I ran into a similar issue with version 0.8 and 0.6 on Ubuntu 14.04; PREROUTE works fine, POSTROUTE crashes. Seems ok so far on 0.7

Problem is at line 65 of netfilterqueue.pyx:

        self.hw_addr = self._hw.hw_addr

When sending packets, self._hw is NULL so the copy crashes. I have no idea how to fix that in the PYX file (what should be the value of self.hw_addr when self._hw is NULL?), but as a workaround, you can just comment the following lines in netfilterqueue.c and compile/install the module again:

  __pyx_t_2 = __pyx_v_self->_hw->hw_addr;
  memcpy(&(__pyx_v_self->hw_addr[0]), __pyx_t_2, sizeof(__pyx_v_self->hw_addr[0]) * (8 - 0));

I ran into the same issue using OUTPUT. Thanks for the workaround.

Thanks for the details. I'll see if I can duplicate and fix within a few days.

The fix leaves calling and parsing of nfq_get_packet_hw data until the get_hw() call, and just returns None if nfq_get_packet_hw returns NULL. I believe hw_addr was private on Packet, so this should be compatible with 0.8.

I've uploaded 0.8.1 to Pypi but reviews and improvements are welcome. Thanks for reporting this, all.

Thanks @mattfox I experience no more crash with 0.8.1.