internal/ethapi: add mutex around signing + nonce assignment

This prevents concurrent assignment of identical nonces when automatic
assignment is used.

internal/ethapi/addrlock.go

@@ -0,0 +1,53 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package ethapi
+
+import (
+	"sync"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+type AddrLocker struct {
+	mu    sync.Mutex
+	locks map[common.Address]*sync.Mutex
+}
+
+// lock returns the lock of the given address.
+func (l *AddrLocker) lock(address common.Address) *sync.Mutex {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	if l.locks == nil {
+		l.locks = make(map[common.Address]*sync.Mutex)
+	}
+	if _, ok := l.locks[address]; !ok {
+		l.locks[address] = new(sync.Mutex)
+	}
+	return l.locks[address]
+}
+
+// LockAddr locks an account's mutex. This is used to prevent another tx getting the
+// same nonce until the lock is released. The mutex prevents the (an identical nonce) from
+// being read again during the time that the first transaction is being signed.
+func (l *AddrLocker) LockAddr(address common.Address) {
+	l.lock(address).Lock()
+}
+
+// UnlockAddr unlocks the mutex of the given account.
+func (l *AddrLocker) UnlockAddr(address common.Address) {
+	l.lock(address).Unlock()
+}