Basic rand infrastructure. #547
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Dirbaio
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On `std` targets, `OsRng` is used by default. The user can supply a custom impl by enabling the `rand-custom-impl` Cargo feature and using the `rand_custom_impl!()` macro. Specifying a custom impl is mandatory when `std` is not enabled.
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| fn random_seq_no() -> TcpSeqNumber { | ||
| #[cfg(test)] | ||
| return TcpSeqNumber(10000); |
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Is the intent to not implement a "bad" rand generator in test so that a user doesn't accidentally enable it for their app? It seems like we should be able to use the OS's rand for test purposes?
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Many tests rely on the starting sequence number to be 10000. Changing them to make them work with a random starting seq number is annoying, and wouldn't really add much value.
One alternative I tried is making the actual RNG a mock when building in test mode, so the tests can "magically influence" what numbers come out of the RNG. The problem is tests would have to be aware of how and when does TCP use the RNG, which is kind of an implementation detail (ie when does it request bytes, how many bytes does it request, are they little/big endian to form the u32 sequence number...?)
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Ah, I see the limitation now. It just feels like addressing it at the tcp.rs layer may be introducing tech-debt for the future, but it looks extremely lightweight, so I'm not worried. Thanks for the explanation!
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bors r+ |
573: Simpler rand r=Dirbaio a=Dirbaio Requires #571 Revisits #547, because it turns out the `rand_custom_impl!` macro stuff was less nice than I thought. It's now a simple PRNG owned by Interface. The builder allows setting the random seed. Co-authored-by: Dario Nieuwenhuis <[email protected]> Co-authored-by: Thibaut Vandervelden <[email protected]> Co-authored-by: bors[bot] <26634292+bors[bot]@users.noreply.github.com>
See previous discussion. Opening a separate PR so it can be discussed separately.
smoltcp::rand.stdtargets,OsRngis used by default.rand-custom-implCargo feature and using therand_custom_impl!()macro.stdis not enabled.