Question about bridging code

[Doug Ambrisko]

kw3wong at engmail.uwaterloo.ca writes:
[ Charset ISO-8859-1 unsupported, converting... ]
| Hi Luigi,
| 
| Thanks for response, the vmnet/tap stuff sounds like neat stuff. After reading 
| the description of tap (from the vtun site), the system seems to make a lot of 
| sense. However, I'm not sure how vmnet comes into play here - what purpose does 
| it serve, shouldn't I just be able to read from the /dev/tap0 and bridge 
| between tap0 and fxp0?
| 
| I tried writing a simple program to use tap. Basically, I have the bridge setup 
| as such
| 
|     net.link.ether.bridge_cfg: fxp0:0,tap0:0 tap1:1 bge0:1
| 
| And I ran this quick test program that I wrote:

How about a simpler one 
	echo hello > /dev/vmnet0
	cat /dev/vmnet0

| Unfortunately, it doesn't work, it only gets a read event when I make changes 
| to the tap interface via ifconfig. I guess I don't fully understand how 
| the /dev/tapN interface works, can you (or anybody who also know) point out 
| what I'm doing wrong? Thanks again!

I use vmnet since it stays persistant across opens and closes.  So the above
would have issues with tap.  For bridging you probably need (for -stable):

Index: if_tap.c
===================================================================
RCS file: /cvs/src/sys/net/if_tap.c,v
retrieving revision 1.3.2.3
diff -c -r1.3.2.3 if_tap.c
*** if_tap.c	14 Apr 2002 21:41:48 -0000	1.3.2.3
--- if_tap.c	11 Jul 2003 01:57:28 -0000
***************
*** 426,431 ****
--- 426,432 ----
  			return (dummy);
  
  		case SIOCSIFFLAGS: /* XXX -- just like vmnet does */
+ 			tapifinit(tp);
  		case SIOCADDMULTI:
  		case SIOCDELMULTI:
  		break;

or you lose stuff.

I have a user-land packet translator that opens a couple of vmnet devices
and then bridge those nodes to the HW I want.  It works well.

Initially I used tap but since every open and closed created a new iface
instance the world started to go bad after a lot of stops and starts
of the program.

Doug A.