[Click] minor bug report with NetBSD

Wed May 24 14:44:29 EDT 2006

Eddie,

Thanks for the help with the kerneltun/tap code. Your re-write will
probably fix the ARP issues with the kerneltap driver in the Linux
code.

I'll take care of the NetBSD porting and send in a patch by tomorrow:

1. I had already patched the kerneltap.cc code to accept all kinds of
Ethernet packets (instead of just IP) by re-writing KernelTap::push()
to use ethertype = ((const click_ether *) p->data())->ether_type.
Those are similar to your changes to kerneltun.cc, and work in NetBSD
just fine.

2. The NetBSD tap driver is different from the NetBSD tun driver in
subtle ways: (From the man page) an open() call on /dev/tunN, will
also create a network interface with the same unit number of that
device if it doesn't exists yet. On the other hand, with the NetBSD
tap, you need to use the cloning device /dev/tap to create an
interface, and then use the TAPGIFNAME ioctl to fetch the name of the
device that's been created. Thus, the code in KernelTap::alloc_tun()
needs to be hacked a bit.

3. Also, AFAIK, the ifconfig/ioctl interface in NetBSD doesn't
(always) allow Ethernet addresses to be set. Fortunately, the tap
device has a sysctl interface to set the hardware address.

4. Finally, as we discussed earlier, the Ethernet frames spit out by
the NetBSD tap driver don't have a 4 byte af_family field.

I've patched the kerneltap.cc code to handle all these cases. It works
on my NetBSD setup -  let me do a little more testing before I send in
the patch.

