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| author | Pavel Emelyanov <xemul@parallels.com> | 2012-11-01 06:01:48 +0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2012-11-01 19:17:15 +0400 |
| commit | a8fc92778080c845eaadc369a0ecf5699a03bef0 (patch) | |
| tree | 2d83a965c40765c52195e32a903bd8c7678f014d /include | |
| parent | 96442e42429e5f268ab97a3586c7694a3acc55a7 (diff) | |
| download | linux-a8fc92778080c845eaadc369a0ecf5699a03bef0.tar.xz | |
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 'include')
| -rw-r--r-- | include/linux/filter.h | 1 | ||||
| -rw-r--r-- | include/uapi/asm-generic/socket.h | 1 |
2 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/filter.h b/include/linux/filter.h index c9f0005c35e2..c45eabc135e1 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -45,6 +45,7 @@ extern void sk_unattached_filter_destroy(struct sk_filter *fp); extern int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk); extern int sk_detach_filter(struct sock *sk); extern int sk_chk_filter(struct sock_filter *filter, unsigned int flen); +extern int sk_get_filter(struct sock *sk, struct sock_filter __user *filter, unsigned len); #ifdef CONFIG_BPF_JIT extern void bpf_jit_compile(struct sk_filter *fp); diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h index b1bea03274d5..2d32d073a6f9 100644 --- a/include/uapi/asm-generic/socket.h +++ b/include/uapi/asm-generic/socket.h @@ -43,6 +43,7 @@ /* 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 |