Original link: https://zdyxry.github.io/2023/06/25/Weekly-Issue-2023-06-25/
Article link to title Technical link to title MTU and UDP (and UDP-based protocols) | Kawabanga!
If you want to implement a protocol based on UDP, you have to deal with the problem of exceeding [[MTU]] yourself.
The last is QUIC, which is the most representative. Its processing method is:
The implementation of QUIC should (the RFC uses SHOULD) use PMTUD, and should record the MTU of each source ip + dest ip
But if there is no PMTUD, it can also be considered that MTU=1280, and the protocol setting max_udp_payload_size = 1200 bytes, so, according to the above algorithm, the IPv4 header can have a maximum of 52 bytes, and the IPv6 header can have 32 bytes, which is enough under normal circumstances If the link cannot even support 1280 PDUs, QUIC will make this UDP unusable (equal to not being able to connect to the port), and then fallback to TCP
The case of the supersized shebang [LWN.net]
A change in how the shebang is truncated prevents NixOS from working properly. [[Perl]] The interpreter will re-read the shebang.
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