Messages in this thread | | | Date | Wed, 10 Nov 1999 12:50:40 +0100 | From | Andi Kleen <> | Subject | Re: [2.2] Network Interface aliasing |
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On Tue, Nov 09, 1999 at 06:48:58PM +0100, Christopher E. Brown wrote: > On 9 Nov 1999, Andi Kleen wrote: > > > cbrown@denalics.net (Christopher E. Brown) writes: > > > > > Example, machines A,B,C all have the same IP on a lookback or > > > dummy interface. A load director/etc is currently routing all traffic > > > to the cluster IP to machine A. > > > > > > Should machine Bs interface get into PROMISC mode all packets > > > (even though they are sent to another MAC addr) will hit the IP layer, > > > and should the IP be found on a local interface, the machine will > > > respond. > > > > This is not true. When an interface in promisc mode receives a packet > > not destined at its MAC address and not a {broad,multi}cast it sets its type > > to PACKET_OTHERHOST. arp_rcv ignores such packets. IP does the same check. > > > > -Andi > > > Hmm, I have not rechecked this in 2.2.x, however with <= 2.0.x > this was not so.
Some early 2.0.x had a bug in this regard, but this was fixed years ago in the 2.0 series.
> > When an interface in promisc mode received a packet destined > for another mac, but to an IP the local host owns it would, as you > said, not arp. It *would* respond to the packets though. > > > To restate, it was assumed that anything with a locally owned > IP that made it to the IP layer was ours. Should one have an > interface in promisc, where we receive a packet with an IP we have but > destined to another MAC addr it would get passed to the IP layer, and > dealt with exactly as if it was sent to our MAC addr.
Except when you have a buggy driver (that does not set PACKET_OTHERHOST correctly -- normally all drivers do because the check is in the shared eth_type_trans function) this should not happen.
-Andi
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