track which namespaces we control

src/namespace/mod.rs

@@ -3,10 +3,12 @@ mod raw;
 use crate::config::NamespaceName;
 use crate::link::{LinkError, link_up_ns};
 use crate::namespace::raw::{NamespaceSetupError, create_network_namespace};
+use either::Either;
 use nix::errno::Errno;
 use nix::mount::{MntFlags, MsFlags, mount, umount2};
-use std::fs::{File, create_dir, remove_file};
+use std::fs::{File, create_dir, read_dir, remove_file};
 use std::io::{Error as IoError, ErrorKind};
+use std::iter::empty;
 use std::os::unix::fs::symlink;
 use std::path::{Path, PathBuf};
 use thiserror::Error;
@@ -15,9 +17,26 @@ use tracing::{debug, error, info};
 pub struct NetNs {
     name: NamespaceName,
     path: PathBuf,
+    nsd_path: PathBuf,
 }
 
 impl NetNs {
+    pub fn existing() -> Result<impl Iterator<Item = NamespaceName>, NamespaceError> {
+        let dir = match read_dir("/var/run/netnsd") {
+            Ok(dir) => Ok(dir),
+            Err(error) if error.kind() == ErrorKind::NotFound => {
+                return Ok(Either::Left(empty()));
+            }
+            Err(error) => Err(NamespaceError::Scan {
+                path: "/var/run/netnsd".into(),
+                error,
+            }),
+        }?;
+        Ok(Either::Right(dir.flatten().flat_map(|entry| {
+            NamespaceName::try_from(entry.file_name()).ok()
+        })))
+    }
+
     /// Create a new named network namespace that will be removed when dropped
     pub fn new(name: NamespaceName) -> Result<Self, NamespaceError> {
         let parent = Path::new("/var/run/netns");
@@ -41,7 +60,8 @@ impl NetNs {
                 }
 
                 return Ok(NetNs {
-                    name: name.clone(),
+                    name,
+                    nsd_path,
                     path,
                 });
             }
@@ -57,7 +77,7 @@ impl NetNs {
                     path: nsd_path.clone(),
                 })?;
             }
-            Result::<_, NamespaceError>::Ok(NetNs { name, path })
+            Result::<_, NamespaceError>::Ok(NetNs { name, path, nsd_path })
         })?;
 
         ns.setup_interfaces()?;
@@ -121,6 +141,10 @@ impl NetNs {
             error,
             path: self.path,
         })?;
+        remove_file(&self.nsd_path).map_err(|error| NamespaceError::Delete {
+            error,
+            path: self.nsd_path,
+        })?;
         Ok(())
     }
 }
@@ -145,6 +169,8 @@ pub enum NamespaceError {
     UnMount(Errno),
     #[error("Failed to setup loopback inside namespace: {0:#}")]
     Link(#[from] LinkError),
+    #[error("Failed to scan {} for namespaces: {error:#}", path.display())]
+    Scan { path: PathBuf, error: IoError },
 }
 
 impl NamespaceError {