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46 lines
1.9 KiB
Markdown
46 lines
1.9 KiB
Markdown
---
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# SPDX-FileCopyrightText: 2023 Steffen Vogel <post@steffenvogel.de>
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# SPDX-License-Identifier: Apache-2.0
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---
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# Auto-configuration
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The auto-configuration feature assigns link-local IP addresses to WireGuard interfaces as well as configures several other common settings such as MTU, IP addresses or DNS settings.
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## Link local IP-addresses
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This feature automatically assigns each interface link-local IPv4 and IPv6 addresses derived from the interface's public key.
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This enables peer-to-peer communication when no site-local or global addresses are assigned yet.
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### Address calculation
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Addresses are generated by concatenating a well-known network prefix (`fe80::/64`, `169.254.0.0/16`) with an host part derived from the public key $PK$ of the peer/interface using the 64-bit [$\mathrm{SipHash}_{64}$](https://en.wikipedia.org/wiki/SipHash) hashing function:
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$$
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\begin{align}
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H~=&~\mathrm{SipHash}_{64}(PK) \\
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H_{fold}~=&~(H \land \mathrm{0xFFFF}) \barwedge (H \gg 16) \\
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\mathrm{IPv6}_{link-local}~=&~\{ \mathrm{fe80:}~||~H~\} /64 \\
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\mathrm{IPv4}_{link-local}~=&~\{ \mathrm{169.254.}~||~H_{fold}~\}/16 \\
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\end{align}
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$$
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This addresses calculation can be performed with the [`cunicu addresses`](../usage/md/cunicu_addresses.md) sub-command.
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## Missing settings
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The following settings are automatically assigned if they have not been set before:
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- **Private Key:** a new random private key will be generated.
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- **Listen port:** the next free port in the configured listen port range is used (see `wireguard.listen_port_range` setting).
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- **MTU:** is automatically determined from the endpoint addresses or the system default route.
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## Configuration
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The following settings can be used in the main section of the [configuration file](../config/) or with-in the `interfaces` section to customize settings of an individual interface.
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import ApiSchema from '@theme/ApiSchema';
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<ApiSchema pointer="#/components/schemas/BasicInterfaceSettings" />
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