rust/ffi: add flow lifecycle callback wrappers

Provide Rust friendly callback registrations for flow init, update and finish events. These
callbacks are implemented as Rust closures.

Ticket: #8446

rust/ffi/src/flow.rs

@@ -0,0 +1,134 @@
+/* Copyright (C) 2026 Open Information Security Foundation
+ *
+ * You can copy, redistribute or modify this Program under the terms of
+ * the GNU General Public License version 2 as published by the Free
+ * Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * version 2 along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+use std::os::raw::c_void;
+
+use suricata_sys::sys::{Flow, Packet, ThreadVars};
+use suricata_sys::sys::{
+    SCFlowRegisterFinishCallback, SCFlowRegisterInitCallback, SCFlowRegisterUpdateCallback,
+};
+
+/// Register a flow initialization callback.
+///
+/// The callback is invoked whenever Suricata initializes a flow. It receives:
+/// - `tv`: the `ThreadVars` for the thread creating the flow
+/// - `f`: the newly initialized `Flow`
+/// - `p`: the packet related to creating the flow
+///
+/// # Safety
+///
+/// The callback receives raw pointers from Suricata. These pointers are only
+/// valid for the duration of the callback invocation and must not be stored.
+///
+/// The callback must not panic.
+pub fn register_init_callback<F>(callback: F) -> Result<(), &'static str>
+where
+    F: Fn(*mut ThreadVars, *mut Flow, *const Packet) + Send + Sync + 'static,
+{
+    let user = Box::into_raw(Box::new(callback)) as *mut c_void;
+    if unsafe { SCFlowRegisterInitCallback(Some(init_callback_wrapper::<F>), user) } {
+        Ok(())
+    } else {
+        unsafe {
+            drop(Box::from_raw(user as *mut F));
+        }
+        Err("Failed to register flow init callback")
+    }
+}
+
+/// Register a flow update callback.
+///
+/// The callback is invoked whenever Suricata updates a flow with a packet. It
+/// receives:
+/// - `tv`: the `ThreadVars` for the thread updating the flow
+/// - `f`: the flow being updated
+/// - `p`: the packet responsible for the flow update
+///
+/// # Safety
+///
+/// The callback receives raw pointers from Suricata. These pointers are only
+/// valid for the duration of the callback invocation and must not be stored.
+///
+/// The callback must not panic.
+pub fn register_update_callback<F>(callback: F) -> Result<(), &'static str>
+where
+    F: Fn(*mut ThreadVars, *mut Flow, *mut Packet) + Send + Sync + 'static,
+{
+    let user = Box::into_raw(Box::new(callback)) as *mut c_void;
+    if unsafe { SCFlowRegisterUpdateCallback(Some(update_callback_wrapper::<F>), user) } {
+        Ok(())
+    } else {
+        unsafe {
+            drop(Box::from_raw(user as *mut F));
+        }
+        Err("Failed to register flow update callback")
+    }
+}
+
+/// Register a flow finish callback.
+///
+/// The callback is invoked when Suricata is finished with a flow. It receives:
+/// - `tv`: the `ThreadVars` for the thread finishing the flow
+/// - `f`: the flow being finished
+///
+/// # Safety
+///
+/// The callback receives raw pointers from Suricata. These pointers are only
+/// valid for the duration of the callback invocation and must not be stored.
+///
+/// The callback must not panic.
+pub fn register_finish_callback<F>(callback: F) -> Result<(), &'static str>
+where
+    F: Fn(*mut ThreadVars, *mut Flow) + Send + Sync + 'static,
+{
+    let user = Box::into_raw(Box::new(callback)) as *mut c_void;
+    if unsafe { SCFlowRegisterFinishCallback(Some(finish_callback_wrapper::<F>), user) } {
+        Ok(())
+    } else {
+        unsafe {
+            drop(Box::from_raw(user as *mut F));
+        }
+        Err("Failed to register flow finish callback")
+    }
+}
+
+unsafe extern "C" fn init_callback_wrapper<F>(
+    tv: *mut ThreadVars, f: *mut Flow, p: *const Packet, user: *mut c_void,
+) where
+    F: Fn(*mut ThreadVars, *mut Flow, *const Packet) + Send + Sync + 'static,
+{
+    let callback = &*(user as *const F);
+    callback(tv, f, p);
+}
+
+unsafe extern "C" fn update_callback_wrapper<F>(
+    tv: *mut ThreadVars, f: *mut Flow, p: *mut Packet, user: *mut c_void,
+) where
+    F: Fn(*mut ThreadVars, *mut Flow, *mut Packet) + Send + Sync + 'static,
+{
+    let callback = &*(user as *const F);
+    callback(tv, f, p);
+}
+
+unsafe extern "C" fn finish_callback_wrapper<F>(
+    tv: *mut ThreadVars, f: *mut Flow, user: *mut c_void,
+) where
+    F: Fn(*mut ThreadVars, *mut Flow) + Send + Sync + 'static,
+{
+    let callback = &*(user as *const F);
+    callback(tv, f);
+}

rust/ffi/src/lib.rs

@@ -20,6 +20,7 @@ pub mod conf;
 pub mod debug;
 pub mod detect;
 pub mod eve;
+pub mod flow;
 pub mod jsonbuilder;
 pub mod plugin;