MagicStack / MagicStack/uvloop

getaddrinfo() returns wrong scope ID for IPv6 link-local addresses when type=SocketKind.SOCK_STREAM

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Description

* **uvloop version**: 0.17.0
* **Python version**: 3.11.3
* **Platform**: Linux
* **Can you reproduce the bug with `PYTHONASYNCIODEBUG` in env?**: yes
* **Does uvloop behave differently from vanilla asyncio? How?**: Vanilla asyncio returns the correct scope ID, uvloop returns 0

When passing `type=SocketKind.SOCK_STREAM` to `getaddrinfo()` in uvloop, the scope ID for link-local addresses is left as 0. This works correctly (returns nonzero scope ID) in `socket.getaddrinfo()` and vanilla asyncio's corresponding function.

Repro script (requires `psutil` installed):
```python
from asyncio import get_running_loop, run
from socket import SocketKind

import psutil
import uvloop

async def main():
for ifname, addresses in psutil.net_if_addrs().items():
for addr in addresses:
if addr.address.startswith("fe80::") and "%" in addr.address:
gai_res = await get_running_loop().getaddrinfo(addr.address, 0, type=SocketKind.SOCK_STREAM)
scope_id = gai_res[-1][-1][-1]
print("Scope id for", gai_res[-1], "is", scope_id)
return

print("Could not find a suitable link-local address")

# Comment out this line, and it works fine
uvloop.install()
run(main())
```

Contributor guide

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Research direction

Start by running the provided reproduction script on Linux with a link-local IPv6 address, comparing uvloop with vanilla asyncio and socket.getaddrinfo(). The issue is done when uvloop returns the correct nonzero scope ID for SOCK_STREAM, matching the other implementations.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
networking
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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