finger: add basic implementation for fetching utmp users

src/server/fingerd.rs

@@ -5,6 +5,7 @@ use std::{
 };
 
 use chrono::{DateTime, Duration, Timelike, Utc};
+use itertools::Itertools;
 use nix::sys::stat::stat;
 use serde::{Deserialize, Serialize};
 use users::all_users;
@@ -71,6 +72,18 @@ pub fn search_for_user(
         .collect()
 }
 
+/// Retrieve information about all users currently logged in, based on utmpx records.
+pub fn finger_utmp_users(
+    _request_info: &FingerRequestInfo,
+) -> Vec<anyhow::Result<FingerResponseUserEntry>> {
+    Utmpx::iter_all_records()
+        .filter(|entry| entry.is_user_process())
+        .map(|entry| entry.user())
+        .dedup()
+        .flat_map(|username| get_local_user(&username).transpose())
+        .collect()
+}
+
 /// Helper function to read the content of a file if it exists and is readable,
 /// returning None if the file does not exist or is not readable.
 fn read_file_content_if_exists(path: &Path) -> anyhow::Result<Option<String>> {

src/server/varlink_api.rs

@@ -8,7 +8,7 @@ use zlink::{ReplyError, service::MethodReply};
 use crate::{
     proto::{WhodStatusUpdate, WhodUserEntry, finger_protocol::FingerResponseUserEntry},
     server::{
-        fingerd::{self, FingerRequestInfo, FingerRequestNetworking},
+        fingerd::{self, FingerRequestInfo, FingerRequestNetworking, finger_utmp_users},
         rwhod::RwhodStatusStore,
     },
 };
@@ -199,10 +199,16 @@ impl VarlinkRoowhoo2ClientServer {
                     }
                 })
                 .collect(),
-            None => {
-                // TODO: fetch logged in users using utmp entries
-                todo!()
-            }
+            None => finger_utmp_users(&request_info)
+                .into_iter()
+                .filter_map(|res| match res {
+                    Ok(user_info) => Some(user_info),
+                    Err(err) => {
+                        tracing::error!("Error retrieving local user information: {}", err);
+                        None
+                    }
+                })
+                .collect(),
         }
     }
 }