Package utils

Class InterfaceToIp

java.lang.Object

utils.InterfaceToIp

public class InterfaceToIp
extends Object

Resolves the process-wide bind address (babel.address) the node binds and announces on.

Why this matters for the demo: for multicast auto-discovery (and for peers to reach each other at all) every node must advertise a reachable address — not 127.0.0.1 and not 0.0.0.0. So the demo never silently defaults to loopback. Instead resolveBindAddress(Properties) picks an address in this order:

1. an explicit babel.address (the user's override always wins — including loopback, e.g. babel.address=127.0.0.1 for running several nodes on one disconnected machine);
2. the IPv4 address of the interface named in babel.interface (e.g. babel.interface=en0 on macOS, eth0 on Linux);
3. experimental auto-detection: the routable IPv4 of the sole real interface — up, non-loopback, non-point-to-point, non-virtual, with a non-link-local IPv4, and whose name is not a bridge / VM / container / VPN adapter (isLikelyNonPhysical(java.net.NetworkInterface)). If several real interfaces qualify it refuses to guess and lists them; if only bridges/VPNs (or nothing) exist it asks the operator to choose.

In the refuse/none cases it fails loudly and tells the operator to pass babel.interface or babel.address explicitly. The auto-detection heuristic is name-based and best-effort — an explicit babel.interface / babel.address always wins and bypasses it.

The parameter keys babel.address / babel.interface / babel.port are owned by babel-core (Babel.PAR_DEFAULT_ADDRESS / Babel.PAR_DEFAULT_INTERFACE / Babel.PAR_DEFAULT_PORT); this class references those constants rather than re-declaring the literals.

Method Summary

Modifier and Type	Method	Description
static String	autoDetectAddress()	Auto-detect a reachable bind address: the routable IPv4 of the sole real (non-loopback, up, non-virtual, non-p2p, non-bridge/VM/VPN) interface.
static String	describeInterfaces()	Logs every network interface and its IPv4 addresses (with up/loopback/virtual/ point-to-point flags) to help diagnose a wrong auto-selection.
static String	getIpOfInterface(String interfaceName)	Returns the first non-loopback IPv4 address of interfaceName, or null if it has none / does not exist.
static String	resolveBindAddress(Properties props)	Resolve the process-wide bind address into babel.address (see the class javadoc for the precedence).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

getIpOfInterface

public static String getIpOfInterface(String interfaceName)
                               throws SocketException

Returns the first non-loopback IPv4 address of interfaceName, or null if it has none / does not exist.

Throws:

SocketException

autoDetectAddress

public static String autoDetectAddress()
                                throws SocketException

Auto-detect a reachable bind address: the routable IPv4 of the sole real (non-loopback, up, non-virtual, non-p2p, non-bridge/VM/VPN) interface. Returns null if none — or more than one — qualifies.

Throws:

SocketException

resolveBindAddress

public static String resolveBindAddress(Properties props)
                                 throws SocketException,
InvalidParameterException

Resolve the process-wide bind address into babel.address (see the class javadoc for the precedence). On return babel.address is guaranteed to be set to a concrete IPv4 address.

Returns:

a short human-readable description of how the address was chosen (for startup logging), e.g. "explicit babel.address", "interface en0", or "auto-detected interface en0".

Throws:

InvalidParameterException - if a named babel.interface has no usable address, or no address could be determined at all — in which case the operator must pass babel.interface or babel.address on the command line.

SocketException

describeInterfaces

public static String describeInterfaces()

Logs every network interface and its IPv4 addresses (with up/loopback/virtual/ point-to-point flags) to help diagnose a wrong auto-selection. Written to the log file; never throws.