Rewrite submit_block relay communication to support SSZ and JSON

.github/workflows/security-audit.yml

@@ -19,6 +19,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v6
-      - uses: actions-rs/audit-check@v1.2.0
+      - uses: taiki-e/install-action@43aecc8d72668fbcfe75c31400bc4f890f1c5853 # v2.83.2
         with:
-          token: ${{ secrets.GITHUB_TOKEN }}
+          tool: cargo-audit
+      - run: cargo audit

crates/common/src/pbs/error.rs

@@ -15,6 +15,9 @@ pub enum PbsError {
     #[error("json decode error: {err:?}, raw: {raw}")]
     JsonDecode { err: serde_json::Error, raw: String },
 
+    #[error("json encode error: {0:?}")]
+    JsonEncode(serde_json::Error),
+
     #[error("ssz decode error: {err:?}, fork: {fork}")]
     SSZDecode { err: String, fork: ForkName },
 

crates/pbs/src/metrics.rs

@@ -60,4 +60,14 @@ lazy_static! {
         &["http_status_code", "endpoint"],
         PBS_METRICS_REGISTRY
     ).unwrap();
+
+    /// Count of v2 submit_block requests that fell back to the v1 endpoint
+    /// because the relay returned 404 on v2. A high value indicates the relay
+    /// fleet has not been upgraded to support submitBlindedBlockV2.
+    pub static ref V2_FALLBACK_TO_V1: IntCounterVec = register_int_counter_vec_with_registry!(
+        "pbs_submit_block_v2_fallback_to_v1_total",
+        "Count of v2 submit_block requests that fell back to v1 because the relay did not support v2",
+        &["relay_id"],
+        PBS_METRICS_REGISTRY
+    ).unwrap();
 }

crates/pbs/src/mev_boost/register_validator.rs

@@ -35,17 +35,19 @@ pub async fn register_validator<S: BuilderApiState>(
         .insert(HEADER_START_TIME_UNIX_MS, HeaderValue::from_str(&utcnow_ms().to_string())?);
     send_headers.insert(USER_AGENT, get_user_agent_with_version(&req_headers)?);
 
-    // prepare the body in advance, ugly dyn
-    let bodies: Box<dyn Iterator<Item = (usize, Bytes)>> =
+    // prepare the body in advance
+    let bodies: Vec<(usize, Bytes)> =
         if let Some(batch_size) = state.config.pbs_config.validator_registration_batch_size {
-            Box::new(registrations.chunks(batch_size).map(|batch| {
-                // SAFETY: unwrap is ok because we're serializing a &[serde_json::Value]
-                let body = serde_json::to_vec(batch).unwrap();
-                (batch.len(), Bytes::from(body))
-            }))
+            registrations
+                .chunks(batch_size)
+                .map(|batch| {
+                    let body = serde_json::to_vec(batch).map_err(PbsError::JsonEncode)?;
+                    Ok((batch.len(), Bytes::from(body)))
+                })
+                .collect::<Result<Vec<_>, PbsError>>()?
         } else {
-            let body = serde_json::to_vec(&registrations).unwrap();
-            Box::new(std::iter::once((registrations.len(), Bytes::from(body))))
+            let body = serde_json::to_vec(&registrations).map_err(PbsError::JsonEncode)?;
+            vec![(registrations.len(), Bytes::from(body))]
         };
     send_headers.insert(CONTENT_TYPE, HeaderValue::from_static("application/json"));