CConnman then passes the current best height into CNode at creation time.
This way CConnman/CNode have no dependency on main for height, and the signals
only move in one direction.
This also helps to prevent identity leakage a tiny bit. Before this change, an
attacker could theoretically make 2 connections on different interfaces. They
would connect fully on one, and only establish the initial connection on the
other. Once they receive a new block, they would relay it to your first
connection, and immediately commence the version handshake on the second. Since
the new block height is reflected immediately, they could attempt to learn
whether the two connections were correlated.
This is, of course, incredibly unlikely to work due to the small timings
involved and receipt from other senders. But it doesn't hurt to lock-in
nBestHeight at the time of connection, rather than letting the remote choose
the time.
This behavior seems to have been quite racy and broken.
Move nLocalHostNonce into CNode, and check received nonces against all
non-fully-connected nodes. If there's a match, assume we've connected
to ourself.
Tests if addresses are online or offline by briefly connecting to them. These short lived connections are referred to as feeler connections. Feeler connections are designed to increase the number of fresh online addresses in tried by selecting and connecting to addresses in new. One feeler connection is attempted on average once every two minutes.
This change was suggested as Countermeasure 4 in
Eclipse Attacks on Bitcoin’s Peer-to-Peer Network, Ethan Heilman,
Alison Kendler, Aviv Zohar, Sharon Goldberg. ePrint Archive Report
2015/263. March 2015.
1a5a4e6 Randomize name lookup result in ConnectSocketByName (Pieter Wuille)
f9f5cfc Prevent duplicate connections where one is by name and another by ip (Pieter Wuille)
1111b80 Rework addnode behaviour (Pieter Wuille)
6ee7f05 Allow disconnecting a netgroup with only one member in eviction. (Gregory Maxwell)
5d0ca81 Add recently accepted blocks and txn to AttemptToEvictConnection. (Gregory Maxwell)
* Use CNode::addeName to track whether a connection to a name is already open
* A new connection to a previously-connected by-name addednode is only opened when
the previous one closes (even if the name starts resolving to something else)
* At most one connection is opened per addednode (even if the name resolves to multiple)
* Unify the code between ThreadOpenAddedNodeConnections and getaddednodeinfo
* Information about open connections is always returned, and the dns argument becomes a dummy
* An IP address and inbound/outbound is only reported for the (at most 1) open connection
eebc232 test: Add more test vectors for siphash (Wladimir J. van der Laan)
8884830 Use C++11 thread-safe static initializers (Pieter Wuille)
c31b24f Use 64-bit SipHash of netgroups in eviction (Pieter Wuille)
9bf156b Support SipHash with arbitrary byte writes (Pieter Wuille)
053930f Avoid recalculating vchKeyedNetGroup in eviction logic. (Patrick Strateman)
6182d10 Do not increment nAttempts by more than one for every Good connection. (Gregory Maxwell)
c769c4a Avoid counting failed connect attempts when probably offline. (Gregory Maxwell)
This reduces the rate of not founds by better matching the far
end expectations, it also improves privacy by removing the
ability to use getdata to probe for a node having a txn before
it has been relayed.
If a node is offline failed outbound connection attempts will crank up
the addrman counter and effectively blow away our state.
This change reduces the problem by only counting attempts made while
the node believes it has outbound connections to at least two
netgroups.
Connect and addnode connections are also not counted, as there is no
reason to unequally penalize them for their more frequent
connections -- though there should be no real effect from this
unless their addnode configureation is later removed.
Wasteful repeated connection attempts while only a few connections are
up are avoided via nLastTry.
This is still somewhat incomplete protection because our outbound
peers could be down but not timed out or might all be on 'local'
networks (although the requirement for multiple netgroups helps).
The ability to GETDATA a transaction which has not (yet) been relayed
is a privacy loss vector.
The use of the mempool for this was added as part of the mempool p2p
message and is only needed to fetch transactions returned by it.
5d5e7a0 net: No need to export ConnectNode (Cory Fields)
e9ed620 net: No need to export DumpBanlist (Cory Fields)
8b8f877 net: make Ban/Unban/ClearBan functionality consistent (Cory Fields)
cca221f net: Drop CNodeRef for AttemptToEvictConnection (Cory Fields)
563f375 net: use the exposed GetNodeSignals() rather than g_signals directly (Cory Fields)
9faa490 net: remove unused set (Cory Fields)
52cbce2 net: don't import std namespace (Cory Fields)
