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net: add V1Transport lock protecting receive state

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Rather than relying on the caller to prevent concurrent calls to the
various receive-side functions of Transport, introduce a private m_cs_recv
inside the implementation to protect the lock state.

Of course, this does not remove the need for callers to synchronize calls
entirely, as it is a stateful object, and e.g. the order in which Receive(),
Complete(), and GetMessage() are called matters. It seems impossible to use
a Transport object in a meaningful way in a multi-threaded way without some
form of external synchronization, but it still feels safer to make the
transport object itself responsible for protecting its internal state.
This commit is contained in:
Pieter Wuille
2023-07-26 13:19:31 -04:00
parent 93594e42c3
commit 27f9ba23ef
2 changed files with 41 additions and 22 deletions
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7
src/net.cpp
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@@ -719,6 +719,7 @@ bool CNode::ReceiveMsgBytes(Span<const uint8_t> msg_bytes, bool& complete)
int V1Transport::readHeader(Span<const uint8_t> msg_bytes)
{
AssertLockHeld(m_recv_mutex);
// copy data to temporary parsing buffer
unsigned int nRemaining = CMessageHeader::HEADER_SIZE - nHdrPos;
unsigned int nCopy = std::min<unsigned int>(nRemaining, msg_bytes.size());
@@ -759,6 +760,7 @@ int V1Transport::readHeader(Span<const uint8_t> msg_bytes)
int V1Transport::readData(Span<const uint8_t> msg_bytes)
{
AssertLockHeld(m_recv_mutex);
unsigned int nRemaining = hdr.nMessageSize - nDataPos;
unsigned int nCopy = std::min<unsigned int>(nRemaining, msg_bytes.size());
@@ -776,7 +778,8 @@ int V1Transport::readData(Span<const uint8_t> msg_bytes)
const uint256& V1Transport::GetMessageHash() const
{
assert(Complete());
AssertLockHeld(m_recv_mutex);
assert(CompleteInternal());
if (data_hash.IsNull())
hasher.Finalize(data_hash);
return data_hash;
@@ -784,9 +787,11 @@ const uint256& V1Transport::GetMessageHash() const
CNetMessage V1Transport::GetMessage(const std::chrono::microseconds time, bool& reject_message)
{
AssertLockNotHeld(m_recv_mutex);
// Initialize out parameter
reject_message = false;
// decompose a single CNetMessage from the TransportDeserializer
LOCK(m_recv_mutex);
CNetMessage msg(std::move(vRecv));
// store message type string, time, and sizes