453b0fa286 bitcoin: Make wrapper not require -m (Ryan Ofsky)
29e836fae6 test: add tool_bitcoin to test bitcoin wrapper behavior (Ryan Ofsky)
0972f55040 init: add exe name to bitcoind, bitcoin-node -version output to be able to distinguish these in tests (Ryan Ofsky)
Pull request description:
This change makes the `bitcoin` command respect IPC command line options and _bitcoin.conf_ settings, so IPC listening can be enabled by just running `bitcoin node -ipcbind=unix` or `bitcoin node` with `ipcbind=unix` in the configuration file, and there is no longer a need to specify a multiprocess `-m` option like `bitcoin -m node [...]`
sipa and theuni in #31802 pointed out that users shouldn't be exposed to multiprocess implementation details just to use IPC features, so current need to specify the `bitcoin -m` option in conjunction with `-ipcbind` could be seen as a design mistake and not just a usage inconvenience.
This PR also adds a dedicated functional test for the `bitcoin` wrapper command and to make sure it calls the right binaries and test the new functionality.
---
This PR is part of the [process separation project](https://github.com/bitcoin/bitcoin/issues/28722).
ACKs for top commit:
Sjors:
re-ACK 453b0fa286
achow101:
ACK 453b0fa286
TheCharlatan:
Re-ACK 453b0fa286
Tree-SHA512: 9e49cb7e183fd220fa7a4e8ac68cef55f3cb2ccec40ad2a9d3e3f31db64c4953db8337f8caf7fce877bc97002ae97568dcf47ee269a06ca1f503f119bfe392c1
Added a minimal system helper to query total physical RAM on [Linux/macOS/Windows](https://stackoverflow.com/a/2513561) (on other platforms we just return an empty optional).
The added test checks if the value is roughly correct by checking if the CI platforms are returning any value and if the value is at least 1 GiB and not more than 10 TiB.
The max value is only validated on 64 bits, since it's not unreasonable for 32 bits to have max memory, but on 64 bits it's likely an error.
https://learn.microsoft.com/en-us/windows/win32/api/sysinfoapi/ns-sysinfoapi-memorystatusex
> ullTotalPhys The amount of actual physical memory, in bytes.
https://man7.org/linux/man-pages/man3/sysconf.3.html:
> _SC_PHYS_PAGES The number of pages of physical memory. Note that it is possible for the product of this value and the value of _SC_PAGESIZE to overflow.
> _SC_PAGESIZE Size of a page in bytes. Must not be less than 1.
See https://godbolt.org/z/ec81Tjvrj for further details
188de70c86 net: Add interrupt to pcp retry loop (TheCharlatan)
Pull request description:
Without this interrupt bitcoind takes a long time to exit if requested to do so after a failed pcp lookup on startup.
ACKs for top commit:
achow101:
ACK 188de70c86
fjahr:
utACK 188de70c86
hodlinator:
utACK 188de70c86
Tree-SHA512: 426dabd10ac0ef5de246c83d281ba70957e4032d251054aa6028b4d7ce4e35cd35ac70e67dc07bd418673bcdd2f4457b76f174ac5e7d0dd3caa05de5da952dac
When the router doesn't support natpmp and PCP, one'd normally expect
the UDP packet to be ignored, and hit a time out. This logs a warning
that is already in the debug category. However, there's also the case in
which sending an UDP packet causes a ICMP response. This is returned to
user space as "connection refused" (despite UDP having no concept of
connections).
Move the warnings from `Send` and `Recv` to debug level too, to reduce
log spam in that case.
Closes#33301.
88db09bafe net: handle multi-part netlink responses (willcl-ark)
42e99ad773 net: skip non-route netlink responses (willcl-ark)
57ce645f05 net: filter for default routes in netlink responses (willcl-ark)
Pull request description:
...for default route in pcp pinholing.
Currently we only make a single recv call, which trucates results from large routing tables, or in the case the kernel may split the message into multiple responses (which may happen with `NLM_F_DUMP`).
We also do not filter on the default route. For IPv6, this led to selecting the first route with an `RTA_GATEWAY` attribute, often a non-default route instead of the actual default. This caused PCP port mapping failures because the wrong gateway was used.
Fix both issues by adding multi-part handling of responses and filter for the default route.
Limit responses to ~ 1MB to prevent any router-based DoS.
