random-util: rename RANDOM_DONT_DRAIN → RANDOM_MAY_FAIL

The old flag name was a bit of a misnomer, as /dev/urandom cannot be
"drained". Once it's initialized it's initialized and then is good
forever. (Only /dev/random has a concept of 'draining', but we never use
that, as it's an obsolete interface).

The flag is still useful though, since it allows us to suppress accesses
to the random pool while it is not initialized, as that trips up the
kernel and it logs about any such attempts, which we really don't want.

src/basic/random-util.h

@@ -8,11 +8,11 @@
 typedef enum RandomFlags {
         RANDOM_EXTEND_WITH_PSEUDO = 1 << 0, /* If we can't get enough genuine randomness, but some, fill up the rest with pseudo-randomness */
         RANDOM_BLOCK              = 1 << 1, /* Rather block than return crap randomness (only if the kernel supports that) */
-        RANDOM_DONT_DRAIN         = 1 << 2, /* If we can't get any randomness at all, return early with -EAGAIN */
+        RANDOM_MAY_FAIL           = 1 << 2, /* If we can't get any randomness at all, return early with -ENODATA */
         RANDOM_ALLOW_RDRAND       = 1 << 3, /* Allow usage of the CPU RNG */
 } RandomFlags;
 
-int genuine_random_bytes(void *p, size_t n, RandomFlags flags); /* returns "genuine" randomness, optionally filled upwith pseudo random, if not enough is available */
+int genuine_random_bytes(void *p, size_t n, RandomFlags flags); /* returns "genuine" randomness, optionally filled up with pseudo random, if not enough is available */
 void pseudo_random_bytes(void *p, size_t n);                    /* returns only pseudo-randommess (but possibly seeded from something better) */
 void random_bytes(void *p, size_t n);                           /* returns genuine randomness if cheaply available, and pseudo randomness if not. */