src/error.rs

@@ -18,6 +18,9 @@ pub enum Error {
     #[error("bad pipe specification: a pipe must have exactly one reader and one writer: {0}")]
     BadPipe(String),
 
+    #[error("bad socket specification: a socket must have exactly one reader and one writer: {0}")]
+    BadFileSocket(String),
+
     #[error("bad specification type: only .json files are supported")]
     BadSpecType,
 

src/lib.rs

@@ -16,7 +16,8 @@ use std::os::unix::io::FromRawFd;
 
 use clap::{App, AppSettings};
 use nix::fcntl::OFlag;
-use nix::unistd::{self};
+use nix::sys::socket;
+use nix::unistd;
 
 pub fn run() -> Result<()> {
     // process arguments
@@ -69,12 +70,17 @@ pub fn run() -> Result<()> {
     let (pipes, _) = spec.pipes();
     let pipes = create_pipes(pipes)?;
 
+    let (sockets, _) = spec.sockets();
+    let sockets = create_sockets(sockets)?;
+
     // spawn all processes
     Spawner {
         spec: &spec,
-        pipes,
         binary,
         trailing: &trailing,
+
+        pipes,
+        sockets,
     }
     .spawn()
 }
@@ -89,6 +95,16 @@ fn create_pipes(names: Vec<&str>) -> Result<HashMap<String, PipePair>> {
     Ok(pipes)
 }
 
+fn create_sockets(names: Vec<&str>) -> Result<HashMap<String, SocketPair>> {
+    let mut sockets = HashMap::new();
+    for socket in names {
+        info!("creating socket pair `{}`", socket);
+        sockets.insert(socket.to_string(), SocketPair::new(socket)?);
+    }
+
+    Ok(sockets)
+}
+
 pub struct PipePair {
     name: String,
 
@@ -123,3 +139,44 @@ impl PipePair {
             .ok_or_else(|| Error::BadPipe(self.name.to_string()))
     }
 }
+
+pub struct SocketPair {
+    name: String,
+
+    read: Option<File>,
+    write: Option<File>,
+}
+
+impl SocketPair {
+    fn new(name: &str) -> Result<SocketPair> {
+        let (read, write) = socket::socketpair(
+            socket::AddressFamily::Unix,
+            socket::SockType::Datagram,
+            None,
+            socket::SockFlag::empty(),
+        )
+        .map_err(|e| Error::Nix {
+            msg: "socketpair",
+            src: e,
+        })?;
+
+        // safe to create files given the successful return of socketpair(2)
+        Ok(SocketPair {
+            name: name.to_string(),
+            read: Some(unsafe { File::from_raw_fd(read) }),
+            write: Some(unsafe { File::from_raw_fd(write) }),
+        })
+    }
+
+    fn take_read(&mut self) -> Result<File> {
+        self.read
+            .take()
+            .ok_or_else(|| Error::BadPipe(self.name.to_string()))
+    }
+
+    fn take_write(&mut self) -> Result<File> {
+        self.write
+            .take()
+            .ok_or_else(|| Error::BadPipe(self.name.to_string()))
+    }
+}

src/spawner.rs

@@ -1,7 +1,7 @@
 use log::{debug, error, info};
 
-use super::specification::{Arg, Entrypoint, Pipe, Specification, Trigger};
-use super::PipePair;
+use super::specification::{Arg, Entrypoint, FileSocket, Pipe, Specification, Trigger};
+use super::{PipePair, SocketPair};
 use crate::void::VoidBuilder;
 use crate::{Error, Result};
 
@@ -10,18 +10,21 @@ use std::ffi::CString;
 use std::fs::File;
 use std::io::Read;
 use std::net::TcpListener;
-use std::os::unix::io::IntoRawFd;
+use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd};
 use std::path::PathBuf;
 
+use nix::sys::socket::{recvmsg, ControlMessageOwned, MsgFlags};
 use nix::unistd;
 
 const BUFFER_SIZE: usize = 1024;
 
 pub struct Spawner<'a> {
     pub spec: &'a Specification,
-    pub pipes: HashMap<String, PipePair>,
     pub binary: &'a str,
     pub trailing: &'a Vec<&'a str>,
+
+    pub pipes: HashMap<String, PipePair>,
+    pub sockets: HashMap<String, SocketPair>,
 }
 
 enum TriggerData<'a> {
@@ -30,6 +33,9 @@ enum TriggerData<'a> {
 
     /// A string sent across a pipe
     Pipe(&'a str),
+
+    /// File(s) sent over a file socket
+    FileSocket(Vec<File>),
 }
 
 impl<'a> TriggerData<'a> {
@@ -37,6 +43,10 @@ impl<'a> TriggerData<'a> {
         match self {
             TriggerData::None => vec![],
             TriggerData::Pipe(s) => vec![CString::new(s.to_string()).unwrap()],
+            TriggerData::FileSocket(fs) => fs
+                .drain(..)
+                .map(|f| CString::new(f.into_raw_fd().to_string()).unwrap())
+                .collect(),
         }
     }
 }
@@ -75,7 +85,7 @@ impl<'a> Spawner<'a> {
                 }
 
