[Python-Dev] socket.setsockopt() with optval=NULL

[Benjamin Peterson]

Another option would be add a setalg method with whatever (nice,
pythonic) API we want. Emulating the crummy C-level API needn't be a
goal I think.

On Sun, Aug 21, 2016, at 05:37, Christian Heimes wrote:
> Hi,
> 
> the socket.setsockopt(level, optname, value) method has two calling
> variants. When it is called with a buffer-like object as value, it calls
> the C API function setsockopt() with optval=buffer.buf and
> optlen=buffer.len. When value is an integer, setsockopt() packs it as
> int32 and sends it with optlen=4.
> 
> ---
> # example.py
> import socket
> sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
> sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR,
>     b'\x00\x00\x00\x00')
> sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
> ---
> 
> $ strace -e setsockopt ./python example.py
> setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [0], 4) = 0
> setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
> 
> 
> For AF_ALG (Linux Kernel crypto) I need a way to call the C API function
> setsockopt() with optval=NULL and optlen as any arbitrary number. I have
> been playing with multiple ideas. So far I liked the idea of
> value=(None, int) most.
> 
> setsockopt(socket.SOL_ALG, socket.ALG_SET_AEAD_AUTHSIZE, (None, taglen))
> 
> What do you think?
> 
> Christian
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