UDP Broadcast Relay

The UDP Broadcast Relay package (FreeSense-pkg-udpbroadcastrelay 1.2.8) runs one udpbroadcastrelay process per configured instance. Each instance listens for UDP broadcasts (and optionally one multicast group) on a given port and retransmits them on the other selected interfaces. Broadcasts never cross a router on their own, so this is how discovery protocols that rely on broadcasts work across VLANs: game and media server discovery, some smart-home and building-automation devices, and similar LAN-only protocols.

For mDNS use mDNS Bridge or Avahi. For routed multicast streams with IGMP/MLD use Multicast Bridge. DHCP has its own relay in Services → DHCP Relay.

Install

1. Open System → Package Manager → Available Packages.
2. Find UDP Broadcast Relay (package FreeSense-pkg-udpbroadcastrelay) and click Install.

The udpbroadcastrelay daemon is installed as a dependency. On Stable 1.1 the package is available for amd64. See Installing packages.

Where to find it

Services → UDP Broadcast Relay (in the Routing group of the Services menu):

• udpbroadcastrelay/udpbroadcastrelay.php: General Settings and the instance table (Port, Interfaces, Description, Actions) with a select-all checkbox for deleting instances.
• udpbroadcastrelay/udpbroadcastrelay_edit.php: Instance Settings for one instance.

First-time setup

1. Open Services → UDP Broadcast Relay.
2. Click Add below the instance table and fill in Instance Settings:
   1. Check Enable.
   2. Enter a Description, for example Game discovery.
   3. Select at least two Network Interfaces, for example LAN and GAMES.
   4. Enter the UDP Port the application broadcasts on.
   5. Leave Spoof Source on Keep Original unless the application needs replies to the relay address.
3. Save the instance.
4. On the main page, check Enable under General Settings and save. The service is reloaded with every enabled instance.
5. Add the firewall rules described below and test discovery between the two networks.

Settings reference

General Settings

Field	What it does	Default
Enable	Enables the UDP Broadcast Relay service.	Off
Track CARP Status	Run only while the selected CARP VIP is MASTER.	none

Instance Settings

Field	What it does	Default
Enable	Run this instance.	Off
Description	Free text for reference.	Empty
Network Interfaces	Interfaces to receive and retransmit on. At least two. Only assigned, enabled interfaces that exist on the system are listed.	None
Spoof Source	Source used for relayed packets: Keep Original (default), Use Interface Address and Destination Port, or Use Interface Address only.	Keep Original
UDP Port	Destination UDP port to listen on, 1 to 65535.	Empty
IP Address (next to UDP Port)	Optional IPv4 multicast group to relay as well as broadcasts.	Empty

Limits and checks:

• Up to 63 instances can be enabled.
• Two enabled instances cannot use the same port on overlapping interfaces.

Firewall rules and interfaces

The package adds no firewall rules.

• On every interface in an instance, allow UDP from the interface network to the instance’s port, with destination any (or the interface broadcast address and, if used, the multicast group).
• Add rules for the application’s follow-up traffic between the networks, which is usually unicast and uses other ports.
• With Keep Original, relayed packets carry the original sender’s address, so replies go straight to the sender and need a rule in that direction.

Service, logs, and status

Item	Value
Service name	udpbroadcastrelay (UDP Broadcast Relay in Status → Services)
rc script	/usr/local/etc/rc.d/udpbroadcastrelay.sh
Processes	/usr/local/sbin/udpbroadcastrelay --id <n> --port <port> --dev <if> ..., one per enabled instance
Logs	Daemon facility with the udpbroadcastrelay tag; see Status → System Logs → System → General. A failed instance start logs Failed to start instance with the error.

Upgrade, backup, and removal

• Settings are stored in config.xml and included in configuration backups.
• Removing the package stops the service, deletes the rc script and the temporary files under /tmp/udpbr_tmp.*. The settings stay in config.xml for a later reinstall.

Troubleshooting

Symptom	Cause and fix
At least two interfaces must be selected	Select two or more interfaces in the instance.
Duplicate port found on an instance with overlaping interfaces	Another enabled instance already relays that port on one of the same interfaces. Merge them or change the interface set.
Instance limit reached	More than 63 instances are enabled.
The log shows Failed to start service due to a configuration error	The stored configuration did not validate, for example an interface was removed. Edit and save each instance.
The log shows Ignoring service start - no valid instances to start	No instance is enabled.
The service keeps running after you uncheck Enable under General Settings	The service is not stopped when the global switch is turned off; see the note below. Stop it from Status → Services.

Changes in FreeSense 1.1

• UDP Broadcast Relay is listed in the Routing group of the 1.1 Services menu (freesense-packages 4ae11df).
• Removing the package now reliably stops the relay: the Package Manager stops a package’s services before deleting them (freesense c767de3).
• Otherwise the package is unchanged from 1.0.x apart from the rebuild for the FreeBSD 16 platform.