The following reply was made to PR kern/29126; it has been noted by GNATS.

From: john heasley <heas@shrubbery.net>
To: gnats-bugs@netbsd.org
Cc: kern-bug-people@netbsd.org, gnats-admin@netbsd.org,
	netbsd-bugs@netbsd.org
Subject: Re: bin/29126: tcpdump leads to packet loss
Date: Thu, 27 Jan 2005 11:21:23 -0800

 Thu, Jan 27, 2005 at 05:49:01PM +0000, Kimmo Suominen:
 >  I can also reproduce this with fxp on NetBSD 2.99.12.  As you can see
 >  from my previous messages, the problem does not exist with fxp on 1.6B.
 >  
 >  So, the list of problem NIC's drivers: ex, fxp, gsip, tlp
 >  
 >  Christos & Manuel:  which drivers are you using that do not exhibit
 >  this problem at all?
 
 Most likely any driver that does not handle SIOCSIFFLAGS itself.  ether_ioctl
 does:
         case SIOCSIFFLAGS:
                 	....
                 } else if ((ifp->if_flags & IFF_UP) != 0) {
                         /*
                          * Reset the interface to pick up changes in any other
                          * flags that affect the hardware state.
                          */
                         error = (*ifp->if_init)(ifp);
                 }
 
 for most drivers that i've looked at, the first thing the init function
 does is stop the chip and reset it.  hme deals with it like this:
 
         case SIOCSIFFLAGS:
 			...
                 } else if ((ifp->if_flags & IFF_UP) != 0) {
                         /*
                          * If setting debug or promiscuous mode, do not reset
                          * the chip; for everything else, call hme_init()
                          * which will trigger a reset.
                          */
 #define RESETIGN (IFF_CANTCHANGE | IFF_DEBUG)
                         if (ifp->if_flags == sc->sc_if_flags)
                                 break;
                         if ((ifp->if_flags & (~RESETIGN))
                             == (sc->sc_if_flags & (~RESETIGN)))
                                 hme_setladrf(sc);
                         else
                                 hme_init(sc);
 #undef RESETIGN
                 }