rust/net: add CCA abstractions

Signed-off-by: Valentin Obst <kernel@valentinobst.de>

Author: Valentin Obst

rust/helpers.c

@@ -188,6 +188,12 @@ struct inet_connection_sock *rust_helper_inet_csk(const struct sock *sk)
 }
 EXPORT_SYMBOL_GPL(rust_helper_inet_csk);
 
+void *rust_helper_inet_csk_ca(struct sock *sk)
+{
+	return inet_csk_ca(sk);
+}
+EXPORT_SYMBOL_GPL(rust_helper_inet_csk_ca);
+
 /*
  * `bindgen` binds the C `size_t` type as the Rust `usize` type, so we can
  * use it in contexts where Rust expects a `usize` like slice (array) indices.

rust/kernel/net/sock.rs

@@ -89,6 +89,46 @@ impl Sock {
         unsafe { &mut *(bindings::tcp_sk(self.sk.get()) as *mut TcpSock) }
     }
 
+    /// Returns the [private data] of the instance of the CCA used by this
+    /// socket.
+    ///
+    /// [private data]: tcp::cong::Algorithm::Data
+    ///
+    /// # Safety
+    ///
+    /// - `sk` must be valid for `inet_csk_ca`,
+    /// - `sk` must use the CCA `T`, the `init` CB of the CCA must have been
+    ///   called, the `release` CB of the CCA must not have been called.
+    #[inline]
+    #[cfg(CONFIG_RUST_TCP_ABSTRACTIONS)]
+    pub(crate) unsafe fn inet_csk_ca<'a, T: tcp::cong::Algorithm + ?Sized>(
+        &'a self,
+    ) -> &'a T::Data {
+        // SAFETY: By the function's preconditions, calling `inet_csk_ca` is OK
+        // and the returned pointer points to a valid instance of `T::Data`.
+        unsafe { &*(bindings::inet_csk_ca(self.sk.get()) as *const T::Data) }
+    }
+
+    /// Returns the [private data] of the instance of the CCA used by this
+    /// socket.
+    ///
+    /// [private data]: tcp::cong::Algorithm::Data
+    ///
+    /// # Safety
+    ///
+    /// - `sk` must be valid for `inet_csk_ca`,
+    /// - `sk` must use the CCA `T`, the `init` CB of the CCA must have been
+    ///   called, the `release` CB of the CCA must not have been called.
+    #[inline]
+    #[cfg(CONFIG_RUST_TCP_ABSTRACTIONS)]
+    pub(crate) unsafe fn inet_csk_ca_mut<'a, T: tcp::cong::Algorithm + ?Sized>(
+        &'a mut self,
+    ) -> &'a mut T::Data {
+        // SAFETY: By the function's preconditions, calling `inet_csk_ca` is OK
+        // and the returned pointer points to a valid instance of `T::Data`.
+        unsafe { &mut *(bindings::inet_csk_ca(self.sk.get()) as *mut T::Data) }
+    }
+
     /// Returns the [`InetConnectionSock`] view of this socket.
     ///
     /// # Safety

rust/kernel/net/tcp.rs

@@ -6,6 +6,8 @@ use crate::time;
 use crate::types::Opaque;
 use core::{num, ptr};
 
+pub mod cong;
+
 /// Representation of a `struct inet_connection_sock`.
 ///
 /// # Invariants
@@ -20,6 +22,21 @@ pub struct InetConnectionSock {
     icsk: Opaque<bindings::inet_connection_sock>,
 }
 
+impl InetConnectionSock {
+    /// Returns the congestion control state of this socket.
+    #[inline]
+    pub fn ca_state(&self) -> Result<cong::State, ()> {
+        const CA_STATE_MASK: u8 = 0b11111;
+        // TODO: Replace code to access the bit field with automatically
+        // generated code by bindgen when it becomes possible.
+        // SAFETY: By the type invariants, it is okay to read `icsk_ca_state`, which is the first
+        // member of the bitfield and has a size of five.
+        cong::State::try_from(unsafe {
+            *(ptr::addr_of!((*self.icsk.get())._bitfield_1).cast::<u8>()) & CA_STATE_MASK
+        })
+    }
+}
+
 /// Representation of a `struct tcp_sock`.
 ///
 /// # Invariants