netdev - Re: iproute2/nstat: Bug in displaying icmp stats

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Message-ID: <1417828247.15618.19.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Fri, 05 Dec 2014 17:10:47 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Vijay Subramanian <subramanian.vijay@...il.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: iproute2/nstat: Bug in displaying icmp stats

On Fri, 2014-12-05 at 15:35 -0800, Vijay Subramanian wrote:
> Hi,
> 
> I noticed nstat is displaying icmp stats incorrectly.
> 
> $ cat /proc/net/snmp | grep Icmp | head -2 | awk '{print $1 " " $2 " "
> $3 " " $4}'
> Icmp: InMsgs InErrors InCsumErrors
> Icmp: 215 0 0
> 
> $ nstat  -az | grep IcmpIn  | head -3
> IcmpInMsgs                      0                  0.0
> IcmpInErrors                    215                0.0
> IcmpInCsumErrors                0                  0.0
> 
> For example, as seen in /proc/net/snmp, IcmpInMsgs should be 215 but
> that value is assigned to IcmpInErrors.
> 
> The issue seems to be the way the values are populated.
> 
> $vim +209 misc/nstat.c
> -----x----
> 
>                        /* Trick to skip "dummy" trailing ICMP MIB in 2.4 */
> 
>                         if (strcmp(idbuf, "IcmpOutAddrMaskReps") == 0)
> 
>                                 idbuf[5] = 0;
> 
>                         else
> 
>                                 n = n->next;
> 
> -----x------
> 
> It seems "IcmpOutAddrMaskReps" is processed twice and values assigned
> are off by one.
> 
> Any idea what the code is doing for 2.4 kernel and how to fix this?
> 
> vijay

According to
git://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git

This was fixed in 2002 :

commit b838c6d5c189d03d3db56c2774de451cf041a39f
Author: Erik Schoenfelder <schoenfr@...ertner.de>
Date:   Sun Sep 29 03:56:52 2002 -0700

    net/ipv4/proc.c: Dont print dummy member of icmp_mib.

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 649620a..3f2dbcb 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -128,7 +128,7 @@ int snmp_get_info(char *buffer, char **start, off_t offset, int length)
        len += sprintf (buffer + len,
                "\nIcmp: InMsgs InErrors InDestUnreachs InTimeExcds InParmProbs InSrcQuenchs InRedirects InEchos InEchoReps InTimestamps InTimestampReps InAddrMasks InAddrMaskReps OutMsgs OutErrors OutDestUnreachs OutTimeExcds OutParmProbs OutSrcQuenchs OutRedirects OutEchos OutEchoReps OutTimestamps OutTimestampReps OutAddrMasks OutAddrMaskReps\n"
                  "Icmp:");
-       for (i=0; i<offsetof(struct icmp_mib, __pad)/sizeof(unsigned long); i++)
+       for (i=0; i<offsetof(struct icmp_mib, dummy)/sizeof(unsigned long); i++)
                len += sprintf(buffer+len, " %lu", fold_field((unsigned long*)icmp_statistics, sizeof(struct icmp_mib), i));
 
        len += sprintf (buffer + len,


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