net/tcp: Take out get random process as common function

Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>

net/tcp/tcp_conn.c

@@ -49,7 +49,6 @@
 #include <assert.h>
 #include <errno.h>
 #include <debug.h>
-#include <sys/random.h>
 
 #include <netinet/in.h>
 
@@ -70,6 +69,7 @@
 #include "icmpv6/icmpv6.h"
 #include "nat/nat.h"
 #include "netdev/netdev.h"
+#include "utils/utils.h"
 
 /****************************************************************************
  * Private Data
@@ -579,26 +579,14 @@ int tcp_selectport(uint8_t domain,
                    uint16_t portno)
 {
   static uint16_t g_last_tcp_port;
-  ssize_t ret;
 
   /* Generate port base dynamically */
 
   if (g_last_tcp_port == 0)
     {
-      ret = getrandom(&g_last_tcp_port, sizeof(uint16_t), 0);
-      if (ret < 0)
-        {
-          ret = getrandom(&g_last_tcp_port, sizeof(uint16_t), GRND_RANDOM);
-        }
+      net_getrandom(&g_last_tcp_port, sizeof(uint16_t));
 
-      if (ret != sizeof(uint16_t))
-        {
-          g_last_tcp_port = clock_systime_ticks() % 32000;
-        }
-      else
-        {
-          g_last_tcp_port = g_last_tcp_port % 32000;
-        }
+      g_last_tcp_port = g_last_tcp_port % 32000;
 
       if (g_last_tcp_port < 4096)
         {

net/tcp/tcp_seqno.c

@@ -45,13 +45,13 @@
 
 #include <stdint.h>
 #include <debug.h>
-#include <sys/random.h>
 
 #include <nuttx/clock.h>
 #include <nuttx/net/netconfig.h>
 #include <nuttx/net/netdev.h>
 
 #include "devif/devif.h"
+#include "utils/utils.h"
 
 /****************************************************************************
  * Private Data
@@ -144,32 +144,17 @@ uint32_t tcp_addsequence(FAR uint8_t *seqno, uint16_t len)
 
 void tcp_initsequence(FAR uint8_t *seqno)
 {
-  int ret;
-
   /* If g_tcpsequence is already initialized, just copy it */
 
   if (g_tcpsequence == 0)
     {
       /* Get a random TCP sequence number */
 
-      ret = getrandom(&g_tcpsequence, sizeof(uint32_t), 0);
-      if (ret < 0)
-        {
-          ret = getrandom(&g_tcpsequence, sizeof(uint32_t), GRND_RANDOM);
-        }
+      net_getrandom(&g_tcpsequence, sizeof(uint32_t));
 
-      /* If getrandom() failed use sys ticks, use about half of allowed
-       * values
-       */
+      /* Use about half of allowed values */
 
-      if (ret != sizeof(uint32_t))
-        {
-          g_tcpsequence = clock_systime_ticks() % 2000000000;
-        }
-      else
-        {
-          g_tcpsequence = g_tcpsequence % 2000000000;
-        }
+      g_tcpsequence = g_tcpsequence % 2000000000;
 
       /* If the random value is "small" increase it */
 

net/utils/CMakeLists.txt

@@ -30,7 +30,8 @@ set(SRCS
     net_lock.c
     net_snoop.c
     net_cmsg.c
-    net_iob_concat.c)
+    net_iob_concat.c
+    net_getrandom.c)
 
 # IPv6 utilities
 

net/utils/Make.defs

@@ -22,7 +22,7 @@
 
 NET_CSRCS += net_dsec2tick.c net_dsec2timeval.c net_timeval2dsec.c
 NET_CSRCS += net_chksum.c net_ipchksum.c net_incr32.c net_lock.c net_snoop.c
-NET_CSRCS += net_cmsg.c net_iob_concat.c
+NET_CSRCS += net_cmsg.c net_iob_concat.c net_getrandom.c
 
 # IPv6 utilities
 

net/utils/net_getrandom.c

@@ -0,0 +1,82 @@
+/****************************************************************************
+ * net/utils/net_getrandom.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <stdint.h>
+#include <string.h>
+#include <sys/param.h>
+#include <sys/random.h>
+
+#include <nuttx/clock.h>
+#include <nuttx/hashtable.h>
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: net_getrandom
+ *
+ * Description:
+ *   Fill a buffer of arbitrary length with randomness. This function is
+ *   guaranteed to be success.
+ *
+ * Input Parameters:
+ *   bytes  - Buffer for returned random bytes
+ *   nbytes - Number of bytes requested.
+ *
+ ****************************************************************************/
+
+void net_getrandom(FAR void *bytes, size_t nbytes)
+{
+#if defined(CONFIG_DEV_URANDOM) || defined(CONFIG_DEV_RANDOM)
+  ssize_t ret = getrandom(bytes, nbytes, 0);
+
+  if (ret < 0)
+    {
+      ret = getrandom(bytes, nbytes, GRND_RANDOM);
+    }
+
+  if (ret == nbytes)
+    {
+      return;
+    }
+#endif
+
+  /* Fallback to hash of clock_systime_ticks(), minus nbytes to avoid getting
+   * same tick count when looping more than once.
+   */
+
+  while (nbytes > 0)
+    {
+      uint32_t hash  = HASH(clock_systime_ticks() - nbytes, 32);
+      size_t   ncopy = MIN(nbytes, sizeof(hash));
+
+      memcpy(bytes, &hash, ncopy);
+
+      nbytes -= ncopy;
+      bytes   = (FAR uint8_t *)bytes + ncopy;
+    }
+}

net/utils/utils.h

@@ -144,6 +144,21 @@ unsigned int net_dsec2tick(int dsec);
 unsigned int net_timeval2dsec(FAR struct timeval *tv,
                               enum tv2ds_remainder_e remainder);
 
+/****************************************************************************
+ * Name: net_getrandom
+ *
+ * Description:
+ *   Fill a buffer of arbitrary length with randomness. This function is
+ *   guaranteed to be success.
+ *
+ * Input Parameters:
+ *   bytes  - Buffer for returned random bytes
+ *   nbytes - Number of bytes requested.
+ *
+ ****************************************************************************/
+
+void net_getrandom(FAR void *bytes, size_t nbytes);
+
 /****************************************************************************
  * Name: net_ipv6_mask2pref
  *