ACKs for top commit:
achow101:
ACK 88db09bafe
davidgumberg:
Code Review re-ACK 88db09b
Sjors:
re-utACK 88db09bafe
Tree-SHA512: ea5948edebfad5896a487a61737aa5af99f529fad3cf3da68dced456266948238a7143383847e79a7bb90134e023eb173c25116d8eb80ff57fa4c4a0377ca1ed
Handle multi-part netlink responses to prevent truncated results from
large routing tables.
Previously, we only made a single recv call, which led to incomplete
results when the kernel split the message into multiple responses (which
happens frequently with NLM_F_DUMP).
Also guard against a potential hanging issue where the code would
indefinitely wait for NLMSG_DONE for non-multi-part responses by
detecting the NLM_F_MULTI flag and only continue waiting when necessary.
Currently this code is not called in unit tests. Calling should make it
possible to write tests for things like IPC exceptions being thrown during
shutdown.
fac90e5261 test: Check that the GUI interactive reindex works (MarcoFalke)
faaaddaaf8 init: [gui] Avoid UB/crash in InitAndLoadChainstate (MarcoFalke)
Pull request description:
`InitAndLoadChainstate` is problematic, when called twice in the GUI. This can happen when it returns a failure and the user selects an interactive reindex.
There are several bugs that have been introduced since the last time this was working correctly:
* The first one is a crash (assertion failure), which happens due to a cached tip block in the notifiications from the previous run. See https://github.com/bitcoin/bitcoin/pull/31346#discussion_r2207914726
* The second one is UB (use-after-free), which happens because the block index db in the blockmanager is not reset. See https://github.com/bitcoin/bitcoin/pull/30965#discussion_r2207822121
Fix both bugs by resetting any dirty state in `InitAndLoadChainstate`.
Also, add a test, because I don't really want to keep testing this manually every time. (A failing test run can be seen in https://github.com/bitcoin/bitcoin/pull/32979/checks)
ACKs for top commit:
achow101:
ACK fac90e5261
TheCharlatan:
ACK fac90e5261
mzumsande:
Tested ACK fac90e5261
Tree-SHA512: 9f744d36e7cdd3f5871764386ec5a5cca1ae144f1bacc26c07e60313c2bdacdc5fca351aa185cb51359540eea4534dda17e4fb6073ad90f91ba0a6936faeead8
faa1c3e80d Revert "Merge bitcoin/bitcoin#32343: common: Close non-std fds before exec in RunCommandJSON" (MarcoFalke)
Pull request description:
After a fork() in a multithreaded program, the child can safely
call only async-signal-safe functions (see [signal-safety(7)](https://www.man7.org/linux/man-pages/man7/signal-safety.7.html))
until such time as it calls execv.
The standard library (`std` namespace) is not async-signal-safe. Also, `throw`, isn't.
There was an alternative implementation using `readdir` (https://github.com/bitcoin/bitcoin/pull/32529), but that isn't async-signal-safe either, and that implementation was still using `throw`.
So temporarily revert this feature.
A follow-up in the future can add it back, using only async-signal-safe functions, or by using a different approach.
Fixes https://github.com/bitcoin/bitcoin/issues/32524
Fixes https://github.com/bitcoin/bitcoin/issues/33015
Fixes https://github.com/bitcoin/bitcoin/issues/32855
For reference, a failure can manifest in the GCC debug mode:
* While `fork`ing, a debug mode mutex is held (by any other thread).
* The `fork`ed child tries to use the stdard libary before `execv` and deadlocks.
