Function parse_frame

nodedb-cluster/src/rpc_codec/header.rs:57–117

Validate the CRC32C of an inbound frame and return the payload slice. `data` must start at byte 0 (version byte). Returns `(rpc_type, payload)`. Side effect: observes the peer's cluster epoch via [`observe_peer_cluster_epoch`] (monotonic max).

(data: &[u8])

/// Side effect: observes the peer's cluster epoch via
/// [`observe_peer_cluster_epoch`] (monotonic max).
pub fn parse_frame(data: &[u8]) -> Result<(u8, &[u8])> {
    if data.is_empty() {
        return Err(ClusterError::Codec {
            detail: format!("frame too short: 0 bytes, need {HEADER_SIZE}"),
        });
    }

    let version = data[0];
    if version != RPC_FRAME_VERSION {
        return Err(ClusterError::UnsupportedWireVersion {
            got: version,
            supported_min: RPC_FRAME_VERSION,
            supported_max: RPC_FRAME_VERSION,
        });
    }

    if data.len() < HEADER_SIZE {
        return Err(ClusterError::Codec {
            detail: format!("frame too short: {} bytes, need {HEADER_SIZE}", data.len()),
        });
    }

    let rpc_type = data[1];
    let payload_len = u32::from_le_bytes([data[2], data[3], data[4], data[5]]);
    let expected_crc = u32::from_le_bytes([data[6], data[7], data[8], data[9]]);
    let peer_epoch = u64::from_le_bytes([
        data[10], data[11], data[12], data[13], data[14], data[15], data[16], data[17],
    ]);

    if payload_len > MAX_RPC_PAYLOAD_SIZE {
        return Err(ClusterError::Codec {
            detail: format!("payload length {payload_len} exceeds maximum {MAX_RPC_PAYLOAD_SIZE}"),
        });
    }

    let expected_total = HEADER_SIZE + payload_len as usize;
    if data.len() < expected_total {
        return Err(ClusterError::Codec {
            detail: format!(
                "frame truncated: got {} bytes, expected {expected_total}",
                data.len()
            ),
        });
    }

    let payload = &data[HEADER_SIZE..expected_total];
    let actual_crc = crc32c::crc32c(payload);
    if actual_crc != expected_crc {
        return Err(ClusterError::Codec {
            detail: format!(
                "CRC32C mismatch: expected {expected_crc:#010x}, got {actual_crc:#010x}"
            ),
        });
    }

    if peer_epoch > 0 {
        observe_peer_cluster_epoch(peer_epoch);
    }