Add a task to publish slash reports

coordinator/src/main.rs

@@ -39,6 +39,8 @@ mod p2p {
   pub use serai_coordinator_libp2p_p2p::Libp2p;
 }
 
+mod serai;
+
 // Use a zeroizing allocator for this entire application
 // While secrets should already be zeroized, the presence of secret keys in a networked application
 // (at increased risk of OOB reads) justifies the performance hit in case any secrets weren't

coordinator/src/serai.rs

@@ -0,0 +1,93 @@
+use core::future::Future;
+use std::sync::Arc;
+
+use serai_db::{Get, DbTxn, Db as DbTrait, create_db};
+
+use scale::Decode;
+use serai_client::{primitives::NetworkId, validator_sets::primitives::Session, Serai};
+
+use serai_task::ContinuallyRan;
+
+create_db! {
+  CoordinatorSerai {
+    SlashReports: (network: NetworkId) -> (Session, Vec<u8>),
+  }
+}
+
+/// Publish `SlashReport`s from `SlashReports` onto Serai.
+pub struct PublishSlashReportTask<CD: DbTrait> {
+  db: CD,
+  serai: Arc<Serai>,
+}
+impl<CD: DbTrait> ContinuallyRan for PublishSlashReportTask<CD> {
+  fn run_iteration(&mut self) -> impl Send + Future<Output = Result<bool, String>> {
+    async move {
+      let mut made_progress = false;
+      for network in serai_client::primitives::NETWORKS {
+        if network == NetworkId::Serai {
+          continue;
+        };
+
+        let mut txn = self.db.txn();
+        let Some((session, slash_report)) = SlashReports::take(&mut txn, network) else {
+          // No slash report to publish
+          continue;
+        };
+        let slash_report = serai_client::Transaction::decode(&mut slash_report.as_slice()).unwrap();
+
+        let serai =
+          self.serai.as_of_latest_finalized_block().await.map_err(|e| format!("{e:?}"))?;
+        let serai = serai.validator_sets();
+        let session_after_slash_report = Session(session.0 + 1);
+        let current_session = serai.session(network).await.map_err(|e| format!("{e:?}"))?;
+        let current_session = current_session.map(|session| session.0);
+        // Only attempt to publish the slash report for session #n while session #n+1 is still
+        // active
+        let session_after_slash_report_retired =
+          current_session > Some(session_after_slash_report.0);
+        if session_after_slash_report_retired {
+          // Commit the txn to drain this SlashReport from the database and not try it again later
+          txn.commit();
+          continue;
+        }
+
+        if Some(session_after_slash_report.0) != current_session {
+          // We already checked the current session wasn't greater, and they're not equal
+          assert!(current_session < Some(session_after_slash_report.0));
+          // This would mean the Serai node is resyncing and is behind where it prior was
+          Err("have a SlashReport for a session Serai has yet to retire".to_string())?;
+        }
+
+        // If this session which should publish a slash report already has, move on
+        let key_pending_slash_report =
+          serai.key_pending_slash_report(network).await.map_err(|e| format!("{e:?}"))?;
+        if key_pending_slash_report.is_none() {
+          txn.commit();
+          continue;
+        };
+
+        /*
+        let tx = serai_client::SeraiValidatorSets::report_slashes(
+          network,
+          slash_report,
+          signature.clone(),
+        );
+        */
+
+        match self.serai.publish(&slash_report).await {
+          Ok(()) => {
+            txn.commit();
+            made_progress = true;
+          }
+          // This could be specific to this TX (such as an already in mempool error) and it may be
+          // worthwhile to continue iteration with the other pending slash reports. We assume this
+          // error ephemeral and that the latency incurred for this ephemeral error to resolve is
+          // miniscule compared to the window available to publish the slash report. That makes
+          // this a non-issue.
+          Err(e) => Err(format!("couldn't publish slash report transaction: {e:?}"))?,
+        }
+      }
+      Ok(made_progress)
+    }
+  }
+}