Vivek

Vivek

On 5/24/06, Eddie Kohler <kohler at cs.ucla.edu> wrote:
> Hi Vivek,
>
> I've updated the KernelTap and KernelTun code to actually work (verified on
> Linux and FreeBSD), and unified the KernelTap and KernelTun code paths.  Have
> a look at elements/userlevel/kerneltun.cc.  Hopefully it will be easier to
> make this work on NetBSD.  (Or maybe, gosh, it'll work out of the box.)
>
> Eddie
>
>
> Vivek raghunathan wrote:
> > Eddie and all,
> >
> > Another question regarding the KernelTap. It seems like you cannot
> > push ARP packets to it, because the code in push(int, Packet *) infers
> > the Ethernet protocol field from the version information in the IP
> > header of the packet (IPv4/IPv6) and prepends it to the packet before
> > writing it to the tap device. It seems like the reason you do this is
> > that the universal tun/tap driver in Linux expects this field
> > prepended to the Ethernet frames written from userspace.
> >
> > Since this information is also in the Ethernet header, why can't we
> > extract it from there? That would make the tap virtual Ethernet device
> > agnostic to which higher layer protocol it is transporting. Or am I
> > missing something fundamental here?
> >
> > Vivek
> >
> >
> >
> >
> >
> > On 5/20/06, Vivek raghunathan <vivek.raghunathan at gmail.com> wrote:
> >> Eddie,
> >>
> >> I am currently interning at BBN with the Internetworking Research
> >> group there. It seems like the KernelTap and KernelTun devices need to
> >> be patched for NetBSD support ... I'll send you the patch as soon as
> >> we are done.
> >>
> >> Vivek
> >>
> >>
> >> On 5/19/06, Eddie Kohler <kohler at cs.ucla.edu> wrote:
> >> > Hi Vivek,
> >> >
> >> > It looks like KernelTun needs to be altered to work on NetBSD.  If
> >> you look at
> >> > the source, in elements/userlevel/kerneltun.{cc,hh}, you'll see that
> >> there are
> >> > several cases built in to the code, for Apple, FreeBSD, Linux
> >> (ethertap and
> >> > universal tun), OpenBSD.  Would you like to provide us with a patch
> >> for NetBSD
> >> > support??  We'd love it...
> >> >
> >> > E
> >> >
> >> >
> >> > Vivek raghunathan wrote:
> >> > > Eddie,
> >> > >
> >> > > SIOCSIFMTU is supported. NetBSD's tun device has a max mtu of
> >> TUNMTU =
> >> > > 1500.
> >> > >
> >> > > Another minor bug in the userlevel/kerneltun.cc file: it seems like
> >> > > NetBSD does not preprend a 4 byte address family field in front of
> >> the
> >> > > IP header. Thus, in elements/kerneltun.cc:348 or so, the af field is
> >> > > in fact the first 4 bytes of the IP header, resulting in  (af !=
> >> > > AF_INET && af != AF_INET6) codepath being entered and userspace does
> >> > > not receive the packets.
> >> > >
> >> > > Vivek
> >> > >
> >> > >
> >> > > On 5/17/06, Eddie Kohler <kohler at cs.ucla.edu> wrote:
> >> > >> Hi Vivek,
> >> > >>
> >> > >> So the point of SIOCSIFMTU is to set the MTU.  Are you saying the
> >> > >> NetBSD's tun
> >> > >> device CANNOT have an MTU larger than 1500?  Or that the SIOCSIFMTU
> >> > >> ioctl is
> >> > >> not supported?
> >> > >>
> >> > >> Eddie
> >> > >>
> >> > >>
> >> > >> Vivek raghunathan wrote:
> >> > >> > The mail was partially sent.
> >> > >> >
> >> > >> > With NetBSD, the conf/test-tun.click script doesn't work.
> >> > >> >
> >> > >> > bash-3.1$ sudo userlevel/click conf/test-tun.click
> >> > >> > conf/test-tun.click:19: While initializing 'tun :: KernelTun':
> >> > >> >   SIOCSIFMTU failed: Invalid argument
> >> > >> > Router could not be initialized!
> >> > >> >
> >> > >> > Reason:
> >> > >> > minor bug in userlevel/kerneltun.cc:
> >> > >> >>     268 ifr.ifr_mtu = _mtu_out;
> >> > >> >>     269     if (ioctl(s, SIOCSIFMTU, &ifr) != 0)
> >> > >> >>     270         return errh->error("SIOCSIFMTU failed: %s",
> >> > >> strerror(errno));
> >> > >> >
> >> > >> > NetBSD's tun device has a default MTU of 1500. _mtu_out is set
> >> to 2048
> >> > >> > by default, and NetBSD returns EINVAL on the ioctl.
> >> > >> >
> >> > >> > Fix:
> >> > >> > set DEFAULT_MTU to <= 1500
> >> > >> >
> >> > >> > -Vivek
> >> > >> >
> >> > >> >
> >> > >> > On 5/17/06, Vivek raghunathan <vivek.raghunathan at gmail.com> wrote:
> >> > >> >> bug in userlevel/kerneltun.cc:
> >> > >> >> 268 ifr.ifr_mtu = _mtu_out;
> >> > >> >>     269     if (ioctl(s, SIOCSIFMTU, &ifr) != 0)
> >> > >> >>     270         return errh->error("SIOCSIFMTU failed: %s",
> >> > >> strerror(errno));
> >> > >> >>
> >> > >> >>
> >> > >> >>
> >> > >> >>
> >> > >> >> --
> >> > >> >>
> >> > >> >> *************************************
> >> > >> >> Vivek Raghunathan,
> >> > >> >> PhD student,
> >> > >> >> University of Illinois, Urbana-Champaign
> >> > >> >>
> >> > >> >> Contact Details:
> >> > >> >> 1012 W. Clark St #31,
> >> > >> >> Urbana IL 61801
> >> > >> >>
> >> > >> >> ph: 217-766-1868 (cell)
> >> > >> >>     217-333-7541 (off)
> >> > >> >>
> >> > >> >
> >> > >> >
> >> > >>
> >> > >
> >> > >
> >> >
> >>
> >>
> >> --
> >>
> >> *************************************
> >> Vivek Raghunathan,
> >> PhD student,
> >> University of Illinois, Urbana-Champaign
> >>
> >> Contact Details:
> >> 1012 W. Clark St #31,
> >> Urbana IL 61801
> >>
> >> ph: 217-766-1868 (cell)
> >>     217-333-7541 (off)
> >>
> >
> >
>

-- 

*************************************
Vivek Raghunathan,
PhD student,
University of Illinois, Urbana-Champaign

Contact Details:
1012 W. Clark St #31,
Urbana IL 61801

ph: 217-766-1868 (cell)
    217-333-7541 (off)