Pavel Emelyanov a8fc927780 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>		2012-11-01 11:17:15 -04:00
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auxvec.h
bitsperlong.h
byteorder.h
errno.h
fcntl.h
ioctl.h
ioctls.h
ipcbuf.h
Kbuild
kvm_para.h
mman.h
msgbuf.h
param.h
poll.h
posix_types.h
ptrace.h
registers.h
resource.h
sembuf.h
setup.h
shmbuf.h
sigcontext.h
siginfo.h
signal.h
socket.h	sk-filter: Add ability to get socket filter program (v2)	2012-11-01 11:17:15 -04:00
sockios.h
stat.h
statfs.h
swab.h
termbits.h
termios.h
types.h
unistd.h