diff options
| author | Pavel Emelyanov | 2012-11-01 02:01:48 +0000 |
|---|---|---|
| committer | David S. Miller | 2012-11-01 11:17:15 -0400 |
| commit | a8fc92778080c845eaadc369a0ecf5699a03bef0 (patch) | |
| tree | 2d83a965c40765c52195e32a903bd8c7678f014d /arch/frv | |
| parent | 96442e42429e5f268ab97a3586c7694a3acc55a7 (diff) | |
sk-filter: Add ability to get socket filter program (v2)
The SO_ATTACH_FILTER option is set only. I propose to add the get
ability by using SO_ATTACH_FILTER in getsockopt. To be less
irritating to eyes the SO_GET_FILTER alias to it is declared. This
ability is required by checkpoint-restore project to be able to
save full state of a socket.
There are two issues with getting filter back.
First, kernel modifies the sock_filter->code on filter load, thus in
order to return the filter element back to user we have to decode it
into user-visible constants. Fortunately the modification in question
is interconvertible.
Second, the BPF_S_ALU_DIV_K code modifies the command argument k to
speed up the run-time division by doing kernel_k = reciprocal(user_k).
Bad news is that different user_k may result in same kernel_k, so we
can't get the original user_k back. Good news is that we don't have
to do it. What we need to is calculate a user2_k so, that
reciprocal(user2_k) == reciprocal(user_k) == kernel_k
i.e. if it's re-loaded back the compiled again value will be exactly
the same as it was. That said, the user2_k can be calculated like this
user2_k = reciprocal(kernel_k)
with an exception, that if kernel_k == 0, then user2_k == 1.
The optlen argument is treated like this -- when zero, kernel returns
the amount of sock_fprog elements in filter, otherwise it should be
large enough for the sock_fprog array.
changes since v1:
* Declared SO_GET_FILTER in all arch headers
* Added decode of vlan-tag codes
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch/frv')
| -rw-r--r-- | arch/frv/include/uapi/asm/socket.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/frv/include/uapi/asm/socket.h b/arch/frv/include/uapi/asm/socket.h index a5b1d7dbb205..871f89b7fbda 100644 --- a/arch/frv/include/uapi/asm/socket.h +++ b/arch/frv/include/uapi/asm/socket.h @@ -40,6 +40,7 @@ /* Socket filtering */ #define SO_ATTACH_FILTER 26 #define SO_DETACH_FILTER 27 +#define SO_GET_FILTER SO_ATTACH_FILTER #define SO_PEERNAME 28 #define SO_TIMESTAMP 29 |