diff options
Diffstat (limited to 'src/shared')
| -rw-r--r-- | src/shared/missing.h | 8 | ||||
| -rw-r--r-- | src/shared/util.c | 24 |
2 files changed, 28 insertions, 4 deletions
diff --git a/src/shared/missing.h b/src/shared/missing.h index 3cd90e39bd..9f6177511e 100644 --- a/src/shared/missing.h +++ b/src/shared/missing.h @@ -57,6 +57,14 @@ static inline int getrandom(void *buffer, size_t count, unsigned flags) { } #endif +#ifndef GRND_NONBLOCK +#define GRND_NONBLOCK 0x0001 +#endif + +#ifndef GRND_RANDOM +#define GRND_RANDOM 0x0002 +#endif + #ifndef BTRFS_IOCTL_MAGIC #define BTRFS_IOCTL_MAGIC 0x94 #endif diff --git a/src/shared/util.c b/src/shared/util.c index 2080d77e05..d58b9f4bed 100644 --- a/src/shared/util.c +++ b/src/shared/util.c @@ -689,10 +689,17 @@ int dev_urandom(void *p, size_t n) { int r, fd; ssize_t k; - /* Use the syscall unless we know we don't have it, or when - * the requested size is too large for it. */ + /* Gathers some randomness from the kernel. This call will + * never block, and will always return some data from the + * kernel, regardless if the random pool is fully initialized + * or not. It thus makes no guarantee for the quality of the + * returned entropy, but is good enough for or usual usecases + * of seeding the hash functions for hashtable */ + + /* Use the getrandom() syscall unless we know we don't have + * it, or when the requested size is too large for it. */ if (have_syscall != 0 || (size_t) (int) n != n) { - r = getrandom(p, n, 0); + r = getrandom(p, n, GRND_NONBLOCK); if (r == (int) n) { have_syscall = true; return 0; @@ -700,8 +707,17 @@ int dev_urandom(void *p, size_t n) { if (r < 0) { if (errno == ENOSYS) - /* we lack the syscall, continue with reading from /dev/urandom */ + /* we lack the syscall, continue with + * reading from /dev/urandom */ have_syscall = false; + else if (errno == EAGAIN) + /* not enough entropy for now. Let's + * remember to use the syscall the + * next time, again, but also read + * from /dev/urandom for now, which + * doesn't care about the current + * amount of entropy. */ + have_syscall = true; else return -errno; } else |