* When accepting an I2P connection, assume the peer has port 0 instead
of the default 8333 (for mainnet). It is not being sent to us, so we
must assume something.
* When deriving our own I2P listen CService use port 0 instead of the
default 8333 (for mainnet). So that we later advertise it to peers
with port 0.
In the I2P protocol SAM 3.1 and older (we use 3.1) ports are not used,
so they are irrelevant. However in SAM 3.2 and newer ports are used and
from the point of view of SAM 3.2, a peer using SAM 3.1 seems to have
specified port=0.
Change the types of `i2p::Connection::sock` and
`i2p::sam::Session::m_control_sock` from `Sock` to
`std::unique_ptr<Sock>`.
Using pointers would allow us to sneak `FuzzedSock` instead of `Sock`
and have the methods of the former called.
After this change a test only needs to replace `CreateSock()` with
a function that returns `FuzzedSock`.
Change `ConnectSocketDirectly()` to take a `Sock` argument instead of a
bare `SOCKET`. With this, use the `Sock`'s (possibly mocked) methods
`Connect()`, `Wait()` and `GetSockOpt()` instead of calling the OS
functions directly.
Put a limit on the amount of data `Sock::RecvUntilTerminator()` can read
if no terminator is received.
In the case of I2P this avoids a runaway (or malicious) I2P proxy
sending us tons of data without a terminator before a timeout is
triggered.
Implement the following commands from the I2P SAM protocol:
* HELLO: needed for all of the remaining ones
* DEST GENERATE: to generate our private key and destination
* NAMING LOOKUP: to convert .i2p addresses to destinations
* SESSION CREATE: needed for STREAM CONNECT and STREAM ACCEPT
* STREAM CONNECT: to make outgoing connections
* STREAM ACCEPT: to accept incoming connections
Vasil Dimov