main: Enable the api-socket to be passed as an fd

To avoid race issues where the api-socket may not be created by the
time a cloud-hypervisor caller is ready to look for it, enable the
caller to pass the api-socket fd directly.

Avoid breaking current callers by allowing the --api-socket path to be
passed as it is now in addition to through the path argument.

Signed-off-by: William Douglas <william.r.douglas@gmail.com>

vmm/src/api/http.rs

@@ -11,6 +11,7 @@ use micro_http::{Body, HttpServer, MediaType, Method, Request, Response, StatusC
 use seccomp::{SeccompAction, SeccompFilter};
 use serde_json::Error as SerdeError;
 use std::collections::HashMap;
+use std::os::unix::io::RawFd;
 use std::path::PathBuf;
 use std::sync::mpsc::Sender;
 use std::sync::Arc;
@@ -253,16 +254,12 @@ fn handle_http_request(
     response
 }
 
-pub fn start_http_thread(
-    path: &str,
+fn start_http_thread(
+    mut server: HttpServer,
     api_notifier: EventFd,
     api_sender: Sender<ApiRequest>,
     seccomp_action: &SeccompAction,
 ) -> Result<thread::JoinHandle<Result<()>>> {
-    std::fs::remove_file(path).unwrap_or_default();
-    let socket_path = PathBuf::from(path);
-    let mut server = HttpServer::new(socket_path).map_err(Error::CreateApiServer)?;
-
     // Retrieve seccomp filter for API thread
     let api_seccomp_filter =
         get_seccomp_filter(seccomp_action, Thread::Api).map_err(Error::CreateSeccompFilter)?;
@@ -299,3 +296,25 @@ pub fn start_http_thread(
         })
         .map_err(Error::HttpThreadSpawn)
 }
+
+pub fn start_http_path_thread(
+    path: &str,
+    api_notifier: EventFd,
+    api_sender: Sender<ApiRequest>,
+    seccomp_action: &SeccompAction,
+) -> Result<thread::JoinHandle<Result<()>>> {
+    std::fs::remove_file(path).unwrap_or_default();
+    let socket_path = PathBuf::from(path);
+    let server = HttpServer::new(socket_path).map_err(Error::CreateApiServer)?;
+    start_http_thread(server, api_notifier, api_sender, seccomp_action)
+}
+
+pub fn start_http_fd_thread(
+    fd: RawFd,
+    api_notifier: EventFd,
+    api_sender: Sender<ApiRequest>,
+    seccomp_action: &SeccompAction,
+) -> Result<thread::JoinHandle<Result<()>>> {
+    let server = HttpServer::new_from_fd(fd).map_err(Error::CreateApiServer)?;
+    start_http_thread(server, api_notifier, api_sender, seccomp_action)
+}

vmm/src/api/mod.rs

@@ -31,7 +31,8 @@
 extern crate vm_device;
 extern crate vmm_sys_util;
 
-pub use self::http::start_http_thread;
+pub use self::http::start_http_fd_thread;
+pub use self::http::start_http_path_thread;
 
 pub mod http;
 pub mod http_endpoint;