Re: arp: SIOCSARP: No such device

Bernd Eckenfels (ecki@tapac.inka.de)
2 Jul 1996 19:22:03 GMT


really kuznet@ms2.inr.ac.ru (inr-linux-kernel@ms2.inr.ac.ru) wrote:
: : arp -i eth0 -D -s 157.158.29.94 eth0 pub
: ^ ^
: Is it misprint? Why twice?
Because the first option (dev eth0) will fill the device field and the
arguemtn (-D eth0) will fill the hardware-address). I dont wanted to asume
that the user intends it, I can think of:

arp -e eth0 -D -s 157.158.29.94 eth1 pub

in a situation where u have 2 network cards connected for fallback securtiy.
What I'm going to do will be:

arp -s 157.158.29.94 dev eth0 pub (==arp -i eth0 -s 157.158.29.94 pub) will set the
entry for eth0 with the address of eth0.
:
: : arp -s 157.158.29.94 xx:xx:Xx:xx:xx:xx pub
: : should work.
:
: It worked in 1.2 if you had one arpable interface. And it still works.
: We cannot make this thing backward compatible because
: old arp COULD NOT handle proxies for multiple arpable devices.

Thats not quitew correct. It could handle the situation of 2 ethernt cards
automatically, since it refused to answer requests on the routed device.
Therefore a lot of hosts with 2 interfaces (which is the most common case
anyway) will not work anymore. I dont think we should 'stretch' linux users
too far away from normal arp-syntax.

: This command published 157.158.29.94 on all arpable interfaces,

except the one interface the net was attached to, which will work fine with
2 nic.

: that was apparently wrong (two ethernets cannot have coincident adresses).

: New arp is FULLY compatible with old, when you have just one arpable
: interface, and it adds new functionality.

: : even if that looks very odd.
:
: Well, it would not look very odd if you omitted redundant device
: specification :-).

As I said before its not redundant, removing one of them will force arp to
guess about the users intention. But I will work around this with the above
solution, this syntx may remain valid.

: It is one of the places, where old functionality should be dropped as soon
: as possible. ARP and proxy ARP are absolutely different things,
: BSD made mess from them and we will have to teach people, that one
: command cannot delete both apples and boxes for oranges :-)

Well, but it used to do that :)

Greetings
Bernd

-- 
  (OO)      -- Bernd_Eckenfels@Wittumstrasse13.76646Bruchsal.de --
 ( .. )  ecki@lina.{inka.de,ka.sub.org}  http://home.pages.de/~eckes/
  o--o     *plush*  2048/93600EFD  eckes@irc  +4972573817  *plush*
(O____O)       If privacy is outlawed only Outlaws have privacy