Inside Bitcoin

251-------------------------
252
253Bitcoind can now (optionally) asynchronously notify clients through a
254ZMQ-based PUB socket of the arrival of new transactions and blocks.
255This feature requires installation of the ZMQ C API library 4.x and
256configuring its use through the command line or configuration file.
257Please see [docs/zmq.md](/doc/zmq.md) for details of operation.
258
259Wallet: Transaction fees
260------------------------
261
262Various improvements have been made to how the wallet calculates
263transaction fees.
264
265Users can decide to pay a predefined fee rate by setting `-paytxfee=<n>`
266(or `settxfee <n>` rpc during runtime). A value of `n=0` signals Bitcoin
267Core to use floating fees. By default, Bitcoin Core will use floating
268fees.
269
270Based on past transaction data, floating fees approximate the fees
271required to get into the `m`th block from now. This is configurable
272with `-txconfirmtarget=<m>` (default: `2`).
273
274Sometimes, it is not possible to give good estimates, or an estimate
275at all. Therefore, a fallback value can be set with `-fallbackfee=<f>`
276(default: `0.0002` BTC/kB).
277
278At all times, Bitcoin Core will cap fees at `-maxtxfee=<x>` (default:
2790.10) BTC.
280Furthermore, Bitcoin Core will never create transactions paying less than
281the current minimum relay fee.
282Finally, a user can set the minimum fee rate for all transactions with
283`-mintxfee=<i>`, which defaults to 1000 satoshis per kB.
284
285Wallet: Negative confirmations and conflict detection
286-----------------------------------------------------
287
288The wallet will now report a negative number for confirmations that indicates
289how deep in the block chain the conflict is found. For example, if a transaction
290A has 5 confirmations and spends the same input as a wallet transaction B, B
291will be reported as having -5 confirmations. If another wallet transaction C
292spends an output from B, it will also be reported as having -5 confirmations.
293To detect conflicts with historical transactions in the chain a one-time
294`-rescan` may be needed.
295
296Unlike earlier versions, unconfirmed but non-conflicting transactions will never
297get a negative confirmation count. They are not treated as spendable unless
298they're coming from ourself (change) and accepted into our local mempool,
299however. The new "trusted" field in the `listtransactions` RPC output
300indicates whether outputs of an unconfirmed transaction are considered
301spendable.
302
303Wallet: Merkle branches removed
304-------------------------------
305
306Previously, every wallet transaction stored a Merkle branch to prove its
307presence in blocks. This wasn't being used for more than an expensive
308sanity check. Since 0.12, these are no longer stored. When loading a
3090.12 wallet into an older version, it will automatically rescan to avoid
310failed checks.
311
312Wallet: Pruning
313---------------
314
315With 0.12 it is possible to use wallet functionality in pruned mode.
316This can reduce the disk usage from currently around 60 GB to
317around 2 GB.
318
319However, rescans as well as the RPCs `importwallet`, `importaddress`,
320`importprivkey` are disabled.
321
322To enable block pruning set `prune=<N>` on the command line or in
323`bitcoin.conf`, where `N` is the number of MiB to allot for
324raw block & undo data.
325
326A value of 0 disables pruning. The minimal value above 0 is 550. Your
327wallet is as secure with high values as it is with low ones. Higher
328values merely ensure that your node will not shut down upon blockchain
329reorganizations of more than 2 days - which are unlikely to happen in
330practice. In future releases, a higher value may also help the network
331as a whole: stored blocks could be served to other nodes.
332
333For further information about pruning, you may also consult the [release
334notes of v0.11.0](https://github.com/bitcoin/bitcoin/blob/v0.11.0/doc/release-notes.md#block-file-pruning).
335
336`NODE_BLOOM` service bit
337------------------------
338
339Support for the `NODE_BLOOM` service bit, as described in [BIP
340111](https://github.com/bitcoin/bips/blob/master/bip-0111.mediawiki), has been
341added to the P2P protocol code.
