[Click] AlignmentInfo Question

[Fischofer William-B09792]

I have the following elementclass:
 
elementclass TrafficClassifier {
   $interface |
   input ->
   c0 :: Classifier (12/0806 20/0001,            // ARP Requests
                          12/0806 20/0002,            // ARP Replies
                          12/0800,                        // IPv4
Packets
                           -);                                 //
Everything else
   c0[0] -> [0]output;
   c0[1] -> [1]output;
   c0[2] -> [2]output;
   c0[3] -> ToHost($interface);                    // Send all
"uninteresting" traffic to host
}
 
Which is then used as follows:
 
FromDevice(eth0) -> tc0::TrafficClassifier(eth0);
FromDevice(eth1) -> tc1::TrafficClassifier(eth1);
...etc.
 
However this results in the following error messages from Click:
 
While configuring 'tc0/c0 :: Classifier':
  no AlignmentInfo available: you may experience unaligned accesses
 
I'm not quite sure what this means or what I should do about it.  I can
make the message go away if I
insert the line:
 
AlignmentInfo(Classifier 4 0);  // Seems to work but is this what I
really need?
 
Into my TrafficClassifier definition but I'd like to understand what's
really going on here.  The online docs are pretty terse in this
area.  Any reading suggestions for better understanding this stuff?
 
Thanks much.
 
Bill Fischofer