ei: add support for libei

src/utils/pid_info.rs

@@ -0,0 +1,44 @@
+use {
+    crate::utils::{errorfmt::ErrorFmt, oserror::OsError, trim::AsciiTrim},
+    bstr::ByteSlice,
+    uapi::{c, OwnedFd},
+};
+
+pub struct PidInfo {
+    pub _uid: c::uid_t,
+    pub pid: c::pid_t,
+    pub comm: String,
+}
+
+pub fn get_pid_info(uid: c::uid_t, pid: c::pid_t) -> PidInfo {
+    let comm = match std::fs::read(format!("/proc/{}/comm", pid)) {
+        Ok(name) => name.trim().as_bstr().to_string(),
+        Err(e) => {
+            log::warn!("Could not read `comm` of pid {}: {}", pid, ErrorFmt(e));
+            "Unknown".to_string()
+        }
+    };
+    PidInfo {
+        _uid: uid,
+        pid,
+        comm,
+    }
+}
+
+pub fn get_socket_creds(socket: &OwnedFd) -> Option<(c::uid_t, c::pid_t)> {
+    let mut cred = c::ucred {
+        pid: 0,
+        uid: 0,
+        gid: 0,
+    };
+    match uapi::getsockopt(socket.raw(), c::SOL_SOCKET, c::SO_PEERCRED, &mut cred) {
+        Ok(_) => Some((cred.uid, cred.pid)),
+        Err(e) => {
+            log::error!(
+                "Cannot determine peer credentials of new connection: {:?}",
+                OsError::from(e)
+            );
+            None
+        }
+    }
+}