Look up realm by pid.

Added RealmManager::realm_by_pid() and dbus method RealmFromCitadelPid

libcitadel/src/realm/manager.rs

@@ -1,6 +1,6 @@
 use std::collections::HashSet;
 use std::fs;
-use std::path::Path;
+use std::path::{Path, PathBuf};
 use std::sync::{Arc, RwLock, RwLockReadGuard, RwLockWriteGuard};
 
 use crate::{Mountpoint, Activation,Result, Realms, RealmFS, Realm, util};
@@ -330,6 +330,28 @@ impl RealmManager {
         self.inner().realms.by_name(name)
     }
 
+    pub fn realm_by_pid(&self, pid: u32) -> Option<Realm> {
+        match Self::read_realm_name_by_pid(pid) {
+            Ok(name) => self.realm_by_name(name.as_str()),
+            Err(_) => None,
+        }
+    }
+
+    fn read_realm_name_by_pid(pid: u32) -> Result<String> {
+        let run = PathBuf::from(format!("/proc/{}/root/run", pid));
+        let realm_name = run.join("realm-name");
+
+        // ensure that /proc/pid/root/run and /proc/pid/root/run/realm-name
+        // are not symlinks
+        let run_meta = run.symlink_metadata()?;
+        let name_meta = realm_name.symlink_metadata()?;
+        if !run_meta.file_type().is_dir() || !name_meta.file_type().is_file() {
+            bail!("invalid path");
+        }
+        let bytes = fs::read(realm_name)?;
+        Ok(String::from_utf8(bytes)?)
+    }
+
     pub fn rescan_realms(&self) -> Result<(Vec<Realm>,Vec<Realm>)> {
         self.inner_mut().realms.rescan_realms()
     }

realmsd/src/dbus.rs

@@ -62,6 +62,10 @@ impl DbusServer {
                 .in_arg(("name", "s"))
                 .in_arg(("args", "as")))
 
+            .add_m(f.method("RealmFromCitadelPid", (), Self::do_pid_to_realm)
+                .in_arg(("pid", "u"))
+                .out_arg(("realm", "s")))
+
             // Signals
             .add_s(f.signal("RealmStarted", ())
                 .arg(("realm", "s")))
@@ -168,6 +172,18 @@ impl DbusServer {
         Ok(vec![m.msg.method_return()])
     }
 
+    fn do_pid_to_realm(m: &MethodInfo) -> MethodResult {
+        let pid = m.msg.read1::<u32>()?;
+        let manager = m.tree.get_data().manager();
+        let ret = m.msg.method_return();
+        let msg = match manager.realm_by_pid(pid) {
+            Some(realm) => ret.append(realm.name()),
+            None => ret.append(""),
+        };
+        Ok(vec![msg])
+    }
+
+
     pub fn start(&self) -> Result<()> {
         let tree = self.build_tree();
         self.connection.register_name(BUS_NAME, NameFlag::ReplaceExisting as u32)?;
@@ -219,6 +235,7 @@ impl DbusServer {
         let member = dbus::Member::new(name).unwrap();
         Message::signal(&path, &iface, &member)
     }
+
 }
 
 /// Wraps a connection instance and only expose the send() method.