feat: add API for process discovery

Resolves [APMAPI-1063]

Author: dmehala

ddcommon-ffi/src/tracer_metadata.rs

@@ -0,0 +1,24 @@
+// Copyright 2021-Present Datadog, Inc. https://www.datadoghq.com/
+// SPDX-License-Identifier: Apache-2.0
+
+//use std::os::raw::c_void;
+use std::ffi::c_void;
+use ddcommon::{TracerMetadata, AnonymousFileHandle, store_tracer_metadata};
+
+impl AnonymousFileHandle {
+    fn as_raw_pointer(&self) -> *mut c_void {
+        match self {
+            #[cfg(target_os = "linux")]
+            AnonymousFileHandle::Linux(memfd) => Box::as_ptr(memfd) as *mut c_void,
+            #[cfg(not(target_os = "linux"))]
+            AnonymousFileHandle::Other(()) => std::ptr::null() as *mut c_void,
+        }
+    }
+}
+
+#[no_mangle]
+#[must_use]
+pub extern "C" fn ddog_store_tracer_metadata(tracer_metadata: TracerMetadata) -> *mut c_void {
+    let handle = store_tracer_metadata(tracer_metadata).unwrap();
+    return handle.as_raw_pointer();
+}

ddcommon/Cargo.toml

@@ -32,7 +32,10 @@ hyper-util = "0.1.3"
 lazy_static = "1.4"
 log = { version = "0.4" }
 pin-project = "1"
+rand = "0.8.3"
 regex = "1.5"
+rmp = "0.8.14"
+rmp-serde = "1.3.0"
 rustls = { version = "0.23", default-features = false }
 rustls-native-certs = { version = "0.7" }
 tokio = { version = "1.23", features = ["rt", "macros"] }
@@ -55,6 +58,7 @@ hyper-rustls = { version = "0.27", default-features = false, features = [
     "tls12",
     "aws-lc-rs",
 ] }
+memfd = { version = "0.6" }
 
 [target.'cfg(not(unix))'.dependencies]
 hyper-rustls = { version = "0.27", default-features = false, features = [

ddcommon/src/lib.rs

@@ -18,6 +18,7 @@ pub mod cstr;
 pub mod config;
 pub mod rate_limiter;
 pub mod tag;
+pub mod tracer_metadata;
 
 pub mod header {
     #![allow(clippy::declare_interior_mutable_const)]

ddcommon/src/tracer_metadata.rs

@@ -0,0 +1,69 @@
+// Copyright 2023-Present Datadog, Inc. https://www.datadoghq.com/
+// SPDX-License-Identifier: Apache-2.0
+
+use serde::Serialize;
+#[cfg(target_os = "linux")]
+use memfd::{Memfd, MemfdOptions};
+
+/// This struct MUST be backward compatible.
+#[derive(Serialize, Debug)]
+#[repr(C)]
+pub struct TracerMetadata {
+   /// Version of the schema.
+   pub schema_version: u8,
+   /// Runtime UUID.
+   #[serde(skip_serializing_if = "Option::is_none")]
+   pub runtime_id: Option<String>,
+   /// Programming language of the tracer library (e.g., “python”). Refers to telemetry        for valid values.
+   pub tracer_language: String,
+   /// Version of the tracer (e.g., "1.0.0").
+   pub tracer_version: String,
+   /// Identifier of the machine running the process.
+   pub hostname: String,
+   /// Name of the service being instrumented.
+   #[serde(skip_serializing_if = "Option::is_none")]
+   pub service_name: Option<String>,
+   /// Environment of the service being instrumented.
+   #[serde(skip_serializing_if = "Option::is_none")]
+   pub service_env: Option<String>,
+   /// Version of the service being instrumented.
+   #[serde(skip_serializing_if = "Option::is_none")]
+   pub service_version: Option<String>,
+}
+
+pub enum AnonymousFileHandle {
+    #[cfg(target_os = "linux")]
+    Linux(Box<Memfd>),
+    #[cfg(not(target_os = "linux"))]
+    Other(()),
+}
+
+/// Create the anonymous file storing the tracer metadata.
+#[cfg(target_os = "linux")]
+pub fn store_tracer_metadata(data: TracerMetadata) -> Result<AnonymousFileHandle, String> {
+    let uid: String = rand::thread_rng().sample_iter(&Alphanumeric).take(8).map(char::from).collect();
+    let mfd_name: String = format!("{}-{}", "datadog-tracer-info", uid);
+
+    let mfd = MemfdOptions::default()
+        .close_on_exec(true)
+        .allow_sealing(true)
+        .create::<&str>(mfd_name.as_ref())
+        .map_err(|e| format!("Unable to create memfd: {}", e))?;
+
+    let mut buf = Vec::new();
+    data.serialize(&mut Serializer::new(&mut buf).with_struct_map()).unwrap();
+
+    mfd.as_file().write_all(&buf).unwrap();
+    mfd.add_seals(&[
+        memfd::FileSeal::SealShrink,
+        memfd::FileSeal::SealGrow,
+        memfd::FileSeal::SealSeal,
+    ]).map_error(|e| format!("Unable to seal: {}", e))?;
+
+    return Ok(AnonymousFileHandle::Linux(Box::new(mfd)));
+}
+
+#[cfg(not(target_os = "linux"))]
+pub fn store_tracer_metadata(_data: TracerMetadata) -> Result<AnonymousFileHandle, String> {
+    return Ok(AnonymousFileHandle::Other(()));
+}