internal/uevent: wrap netlink socket

Unfortunately these messages do not have the same format as rtnetlink.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/uevent/uevent.go

@@ -0,0 +1,26 @@
+// Package uevent provides userspace client for consuming events from a
+// NETLINK_KOBJECT_UEVENT socket, as well as helpers for supplementing
+// events received from the kernel.
+package uevent
+
+import (
+	"syscall"
+
+	"hakurei.app/internal/netlink"
+)
+
+// Conn represents a NETLINK_KOBJECT_UEVENT socket.
+type Conn struct{ conn *netlink.Conn }
+
+// Close closes the underlying socket.
+func (c *Conn) Close() error { return c.conn.Close() }
+
+// Dial returns the address of a newly connected [Conn].
+func Dial() (*Conn, error) {
+	// kernel group is hard coded in lib/kobject_uevent.c, undocumented
+	c, err := netlink.Dial(syscall.NETLINK_KOBJECT_UEVENT, 1)
+	if err != nil {
+		return nil, err
+	}
+	return &Conn{c}, err
+}