Fix merge rpc length limits (#3133)

## Issue Addressed

N/A

## Proposed Changes

Fix the upper bound for blocks by root responses to be equal to the max merge block size instead of altair.
Further make the rpc response limits fork aware.

beacon_node/lighthouse_network/src/rpc/codec/base.rs

@@ -184,13 +184,25 @@ mod tests {
     use crate::rpc::protocol::*;
 
     use std::sync::Arc;
-    use types::{ForkContext, Hash256};
+    use types::{Epoch, ForkContext, ForkName, Hash256, Slot};
     use unsigned_varint::codec::Uvi;
 
     type Spec = types::MainnetEthSpec;
 
-    fn fork_context() -> ForkContext {
-        ForkContext::new::<Spec>(types::Slot::new(0), Hash256::zero(), &Spec::default_spec())
+    fn fork_context(fork_name: ForkName) -> ForkContext {
+        let mut chain_spec = Spec::default_spec();
+        let altair_fork_epoch = Epoch::new(1);
+        let merge_fork_epoch = Epoch::new(2);
+
+        chain_spec.altair_fork_epoch = Some(altair_fork_epoch);
+        chain_spec.bellatrix_fork_epoch = Some(merge_fork_epoch);
+
+        let current_slot = match fork_name {
+            ForkName::Base => Slot::new(0),
+            ForkName::Altair => altair_fork_epoch.start_slot(Spec::slots_per_epoch()),
+            ForkName::Merge => merge_fork_epoch.start_slot(Spec::slots_per_epoch()),
+        };
+        ForkContext::new::<Spec>(current_slot, Hash256::zero(), &chain_spec)
     }
 
     #[test]
@@ -202,9 +214,12 @@ mod tests {
         let snappy_protocol_id =
             ProtocolId::new(Protocol::Status, Version::V1, Encoding::SSZSnappy);
 
-        let fork_context = Arc::new(fork_context());
-        let mut snappy_outbound_codec =
-            SSZSnappyOutboundCodec::<Spec>::new(snappy_protocol_id, 1_048_576, fork_context);
+        let fork_context = Arc::new(fork_context(ForkName::Base));
+        let mut snappy_outbound_codec = SSZSnappyOutboundCodec::<Spec>::new(
+            snappy_protocol_id,
+            max_rpc_size(&fork_context),
+            fork_context,
+        );
 
         // remove response code
         let mut snappy_buf = buf.clone();
@@ -234,9 +249,12 @@ mod tests {
         let snappy_protocol_id =
             ProtocolId::new(Protocol::Status, Version::V1, Encoding::SSZSnappy);
 
-        let fork_context = Arc::new(fork_context());
-        let mut snappy_outbound_codec =
-            SSZSnappyOutboundCodec::<Spec>::new(snappy_protocol_id, 1_048_576, fork_context);
+        let fork_context = Arc::new(fork_context(ForkName::Base));
+        let mut snappy_outbound_codec = SSZSnappyOutboundCodec::<Spec>::new(
+            snappy_protocol_id,
+            max_rpc_size(&fork_context),
+            fork_context,
+        );
 
         let snappy_decoded_message = snappy_outbound_codec.decode(&mut dst).unwrap_err();
 
@@ -260,36 +278,50 @@ mod tests {
             ProtocolId::new(Protocol::BlocksByRange, Version::V1, Encoding::SSZSnappy);
 
         // Response limits
-        let limit = protocol_id.rpc_response_limits::<Spec>();
+        let fork_context = Arc::new(fork_context(ForkName::Base));
+        let max_rpc_size = max_rpc_size(&fork_context);
+        let limit = protocol_id.rpc_response_limits::<Spec>(&fork_context);
         let mut max = encode_len(limit.max + 1);
-        let fork_context = Arc::new(fork_context());
         let mut codec = SSZSnappyOutboundCodec::<Spec>::new(
             protocol_id.clone(),
-            1_048_576,
+            max_rpc_size,
             fork_context.clone(),
         );
-        assert_eq!(codec.decode(&mut max).unwrap_err(), RPCError::InvalidData);
+        assert!(matches!(
+            codec.decode(&mut max).unwrap_err(),
+            RPCError::InvalidData(_)
+        ));
 
         let mut min = encode_len(limit.min - 1);
         let mut codec = SSZSnappyOutboundCodec::<Spec>::new(
             protocol_id.clone(),
-            1_048_576,
+            max_rpc_size,
             fork_context.clone(),
         );
-        assert_eq!(codec.decode(&mut min).unwrap_err(), RPCError::InvalidData);
+        assert!(matches!(
+            codec.decode(&mut min).unwrap_err(),
+            RPCError::InvalidData(_)
+        ));
 
         // Request limits
         let limit = protocol_id.rpc_request_limits();
         let mut max = encode_len(limit.max + 1);
         let mut codec = SSZSnappyOutboundCodec::<Spec>::new(
             protocol_id.clone(),
-            1_048_576,
+            max_rpc_size,
             fork_context.clone(),
         );
-        assert_eq!(codec.decode(&mut max).unwrap_err(), RPCError::InvalidData);
+        assert!(matches!(
+            codec.decode(&mut max).unwrap_err(),
+            RPCError::InvalidData(_)
+        ));
 
         let mut min = encode_len(limit.min - 1);
-        let mut codec = SSZSnappyOutboundCodec::<Spec>::new(protocol_id, 1_048_576, fork_context);
-        assert_eq!(codec.decode(&mut min).unwrap_err(), RPCError::InvalidData);
+        let mut codec =
+            SSZSnappyOutboundCodec::<Spec>::new(protocol_id, max_rpc_size, fork_context);
+        assert!(matches!(
+            codec.decode(&mut min).unwrap_err(),
+            RPCError::InvalidData(_)
+        ));
     }
 }