This may look like the following:
```
(gdb) thread apply all bt
Thread 1 (Thread 0xf58f4b40 (LWP 774911) "b-httpworker.2"):
#0 0xf7f4f589 in __kernel_vsyscall ()
#1 0xf79e467e in ?? () from /lib32/libc.so.6
#2 0xf79eb582 in pthread_mutex_lock () from /lib32/libc.so.6
#3 0xf7d93bf2 in ?? () from /lib32/libstdc++.so.6
#4 0xf7d93f36 in __gnu_debug::_Safe_iterator_base::_M_attach(__gnu_debug::_Safe_sequence_base*, bool) () from /lib32/libstdc++.so.6
#5 0x5668810a in __gnu_debug::_Safe_iterator_base::_Safe_iterator_base (this=0xf58f13ac, __seq=0xf58f13f8, __constant=false) at /bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/debug/safe_base.h:91
#6 0x56ddfb50 in __gnu_debug::_Safe_iterator<__gnu_cxx::__normal_iterator<int*, std::__cxx1998::vector<int, std::allocator<int> > >, std::__debug::vector<int, std::allocator<int> >, std::forward_iterator_tag>::_Safe_iterator (this=0xf58f13a8, __i=3, __seq=0xf58f13f8) at /bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/debug/safe_iterator.h:162
#7 0x56ddfacb in __gnu_debug::_Safe_iterator<__gnu_cxx::__normal_iterator<int*, std::__cxx1998::vector<int, std::allocator<int> > >, std::__debug::vector<int, std::allocator<int> >, std::bidirectional_iterator_tag>::_Safe_iterator (this=0xf58f13a8, __i=3, __seq=0xf58f13f8) at /bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/debug/safe_iterator.h:539
#8 0x56ddfa5b in __gnu_debug::_Safe_iterator<__gnu_cxx::__normal_iterator<int*, std::__cxx1998::vector<int, std::allocator<int> > >, std::__debug::vector<int, std::allocator<int> >, std::random_access_iterator_tag>::_Safe_iterator (this=0xf58f13a8, __i=3, __seq=0xf58f13f8) at /bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/debug/safe_iterator.h:687
#9 0x56ddd3f6 in std::__debug::vector<int, std::allocator<int> >::begin (this=0xf58f13f8) at /bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/debug/vector:300
#10 0x57d83701 in subprocess::detail::Child::execute_child (this=0xf58f156c) at ./util/subprocess.h:1372
#11 0x57d80a7c in subprocess::Popen::execute_process (this=0xf58f1cd8) at ./util/subprocess.h:1231
#12 0x57d6d2b4 in subprocess::Popen::Popen<subprocess::input, subprocess::output, subprocess::error, subprocess::close_fds> (this=0xf58f1cd8, cmd_args="fake.py enumerate", args=..., args=..., args=..., args=...) at ./util/subprocess.h:964
#13 0x57d6b597 in RunCommandParseJSON (str_command="fake.py enumerate", str_std_in="") at ./common/run_command.cpp:27
#14 0x57a90547 in ExternalSigner::Enumerate (command="fake.py", signers=std::__debug::vector of length 0, capacity 0, chain="regtest") at ./external_signer.cpp:28
#15 0x56defdab in enumeratesigners()::$_0::operator()(RPCHelpMan const&, JSONRPCRequest const&) const (this=0xf58f2ba0, self=..., request=...) at ./rpc/external_signer.cpp:51
...
(truncated, only one thread exists)
```
ACKs for top commit:
fanquake:
ACK faa1c3e80d
darosior:
ACK faa1c3e80d
Tree-SHA512: 602da5f2eba08d7fe01ba19baf411e287ae27fe2d4b82f41734e05b7b1d938ce94cc0041e86ba677284fa92838e96ebee687023ff28047e2b036fd9a53567e0a
fa9ca13f35 refactor: Sort includes of touched source files (MarcoFalke)
facb152697 scripted-diff: Bump copyright headers after include changes (MarcoFalke)
fae71d30f7 clang-tidy: Apply modernize-deprecated-headers (MarcoFalke)
Pull request description:
Bitcoin Core is written in C++, so it is confusing to sometimes use the deprecated C headers (with the `.h` extension). For example, it is less clear whether `string.h` refers to the file in this repo or the cstring stdlib header (https://github.com/bitcoin/bitcoin/pull/31308#discussion_r2121492797).
The check is currently disabled for headers, to exclude subtree headers.
ACKs for top commit:
l0rinc:
ACK fa9ca13f35
achow101:
ACK fa9ca13f35
janb84:
ACK fa9ca13f35
stickies-v:
ACK fa9ca13f35
Tree-SHA512: 6639608308c598d612e24435aa519afe92d71b955874b87e527245291fb874b67f3ab95d3a0a5125c6adce5eb41c0d62f6ca488fbbfd60a94f2063d734173f4d
Historically, the headers have been bumped some time after a file has
been touched. Do it now to avoid having to touch them again in the
future for that reason.
