[Click] minor bug report with NetBSD

[Eddie Kohler]

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)
>>
> 
>