342
343BIP 111 defines a service bit to allow peers to advertise that they support
344bloom filters (such as used by SPV clients) explicitly. It also bumps the protocol
345version to allow peers to identify old nodes which allow bloom filtering of the
346connection despite lacking the new service bit.
347
348In this version, it is only enforced for peers that send protocol versions
349`>=70011`. For the next major version it is planned that this restriction will be
350removed. It is recommended to update SPV clients to check for the `NODE_BLOOM`
351service bit for nodes that report versions newer than 70011.
352
353Option parsing behavior
354-----------------------
355
356Command line options are now parsed strictly in the order in which they are
357specified. It used to be the case that `-X -noX` ends up, unintuitively, with X
358set, as `-X` had precedence over `-noX`. This is no longer the case. Like for
359other software, the last specified value for an option will hold.
360
361RPC: Low-level API changes
362--------------------------
363
364- Monetary amounts can be provided as strings. This means that for example the
365  argument to sendtoaddress can be "0.0001" instead of 0.0001. This can be an
366  advantage if a JSON library insists on using a lossy floating point type for
367  numbers, which would be dangerous for monetary amounts.
368
369* The `asm` property of each scriptSig now contains the decoded signature hash
370  type for each signature that provides a valid defined hash type.
371
372* OP_NOP2 has been renamed to OP_CHECKLOCKTIMEVERIFY by [BIP 65](https://github.com/bitcoin/bips/blob/master/bip-0065.mediawiki)
373
374The following items contain assembly representations of scriptSig signatures
375and are affected by this change:
376
377- RPC `getrawtransaction`
378- RPC `decoderawtransaction`
379- RPC `decodescript`
380- REST `/rest/tx/` (JSON format)
381- REST `/rest/block/` (JSON format when including extended tx details)
382- `bitcoin-tx -json`
383
384For example, the `scriptSig.asm` property of a transaction input that
385previously showed an assembly representation of:
386
387    304502207fa7a6d1e0ee81132a269ad84e68d695483745cde8b541e3bf630749894e342a022100c1f7ab20e13e22fb95281a870f3dcf38d782e53023ee313d741ad0cfbc0c509001 400000 OP_NOP2
388
389now shows as:
390
391    304502207fa7a6d1e0ee81132a269ad84e68d695483745cde8b541e3bf630749894e342a022100c1f7ab20e13e22fb95281a870f3dcf38d782e53023ee313d741ad0cfbc0c5090[ALL] 400000 OP_CHECKLOCKTIMEVERIFY
392
393Note that the output of the RPC `decodescript` did not change because it is
394configured specifically to process scriptPubKey and not scriptSig scripts.
395
396RPC: SSL support dropped
397------------------------
398
399SSL support for RPC, previously enabled by the option `rpcssl` has been dropped
400from both the client and the server. This was done in preparation for removing
401the dependency on OpenSSL for the daemon completely.
402
403Trying to use `rpcssl` will result in an error:
404
405    Error: SSL mode for RPC (-rpcssl) is no longer supported.
406
407If you are one of the few people that relies on this feature, a flexible
408migration path is to use `stunnel`. This is an utility that can tunnel
409arbitrary TCP connections inside SSL. On e.g. Ubuntu it can be installed with:
410
411    sudo apt-get install stunnel4
412
413Then, to tunnel a SSL connection on 28332 to a RPC server bound on localhost on port 18332 do:
414
415    stunnel -d 28332 -r 127.0.0.1:18332 -p stunnel.pem -P ''
416
417It can also be set up system-wide in inetd style.
418
419Another way to re-attain SSL would be to setup a httpd reverse proxy. This solution
420would allow the use of different authentication, loadbalancing, on-the-fly compression and
421caching. A sample config for apache2 could look like:
422
423    Listen 443
424
425    NameVirtualHost *:443
426    <VirtualHost *:443>
427
428    SSLEngine On
429    SSLCertificateFile /etc/apache2/ssl/server.crt
430    SSLCertificateKeyFile /etc/apache2/ssl/server.key
431
432    <Location /bitcoinrpc>
433        ProxyPass http://127.0.0.1:8332/
434        ProxyPassReverse http://127.0.0.1:8332/
435        # optional enable digest auth
436        # AuthType Digest
437        # ...
