btcd

server: fix linter issue

psbt: move to top-level module, use v2, remove btcutil dep

btcutil: remove circular dependency, use v2

txscript: turn into own module, use v2

address: move to top-level module, use v2

wire: make own module, use v2

chaincfg: add own module, use v2

btcec: use new chainhash/v2 module

chainhash: move to top-level module, use v2

multi: appease go 1.26 vet for non-const format + goroutine Fatalf

In this commit, we fix two go vet errors that go 1.26 now treats as
hard failures during test compilation.

In btcjson/help.go, the final result row of a complex help description
was emitted via fmt.Fprintf with a non-constant format string (the
result text could contain '%' chars). Switch to fmt.Fprint, since
there are no format args here anyway.

In btcec/schnorr/musig2/musig2_test.go, the nonce-registration loop
ran inside a goroutine and called t.Fatalf on failure. Fatalf only
exits the calling goroutine, so the test goroutine would keep running
with stale state. Use t.Errorf + return so the failure is recorded
correctly and the goroutine exits cleanly.

multi: bump Go toolchain to 1.25, build CI with 1.26.3

In this commit, we update every in-tree go.mod to declare go 1.25 and
have CI build with 1.26.3 (Dockerfile uses the golang:1.26-alpine base).
Docs that mention the minimum required Go version are aligned with the
new floor as well.

Fixes #2527, which flagged the README.md / go.mod version mismatch (the
README claimed 1.22 while the root + v2transport go.mod files already
required 1.23.2).

multi: bump in-tree go.mod files to newly tagged submodule versions

In this commit, we pin every in-tree go.mod to the freshly cut submodule
tags ahead of a btcd point release: btcec/v2.4.0, btcutil/v1.2.0,
btcutil/psbt/v1.2.0, and chaincfg/chainhash/v1.2.0. The btcec bump also
drags secp256k1 up to v4.4.0 (and blake256 to v1.1.0 transitively) for
every module that imports btcec.

v2transport stays at v1.0.1 since no v2transport code changed since the
last tag, but its go.mod is bumped here so the workspace resolves to a
consistent set of internal deps.

github: cross-compile android/arm64 in CI

Add a build step to the existing Build job that cross-compiles both the
top-level module and btcutil for GOOS=android GOARCH=arm64.

This catches regressions in the android-specific build path (e.g. the
net_android.go wrapper around anet.InterfaceAddrs) without needing an
emulator or NDK toolchain - android/arm64 builds without cgo.

btcutil: rename interfaceAddrs to InterfaceAddrs in appengine variant

The previous commit exported the interfaceAddrs helper in net.go but
missed the parallel definition in net_noop.go (build tag: appengine),
which left builds with -tags appengine broken with:

./certgen.go:79:16: undefined: InterfaceAddrs

Rename the appengine no-op variant to match, restoring the appengine
build.

main: use btcutil.InterfaceAddr

We use this as the net.InterfaceAddr is broken from android 11.

btcutil: export interfaceAddr

btcutil: use anet instead of net for android builds

Golang's net package has been broken for android since android 11
and the node will not be able to call net.InterfaceAddr() without
root.

For android builds, we use anet so that the btcd node can be used
without root.

main: update go.mod and go.sum

We update go.mod and go.sum to point to the local btcutil library.

This commit should be updated later on so that we do it right.

rpcclient: compute httpURL once at construction time

httpURL was being recomputed on every JSON-RPC POST. It went through
ParseAddressString to discriminate Unix sockets from TCP, which
called net.ResolveTCPAddr and triggered a DNS lookup whose result
was thrown away.

Both inputs (config.Host and config.DisableTLS) are immutable after
New, so the URL is constant for the life of the Client. Compute it
once and store it on the Client, mirroring the parsedDialAddr cache
already in newHTTPClient.

The httpURL method now uses HasPrefix and runs exactly once per
Client. Drop its (string, error) signature — with the resolve gone
nothing can fail. Add table coverage for the URL strings, plus a
wiring test that catches refactors of New silently dropping the
assignment to Client.httpURL.

server: document peerLifecycle channel buffer sizing

The peerLifecycle channel is sized cfg.MaxPeers*2 because each
peer can emit two lifecycle events (peerAdd followed by peerDone).
Without an inline comment a future reader could "simplify" the
factor to cfg.MaxPeers and tighten back-pressure under normal
connect/disconnect churn, causing peerLifecycleHandler goroutines
to block.

server: gate handleDonePeerMsg on peerAdded, not VerAckReceived

peer.processRemoteVerAckMsg sets verAckReceived=true *before* it
invokes the OnVerAck listener that closes verAckCh. If the peer
disconnects in that window, the peerLifecycleHandler select may
pick Peer.Done() over verAckCh and skip the peerAdd send -- yet
VerAckReceived() still returns true. handleDonePeerMsg would then
call syncManager.DonePeer for a peer that was never NewPeer'd
(sync manager logs a warning and discards).

Add an explicit peerAdded atomic.Bool on serverPeer. Set it in
peerLifecycleHandler after peerAdd has been enqueued. Gate the
syncManager.DonePeer + orphan eviction in handleDonePeerMsg on
peerAdded.Load() so those side effects only fire for peers that
were actually registered.

This tightens the "peerAdd precedes peerDone, or peerAdd is
skipped entirely" invariant from this PR into something explicit
rather than something derived from a flag that races OnVerAck.

server: guard OnVerAck with sync.Once

The prior select/default+close() guard on verAckCh is correct only
under the invariant that OnVerAck is invoked from a single goroutine
(peer.processRemoteVerAckMsg on the input handler). The two steps
are not atomic: any future change that invokes listeners off the
input goroutine would let two concurrent callers both observe
default and panic on double-close.

Replace the guard with sync.Once. This makes the close-once
contract obviously correct rather than correct-by-distant-invariant
and drops the dead "called more than once" log path.

btcutil: add new AddressPayToAnchor addr type

txscript: recognize P2A scripts in ParsePkScript

rpctest: add new e2e test for new P2A behavior

We make sure it'll be accepted into the mempool, and can be spent
without a witness.