter exchange
    51  	p2pRequestCode       = 126 // peer-to-peer message, used by Dapp protocol
    52  	p2pMessageCode       = 127 // peer-to-peer message (to be consumed by the peer, but not forwarded any further)
    53  	NumberOfMessageCodes = 128
    54  
    55  	SizeMask      = byte(3) // mask used to extract the size of payload size field from the flags
    56  	signatureFlag = byte(4)
    57  
    58  	TopicLength     = 4  // in bytes
    59  	signatureLength = 65 // in bytes
    60  	aesKeyLength    = 32 // in bytes
    61  	aesNonceLength  = 12 // in bytes; for more info please see cipher.gcmStandardNonceSize & aesgcm.NonceSize()
    62  	keyIDSize       = 32 // in bytes
    63  	BloomFilterSize = 64 // in bytes
    64  	flagsLength     = 1
    65  
    66  	EnvelopeHeaderLength = 20
    67  
    68  	MaxMessageSize        = uint32(10 * 1024 * 1024) // maximum accepted size of a message.
    69  	DefaultMaxMessageSize = uint32(1024 * 1024)
    70  	DefaultMinimumPoW     = 0.2
    71  
    72  	padSizeLimit      = 256 // just an arbitrary number, could be changed without breaking the protocol
    73  	messageQueueLimit = 1024
    74  
    75  	expirationCycle   = time.Second
    76  	transmissionCycle = 300 * time.Millisecond
    77  
    78  	DefaultTTL           = 50 // seconds
    79  	DefaultSyncAllowance = 10 // seconds
    80  )
    81  
    82  type unknownVersionError uint64
    83  
    84  func (e unknownVersionError) Error() string {
    85  	return fmt.Sprintf("invalid envelope version %d", uint64(e))
    86  }
    87  
    88  // MailServer represents a mail server, capable of
    89  // archiving the old messages for subsequent delivery
    90  // to the peers. Any implementation must ensure that both
    91  // functions are thread-safe. Also, they must return ASAP.
    92  // DeliverMail should use directMessagesCode for delivery,
    93  // in order to bypass the expiry checks.
    94  type MailServer interface {
    95  	Archive(env *Envelope)
    96  	DeliverMail(whisperPeer *Peer, request *Envelope)
    97  }