-BEGIN VERIFY SCRIPT-
sed -i --regexp-extended 's;( 20[0-2][0-9])(-20[0-2][0-9])? The Bitcoin Core developers;\1-present The Bitcoin Core developers;g' $( git show --pretty="" --name-only HEAD~0 )
-END VERIFY SCRIPT-
This can be reproduced according to the developer notes with something
like
( cd ./src/ && ../contrib/devtools/run-clang-tidy.py -p ../bld-cmake -fix -j $(nproc) )
Also, the header related changes were done manually.
ee045b61ef rpc, psbt: Require sighashes match for descriptorprocesspsbt (Ava Chow)
2b7682c372 psbt: use sighash type field to determine whether to remove non-witness utxos (Ava Chow)
28781b5f06 psbt: Add sighash types to PSBT when not DEFAULT or ALL (Ava Chow)
15ce1bd73f psbt: Enforce sighash type of signatures matches psbt (Ava Chow)
1f71cd337a wallet: Remove sighash type enforcement from FillPSBT (Ava Chow)
4c7d767e49 psbt: Check sighash types in SignPSBTInput and take sighash as optional (Ava Chow)
a118256948 script: Add IsPayToTaproot() (Ava Chow)
d6001dcd4a wallet: change FillPSBT to take sighash as optional (Ava Chow)
e58b680923 psbt: Return PSBTError from SignPSBTInput (Ava Chow)
2adfd81532 tests: Test PSBT sighash type mismatch (Ava Chow)
5a5d26d612 psbt: Require ECDSA signatures to be validly encoded (Ava Chow)
Pull request description:
Currently, we do not add the sighash field to PSBTs at all, even when we have signed with a non-default sighash. This PR changes the behavior such that when we (attempt to) sign with a sighash other than DEFAULT or ALL, the sighash type field will be added to the PSBT to inform the later signers that a different sighash type was used by a signer. Notably, this is necessary for MuSig2 support as all signers must sign using the same sighash type, but the sighash is not provided in partial signatures.
Furthermore, because the sighash type can also be provided on the command line, we require that if both a command line sighash type and the sighash field is present, they must specify the same sighash type. However, this was being checked by the wallet, rather than the signing code, so the `descriptorprocesspsbt` RPC was not enforcing this restriction at all, and in fact ignored the sighash field entirely. This PR refactors the checking code so that the underlying PSBT signing function `SignPSBTInput` does the check.
ACKs for top commit:
theStack:
re-ACK ee045b61ef
rkrux:
re-ACK ee045b61ef
fjahr:
Code review ACK ee045b61ef
Tree-SHA512: 4ead5be1ef6756251b827f594beba868a145d75bf7f4ef6f15ad21f0ae4b8d71b38c83494e5a6b75f37fadd097178cddd93d614b962a2c72fc134f00ba2f74ae
We don't add or maintain these, and they are of little value, as
well as having the effect of polluting diffs.
They are also wrong, i.e DEFAULT_SCRIPTCHECK_THREADS is not in
validation.h.
a0eed55398 run_command: Enable close_fds option to avoid lingering fds (Luke Dashjr)
c7c356a448 cpp-subprocess: Iterate through /proc/self/fd for close_fds option on Linux (Luke Dashjr)
4f5e04da13 Revert "remove unneeded close_fds option from cpp-subprocess" (Luke Dashjr)
Pull request description:
Picks up stale #30756, while addressing my fallback comment (https://github.com/bitcoin/bitcoin/pull/30756#discussion_r2030844440).
> Currently, RunCommandParseJSON runs its target with whatever fds happen to be open inherited on POSIX platforms. I don't think there's any practical scenario where this is a problem right now, but there's a lot of potential for weird problems (eg, if a process manages to outlive bitcoind - perhaps it's hanging - the listening port(s) won't get released and starting bitcoind again will fail). It's also a potential security issue if a child process is intended to be sandboxed at some point. Not to mention plain ugly :)
>
> cpp-subprocess has a feature to address this called close_fds. Not sure why it was removed in https://github.com/bitcoin/bitcoin/pull/29961 rather than fixing this during the migration, but this PR restores it, enables it for RunCommandParseJSON, and optimises it by iterating over /proc/self/fd/ like most other libraries do these days ([eg, glib]> (487b1fd20c/glib/gspawn.c (L1094))) since iterating all possible fd numbers [has been found to be problematic](https://bugzilla.redhat.com/show_bug.cgi?id=1537564).
