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docs(readme) update WireGuard MTU calculation to take into account for

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padding truncation
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Datong Sun 2021-10-16 10:55:01 -07:00
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README.md
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@ -218,18 +218,13 @@ of obfuscation.
For people who use Phantun to tunnel [WireGuard®](https://www.wireguard.com) UDP packets, here are some guidelines on figuring For people who use Phantun to tunnel [WireGuard®](https://www.wireguard.com) UDP packets, here are some guidelines on figuring
out the correct MTU to use for your WireGuard interface. out the correct MTU to use for your WireGuard interface.
WireGuard MTU = `MAX_OF_16`(Interface MTU - IP header (20 bytes) - TCP header (20 bytes) - WireGuard overhead (32 bytes)) WireGuard MTU = Interface MTU - IP header (20 bytes) - TCP header (20 bytes) - WireGuard overhead (32 bytes)
Where:
`MAX_OF_16` takes an input integer and calculates the maximum multiple of 16 not exceeding the input. This
is needed because WireGuard will always pad it's payloads to multiple of 16 bytes.
For example, for a Ethernet interface with 1500 bytes MTU, the WireGuard interface MTU should be set as: For example, for a Ethernet interface with 1500 bytes MTU, the WireGuard interface MTU should be set as:
`MAX_OF_16`(1500 - 20 - 20 - 32) = 1424 bytes 1500 - 20 - 20 - 32 = 1428 bytes
The resulted Phantun TCP data packet will be 1424 + 20 + 20 + 32 = 1496 bytes which does not exceed the The resulted Phantun TCP data packet will be 1500 bytes which does not exceed the
interface MTU of 1500. interface MTU of 1500.
[Back to TOC](#table-of-contents) [Back to TOC](#table-of-contents)