[Click] Mac OS X assert failed when trying to use KernelTun

[Pekka Nikander]

Eddie,

Thanks, it works!  

I needed to do two other small things to get it working:

1. It didn't compile out of last night's git; the following patch made it to compile:

--- a/lib/timestamp.cc
+++ b/lib/timestamp.cc
@@ -67,7 +67,7 @@ Timestamp::warp(bool from_now)
     if (_warp_class == warp_simulation) {
        *this = _warp_flat_offset;
        if (from_now) {
-# if TIMESTAMP_MATH_FLAT64
+# if TIMESTAMP_REP_FLAT64 || TIMESTAMP_MATH_FLAT64
            ++_warp_flat_offset._t.x;
 # else
            ++_warp_flat_offset._t.subsec;

I'm not sure if that is the right patch, though...


2. Mac OS X tun devices are point-to-point links, requiring both a local and remote IP address.

Right now click configures only the local one, resulting in an interface like the following:

$ ifconfig tun0
tun0: flags=8951<UP,POINTOPOINT,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500
	inet 192.168.15.1 --> 0.0.0.0 netmask 0xffffff00 
	open (pid 63049)

Once I added a remote address there with ifconfig, it started to work:

# ifconfig tun0 192.168.15.1 192.168.16.1
# click -e "tun :: KernelTun(192.168.15.1/24); tun -> IPPrint -> Discard" &
# ping 192.168.16.1 > /dev/null 2>&1
1259231868.596160: 192.168.15.1 > 192.168.16.1: icmp echo (63066, 0)
1259231869.596198: 192.168.15.1 > 192.168.16.1: icmp echo (63066, 256)
1259231870.596240: 192.168.15.1 > 192.168.16.1: icmp echo (63066, 512)
1259231871.596328: 192.168.15.1 > 192.168.16.1: icmp echo (63066, 768)
1259231872.596394: 192.168.15.1 > 192.168.16.1: icmp echo (63066, 1024)
1259231873.596553: 192.168.15.1 > 192.168.16.1: icmp echo (63066, 1280)

Alternatively, I was also able to do the same by manipulating the routing table:
# route add -net 192.168.16.0 192.168.15.1

However, pinging anything on the local subnet 192.168.15.0/24 doesn't go to the click process.

I guess the documentation should be updated...


Anyway, this should be enough slay some GMPLS Dragons locally on Mac OS X. :-)

--Pekka

On 2009-11 -25, at 12:21 , Eddie Kohler wrote:

> Pekka,
> 
> Thans very much for this note!  There was indeed a bug in the select handling -- we essentially assumed that every file descriptor was present in some array for both reading and writing.  This should be fixed now.  Let us know if you have any further issues.
> 
> Eddie
> 
> 
> Pekka Nikander wrote:
>> I'm a relative newbie to Click, and trying to use KernelTun on Mac OS X, with the latest GIT version.  Unfortunately it looks like that there is a bug, apparently related to the interactions between kevents and select/poll.  The OS X tun/tap devices don't currently support kevents, and therefore click tries to back off to use select/poll.  However, once it gets to the actual poll in master.cc, something has gone wrong and I get a an assertion failure on line 850 in master.cc:
>> 	Element *read_elt = (p->revents & ~POLLOUT ? _read_elements[fd] : 0);
>> This results in an assertion failure, with this trivial script:
>> click -e "KernelTun(192.168.15.1/24) -> Discard"
>> Assertion failed: (i>=0 && i<_n), function operator[], file ../include/click/vector.hh, line 184.
>> Abort trap
>> My gut feeling is that the bug may line somewhere in master.cc Master:add_select, in the code that tries to make sure that one can fall back to select/poll in the case of kqueue error.  But I may be wrong.
>> In any case, when tracing the execution in opening the tun/tap device, the kevent system call at line 602 of master.cc fails, causing the _kqueue socket to be closed and made unused.   However, much before that I can see with ifconfig that the tun/tap interface is indeed open and correctly ifconfig'ed.
>> Anyone an idea where to continue debugging?  Or would it be easier to add KEVENT support to the Mac tun/tap kexts?
>> --Pekka Nikander
>> _______________________________________________
>> click mailing list
>> click at amsterdam.lcs.mit.edu
>> https://amsterdam.lcs.mit.edu/mailman/listinfo/click
>