Add some comments so that people know why we are performing a fallback
from getrandom() and what that fallback aims to achieve.
Signed-off-by: Doug Goldstein <cardoe@cardoe.com>
If we attempt a read with getrandom() on Linux the syscall can block
before the random pool is initialized unless the GRND_NONBLOCK flag is
passed. This flag causes getrandom() to instead return EAGAIN while the
pool is uninitialized. To avoid downstream users of crate or std
functionality that have no ability to avoid this blocking behavior this
change causes Rust to read bytes from /dev/urandom while getrandom()
would block and once getrandom() is available to use that. Fixes#32953.
Signed-off-by: Doug Goldstein <cardoe@cardoe.com>
Automated conversion using the untry tool [1] and the following command:
```
$ find -name '*.rs' -type f | xargs untry
```
at the root of the Rust repo.
[1]: https://github.com/japaric/untry
