SPV checklist

[jrick]

dcrd

• return headers starting at the fork point for a getheaders request (getheaders does not handle sidechains correctly at all dcrd#427)
  • fixed in btcd by btcsuite/btcd@34b1373
• add gcs and gcs/builder packages
• advertise cf support with a service flag when enabled
• bump protocol version for the new service flag and new messages
• support new cf messages in the serverPeer: getcfheaders, getcfilter, getcftypes, cfheaders, cfilter, cftypes
• add json-rpc support for cfilters so wallet can continue to save cfilters to the database when not running in spv mode
• add json-rpc client support for the new RPCs

dcrwallet

• Basic header verification
  • Check reported difficulty in header is valid
  • Check proof of work against the header's reported difficulty
  • Validate sdiff when DCP0001 deployment is active
  • Validate merkle roots of fetched blocks
  • Validate cfilters of matched and fetched blocks
• Validate that fetched full blocks' transaction merkle trees match the merkle roots in the header
• Save compact filters to DB
  • filter headers will not be saved nor checked at this time, but will need to be handled later for multipeer
  • all filters will be saved so that the client can more quickly perform an "exists address" check, and then only pull blocks which may contain the address
  • database upgrade will be a two step process
    • upgrade schema to add fields for the filters
    • on first start after upgrade, download all missing cfilters
      • this is extremely slow currently and we need a batched request a la getheaders
• Fetch and save cfilters even when running with the JSON-RPC backend
• implement the wallet.NetworkBackend interface using the wire protocol
  • GetHeaders
  • LoadTxFilter
  • Rescan
  • AddressesUsed (removing, address usage scanning will get new algorithm)
  • GetBlock (new addition to the interface)
  • GetBlocks (also new)
  • PublishTransaction
  • StakeDifficulty (when DCP0001 is active, sdiff will be calculated by the wallet. this is a fallback when not active, and is only queryable with dcrd RPC)
• GetBlockHash (being removed when the dcrd getheaders bug is fixed)
• Implement new DiscoverActiveAddresses algorithm that scans saved cfilters and fetches full blocks
  • new implementation is significantly slower on a lightly used testnet wallet. many places to apply optimization still. fixed
• Implement account restores during DiscoverActiveAddresses
• Add DNS peer discovery
• Add P2P peer discovery
• Implement multipeer syncing
• Disconnect from peers behind our main chain
• Disconnect peers that aren't announcing new blocks announced by other peers within some time limit ignoring for now, dcrd has same issue currently
• Remove reorg handling as it is currently performed through dcrd notifications and replace with determining locally which is the best fork
  • Implement sidechain and orphan block management
  • Choose best sidechain based on total work, not height
• Listen for transaction invs and save unmined transactions which are relevant to the wallet
  • May need some protection and additional data in the unmined transaction records in the database to prevent announcing invalid transactions to other peers
• Write a new ticketbuyer that doesn't rely on dcrd RPC.
• Disable certain functionality when operating in SPV mode
  • Voting (winning tickets are not in the header nor is there anything anchoring them with a merkleroot)
  • Revoking missed tickets before their expiry period (unknown whether the ticket is live or missed)

[vctt94]

Can I work on Disable certain functionality when operating in SPV mode ?

[jrick]

All items have been completed. See #1213 for implementation.