438
439        # optional bypass bitcoind rpc basic auth
440        # RequestHeader set Authorization "Basic <hash>"
441        # get the <hash> from the shell with: base64 <<< bitcoinrpc:<password>
442    </Location>
443
444    # Or, balance the load:
445    # ProxyPass / balancer://balancer_cluster_name
446
447    </VirtualHost>
448
449Mining Code Changes
450-------------------
451
452The mining code in 0.12 has been optimized to be significantly faster and use less
453memory. As part of these changes, consensus critical calculations are cached on a
454transaction's acceptance into the mempool and the mining code now relies on the
455consistency of the mempool to assemble blocks. However all blocks are still tested
456for validity after assembly.
457
458Other P2P Changes
459-----------------
460
461The list of banned peers is now stored on disk rather than in memory.
462Restarting bitcoind will no longer clear out the list of banned peers; instead
463a new RPC call (`clearbanned`) can be used to manually clear the list.  The new
464`setban` RPC call can also be used to manually ban or unban a peer.
465
4660.12.0 Change log
467=================
468
469Detailed release notes follow. This overview includes changes that affect
470behavior, not code moves, refactors and string updates. For convenience in locating
471the code changes and accompanying discussion, both the pull request and
472git merge commit are mentioned.
473
474### RPC and REST
475
476- #6121 `466f0ea` Convert entire source tree from json_spirit to UniValue (Jonas Schnelli)
477- #6234 `d38cd47` fix rpcmining/getblocktemplate univalue transition logic error (Jonas Schnelli)
478- #6239 `643114f` Don't go through double in AmountFromValue and ValueFromAmount (Wladimir J. van der Laan)
479- #6266 `ebab5d3` Fix univalue handling of \u0000 characters. (Daniel Kraft)
480- #6276 `f3d4dbb` Fix getbalance * 0 (Tom Harding)
481- #6257 `5ebe7db` Add `paytxfee` and `errors` JSON fields where appropriate (Stephen)
482- #6271 `754aae5` New RPC command disconnectnode (Alex van der Peet)
483- #6158 `0abfa8a` Add setban/listbanned RPC commands (Jonas Schnelli)
484- #6307 `7ecdcd9` rpcban fixes (Jonas Schnelli)
485- #6290 `5753988` rpc: make `gettxoutsettinfo` run lock-free (Wladimir J. van der Laan)
486- #6262 `247b914` Return all available information via RPC call "validateaddress" (dexX7)
487- #6339 `c3f0490` UniValue: don't escape solidus, keep espacing of reverse solidus (Jonas Schnelli)
488- #6353 `6bcb0a2` Show softfork status in getblockchaininfo (Wladimir J. van der Laan)
489- #6247 `726e286` Add getblockheader RPC call (Peter Todd)
490- #6362 `d6db115` Fix null id in RPC response during startup (Forrest Voight)
491- #5486 `943b322` [REST] JSON support for /rest/headers (Jonas Schnelli)
492- #6379 `c52e8b3` rpc: Accept scientific notation for monetary amounts in JSON (Wladimir J. van der Laan)
493- #6388 `fd5dfda` rpc: Implement random-cookie based authentication (Wladimir J. van der Laan)
494- #6457 `3c923e8` Include pruned state in chaininfo.json (Simon Males)
495- #6456 `bfd807f` rpc: Avoid unnecessary parsing roundtrip in number formatting, fix locale issue (Wladimir J. van der Laan)
496- #6380 `240b30e` rpc: Accept strings in AmountFromValue (Wladimir J. van der Laan)
497- #6346 `6bb2805` Add OP_RETURN support in createrawtransaction RPC call, add tests. (paveljanik)
498- #6013 `6feeec1` [REST] Add memory pool API (paveljanik)
499- #6576 `da9beb2` Stop parsing JSON after first finished construct. (Daniel Kraft)
500- #5677 `9aa9099` libevent-based http server (Wladimir J. van der Laan)