cvs commit: src/sys/dev/hfa fore_buffer.c fore_receive.c

[Hartmut Brandt]

harti       2003/08/22 03:32:20 PDT

  FreeBSD src repository

  Modified files:        (Branch: RELENG_4)
    sys/dev/hfa          fore_buffer.c fore_receive.c 
  Log:
  For some reason the hfa driver behaves differently between current and
  stable when loaded with 4.X.Y firmware. This difference manifests itself
  in the card returning receive buffer chains that start with a large buffer
  under certain circumstances. This uncovered an inherent bug in the
  mbuf handling of the atm stack: the driver prefixes 8 bytes to the mbuf
  that contain a function address to dispatch this buffer to and a cookie
  for this function. When the driver finds, that it has no space at the
  head of the mbuf chain, it allocates a new packet header mbuf and
  prepends it to the chain and moves the header to the new mbuf.
  
  atm_intr() strips the additional 8 bytes from the mbuf chain and, if it
  finds the first mbuf to become empty, removes that mbuf from the chain, but
  does not care to move the header to the next mbuf. Here the packet
  header is lost.
  
  Work around:
  
  1. Allocate all large buffers for the Fore card with a packet header.
  2. When prefixing the new mbuf to the chain, don't move the packet header,
     but initialize it with the correct values. This results in an mbuf
     chain with two packet headers. When atm_intr strips the first mbuf,
     everything is ok.
  
  It would probably be better to fix the problem instead of working around it,
  but this could break other drivers (hea and proatm).
  
  Revision  Changes    Path
  1.5.2.1   +10 -3     src/sys/dev/hfa/fore_buffer.c
  1.5.2.3   +15 -1     src/sys/dev/hfa/fore_receive.c