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HostBridge component

This section describes the HostBridge component.

HostBridge - about

This component is written in C++. It is a model that acts as a networking proxy for target NIC device models, to forward and receive Ethernet packets to and from the host.

Two kinds of proxy backend are integrated into this component. The default is to use a host TAP/TUN-like network device, which is an ordinary TAP or MacVTap. The alternative to this TAP/TUN method is user-mode networking, which emulates a built-in IP router and DHCP server to route traffic using the host user-mode socket layer.

HostBridge contains the following CADI targets:

  • HostBridge

HostBridge - ports

This section describes the ports.

Table 4-96 HostBridge ports

Name Protocol Type Description
eth VirtualEthernet Slave Send or receive Ethernet frame.
state ValueState_64 Slave Configure or retrieve states of network proxy backend.

HostBridge - parameters

This section describes the parameters.

Table 4-97 HostBridge parameters

Name Type Allowed values Default value Description
userNetworking bool true, false false If true, the outgoing Ethernet packets of the model go to a proxy router that translates them into host socket calls. If false (default) the model attempts to open a TAP/TUN device.a



Valid string characters


The host TAP/TUN-like device that is used by the HostBridge. This should be specified with a non-empty valid interface name when hostbridge.userNetworking=false. The device could be an ordinary TAP or MacVTap (Linux only).

userNetPorts string Formatted string ""

Specifies an optional port number mapping between listening ports on the host and listening ports on the model. The syntax is a comma-separated list of items in the form [host-ip:]hostport=[model-ip:]modelport. For example, 5022=22,5080=80 causes sshd and httpd services on the model to listen on ports 5022 and 5080 on the host. You can use the optional host-ip or model-ip to select a specific interface for the mapping, for example The default is to accept connections on any interface (INADDR_ANY).

userNetSubnet string Formatted string '' Presents a range of subnet network addresses to the model, in the ip-address/significant-bits syntax, for example or Omitting trailing zero octets is acceptable, for example 192.168/16. The default subnet is, taken from the RFC1918 private-use area.

HostBridge - verification and testing

This component passes tests as part of a system with network functionalities.

HostBridge - performance

Arm expects this component to have little effect on the performance of PV systems. However, heavy usage on the networking of the model, for example to run networking performance tests, might slow down the simulation.


TAP/TUN mode is enabled by default, and is disabled when user mode is in use.

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