All Rust programs call out to platform-dependent unsafe code sooner or later in the form of the standard library. Otherwise, you wouldn't be able to allocate memory or do any I/O whatsoever.
Sometimes the standard library doesn't expose functionality you want, like the capability to read/write the ECN bits of your UDP packets, so you have to bind some syscalls yourself. The capability to do this is one of Rust's core strengths, and it does not compromise a program's rustiness any moreso than calling a wrapper around write to print "Hello, world!" does.
Sometimes the standard library doesn't expose functionality you want, like the capability to read/write the ECN bits of your UDP packets, so you have to bind some syscalls yourself. The capability to do this is one of Rust's core strengths, and it does not compromise a program's rustiness any moreso than calling a wrapper around write to print "Hello, world!" does.