Method accept

nodedb-cluster/src/rpc_codec/peer_seq.rs:94–137

Accept `seq` from `peer_id`, rejecting replays and out-of-window stale frames. Returns `Err(ClusterError::Codec)` on rejection. Sequence `0` is always rejected — a well-formed sender starts at 1, so `0` means "nothing sent", which is not a valid inbound frame.

(&self, peer_id: u64, seq: u64)

    /// Sequence `0` is always rejected — a well-formed sender starts at
    /// 1, so `0` means "nothing sent", which is not a valid inbound frame.
    pub fn accept(&self, peer_id: u64, seq: u64) -> Result<()> {
        if seq == 0 {
            return Err(ClusterError::Codec {
                detail: format!("peer {peer_id} sent reserved sequence 0"),
            });
        }

        let mut guard = self.windows.write().unwrap_or_else(|p| p.into_inner());
        let state = guard.entry(peer_id).or_default();

        if seq > state.high {
            // Frame advances the window. Shift by the delta and set bit 0.
            let delta = seq - state.high;
            state.mask = if delta >= REPLAY_WINDOW {
                1
            } else {
                (state.mask << delta) | 1
            };
            state.high = seq;
            return Ok(());
        }

        // Frame is `state.high - seq` positions back in the window.
        let offset = state.high - seq;
        if offset >= REPLAY_WINDOW {
            return Err(ClusterError::Codec {
                detail: format!(
                    "peer {peer_id} sent stale sequence {seq}, window high is {}",
                    state.high
                ),
            });
        }
        let bit = 1u64 << offset;
        if state.mask & bit != 0 {
            return Err(ClusterError::Codec {
                detail: format!(
                    "peer {peer_id} replayed sequence {seq} (window high {})",
                    state.high
                ),
            });
        }
        state.mask |= bit;
        Ok(())
    }

    #[cfg(test)]
    pub fn highest(&self, peer_id: u64) -> u64 {