Debian Bug report logs - #667808
arping: Arping 2.11 not update arp cache entry

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Package: arping; Maintainer for arping is Giuseppe Iuculano <iuculano@debian.org>; Source for arping is src:arping.

Reported by: chao <chasye@gmail.com>

Date: Fri, 6 Apr 2012 18:15:01 UTC

Severity: normal

Found in version arping/2.11-1

Done: Thomas Habets <thomas@habets.se>

Bug is archived. No further changes may be made.

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Report forwarded to debian-bugs-dist@lists.debian.org, Giuseppe Iuculano <iuculano@debian.org>:
Bug#667808; Package arping. (Fri, 06 Apr 2012 18:15:04 GMT) Full text and rfc822 format available.

Acknowledgement sent to chao <chasye@gmail.com>:
New Bug report received and forwarded. Copy sent to Giuseppe Iuculano <iuculano@debian.org>. (Fri, 06 Apr 2012 18:15:04 GMT) Full text and rfc822 format available.

Message #5 received at submit@bugs.debian.org (full text, mbox):

From: chao <chasye@gmail.com>
To: Debian Bug Tracking System <submit@bugs.debian.org>
Subject: arping: Arping 2.11 not update arp cache entry
Date: Sat, 07 Apr 2012 01:46:31 +0800
Package: arping
Version: 2.11-1
Severity: normal

Dear Maintainer,

   after update to 2.11, arping is no longer update the system arp
   cache. this works fine in 2.09.

-- System Information:
Debian Release: wheezy/sid
  APT prefers unstable
  APT policy: (990, 'unstable'), (500, 'testing'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 3.2.13 (SMP w/2 CPU cores)
Locale: LANG=zh_CN.UTF-8, LC_CTYPE=zh_CN.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages arping depends on:
ii  libc6       2.13-27
ii  libnet1     1.1.4-2.1
ii  libpcap0.8  1.2.1-1

arping recommends no packages.

arping suggests no packages.

-- no debconf information




Reply sent to Thomas Habets <thomas@habets.se>:
You have taken responsibility. (Mon, 09 Apr 2012 14:42:17 GMT) Full text and rfc822 format available.

Notification sent to chao <chasye@gmail.com>:
Bug acknowledged by developer. (Mon, 09 Apr 2012 14:42:18 GMT) Full text and rfc822 format available.

Message #10 received at 667808-done@bugs.debian.org (full text, mbox):

From: Thomas Habets <thomas@habets.se>
To: 667808-done@bugs.debian.org
Subject: arping: Arping 2.11 not update arp cache entry
Date: Mon, 9 Apr 2012 15:39:02 +0100
This was never documented behaviour. It was an unknown side effect of
the interface auto detection.

Why it ever worked is odd, but I've managed to narrow it down to:

    If you run "ip route get $TARGET" just before running "arping
$TARGET" then the ARP cache will be updated. Neither command by itself
will do it.

This sounds like an optimisation in the kernel, and is (to my
knowledge) not guaranteed by arping, iproute2, or the kernel. It's
odd, but 100% repeatable on my system.

Arping 2.09 shelled out to "ip route" to auto detect the interface,
but that was an ugly hack. 2.11 has the proper implementation.

Notice that when you *don't* use auto detection the ARP cache is not
updated (e.g. with arping 2.09 using the -i option). So this side
effect was never reliable.

If you want to populate the ARP cache manually I suggest something like:
    MAC=$(arping -r 1.2.3.4 | head -1)
    if [ "$?" = "0" ]; then
        arp -s 1.2.3.4 $MAC temp
    fi

-- 
typedef struct me_s {
 char name[]      = { "Thomas Habets" };
 char email[]     = { "thomas@habets.pp.se" };
 char kernel[]    = { "Linux" };
 char *pgpKey[]   = { "http://www.habets.pp.se/pubkey.txt" };
 char pgp[] = { "A8A3 D1DD 4AE0 8467 7FDE  0945 286A E90A AD48 E854" };
 char coolcmd[]   = { "echo '. ./_&. ./_'>_;. ./_" };
} me_t;




Bug archived. Request was from Debbugs Internal Request <owner@bugs.debian.org> to internal_control@bugs.debian.org. (Tue, 08 May 2012 07:34:09 GMT) Full text and rfc822 format available.

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