TCP SYNs broken in 2.3.41

[Russell King]

David S. Miller writes:
> The networking never has, and probably never will, guarentee the
> alignment of packets.  This means that all of your checksum support
> needs to handle completely arbitrary alignment cases.

It's not the checksum code which is broken.

> The networking also requires that unaligned load/store will work
> in the kernel.  If you don't handle this, then IPX, Appletalk, and
> some of the other more esoteric protocols will simply not work
> on your platform.

I am aware that the other protocols will not work, however, since I'm
using only IP, it "should" work.

> So does the ARM code handle this?

The processor does not handle unaligned accesses by itself - you have
to take an unaligned trap handler just like the ALPHA has to.  This
means that performance is hit badly.

Since I don't have a requirement for the trap handler, I have it
disabled, especially as outgoing IP packets over ethernet definitely
should always be aligned.

And thanks to Alexy for confirming the problem.
   _____
  |_____| ------------------------------------------------- ---+---+-
  |   |         Russell King        rmk en arm.linux.org.uk      --- ---
  | | | |   http://www.arm.linux.org.uk/~rmk/aboutme.html    /  /  |
  | +-+-+                                                     --- -+-
  /   |               THE developer of ARM Linux              |+| /|\
 /  | | |                                                     ---  |
    +-+-+ -------------------------------------------------  /\\\  |

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