----- Original Message ----- From: "Remco Post" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Friday, June 06, 2003 4:15 AM Subject: Re: where the ip packet is discarded?
> On 6 Jun 2003 09:26:00 +0800 > "forge" <[EMAIL PROTECTED]> wrote: > > > Hello, everyone > > > > I have a hub and several computers connected to it, e.g. > > > > HUB > > |----B > > A ---| > > | > > |----C > > > > > > Now, when A sends a packet to B, C will also receive the packet > > on datalink layer. > > But the packet is discarded before it reaches ip_input(). > > I think it's discarded in datalink layer because the MAC address > > is not matched. > > > > Now I tried to find the function discarding the unmatched packets, > > but I failed because I'm not familiar to the code in datalink layer. > > > > Usually, the ethernetcard takes care of that. This has a hardware filter > that is programmed with the mac from a config rom on the NIC. That is why > you can set your mac-address. If you subscribe to a ethernet multicast > address (rarely used) the crc of the ethernet multicast is matched in a > smart filter. A NIC can be set to promiscues mode to accept all packets, in > that case, the IP layer has to do all the filtering... Does this means that a multi-homed FreeBSD will start to route packets on its connected network if its NICs were in promiscues mode? I don't believe so. I think only the BPF devices are affected, not ip_input. > > > I use FreeBSD 4.5 system and can anyone give me some advice? > > > > Much thanks. > > Forge > > > > > -- > Met vriendelijke groeten, > > Remco Post > > SARA - Stichting Academisch Rekencentrum Amsterdam http://www.sara.nl > High Performance Computing Tel. +31 20 592 8008 Fax. +31 20 668 3167 > > "I really didn't foresee the Internet. But then, neither did the computer > industry. Not that that tells us very much of course - the computer industry > didn't even foresee that the century was going to end." -- Douglas Adams >
