socket: properly support SO_ATTACH_FILTER sockopt

The SO_ATTACH_FILTER socket option requires special handling as it is not
passing a self-contained structure to the kernel but a pointer to user
memory holding the actual BPF bytecode.

In order to properly support this, first rework the ucode value to C struct
conversion callback machinery to pass an indirect struct base pointer,
allowing conversion callbacks to realloc the struct memory as needed.

Finally introduce custom uv to C conversion for the BPF data which accepts
either a raw bytecode string, an array of opcode arrays or a flat array of
opcode values which are converted into a C array of struct sock_filter
records appended to the reallocated struct memory.

Attaching a BPF program equivalent to the tcpdump expression
`vlan 20 && ether proto 0x1234` would then look like this:

    sock.setopt(SOL_SOCKET, SO_ATTACH_FILTER, {
      filter: [
        [ 0x28, 0, 0, 0x0000000c ],
        [ 0x15, 2, 0, 0x00008100 ],
        [ 0x15, 1, 0, 0x000088a8 ],
        [ 0x15, 0, 6, 0x00009100 ],
        [ 0x28, 0, 0, 0x0000000e ],
        [ 0x54, 0, 0, 0x00000fff ],
        [ 0x15, 0, 3, 0x00000014 ],
        [ 0x28, 0, 0, 0x00000010 ],
        [ 0x15, 0, 1, 0x00001234 ],
        [ 0x6, 0, 0, 0x00040000 ],
        [ 0x6, 0, 0, 0x00000000 ],
      ]
    });

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

0 files changed, 0 insertions, 0 deletions