                 Trigger::Pipe(s) => {
-                    let pipe = self.pipes.get_mut(s).unwrap().take_read().unwrap();
+                    let pipe = self.pipes.get_mut(s).unwrap().take_read()?;
                     let binary = PathBuf::from(self.binary).canonicalize()?;
 
                     let mut builder = VoidBuilder::new();
@@ -92,6 +102,25 @@ impl<'a> Spawner<'a> {
 
                     builder.spawn(closure)?;
                 }
+
+                Trigger::FileSocket(s) => {
+                    let socket = self.sockets.get_mut(s).unwrap().take_read()?;
+                    let binary = PathBuf::from(self.binary).canonicalize()?;
+
+                    let mut builder = VoidBuilder::new();
+                    builder.mount(binary, "/entrypoint");
+                    builder.keep_fd(&socket);
+
+                    let closure = || match self.file_socket_trigger(socket, entrypoint, name) {
+                        Ok(()) => std::process::exit(exitcode::OK),
+                        Err(e) => {
+                            error!("error in file_socket_trigger: {}", e);
+                            std::process::exit(1)
+                        }
+                    };
+
+                    builder.spawn(closure)?;
+                }
             }
         }
 
@@ -100,7 +129,6 @@ impl<'a> Spawner<'a> {
 
     fn pipe_trigger(&self, mut pipe: File, spec: &Entrypoint, name: &str) -> Result<()> {
         let mut buf = [0_u8; BUFFER_SIZE];
-
         loop {
             let read_bytes = pipe.read(&mut buf)?;
             if read_bytes == 0 {
@@ -109,6 +137,9 @@ impl<'a> Spawner<'a> {
 
             debug!("triggering from pipe read");
 
+            let mut builder = VoidBuilder::new();
+            builder.mount("/entrypoint", "/entrypoint");
+
             let closure =
                 || {
                     let pipe_trigger = std::str::from_utf8(&buf[0..read_bytes]).unwrap();
@@ -129,11 +160,68 @@ impl<'a> Spawner<'a> {
                     }
                 };
 
-            let mut builder = VoidBuilder::new();
             builder.spawn(closure)?;
         }
     }
 
+    fn file_socket_trigger(&self, socket: File, spec: &Entrypoint, name: &str) -> Result<()> {
+        let mut buf = Vec::new();
+        loop {
+            let msg = recvmsg(socket.as_raw_fd(), &[], Some(&mut buf), MsgFlags::empty()).map_err(
+                |e| Error::Nix {
+                    msg: "recvmsg",
+                    src: e,
+                },
+            )?;
+
+            debug!("triggering from socket recvmsg");
+
+            for cmsg in msg.cmsgs() {
+                match cmsg {
+                    ControlMessageOwned::ScmRights(fds) => {
+                        let fds = fds
+                            .into_iter()
+                            .map(|fd| unsafe { File::from_raw_fd(fd) })
+                            .collect();
+
+                        let mut builder = VoidBuilder::new();
+                        builder.mount("/entrypoint", "/entrypoint");
+                        for fd in &fds {
+                            builder.keep_fd(fd);
+                        }
+
+                        let closure = || {
+                            let args = self
+                                .prepare_args_ref(
+                                    name,
+                                    &spec.args,
+                                    &mut TriggerData::FileSocket(fds),
+                                )
+                                .unwrap();
+
+                            if let Err(e) =
+                                unistd::execv(&CString::new("/entrypoint").unwrap(), &args).map_err(
+                                    |e| Error::Nix {
+                                        msg: "execv",
+                                        src: e,
+                                    },
+                                )
+                            {
+                                error!("error: {}", e);
+                                1
+                            } else {
+                                0
+                            }
+                        };
+
+                        builder.spawn(closure)?;
+                    }
+                    _ => unimplemented!(),
+                }
+            }
+        }
+    }
+
     fn prepare_args(
         &mut self,
         entrypoint: &str,
@@ -144,8 +232,10 @@ impl<'a> Spawner<'a> {
         for arg in args {
             out.extend(self.prepare_arg(entrypoint, arg, trigger)?);
         }
+
         Ok(out)
     }
+
     fn prepare_args_ref(
         &self,
         entrypoint: &str,
@@ -156,6 +246,7 @@ impl<'a> Spawner<'a> {
         for arg in args {
             out.extend(self.prepare_arg_ref(entrypoint, arg, trigger)?);
         }
+
         Ok(out)
     }
 
