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

[Martin Panter]

On 21 August 2016 at 12:37, Christian Heimes  wrote:
> 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))

Would this new functionality be open-ended? What would happen if you did

sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, (None, 4))

On Linux, this seems to fail with errno = EFAULT, which would be fine.
But this does not seem to be specified by Posix, and I imagine other
platforms might crash. On the other hand, these sort of holes are
already present in the socket module. E.g. with MSG_TRUNC
 you can apparently get Python to
copy from unallocated memory.
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Re: [Python-Dev] socket.setsockopt() with optval=NULL

[Guido van Rossum]

Wouldn't

setsockopt(socket.SOL_ALG, socket.ALG_SET_AEAD_AUTHSIZE, None, taglen)

be more consistent?

--Guido (mobile)

On Aug 21, 2016 5:40 AM, "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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> guido%40python.org
>
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[Python-Dev] socket.setsockopt() with optval=NULL

[Christian Heimes]

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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