Fix prandom_u32{,_max} => get_random_u32{,_below}

For backwards compatiblity this gets pretty nasty.  This should work
fairly well.

Signed-off-by: Jaco Kroon <jaco@uls.co.za>

Author: jkroonza

compat.h

@@ -108,17 +108,34 @@ union nf_inet_addr {
 # define time_is_after_jiffies(a) time_before(jiffies, a)
 #endif
 
-#if LINUX_VERSION_CODE < KERNEL_VERSION(3,14,0)
-# if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,19)
-#  define prandom_u32 get_random_int
-# elif LINUX_VERSION_CODE < KERNEL_VERSION(3,8,0)
-#  define prandom_u32 random32
+#ifndef HAVE_GET_RANDOM_U32
+# ifdef HAVE_PRANDOM_U32
+#  ifdef HAVE_PRANDOM_H
+#   include <linux/prandom.h>
+#  endif
+static inline u32 get_random_u32() {
+	return prandom_u32();
+}
+# else
+#  pragma error Need fallback for get_random_u32
+# endif
 #endif
-#define prandom_u32_max compat_prandom_u32_max
-static inline u32 prandom_u32_max(u32 ep_ro)
+
+#ifndef HAVE_GET_RANDOM_U32_BELOW
+# ifdef HAVE_PRANDOM_U32_MAX
+#  ifdef HAVE_PRANDOM_H
+#   include <linux/prandom.h>
+#  endif
+static inline u32 get_random_u32_below(u32 ep_ro)
 {
-	return (u32)(((u64) prandom_u32() * ep_ro) >> 32);
+	return prandom_u32_max(ep_ro);
 }
+# else
+static inline u32 get_random_u32_below(u32 ep_ro)
+{
+	return (u32)(((u64) get_random_u32() * ep_ro) >> 32);
+}
+# endif
 #endif
 
 #ifndef min_not_zero

gen_compat_def

@@ -1,4 +1,4 @@
-#!/bin/bash -efu
+#!/bin/bash -fu
 # SPDX-License-Identifier: GPL-2.0-only
 #
 # Generate defines based on kernel having some symbols declared.
@@ -21,7 +21,7 @@ WD=cc-test-build
 mkdir -p $WD
 cd ./$WD || fatal "cannot cd to $WD"
 
-# args: HAVE_SUMBOL symbol include
+# args: HAVE_SYMBOL symbol [include] [success] [failure]
 kbuild_test_compile() {
   local cmd
 
@@ -30,14 +30,15 @@ kbuild_test_compile() {
   cmd="make -s -B -C $KDIR M=$PWD modules"
   echo "$cmd" > log
   if $cmd >> log 2>&1; then
-    echo " declared" >&2
-    [ "$2" ] && echo "// $2 is declared ${3:+in <$3>}"
+    echo " ${4-declared}" >&2
+    [ "$2" ] && echo "// $2 ${4-is declared}${3:+ in <$3>}"
     echo "#define HAVE_$1"
     echo
+    return 0
   else
-    echo " undeclared" >&2
+    echo " ${5-undeclared}" >&2
     echo "#undef HAVE_$1"
-    echo "// ${2:-symbol} is undeclared${3:+ in <$3>}. Compile:"
+    echo "// ${2:-symbol} ${5-is undeclared}${3:+ in <$3>}. Compile:"
     sed  "s/^/\/\/   /" test.c
     echo "// Output:"
     sed  "s/^/\/\/   /" log
@@ -56,6 +57,7 @@ kbuild_test_compile() {
       echo >&2
       exit 3
     fi
+    return 1
   fi
 }
 
@@ -105,6 +107,22 @@ kbuild_test_member() {
 	typeof(((struct $structname*)0)->$member) test;
 	EOF
 }
+
+# Test that a header is available/exist
+kbuild_test_header() {
+  echo -n "Test header $*" >&2
+  structname=${1%.*}
+  member=${1#*.}
+  def=${1^^}
+  def=${def##*/}
+  def=${def//./_}
+  kbuild_test_compile $def "header $1" "" "exists" "doesn't exist" <<-EOF
+	#include <linux/module.h>
+	#include <$1>
+	MODULE_LICENSE("GPL");
+	EOF
+}
+
 echo "// Autogenerated for $KDIR"
 echo
 
@@ -136,6 +154,20 @@ kbuild_test_member nf_ct_event_notifier.ct_event net/netfilter/nf_conntrack_ecac
 kbuild_test_symbol register_sysctl_paths linux/sysctl.h
 # If we have strscpy, we can use that (more optimal compared to strlcpy).
 kbuild_test_symbol sized_strscpy linux/string.h
+# Do we have get_random_u32_below
+kbuild_test_symbol get_random_u32_below linux/random.h
+# Do we have get_random_u32
+kbuild_test_symbol get_random_u32 linux/random.h
+
+# prandom functions moved from random.h to prandom.h recentish.
+# We use these for fallback for the above only.
+if kbuild_test_header linux/prandom.h; then
+  prand_h=linux/prandom.h
+else
+  prand_h=linux/random.h
+fi
+kbuild_test_symbol prandom_u32 $prand_h
+kbuild_test_symbol prandom_u32_max $prand_h
 
 echo "// End of compat_def.h"
 

ipt_NETFLOW.c

@@ -4460,7 +4460,7 @@ static int netflow_scan_and_export(const int flush)
 				val = nf->sampler_count % interval;
 				break;
 			case SAMPLER_RANDOM:
-				val = prandom_u32_max(interval);
+				val = get_random_u32_below(interval);
 				break;
 			default: /* SAMPLER_HASH */
 				val = 0;
@@ -5717,12 +5717,12 @@ static int __init ipt_netflow_init(void)
 	}
 	parse_sampler(sampler);
 #ifdef SAMPLING_HASH
-	hash_seed = prandom_u32();
+	hash_seed = get_random_u32();
 #endif
 #endif
 
 #ifdef ENABLE_RANDOM_TEMPLATE_IDS
-	template_ids = FLOWSET_DATA_FIRST | prandom_u32_max(0x00010000);
+	template_ids = FLOWSET_DATA_FIRST | get_random_u32_below(0x00010000);
 #endif
 
 #ifdef SNMP_RULES