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| author | Alexei Starovoitov <ast@kernel.org> | 2018-05-21 19:22:30 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-05-23 13:23:40 -0400 |
| commit | d2ba09c17a0647f899d6c20a11bab9e6d3382f07 (patch) | |
| tree | 96f528cd9829377165a7357e02438248a88c93b9 /net/Makefile | |
| parent | 449325b52b7a6208f65ed67d3484fd7b7184477b (diff) | |
| download | linux-0-day-d2ba09c17a0647f899d6c20a11bab9e6d3382f07.tar.gz linux-0-day-d2ba09c17a0647f899d6c20a11bab9e6d3382f07.tar.xz | |
net: add skeleton of bpfilter kernel module
bpfilter.ko consists of bpfilter_kern.c (normal kernel module code)
and user mode helper code that is embedded into bpfilter.ko
The steps to build bpfilter.ko are the following:
- main.c is compiled by HOSTCC into the bpfilter_umh elf executable file
- with quite a bit of objcopy and Makefile magic the bpfilter_umh elf file
is converted into bpfilter_umh.o object file
with _binary_net_bpfilter_bpfilter_umh_start and _end symbols
Example:
$ nm ./bld_x64/net/bpfilter/bpfilter_umh.o
0000000000004cf8 T _binary_net_bpfilter_bpfilter_umh_end
0000000000004cf8 A _binary_net_bpfilter_bpfilter_umh_size
0000000000000000 T _binary_net_bpfilter_bpfilter_umh_start
- bpfilter_umh.o and bpfilter_kern.o are linked together into bpfilter.ko
bpfilter_kern.c is a normal kernel module code that calls
the fork_usermode_blob() helper to execute part of its own data
as a user mode process.
Notice that _binary_net_bpfilter_bpfilter_umh_start - end
is placed into .init.rodata section, so it's freed as soon as __init
function of bpfilter.ko is finished.
As part of __init the bpfilter.ko does first request/reply action
via two unix pipe provided by fork_usermode_blob() helper to
make sure that umh is healthy. If not it will kill it via pid.
Later bpfilter_process_sockopt() will be called from bpfilter hooks
in get/setsockopt() to pass iptable commands into umh via bpfilter.ko
If admin does 'rmmod bpfilter' the __exit code bpfilter.ko will
kill umh as well.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/Makefile')
| -rw-r--r-- | net/Makefile | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/net/Makefile b/net/Makefile index 77aaddedbd29f..bdaf53925acd5 100644 --- a/net/Makefile +++ b/net/Makefile @@ -20,6 +20,7 @@ obj-$(CONFIG_TLS) += tls/ obj-$(CONFIG_XFRM) += xfrm/ obj-$(CONFIG_UNIX) += unix/ obj-$(CONFIG_NET) += ipv6/ +obj-$(CONFIG_BPFILTER) += bpfilter/ obj-$(CONFIG_PACKET) += packet/ obj-$(CONFIG_NET_KEY) += key/ obj-$(CONFIG_BRIDGE) += bridge/ |