>
> (Equivalent to https://github.com/bitcoin/bitcoin/pull/22417 was for boost::process)
ACKs for top commit:
achow101:
ACK a0eed55398
hebasto:
ACK a0eed55398, tested on Ubuntu 25.04:
vasild:
ACK a0eed55398
Tree-SHA512: 7dc1cb6cc1f45ff7c4f53512e400baad1a033b4ebf14ba6f6ffa38588314932d6d01ef67b197f081e8202bb802659ac6a87998277797721d6d7b20efde8e9a6b
SignPSBTInput will need to report the specific things that caused an
error to callers, so change it to return a PSBTError. Additionally some
callers will now check the return value and report an error to the user.
Currently, this should not change any behavior as the things that
SignPBSTInput will error on are all first checked by its callers.
We really just want to skip this when building for Windows. So do that,
and remove the two header checks (we also already use both of these
headers, unguarded, in the !windows part of the codebase).
Squash the two *iffaddrs defines into one, as I haven't seen an
iffaddrs.h that implements one, but not the other.
b9d4d5f66a net: Use GetAdaptersAddresses to get local addresses on Windows (laanwj)
Pull request description:
Instead of a `gethostname` hack, which is not guaranteed to return all addresses, use the official way of calling `GetAdaptersAddresses` to get local network addresses on Windows.
Do the same checks as the UNIX path: interface is up, interface is not loopback.
Suggested by Ava Chow.
Addiional changes:
- Cleanup: move out `FromSockAddr` in `netif.cpp` from MacOS and use it everywhere appropriate. This avoids code duplication.
ACKs for top commit:
davidgumberg:
utreACK b9d4d5f66a
achow101:
ACK b9d4d5f66a
Tree-SHA512: e9f0a7ec0c46f21c0377d5174e054a6569f858630727f94dac00c0cb7c241c56892d0b902706d6dd53880cc3b5ae1f2dba9caa1fec40e64cd4cf0d34493a49c1
Filter netlink responses to only consider default routes by checking the
destination prefix length (rtm_dst_len == 0).
Previously, we selected the first route with an RTA_GATEWAY attribute,
which for IPv6 often resulted in choosing a non-default route instead of
the actual default.
This caused occasional PCP port mapping failures because a gateway for a
non-default route was selected.
Historically, the headers have been bumped some time after a file has
been touched. Do it now to avoid having to touch them again in the
future for that reason.
-BEGIN VERIFY SCRIPT-
sed -i --regexp-extended 's;( 20[0-2][0-9])(-20[0-2][0-9])? The Bitcoin Core developers;\1-present The Bitcoin Core developers;g' $( git show --pretty="" --name-only HEAD~1 )
-END VERIFY SCRIPT-
Instead of a `gethostname` hack, use the official way of calling
`GetAdaptersAddresses` to get local network addresses on Windows.
As additional cleanup, move out `FromSockAddr` from MacOS and use it
everywhere appropriate.
Suggested by Ava Chow.
In almost all cases (the only exception is `getifaddrs`), we know the
size of the data passed into SetSockAddr, so we can check this to be
what is expected.
-noconf would previously lead to an ifstream "successfully" being opened to the ".bitcoin"-directory (not a file). (Guards against the general case of directories as configs are added in grandchild commit to this one).
Other users of AbsPathForConfigVal() in combination with negated args have been updated earlier in this PR ("args: Support -nopid" and "args: Support -norpccookiefile...").
e60cecc811 doc: add release note for 31156 (Martin Zumsande)
fc7dfb3df5 test: Don't enforce BIP94 on regtest unless specified by arg (Martin Zumsande)
Pull request description:
The added arg `-test=bip94` is only used in a functional test for BIP94. This is done because the default regtest consensus rules should follow mainnet, not testnet.
Fixes#31137.
ACKs for top commit:
achow101:
ACK e60cecc811
tdb3:
cr and light test ACK e60cecc811
rkrux:
tACK e60cecc811
BrandonOdiwuor:
utACK e60cecc811
laanwj:
Code review ACK e60cecc811
Tree-SHA512: ca2f322f89d8808dfc3565fe020d2615cfcc110e188a02128ad7108fef51c735b33d55b5e6a70c505d78f7291f3c635dc7dfbcd78be1348d4d6e483883be4216
The added regtest option -test=bip94 is only used in the functional
test for BIP94.
This is done because the default regtest consensus rules
should aim to follow to mainnet, not testnet.
33a28e252a Change default help arg to `-help` and mention `-h` and `-?` as alternatives (Lőrinc)
f0130ab1a1 doc: replace `-?` with `-h` for bench_bitcoin help (Lőrinc)
Pull request description:
The question mark is interpreted as a wildcard for any single character in Zsh (see https://www.techrepublic.com/article/globbing-wildcard-characters-with-zsh), so `bench_bitcoin -?` will not show the help message on systems using Zsh, such as macOS.