@@ -176,6 +267,18 @@ impl<'a> Spawner<'a> {
                     Ok(vec![CString::new(pipe.into_raw_fd().to_string()).unwrap()])
                 }
             },
+
+            Arg::FileSocket(s) => match s {
+                FileSocket::Rx(s) => {
+                    let pipe = self.sockets.get_mut(s).unwrap().take_read()?;
+                    Ok(vec![CString::new(pipe.into_raw_fd().to_string()).unwrap()])
+                }
+                FileSocket::Tx(s) => {
+                    let pipe = self.sockets.get_mut(s).unwrap().take_write()?;
+                    Ok(vec![CString::new(pipe.into_raw_fd().to_string()).unwrap()])
+                }
+            },
+
             a => self.prepare_arg_ref(entrypoint, a, trigger),
         }
     }
@@ -191,6 +294,12 @@ impl<'a> Spawner<'a> {
             Arg::Entrypoint => Ok(vec![CString::new(entrypoint).unwrap()]),
 
             Arg::Pipe(p) => Err(Error::BadPipe(p.get_name().to_string())),
+            Arg::FileSocket(s) => Err(Error::BadFileSocket(s.get_name().to_string())),
+
+            Arg::File(p) => {
+                let f = File::open(p)?.into_raw_fd();
+                Ok(vec![CString::new(f.to_string()).unwrap()])
+            }
 
             Arg::Trigger => Ok(trigger.args()),
 

src/specification.rs

@@ -25,8 +25,14 @@ pub struct Entrypoint {
 
 #[derive(Serialize, Deserialize, Debug)]
 pub enum Trigger {
+    /// Start this entrypoint at application startup
     Startup,
+
+    /// Trigger this entrypoint when a named pipe receives data
     Pipe(String),
+
+    /// Trigger this entrypoint when a named file socket receives data
+    FileSocket(String),
 }
 
 impl Default for Trigger {
@@ -36,7 +42,6 @@ impl Default for Trigger {
 }
 
 #[derive(Serialize, Deserialize, PartialEq, Debug)]
-// #[serde(tag = "type")]
 pub enum Arg {
     /// The binary name, or argv[0], of the original program start
     BinaryName,
@@ -44,11 +49,17 @@ pub enum Arg {
     /// The name of this entrypoint
     Entrypoint,
 
+    /// A file descriptor for a file on the filesystem in the launching namespace
+    File(PathBuf),
+
     /// A chosen end of a named pipe
     Pipe(Pipe),
 
+    /// File socket
+    FileSocket(FileSocket),
+
     /// A value specified by the trigger
-    /// NOTE: Only valid if the trigger is of type Pipe(...)
+    /// NOTE: Only valid if the trigger is of type Pipe(...) or FileSocket(...)
     Trigger,
 
     /// A TCP Listener
@@ -79,6 +90,21 @@ impl Pipe {
     }
 }
 
+#[derive(Serialize, Deserialize, PartialEq, Debug)]
+pub enum FileSocket {
+    Rx(String),
+    Tx(String),
+}
+
+impl FileSocket {
+    pub fn get_name(&self) -> &str {
+        match self {
+            FileSocket::Rx(n) => n,
+            FileSocket::Tx(n) => n,
+        }
+    }
+}
+
 #[derive(Serialize, Deserialize, PartialEq, Eq, Hash, Debug)]
 pub enum Permission {
     Filesystem {
@@ -105,9 +131,8 @@ impl Specification {
         let mut write = Vec::new();
 
         for entry in self.entrypoints.values() {
-            match &entry.trigger {
-                Trigger::Startup => {}
-                Trigger::Pipe(s) => read.push(s.as_str()),
+            if let Trigger::Pipe(s) = &entry.trigger {
+                read.push(s.as_str());
             }
 
             for arg in &entry.args {
@@ -125,6 +150,30 @@ impl Specification {
         (read, write)
     }
 
+    pub fn sockets(&self) -> (Vec<&str>, Vec<&str>) {
+        let mut read = Vec::new();
+        let mut write = Vec::new();
+
+        for entry in self.entrypoints.values() {
+            if let Trigger::FileSocket(s) = &entry.trigger {
+                read.push(s.as_str());
+            }
+
+            for arg in &entry.args {
+                if let Arg::FileSocket(p) = arg {
+                    match p {
+                        FileSocket::Rx(s) => read.push(s.as_str()),
+                        FileSocket::Tx(s) => write.push(s.as_str()),
+                    }
+                }
+            }
+        }
+
+        debug!("read sockets: {:?}", &read);
+        debug!("write sockets: {:?}", &write);
+        (read, write)
+    }
+
     pub fn validate(&self) -> Result<()> {
         // validate pipes match
         let (read, write) = self.pipes();
@@ -153,11 +202,12 @@ impl Specification {
             return Err(Error::BadPipe(pipe.to_string()));
         }
 
-        // validate pipe trigger arguments make sense
+        // validate trigger arguments make sense
         for entrypoint in self.entrypoints.values() {
             if entrypoint.args.contains(&Arg::Trigger) {
                 match entrypoint.trigger {
                     Trigger::Pipe(_) => {}
+                    Trigger::FileSocket(_) => {}
                     _ => return Err(Error::BadTriggerArgument),
                 }
             }