Different types of connections to a peer. This enum encapsulates the information we have available at the time of opening or accepting the connection. Aside from INBOUND, all types are initiated by us.
Declared in <node/connection_types.h>
enum class ConnectionType : int;If adding or removing types, please update CONNECTION_TYPE_DOC in src/rpc/net.cpp and src/qt/rpcconsole.cpp, as well as the descriptions in src/qt/guiutil.cpp and src/bitcoin-cli.cpp::NetinfoRequestHandler.
| Name | Description |
|---|---|
INBOUND | Inbound connections are those initiated by a peer. This is the only property we know at the time of connection, until P2P messages are exchanged. |
OUTBOUND_FULL_RELAY | These are the default connections that we use to connect with the network. There is no restriction on what is relayed; by default we relay blocks, addresses & transactions. We automatically attempt to open MAX_OUTBOUND_FULL_RELAY_CONNECTIONS using addresses from our AddrMan. |
MANUAL | We open manual connections to addresses that users explicitly requested via the addnode RPC or the -addnode/-connect configuration options. Even if a manual connection is misbehaving, we do not automatically disconnect or add it to our discouragement filter. |
FEELER | Feeler connections are short-lived connections made to check that a node is alive. They can be useful for: - test-before-evict: if one of the peers is considered for eviction from our AddrMan because another peer is mapped to the same slot in the tried table, evict only if this longer-known peer is offline. - move node addresses from New to Tried table, so that we have more connectable addresses in our AddrMan. Note that in the literature ("Eclipse Attacks on Bitcoin’s Peer-to-Peer Network") only the latter feature is referred to as "feeler connections", although in our codebase feeler connections encompass test-before-evict as well. We make these connections approximately every FEELER_INTERVAL: first we resolve previously found collisions if they exist (test-before-evict), otherwise we connect to a node from the new table. |
BLOCK_RELAY | We use block-relay-only connections to help prevent against partition attacks. By not relaying transactions or addresses, these connections are harder to detect by a third party, thus helping obfuscate the network topology. We automatically attempt to open MAX_BLOCK_RELAY_ONLY_ANCHORS using addresses from our anchors.dat. Then addresses from our AddrMan if MAX_BLOCK_RELAY_ONLY_CONNECTIONS isn't reached yet. |
ADDR_FETCH | AddrFetch connections are short lived connections used to solicit addresses from peers. These are initiated to addresses submitted via the -seednode command line argument, or under certain conditions when the AddrMan is empty. |
PRIVATE_BROADCAST | Private broadcast connections are short-lived and only opened to privacy networks (Tor, I2P) for relaying privacy-sensitive data (like our own transactions) and closed afterwards. |
| Name | Description |
|---|---|
ConnectionTypeAsString | Convert ConnectionType enum to a string value |