cvs commit: src/sys/net bpf.c bpf.h bpf_buffer.c bpf_buffer.h bpf_zerocopy.c bpf_zerocopy.h bpfdesc.h src/share/man/man4 bpf.4 src/sys/conf files

Christian S.J. Peron csjp at
Mon Mar 24 06:49:19 PDT 2008

csjp        2008-03-24 13:49:18 UTC

  FreeBSD src repository

  Modified files:
    sys/net              bpf.c bpf.h bpfdesc.h 
    share/man/man4       bpf.4 
    sys/conf             files 
  Added files:
    sys/net              bpf_buffer.c bpf_buffer.h bpf_zerocopy.c 
  Introduce support for zero-copy BPF buffering, which reduces the
  overhead of packet capture by allowing a user process to directly "loan"
  buffer memory to the kernel rather than using read(2) to explicitly copy
  data from kernel address space.
  The user process will issue new BPF ioctls to set the shared memory
  buffer mode and provide pointers to buffers and their size. The kernel
  then wires and maps the pages into kernel address space using sf_buf(9),
  which on supporting architectures will use the direct map region. The
  current "buffered" access mode remains the default, and support for
  zero-copy buffers must, for the time being, be explicitly enabled using
  a sysctl for the kernel to accept requests to use it.
  The kernel and user process synchronize use of the buffers with atomic
  operations, avoiding the need for system calls under load; the user
  process may use select()/poll()/kqueue() to manage blocking while
  waiting for network data if the user process is able to consume data
  faster than the kernel generates it. Patchs to libpcap are available
  to allow libpcap applications to transparently take advantage of this
  support. Detailed information on the new API may be found in bpf(4),
  including specific atomic operations and memory barriers required to
  synchronize buffer use safely.
  These changes modify the base BPF implementation to (roughly) abstrac
  the current buffer model, allowing the new shared memory model to be
  added, and add new monitoring statistics for netstat to print. The
  implementation, with the exception of some monitoring hanges that break
  the netstat monitoring ABI for BPF, will be MFC'd.
  Zerocopy bpf buffers are still considered experimental are disabled
  by default. To experiment with this new facility, adjust the
  net.bpf.zerocopy_enable sysctl variable to 1.
  Changes to libpcap will be made available as a patch for the time being,
  and further refinements to the implementation are expected.
  Sponsored by:           Seccuris Inc.
  In collaboration with:  rwatson
  Tested by:              pwood, gallatin
  MFC after:              4 months [1]
  [1] Certain portions will probably not be MFCed, specifically things
      that can break the monitoring ABI.
  Revision  Changes    Path
  1.49      +240 -15   src/share/man/man4/bpf.4
  1.1283    +2 -0      src/sys/conf/files
  1.188     +313 -109  src/sys/net/bpf.c
  1.50      +66 -0     src/sys/net/bpf.h
  1.1       +210 -0    src/sys/net/bpf_buffer.c (new)
  1.1       +50 -0     src/sys/net/bpf_buffer.h (new)
  1.1       +510 -0    src/sys/net/bpf_zerocopy.c (new)
  1.1       +53 -0     src/sys/net/bpf_zerocopy.h (new)
  1.39      +25 -13    src/sys/net/bpfdesc.h

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