Errors for all RPC Requests (#5867)

* Return and error if peer has disconnected

* Report errors for rate limited requests

* Code improvement

* Bump rust version to 1.78

* Downgrade to 1.77

* Update beacon_node/lighthouse_network/src/service/mod.rs

Co-authored-by: João Oliveira <hello@jxs.pt>

* fix fmt

* Merge branch 'unstable' of https://github.com/sigp/lighthouse into rpc-peer-disconnect-error

* update lockfile

beacon_node/lighthouse_network/src/service/gossip_cache.rs

@@ -240,7 +240,7 @@ impl futures::stream::Stream for GossipCache {
 
     fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
         match self.expirations.poll_expired(cx) {
-            Poll::Ready(Some(Ok(expired))) => {
+            Poll::Ready(Some(expired)) => {
                 let expected_key = expired.key();
                 let (topic, data) = expired.into_inner();
                 match self.topic_msgs.get_mut(&topic) {
@@ -259,7 +259,6 @@ impl futures::stream::Stream for GossipCache {
                 }
                 Poll::Ready(Some(Ok(topic)))
             }
-            Poll::Ready(Some(Err(x))) => Poll::Ready(Some(Err(x.to_string()))),
             Poll::Ready(None) => Poll::Ready(None),
             Poll::Pending => Poll::Pending,
         }

beacon_node/lighthouse_network/src/service/mod.rs

@@ -917,12 +917,23 @@ impl<AppReqId: ReqId, E: EthSpec> Network<AppReqId, E> {
     /* Eth2 RPC behaviour functions */
 
     /// Send a request to a peer over RPC.
-    pub fn send_request(&mut self, peer_id: PeerId, request_id: AppReqId, request: Request) {
+    pub fn send_request(
+        &mut self,
+        peer_id: PeerId,
+        request_id: AppReqId,
+        request: Request,
+    ) -> Result<(), (AppReqId, RPCError)> {
+        // Check if the peer is connected before sending an RPC request
+        if !self.swarm.is_connected(&peer_id) {
+            return Err((request_id, RPCError::Disconnected));
+        }
+
         self.eth2_rpc_mut().send_request(
             peer_id,
             RequestId::Application(request_id),
             request.into(),
-        )
+        );
+        Ok(())
     }
 
     /// Send a successful response to a peer over RPC.