a701fcf01f net: Do not skip the I2P network from GetNetworkNames() (Vasil Dimov)
0181e24439 net: recognize I2P from ParseNetwork() so that -onlynet=i2p works (Vasil Dimov)
b905363fa8 net: accept incoming I2P connections from CConnman (Vasil Dimov)
0635233a1e net: make outgoing I2P connections from CConnman (Vasil Dimov)
9559bd1404 net: add I2P to the reachability map (Vasil Dimov)
76c35c60f3 init: introduce I2P connectivity options (Vasil Dimov)
c22daa2ecf net: implement the necessary parts of the I2P SAM protocol (Vasil Dimov)
5bac7e45e1 net: extend Sock with a method to check whether connected (Vasil Dimov)
42c779f503 net: extend Sock with methods for robust send & read until terminator (Vasil Dimov)
ea1845315a net: extend Sock::Wait() to report a timeout (Vasil Dimov)
78fdfbea66 net: dedup MSG_NOSIGNAL and MSG_DONTWAIT definitions (Vasil Dimov)
34bcfab562 net: move the constant maxWait out of InterruptibleRecv() (Vasil Dimov)
cff65c4a27 net: extend CNetAddr::SetSpecial() to support I2P (Vasil Dimov)
f6c267db3b net: avoid unnecessary GetBindAddress() call (Vasil Dimov)
7c224fdac4 net: isolate the protocol-agnostic part of CConnman::AcceptConnection() (Vasil Dimov)
1f75a653dd net: get the bind address earlier in CConnman::AcceptConnection() (Vasil Dimov)
25605895af net: check for invalid socket earlier in CConnman::AcceptConnection() (Vasil Dimov)
545bc5f81d util: fix WriteBinaryFile() claiming success even if error occurred (Vasil Dimov)
8b6e4b3b23 util: fix ReadBinaryFile() returning partial contents (Vasil Dimov)
4cba2fdafa util: extract {Read,Write}BinaryFile() to its own files (Vasil Dimov)
Pull request description:
Add I2P support by using the [I2P SAM](https://geti2p.net/en/docs/api/samv3) protocol. Unlike Tor, for incoming connections we get the I2P address of the peer (and they also receive ours when we are the connection initiator).
Two new options are added:
```
-i2psam=<ip:port>
I2P SAM proxy to reach I2P peers and accept I2P connections (default:
none)
-i2pacceptincoming
If set and -i2psam is also set then incoming I2P connections are
accepted via the SAM proxy. If this is not set but -i2psam is set
then only outgoing connections will be made to the I2P network.
Ignored if -i2psam is not set. Notice that listening for incoming
I2P connections is done through the SAM proxy, not by binding to
a local address and port (default: true)
```
# Overview of the changes
## Make `ReadBinary()` and `WriteBinary()` reusable
We would need to dump the I2P private key to a file and read it back later. Move those two functions out of `torcontrol.cpp`.
```
util: extract {Read,Write}BinaryFile() to its own files
util: fix ReadBinaryFile() returning partial contents
util: fix WriteBinaryFile() claiming success even if error occurred
```
## Split `CConnman::AcceptConnection()`
Most of `CConnman::AcceptConnection()` is agnostic of how the socket was accepted. The other part of it deals with the details of the `accept(2)` system call. Split those so that the protocol-agnostic part can be reused if we accept a socket by other means.
```
net: check for invalid socket earlier in CConnman::AcceptConnection()
net: get the bind address earlier in CConnman::AcceptConnection()
net: isolate the protocol-agnostic part of CConnman::AcceptConnection()
net: avoid unnecessary GetBindAddress() call
```
## Implement the I2P [SAM](https://geti2p.net/en/docs/api/samv3) protocol (not all of it)
Just the parts that would enable us to make outgoing and accept incoming I2P connections.
```
net: extend CNetAddr::SetSpecial() to support I2P
net: move the constant maxWait out of InterruptibleRecv()
net: dedup MSG_NOSIGNAL and MSG_DONTWAIT definitions
net: extend Sock::Wait() to report a timeout
net: extend Sock with methods for robust send & read until terminator
net: extend Sock with a method to check whether connected
net: implement the necessary parts of the I2P SAM protocol
```
## Use I2P SAM to connect to and accept connections from I2P peers
Profit from all of the preceding commits.
```
init: introduce I2P connectivity options
net: add I2P to the reachability map
net: make outgoing I2P connections from CConnman
net: accept incoming I2P connections from CConnman
net: recognize I2P from ParseNetwork() so that -onlynet=i2p works
net: Do not skip the I2P network from GetNetworkNames()
```
ACKs for top commit:
laanwj:
re-ACK a701fcf01f
jonatack:
re-ACK a701fcf01f reviewed diff per `git range-diff ad89812 2a7bb34 a701fcf`, debug built and launched bitcoind with i2pd v2.35 running a dual I2P+Torv3 service with the I2P config settings listed below (did not test `onlynet=i2p`); operation appears nominal (same as it has been these past weeks), and tested the bitcoind help outputs grepping for `-i i2p` and the rpc getpeerinfo and getnetworkinfo helps
Tree-SHA512: de42090c9c0bf23b43b5839f5b4fc4b3a2657bde1e45c796b5f3c7bf83cb8ec6ca4278f8a89e45108ece92f9b573cafea3b42a06bc09076b40a196c909b6610e
b9f41df1ea