Simplify API by removing RNG interface #8
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cobusve
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| * | ||
| * For the simplicity of the code example, the pseudo random number generator, rand() function | ||
| * is used. */ | ||
| retryStatus = BackoffAlgorithm_GetNextBackoff( &retryParams, rand(), &nextRetryBackOff ); |
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Where is this PRNG seeded? I ask because if you do an OTA on a fleet they will all start up with the same seed and you will have exactly the connection storm this is intended to avoid.
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Good catch. I have added seeding logic of RNG in the example.
source/include/backoff_algorithm.h
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| * the random value. Using a random number generator that generates device-specific unique values | ||
| * specific mitigates possibility of collision between multiple devices retrying the network operations. |
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This last sentence seems problematic to me. A TRNG does not generate unique values, it generates random values. The entropy pool may be device specific, but conceptually the random number is not device-specific; it's just random.
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Yes I agree we should just say that using random adds diversity, too much detail here is just a trap, random is hard.
To improve usability of API, the existing
BackoffAlgorithm_RNG_tinterface for passing a random number generator function to the library is removed in this PR. This helps avoid the need of "wrappers" around platform-specific RNGs to pass to the library. Instead, the application can generate the random number using their platform-specific RNG and just directly pass to the library for calculating the next retry backoff period.Note: Removal of the random number generator dependency makes this library completely platform-independent!