Mix: Re-define max_payload_size parameter

nomos-mix/message/src/mock/mod.rs

@@ -9,12 +9,13 @@ use crate::MixMessage;
 
 const NODE_ID_SIZE: usize = 32;
 
-// TODO: Move PADDED_PAYLOAD_SIZE and MAX_LAYERS to the upper layer (service layer).
-const PADDED_PAYLOAD_SIZE: usize = 2048;
+// TODO: Move MAX_PAYLOAD_SIZE and MAX_LAYERS to the upper layer (service layer).
+const MAX_PAYLOAD_SIZE: usize = 2048;
 const PAYLOAD_PADDING_SEPARATOR: u8 = 0x01;
 const PAYLOAD_PADDING_SEPARATOR_SIZE: usize = 1;
 const MAX_LAYERS: usize = 5;
-pub const MESSAGE_SIZE: usize = NODE_ID_SIZE * MAX_LAYERS + PADDED_PAYLOAD_SIZE;
+pub const MESSAGE_SIZE: usize =
+    NODE_ID_SIZE * MAX_LAYERS + MAX_PAYLOAD_SIZE + PAYLOAD_PADDING_SEPARATOR_SIZE;
 
 #[derive(Clone, Debug)]
 pub struct MockMixMessage;
@@ -38,7 +39,7 @@ impl MixMessage for MockMixMessage {
         if node_ids.is_empty() || node_ids.len() > MAX_LAYERS {
             return Err(Error::InvalidNumberOfLayers);
         }
-        if payload.len() > PADDED_PAYLOAD_SIZE - PAYLOAD_PADDING_SEPARATOR_SIZE {
+        if payload.len() > MAX_PAYLOAD_SIZE {
             return Err(Error::PayloadTooLarge);
         }
 
@@ -53,10 +54,7 @@ impl MixMessage for MockMixMessage {
         // Append payload with padding
         message.extend(payload);
         message.push(PAYLOAD_PADDING_SEPARATOR);
-        message.extend(
-            std::iter::repeat(0)
-                .take(PADDED_PAYLOAD_SIZE - payload.len() - PAYLOAD_PADDING_SEPARATOR_SIZE),
-        );
+        message.extend(std::iter::repeat(0).take(MAX_PAYLOAD_SIZE - payload.len()));
         Ok(message)
     }
 

nomos-mix/message/src/sphinx/mod.rs

@@ -12,7 +12,7 @@ pub struct SphinxMessage;
 
 const ASYM_KEY_SIZE: usize = 32;
 // TODO: Move these constants to the upper layer (service layer).
-const PADDED_PAYLOAD_SIZE: usize = 2048;
+const MAX_PAYLOAD_SIZE: usize = 2048;
 const MAX_LAYERS: usize = 5;
 
 impl MixMessage for SphinxMessage {
@@ -20,7 +20,7 @@ impl MixMessage for SphinxMessage {
     type PrivateKey = [u8; ASYM_KEY_SIZE];
     type Error = Error;
 
-    const DROP_MESSAGE: &'static [u8] = &[0; Packet::size(MAX_LAYERS, PADDED_PAYLOAD_SIZE)];
+    const DROP_MESSAGE: &'static [u8] = &[0; Packet::size(MAX_LAYERS, MAX_PAYLOAD_SIZE)];
 
     fn build_message(
         payload: &[u8],
@@ -33,7 +33,7 @@ impl MixMessage for SphinxMessage {
                 .collect::<Vec<_>>(),
             MAX_LAYERS,
             payload,
-            PADDED_PAYLOAD_SIZE,
+            MAX_PAYLOAD_SIZE,
         )?;
         Ok(packet.to_bytes())
     }

nomos-mix/message/src/sphinx/packet.rs

@@ -4,7 +4,7 @@ use sphinx_packet::{
         keys::RoutingKeys,
         routing::{FINAL_HOP, FORWARD_HOP},
     },
-    payload::Payload,
+    payload::{Payload, PAYLOAD_OVERHEAD_SIZE},
 };
 
 use crate::sphinx::ASYM_KEY_SIZE;
@@ -55,7 +55,8 @@ impl Packet {
         let payload = sphinx_packet::payload::Payload::encapsulate_message(
             payload,
             &payload_keys,
-            max_payload_size,
+            // sphinx_packet::payload requires this parameter to include the overhead size.
+            max_payload_size + PAYLOAD_OVERHEAD_SIZE,
         )?;
 
         Ok(Packet {
@@ -191,7 +192,10 @@ impl Packet {
     }
 
     pub const fn size(max_layers: usize, max_payload_size: usize) -> usize {
-        ASYM_KEY_SIZE + EncryptedRoutingInformation::size(max_layers) + max_payload_size
+        ASYM_KEY_SIZE
+            + EncryptedRoutingInformation::size(max_layers)
+            + max_payload_size
+            + PAYLOAD_OVERHEAD_SIZE
     }
 }