Since `-h` provides equivalent help functionality (as defined in https://github.com/bitcoin/bitcoin/blob/master/src/common/args.cpp#L684-L693), the `benchmarking.md` documentation has been updated to ensure compatibility with macOS.
----
### -?
> % cmake -B build -DBUILD_BENCH=ON && cmake --build build && build/src/bench/bench_bitcoin -?
zsh: no matches found: -?
### -h
> % cmake -B build -DBUILD_BENCH=ON && cmake --build build && build/src/bench/bench_bitcoin -h
Usage: bench_bitcoin [options]
Options:
...
----
Based on the comments the args help default was also changed to `-help`, mentioning `-h` and `-?` (instead of `-?` being the default)
ACKs for top commit:
edilmedeiros:
tACK 33a28e252a
maflcko:
lgtm ACK 33a28e252a
achow101:
ACK 33a28e252a
rkrux:
tACK 33a28e252a
laanwj:
Code review ACK 33a28e252a
Tree-SHA512: 8c6e27488462be9ba9186b34abe6249c1d93026b3963acc0f42c75496f39407563766ae518cf1839156039cc0047e29d91f70d191cfb97e0fbde85665e88c71e
Add `-ipcbind` option to `bitcoin-node` to listen on an IPC socket and accept
connections from other processes. In the future, there will be an `-ipcconnect`
option added to `bitcoin-wallet` and `bitcoin-node` to allow wallet and gui
processes to connect to the node and access it.
Example usage:
src/bitcoin-node -regtest -debug -ipcbind=unix
src/bitcoin-wallet -regtest -ipcconnect=unix info
src/bitcoin-gui -regtest -ipcconnect=unix
src/bitcoin-mine -regtest -ipcconnect=unix
c8e6771af0 test: restrict multiple CLI arguments (naiyoma)
8838c4f171 common/args.h: automate check for multiple cli commands (naiyoma)
Pull request description:
This PR is a continuation of the validation suggested [here](https://github.com/bitcoin/bitcoin/pull/27815) to ensure that only one Request Handler can be specified at a time.
ACKs for top commit:
stratospher:
reACK c8e6771.
achow101:
ACK c8e6771af0
tdb3:
cr re ACK c8e6771af0
Tree-SHA512: f4fe036fee342a54f1a7ac702ac35c40bf3d420fde6ab16313a75327292d5ee5c8ece1be9f852a13fcf73da1148b143b37b4894e294052abdde6eefb2e8c6f3f
6bfa26048d testnet: Add timewarp attack prevention for Testnet4 (Fabian Jahr)
0100907ca1 testnet: Add Testnet4 difficulty adjustment rules fix (Fabian Jahr)
74a04f9e7a testnet: Introduce Testnet4 (Fabian Jahr)
Pull request description:
To supplement the [ongoing conceptual discussion about a testnet reset](https://groups.google.com/g/bitcoindev/c/9bL00vRj7OU/m/9yCPo3uUBwAJ) I have drafted a move to v4 including a fix to the difficulty adjustment mechanism, which was part of the motivation that started the discussion.
Conceptual considerations:
- The conceptual discussion about doing a testnet4 or softforking the fix into testnet3 is outside of the scope of this PR and I would ask reviewers to contribute their opinions on this on the ML instead. However, I am happy to adapt this PR to a softfork change on testnet3 if there is consensus for that instead.
- The difficulty adjustment fix suggested here touches the `CalculateNextWorkRequired` function and uses the same logic used in `GetNextWorkRequired` to find the last previous block that was not mined with difficulty 1 under the exceptionf. An alternative fix briefly mentioned on the mailing list by Jameson Lopp would be to "restrict the special testnet minimum difficulty rule so that it can't be triggered on the block right before a difficulty retarget". That would also fix the issue but I find my suggestion here a bit more elegant.
ACKs for top commit:
jsarenik:
tACK 6bfa26048d
achow101:
ACK 6bfa26048d
murchandamus:
tACK 6bfa26048d
Tree-SHA512: 0b8b69a621406a944da5be551b863d065358ba94d85dd3b80d83c412660e230ee93b27316081fbee9b4851cc4ff8585db64c7dfa26cb5148ac835663f2712c3d
