mlx5: Use getrandom() to seed a strong PRNG

Add get_random() API to get random data with static seed, which is
generated with getrandom() for better randomness.

Signed-off-by: Mark Zhang <[email protected]>
Signed-off-by: Yishai Hadas <[email protected]>

CMakeLists.txt

@@ -575,6 +575,13 @@ if (NOT NL_KIND EQUAL 0)
 endif()
 RDMA_AddOptCFlag(CMAKE_C_FLAGS HAVE_C_WREDUNDANT_DECLS "-Wredundant-decls")
 
+# Support of getrandom() was added to glibc in version 2.25
+CHECK_C_SOURCE_COMPILES("
+ #include <sys/random.h>
+ int main(int argc,const char *argv[]) {char buf[64]; return getrandom(buf, 64, GRND_NONBLOCK);}"
+ HAVE_GLIBC_GETRANDOM)
+RDMA_DoFixup("${HAVE_GLIBC_GETRANDOM}" "sys/random.h")
+
 #-------------------------
 # Build Prep
 # Write out a git ignore file to the build directory if it isn't the source

buildlib/fixup-include/sys-random.h

@@ -0,0 +1,13 @@
+#ifndef _FIXUP_SYS_RANDOM_H
+#define _FIXUP_SYS_RANDOM_H
+
+#include <sys/types.h>
+
+/* Flags for use with getrandom. */
+#define GRND_NONBLOCK 0x01
+
+static inline ssize_t getrandom(void *buf, size_t buflen, unsigned int flags)
+{
+ return -1;
+}
+#endif

providers/mlx5/verbs.c

@@ -48,6 +48,7 @@
 
 #include <util/compiler.h>
 #include <util/mmio.h>
+#include <util/util.h>
 #include <rdma/ib_user_ioctl_cmds.h>
 #include <rdma/mlx5_user_ioctl_cmds.h>
 #include <infiniband/cmd_write.h>
@@ -2905,8 +2906,8 @@ static void mlx5_ah_set_udp_sport(struct mlx5_ah *ah,
  if (fl)
  sport = ibv_flow_label_to_udp_sport(fl);
  else
- sport = rand() % (IB_ROCE_UDP_ENCAP_VALID_PORT_MAX + 1
-  - IB_ROCE_UDP_ENCAP_VALID_PORT_MIN)
+ sport = get_random() % (IB_ROCE_UDP_ENCAP_VALID_PORT_MAX + 1
+  - IB_ROCE_UDP_ENCAP_VALID_PORT_MIN)
  + IB_ROCE_UDP_ENCAP_VALID_PORT_MIN;
 
  ah->av.rlid = htobe16(sport);

util/util.c

@@ -1,4 +1,8 @@
 /* GPLv2 or OpenIB.org BSD (MIT) See COPYING file */
+#include <stdlib.h>
+#include <sys/random.h>
+#include <sys/types.h>
+#include <time.h>
 #include <util/util.h>
 #include <unistd.h>
 #include <fcntl.h>
@@ -20,3 +24,24 @@ int set_fd_nonblock(int fd, bool nonblock)
  return -1;
  return 0;
 }
+
+#ifndef GRND_INSECURE
+#define GRND_INSECURE 0x0004
+#endif
+unsigned int get_random(void)
+{
+ static unsigned int seed;
+ ssize_t sz;
+
+ if (!seed) {
+ sz = getrandom(&seed, sizeof(seed),
+ GRND_NONBLOCK | GRND_INSECURE);
+ if (sz < 0)
+ sz = getrandom(&seed, sizeof(seed), GRND_NONBLOCK);
+
+ if (sz != sizeof(seed))
+ seed = time(NULL);
+ }
+
+ return rand_r(&seed);
+}

util/util.h

@@ -42,4 +42,5 @@ int set_fd_nonblock(int fd, bool nonblock);
 
 int open_cdev(const char *devname_hint, dev_t cdev);
 
+unsigned int get_random(void);
 #endif