udp: uring: improve SendBuffers code

aquatic_udp/src/workers/socket/uring/send_buffers.rs

@@ -46,7 +46,7 @@ struct SendBuffer {
 }
 
 impl SendBuffer {
-    fn new() -> Self {
+    fn new_with_null_pointers() -> Self {
         Self {
             name_v4: UnsafeCell::new(libc::sockaddr_in {
                 sin_family: libc::AF_INET as u16,
@@ -80,6 +80,86 @@ impl SendBuffer {
             response_type: ResponseType::Connect,
         }
     }
+
+    /// # Safety
+    ///
+    /// - SendBuffer must be stored at a fixed location in memory
+    unsafe fn setup_pointers(&mut self, socket_is_ipv4: bool) {
+        let iovec = &mut *self.iovec.get();
+
+        iovec.iov_base = self.bytes.get() as *mut libc::c_void;
+        iovec.iov_len = (&*self.bytes.get()).len();
+
+        let msghdr = &mut *self.msghdr.get();
+
+        msghdr.msg_iov = self.iovec.get();
+
+        if socket_is_ipv4 {
+            msghdr.msg_name = self.name_v4.get() as *mut libc::c_void;
+            msghdr.msg_namelen = core::mem::size_of::<libc::sockaddr_in>() as u32;
+        } else {
+            msghdr.msg_name = self.name_v6.get() as *mut libc::c_void;
+            msghdr.msg_namelen = core::mem::size_of::<libc::sockaddr_in6>() as u32;
+        }
+    }
+
+    /// # Safety
+    ///
+    /// - SendBuffer must be stored at a fixed location in memory
+    /// - SendBuffer.setup_pointers must have been called previously
+    unsafe fn prepare_entry(
+        &mut self,
+        response: &Response,
+        addr: CanonicalSocketAddr,
+        socket_is_ipv4: bool,
+    ) -> Result<io_uring::squeue::Entry, Error> {
+        // Set receiver socket addr
+        if socket_is_ipv4 {
+            self.receiver_is_ipv4 = true;
+
+            let addr = if let Some(SocketAddr::V4(addr)) = addr.get_ipv4() {
+                addr
+            } else {
+                panic!("ipv6 address in ipv4 mode");
+            };
+
+            let name = &mut *self.name_v4.get();
+
+            name.sin_port = addr.port().to_be();
+            name.sin_addr.s_addr = u32::from(*addr.ip()).to_be();
+        } else {
+            self.receiver_is_ipv4 = addr.is_ipv4();
+
+            let addr = if let SocketAddr::V6(addr) = addr.get_ipv6_mapped() {
+                addr
+            } else {
+                panic!("ipv4 address when ipv6 or ipv6-mapped address expected");
+            };
+
+            let name = &mut *self.name_v6.get();
+
+            name.sin6_port = addr.port().to_be();
+            name.sin6_addr.s6_addr = addr.ip().octets();
+        }
+
+        let bytes = (&mut *self.bytes.get()).as_mut_slice();
+
+        let mut cursor = Cursor::new(bytes);
+
+        match response.write(&mut cursor) {
+            Ok(()) => {
+                (&mut *self.iovec.get()).iov_len = cursor.position() as usize;
+
+                self.response_type = ResponseType::from_response(response);
+                self.free = false;
+
+                let sqe = SendMsg::new(SOCKET_IDENTIFIER, self.msghdr.get()).build();
+
+                Ok(sqe)
+            }
+            Err(err) => Err(Error::SerializationFailed(err)),
+        }
+    }
 }
 
 pub struct SendBuffers {
@@ -92,30 +172,15 @@ impl SendBuffers {
     pub fn new(config: &Config, capacity: usize) -> Self {
         let socket_is_ipv4 = config.network.address.is_ipv4();
 
-        let mut buffers = ::std::iter::repeat_with(|| SendBuffer::new())
+        let mut buffers = ::std::iter::repeat_with(|| SendBuffer::new_with_null_pointers())
             .take(capacity)
             .collect::<Vec<_>>()
             .into_boxed_slice();
 
         for buffer in buffers.iter_mut() {
+            // Safety: OK because buffers are stored in fixed memory location
             unsafe {
-                let iovec = &mut *buffer.iovec.get();
+                buffer.setup_pointers(socket_is_ipv4);
-
-                iovec.iov_base = buffer.bytes.get() as *mut libc::c_void;
-                iovec.iov_len = (&*buffer.bytes.get()).len();
-            }
-            unsafe {
-                let msghdr = &mut *buffer.msghdr.get();
-
-                msghdr.msg_iov = buffer.iovec.get();
-
-                if socket_is_ipv4 {
-                    msghdr.msg_name = buffer.name_v4.get() as *mut libc::c_void;
-                    msghdr.msg_namelen = core::mem::size_of::<libc::sockaddr_in>() as u32;
-                } else {
-                    msghdr.msg_name = buffer.name_v6.get() as *mut libc::c_void;
-                    msghdr.msg_namelen = core::mem::size_of::<libc::sockaddr_in6>() as u32;
-                }
             }
         }
 
@@ -152,60 +217,16 @@ impl SendBuffers {
 
         let buffer = self.buffers.index_mut(index);
 
-        // Set receiver socket addr
+        // Safety: OK because buffers are stored in fixed memory location
-        if self.socket_is_ipv4 {
+        // and buffer pointers were set up in SendBuffers::new()
-            buffer.receiver_is_ipv4 = true;
-
-            let addr = if let Some(SocketAddr::V4(addr)) = addr.get_ipv4() {
-                addr
-            } else {
-                panic!("ipv6 address in ipv4 mode");
-            };
-
-            unsafe {
-                let name = &mut *buffer.name_v4.get();
-
-                name.sin_port = addr.port().to_be();
-                name.sin_addr.s_addr = u32::from(*addr.ip()).to_be();
-            }
-        } else {
-            buffer.receiver_is_ipv4 = addr.is_ipv4();
-
-            let addr = if let SocketAddr::V6(addr) = addr.get_ipv6_mapped() {
-                addr
-            } else {
-                panic!("ipv4 address when ipv6 or ipv6-mapped address expected");
-            };
-
-            unsafe {
-                let name = &mut *buffer.name_v6.get();
-
-                name.sin6_port = addr.port().to_be();
-                name.sin6_addr.s6_addr = addr.ip().octets();
-            }
-        }
-
         unsafe {
-            let bytes = (&mut *buffer.bytes.get()).as_mut_slice();
+            match buffer.prepare_entry(response, addr, self.socket_is_ipv4) {
-
+                Ok(entry) => {
-            let mut cursor = Cursor::new(bytes);
-
-            match response.write(&mut cursor) {
-                Ok(()) => {
-                    (&mut *buffer.iovec.get()).iov_len = cursor.position() as usize;
-
-                    buffer.response_type = ResponseType::from_response(response);
-                    buffer.free = false;
-
                     self.likely_next_free_index = index + 1;
 
-                    let sqe = SendMsg::new(SOCKET_IDENTIFIER, buffer.msghdr.get())
+                    Ok(entry.user_data(index as u64))
-                        .build()
-                        .user_data(index as u64);
-
-                    Ok(sqe)
                 }
-                Err(err) => Err(Error::SerializationFailed(err)),
+                Err(err) => Err(err),
             }
         }
     }