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This patch changes the top-level directory layout as a preparatory step for improving the tools for managing 3rd-party source codes. The rationale is described in the issue referenced below. Issue #1082
44 lines
2.0 KiB
Plaintext
44 lines
2.0 KiB
Plaintext
The NIC bridge provides multiple sessions of the 'Nic' service while using a
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single 'Nic' session for forwarding requests. It implements a flavour of the
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Proxy-ARP protocol (rfc1027). That means it allocates a virtual MAC address for
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each client. Whenever a client sends a packet, NIC bridge changes the sender's
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MAC address to the one it memorized for the client. Moreover, it monitors DHCP
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packets, and tracks the IP addresses assigned to each of its clients. Whenever
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ARP packets come from the outside, NIC bridge will answer them with the
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corresponding MAC address.
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By adding a 'mac' attribute to the 'nic_bridge' config node: one can define the
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first MAC address from which the NIC bridge will allocate MACs for its clients.
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For example:
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! <config mac="02:02:02:02:02:00"/>
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Note that the least relevant byte will be ignored. NIC bridge will use it for
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enumerating its clients, starting from 0.
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Normally, NIC bridge is expected to be used in scenarios where an DHCP server
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is available. However, there are situations where the use of static IPs for
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virtual NICs is useful. For example, when using the NIC bridge to create a
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virtual network between the lighttpd web server and the Arora web browser, both
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running as Genode processes without real network connectivity.
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The static IP can be configured per client of the NIC bridge using a '<policy>'
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node of the configuration. For example, the following policy assigns a static
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address to a client with the session label "lighttpd".
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!<start name="nic_bridge">
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! ...
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! <config>
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! <policy label="lighttpd" ip_addr="10.0.2.55"/>
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! </config>
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!</start>
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Of course, the client needs to configure its TCP/IP stack to use the assigned
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IP address. This can be done via configuration arguments examined by the
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'lwip_nic_dhcp' libc plugin. For the given example, the configuration for the
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lighttpd process would look as follows.
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!<start name="lighttpd">
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! <config>
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! <interface ip_addr="10.0.2.55"
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! netmask="255.255.255.0"
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! gateway="10.0.2.1"/>
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! </config>
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!</start>
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