Re: kern/40139: bridge(4) does not transmit DHCP replies to tap(4)

[Quentin Garnier <cube%cubidou.net@localhost>]

The following reply was made to PR kern/40139; it has been noted by GNATS.

From: Quentin Garnier <cube%cubidou.net@localhost>
To: David Young <dyoung%pobox.com@localhost>, gnats-bugs%NetBSD.org@localhost,
        Taylor R Campbell <campbell%mumble.net@localhost>
Cc: 
Subject: Re: kern/40139: bridge(4) does not transmit DHCP replies to tap(4)
Date: Sat, 21 Mar 2009 21:59:54 +0100

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 On Sat, Mar 21, 2009 at 03:50:54PM -0500, David Young wrote:
 > On Sat, Mar 21, 2009 at 07:10:06PM +0000, Quentin Garnier wrote:
 > > The following reply was made to PR kern/40139; it has been noted by GNA=
 TS.
 > >=20
 > > From: Quentin Garnier <cube%cubidou.net@localhost>
 > > To: gnats-bugs%NetBSD.org@localhost
 > > Cc:=20
 > > Subject: Re: kern/40139: bridge(4) does not transmit DHCP replies to ta=
 p(4)
 > > Date: Sat, 21 Mar 2009 20:09:51 +0100
 > >=20
 > >  On Tue, Dec 09, 2008 at 09:00:01AM +0000, Taylor R Campbell wrote:
 > >  > >Number:         40139
 > >  > >Category:       kern
 > >  > >Synopsis:       bridge(4) does not transmit DHCP replies to tap(4)
 > > =20
 > >  It's not an issue with tap(4) (the same happens if you replace it with
 > >  any other Ethernet interface).  If you run ktrace on dhclient, you'll
 > >  see that it receives the packet on its udp socket for port 68.  I don't
 > >  know why it rejects it though.
 >=20
 > dhclient does not log any complaints about those packets?
 
 No.  ktrace shows it going almost directly back to select(2) after the
 recvfrom(2).
 
 > Some NICs pass the FCS to the host in promiscuous mode, but not
 > otherwise.  Their drivers neither apply M_HASFCS nor trim the ethernet
 > checksum from the input mbufs when the NIC is in promiscuous. bridge(4)
 > may conceal or compound the defect in those input mbufs.
 
 Yeah, I have machines on which dhclient complain about getting 4 extra
 bytes.  It's not fatal though.
 
 --=20
 Quentin Garnier - cube%cubidou.net@localhost - cube%NetBSD.org@localhost
 "See the look on my face from staying too long in one place
 [...] every time the morning breaks I know I'm closer to falling"
 KT Tunstall, Saving My Face, Drastic Fantastic, 2007.
 
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