From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Leckey Subject: Net device queries. Date: Wed, 06 Nov 2002 21:11:45 +1100 Sender: netdev-bounce@oss.sgi.com Message-ID: <3DC8EAE1.80001@tpg.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: To: netdev@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org I've been coding an ethernet driver for some new hardware we're developing and while it's working, there are a few issues I'm still unsure of. I couldn't find any archives for this list, so I'm suspecting I'm going to cover a lot of 'old ground'. Firstly some background. With these cards I can have up to 25 point to point connections (to the same destination machine, or 25 destination machines). I have almost total control of what goes out on the wire, so I've chosen a minimal header that contains the type (passed in to hard_header) and a 16 bit field that contains misc other information. So, 32 bits, plus the data. The hardware provides things like length, and CRC checking. Currently I'm setting dev->hard_header_len to 4. The part that concerns me is what I set dev->type, dev->addr_len and dev->flags to. We don't technically have a hardware address so I set dev->addr_len to 0. I set dev->type to ARPHRD_VOID, simply because I'm not sure what the consequences of setting it to anything else are. I set dev->flags to IFF_POINTOPOINT | IFF_NOARP This appears to all work correctly, however both ifconfig and tcpdump aren't really happy. TCPDUMP doesn't know what to do with the ARPHRD_VOID and drops to 'raw' mode, so it still does what I need, even if it prints an annoying message for each packet. ifconfig isn't sure what to do about the HWaddr. For instance, this is the ifconfig for one of the links: hssl0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:192.168.2.1 P-t-P:192.168.2.2 Mask:255.255.255.255 UP POINTOPOINT RUNNING NOARP MTU:1500 Metric:1 RX packets:3509748 errors:459 dropped:0 overruns:0 frame:363 TX packets:3013210 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:368907445 (351.8 Mb) TX bytes:266074976 (253.7 Mb) Any thoughts, comments or otherwise on what I've done, or what I /should/ be doing would be appreciated as I'm still not fully across how the networking stuff works. Bill -- Bill Leckey - Senior Software Design Engineer TPG Research and Development Ph: +61 2 62851711 Fax: +61 2 62853939