up and down commands

src/up.rs

@@ -0,0 +1,27 @@
+use crate::config::{Config, NamespaceName};
+use crate::namespace::NetNs;
+use main_error::MainResult;
+
+pub fn up(config: Config) -> MainResult {
+    let mut namespaces = NetNs::existing()?
+        .map(NetNs::new)
+        .collect::<Result<Vec<_>, _>>()?;
+
+    for removed in namespaces.extract_if(.., |namespace| {
+        config.get_namespace(namespace.name()).is_none()
+    }) {
+        removed.delete()?;
+    }
+
+    for new in config.namespaces {
+        if !has_namespace(&namespaces, &new.name) {
+            namespaces.push(NetNs::new(new.name)?);
+        }
+    }
+
+    Ok(())
+}
+
+fn has_namespace(namespaces: &[NetNs], name: &NamespaceName) -> bool {
+    namespaces.iter().any(|existing| existing.name() == name)
+}