Add support for file descriptor passing

Signed-off-by: Martin Michaelis <code@mgjm.de>
containers · Aug 9, 2023 · 3e22234 · 3e22234
1 parent b075bfd
commit 3e22234
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Showing 15 changed files with 1,370 additions and 225 deletions.
diff --git a/Cargo.lock b/Cargo.lock
diff --git a/conmon-rs/common/proto/conmon.capnp b/conmon-rs/common/proto/conmon.capnp
@@ -41,6 +41,8 @@ interface Conmon {
         metadata @11 :Metadata; # Standard metadata to carry.
         envVars @12 :TextTextMap;
         cgroupManager @13 :CgroupManager;
+        additionalFds @14 :List(UInt64);
+        leakFds @15 :List(UInt64);
     }
 
     struct LogDriver {
@@ -169,6 +171,18 @@ interface Conmon {
 
     createNamespaces @6 (request: CreateNamespacesRequest) -> (response: CreateNamespacesResponse);
 
+    ###############################################
+    # StartFdSocket
+    struct StartFdSocketRequest {
+        metadata @0 :Metadata; # Standard metadata to carry.
+    }
+
+    struct StartFdSocketResponse {
+        path @0 :Text; # The path to the fd socket.
+    }
+
+    startFdSocket @7 (request: StartFdSocketRequest) -> (response: StartFdSocketResponse);
+
     ###############################################
     # Helper types
 

diff --git a/conmon-rs/server/Cargo.toml b/conmon-rs/server/Cargo.toml
@@ -12,6 +12,7 @@ anyhow = "1.0.72"
 capnp = "0.17.2"
 capnp-rpc = "0.17.0"
 clap = { version = "4.3.8", features = ["color", "cargo", "deprecated", "derive", "deprecated", "env", "string", "unicode", "wrap_help"] }
+command-fds = { version = "0.2.2", features = ["tokio"] }
 conmon-common = { path = "../common" }
 futures = "0.3.28"
 getset = "0.1.2"
@@ -37,6 +38,7 @@ tempfile = "3.7.0"
 tokio = { version = "1.29.1", features = ["fs", "io-std", "io-util", "macros", "net", "process", "rt", "rt-multi-thread", "signal", "time"] }
 tokio-eventfd = "0.2.0"
 tokio-fd = "0.3.0"
+tokio-seqpacket = "0.7.0"
 tokio-util = { version = "0.7.8", features = ["compat"] }
 tracing = "0.1.37"
 tracing-opentelemetry = "0.19.0"

diff --git a/conmon-rs/server/src/child_reaper.rs b/conmon-rs/server/src/child_reaper.rs
@@ -4,7 +4,8 @@ use crate::{
     container_io::{ContainerIO, ContainerIOType, SharedContainerIO},
     oom_watcher::OOMWatcher,
 };
-use anyhow::{bail, format_err, Context, Result};
+use anyhow::{bail, Context, Result};
+use command_fds::{tokio::CommandFdAsyncExt, FdMapping};
 use getset::{CopyGetters, Getters, Setters};
 use libc::pid_t;
 use multimap::MultiMap;
@@ -19,6 +20,7 @@ use nix::{
 use std::{
     ffi::OsStr,
     fmt::Write,
+    os::fd::{AsRawFd, OwnedFd, RawFd},
     path::{Path, PathBuf},
     process::Stdio,
     str,
@@ -41,11 +43,8 @@ pub struct ChildReaper {
     grandchildren: Arc<Mutex<MultiMap<String, ReapableChild>>>,
 }
 
-macro_rules! lock {
-    ($x:expr) => {
-        $x.lock().map_err(|e| format_err!("{:#}", e))?
-    };
-}
+/// first usable file descriptor after stdin, stdout and stderr
+const FIRST_FD_AFTER_STDIO: RawFd = 3;
 
 impl ChildReaper {
     pub fn get(&self, id: &str) -> Result<ReapableChild> {
@@ -56,6 +55,7 @@ impl ChildReaper {
         Ok(r)
     }
 
+    #[allow(clippy::too_many_arguments)]
     pub async fn create_child<P, I, S>(
         &self,
         cmd: P,
@@ -64,6 +64,7 @@ impl ChildReaper {
         container_io: &mut ContainerIO,
         pidfile: &Path,
         env_vars: Vec<(String, String)>,
+        additional_fds: Vec<OwnedFd>,
     ) -> Result<(u32, CancellationToken)>
     where
         P: AsRef<OsStr>,
@@ -81,9 +82,22 @@ impl ChildReaper {
             .stdout(Stdio::piped())
             .stderr(Stdio::piped())
             .envs(env_vars)
+            .fd_mappings(
+                additional_fds
+                    .iter()
+                    .enumerate()
+                    .map(|(i, fd)| FdMapping {
+                        parent_fd: fd.as_raw_fd(),
+                        child_fd: i as RawFd + FIRST_FD_AFTER_STDIO,
+                    })
+                    .collect(),
+            )?
             .spawn()
             .context("spawn child process: {}")?;
 
+        // close file descriptors after spawn
+        drop(additional_fds);
+
         let token = CancellationToken::new();
 
         match container_io.typ_mut() {
@@ -134,7 +148,11 @@ impl ChildReaper {
         Ok((grandchild_pid, token))
     }
 
-    pub fn watch_grandchild(&self, child: Child) -> Result<Receiver<ExitChannelData>> {
+    pub fn watch_grandchild(
+        &self,
+        child: Child,
+        leak_fds: Vec<OwnedFd>,
+    ) -> Result<Receiver<ExitChannelData>> {
         let locked_grandchildren = &self.grandchildren().clone();
         let mut map = lock!(locked_grandchildren);
         let mut reapable_grandchild = ReapableChild::from_child(&child);
@@ -148,6 +166,7 @@ impl ChildReaper {
         task::spawn(
             async move {
                 exit_tx.subscribe().recv().await?;
+                drop(leak_fds);
                 Self::forget_grandchild(&cleanup_grandchildren, pid)
             }
             .instrument(debug_span!("watch_grandchild", pid)),

diff --git a/conmon-rs/server/src/config.rs b/conmon-rs/server/src/config.rs
@@ -303,6 +303,7 @@ impl Default for Config {
 // Sync with `pkg/client/client.go`
 const SOCKET: &str = "conmon.sock";
 const PIDFILE: &str = "pidfile";
+const FD_SOCKET: &str = "conmon-fd.sock";
 
 impl Config {
     /// Validate the configuration integrity.
@@ -354,6 +355,10 @@ impl Config {
             fs::remove_file(self.socket())?;
         }
 
+        if self.fd_socket().exists() {
+            fs::remove_file(self.fd_socket())?;
+        }
+
         Ok(())
     }
     pub fn socket(&self) -> PathBuf {
@@ -362,4 +367,7 @@ impl Config {
     pub fn conmon_pidfile(&self) -> PathBuf {
         self.runtime_dir().join(PIDFILE)
     }
+    pub fn fd_socket(&self) -> PathBuf {
+        self.runtime_dir().join(FD_SOCKET)
+    }
 }