This moves header size and netmagic checking out of net_processing and
into net. This check now runs in ReadHeader, so that net can exit early
out of receiving bytes from the peer. IsValid is now slimmed down, so
it no longer needs a MessageStartChars& parameter.
Additionally this removes the rest of the m_valid_* members from
CNetMessage.
This adds a CChainParams& member to V1TransportDeserializer member, and
use it in place of many Params() calls. In addition to reducing the
number of calls to a global, this removes a parameter from GetMessage
(and will later allow us to remove one from CMessageHeader::IsValid())
This commit removes the single-parameter contructor of CMessageHeader
and replaces it with a default constructor.
The single parameter contructor isn't used anywhere except for tests.
There is no reason to initialize a CMessageHeader with a particular
messagestart. This messagestart should always be replaced when
deserializing an actual message header so that we can run checks on it.
The default constructor initializes it to zero, just like the command
and checksum.
This also removes a parameter of a V1TransportDeserializer constructor,
as it was only used for this purpose.
This removes the m_valid_checksum member from CNetMessage. Instead,
GetMessage() returns an Optional.
Additionally, GetMessage() has been given an out parameter to be used to
hold error information. For now it is specifically a uint32_t used to
hold the raw size of the corrupt message.
The checksum check is now done in GetMessage.
This is intended to only be used for logging.
This will allow log messages in the following commits to keep recording
the peer's ID, even when logging is moved into V1TransportDeserializer.
