[2.6.0, pktgen] divide-by-zero

[2.6.0, pktgen] divide-by-zero

[Lennert Buytenhek]

Hi,

When generating packets with pktgen with count=10, I get a divide-by-zero
oops in inject().

Line 273 in net/core/pktgen.c seems unsafe:
	__u64 pps = (__u32)(info->sofar * 1000) / ((__u32)(total) / 1000);

What if total < 1000 ?


cheers,
Lennert

[PATCH] Re: [2.6.0, pktgen] divide-by-zero

[Jörn Engel]

On Wed, 31 December 2003 06:13:16 -0500, Lennert Buytenhek wrote:
> 
> When generating packets with pktgen with count=10, I get a divide-by-zero
> oops in inject().
> 
> Line 273 in net/core/pktgen.c seems unsafe:
> 	__u64 pps = (__u32)(info->sofar * 1000) / ((__u32)(total) / 1000);
> 
> What if total < 1000 ?

Since noone else seemed to care, try this patch.  Against -test11,
yeah, I'm lazy again.

Jörn

-- 
Time? What's that? Time is only worth what you do with it.
-- Theo de Raadt

--- old/net/core/pktgen.c	2003-11-26 21:44:47.000000000 +0100
+++ new/net/core/pktgen.c	2004-01-18 16:27:10.000000000 +0100
@@ -720,7 +720,9 @@
 
 	{
 		char *p = info->result;
-		__u64 pps = (__u32)(info->sofar * 1000) / ((__u32)(total) / 1000);
+		__u32 safe_total = (__u32)(total) / 1000;
+		safe_total += 1 - (!!safe_total); /* avoid divide-by-zero */
+		__u64 pps = (__u32)(info->sofar * 1000) / safe_total;
 		__u64 bps = pps * 8 * (info->pkt_size + 4); /* take 32bit ethernet CRC into account */
 		p += sprintf(p, "OK: %llu(c%llu+d%llu) usec, %llu (%dbyte,%dfrags) %llupps %lluMb/sec (%llubps)  errors: %llu",
 			     (unsigned long long) total,

[PATCH] Re: [2.6.0, pktgen] divide-by-zero

[Robert Olsson]

Hello!

Jörn Engel writes:
 > On Wed, 31 December 2003 06:13:16 -0500, Lennert Buytenhek wrote:
 > > 
 > > When generating packets with pktgen with count=10, I get a divide-by-zero
 > > oops in inject().
 > > 
 > > Line 273 in net/core/pktgen.c seems unsafe:
 > > 	__u64 pps = (__u32)(info->sofar * 1000) / ((__u32)(total) / 1000);
 > > 
 > > What if total < 1000 ?
 > 
 > Since noone else seemed to care, try this patch.  Against -test11,
 > yeah, I'm lazy again.


 Sorry I missed Lennerts original posting... 

 I suggest the patch below to get integer precision at very short time 
 intervals too.


--- linux-2.6.1/net/core/pktgen.c.orig	Sun Jan 18 21:56:56 2004
+++ linux-2.6.1/net/core/pktgen.c	Sun Jan 18 23:15:03 2004
@@ -88,7 +88,7 @@
 #define cycles()	((u32)get_cycles())
 
 
-#define VERSION "pktgen version 1.3"
+#define VERSION "pktgen version 1.31"
 static char version[] __initdata = 
   "pktgen.c: v1.3: Packet Generator for packet performance testing.\n";
 
@@ -720,8 +720,18 @@
 
 	{
 		char *p = info->result;
-		__u64 pps = (__u32)(info->sofar * 1000) / ((__u32)(total) / 1000);
-		__u64 bps = pps * 8 * (info->pkt_size + 4); /* take 32bit ethernet CRC into account */
+		__u64 bps, pps = 0;
+
+		if (total > 1000)
+			pps = (__u32)(info->sofar * 1000) / ((__u32)(total) / 1000);
+		else if(total > 100)
+			pps = (__u32)(info->sofar * 10000) / ((__u32)(total) / 100);
+		else if(total > 10)
+			pps = (__u32)(info->sofar * 100000) / ((__u32)(total) / 10);
+		else if(total > 1)
+			pps = (__u32)(info->sofar * 1000000) / (__u32)total;
+
+		bps = pps * 8 * (info->pkt_size + 4); /* take 32bit ethernet CRC into account */
 		p += sprintf(p, "OK: %llu(c%llu+d%llu) usec, %llu (%dbyte,%dfrags) %llupps %lluMb/sec (%llubps)  errors: %llu",
 			     (unsigned long long) total,
 			     (unsigned long long) (total - idle),



Cheers.
						--ro

Re: [PATCH] Re: [2.6.0, pktgen] divide-by-zero

[David S. Miller]

On Mon, 19 Jan 2004 00:15:41 +0100
Robert Olsson <Robert.Olsson@data.slu.se> wrote:

>  I suggest the patch below to get integer precision at very short time 
>  intervals too.

Applied, thanks Robert.