fix linux read permissions issue

Cargo.toml

@@ -26,3 +26,6 @@ rustix = {version = "0.38.31", features = ["fs"]}
 #[target.'cfg(all(not(target_os = "linux"), not(target_os = "macos"), not(target_os = "windows")))'.dependencies]
 #bsd-kvm = "0.1.5"
 #sysctl = "0.5.5"
+[target.'cfg(target_os = "linux")'.dev-dependencies]
+http-test-server = "2.1.1"
+

src/platform/linux/helpers.rs

@@ -4,7 +4,7 @@ use std::os::fd::{AsFd, BorrowedFd, RawFd};
 use std::path::Path;
 use std::str::FromStr;
 
-use rustix::fs::{Mode, OFlags};
+use rustix::fs::{Access, AtFlags, Mode, OFlags};
 
 use crate::platform::linux::proc_fd::ProcFd;
 use crate::platform::linux::proc_info::ProcInfo;
@@ -14,9 +14,14 @@ pub(super) fn build_inode_proc_map(proc_fds: Vec<ProcFd>) -> crate::Result<HashM
     let mut map: HashMap<u64, ProcInfo> = HashMap::new();
 
     for proc_fd in proc_fds {
+        let dirfd = proc_fd.as_fd();
+        let path = "fd";
+        if rustix::fs::accessat(dirfd, path, Access::READ_OK, AtFlags::empty()).is_err() {
+            continue;
+        }
         let dir_fd = rustix::fs::openat(
-            proc_fd.as_fd(),
-            "fd",
+            dirfd,
+            path,
             OFlags::RDONLY | OFlags::DIRECTORY | OFlags::CLOEXEC,
             Mode::empty(),
         )?;

tests/integration_tests.rs

@@ -1,5 +1,3 @@
-use listeners;
-
 #[test]
 #[cfg(not(target_os = "linux"))]
 fn test_consistency() {
@@ -37,3 +35,22 @@ fn test_macos() {
     let ports = listeners::get_ports_by_process_name("launchd").unwrap();
     assert!(!ports.is_empty());
 }
+
+#[test]
+#[cfg(target_os = "linux")]
+fn test_linux() {
+    // starts test server
+    use http_test_server::TestServer;
+    let test_server = TestServer::new().unwrap();
+    let test_server_port = test_server.port();
+
+    // get process by port
+    let processes = listeners::get_processes_by_port(test_server_port).unwrap();
+    assert_eq!(processes.len(), 1);
+
+    // get port by process
+    let pid = processes.into_iter().next().unwrap().pid;
+    let ports = listeners::get_ports_by_pid(pid).unwrap();
+    assert_eq!(ports.len(), 1);
+    assert_eq!(ports.into_iter().next().unwrap(), test_server_port);
+}