phew

satrs-core/src/cfdp/mod.rs

@@ -1,11 +1,21 @@
 use crc::{Crc, CRC_32_CKSUM};
-use spacepackets::util::UnsignedByteField;
+use spacepackets::{
+    cfdp::{
+        pdu::{FileDirectiveType, PduError, PduHeader},
+        PduType,
+    },
+    util::UnsignedByteField,
+};
+
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
 
 #[cfg(feature = "std")]
 pub mod dest;
 pub mod user;
 
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct TransactionId {
     source_id: UnsignedByteField,
     seq_num: UnsignedByteField,
@@ -26,6 +36,7 @@ impl TransactionId {
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum TransactionStep {
     Idle = 0,
     TransactionStart = 1,
@@ -36,6 +47,7 @@ pub enum TransactionStep {
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum State {
     Idle = 0,
     BusyClass1Nacked = 2,
@@ -44,6 +56,105 @@ pub enum State {
 
 pub const CRC_32: Crc<u32> = Crc::<u32>::new(&CRC_32_CKSUM);
 
+#[derive(Debug, PartialEq, Eq, Copy, Clone)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub enum PacketTarget {
+    SourceEntity,
+    DestEntity,
+}
+
+/// This is a helper struct which contains base information about a particular PDU packet.
+/// This is also necessary information for CFDP packet routing. For example, some packet types
+/// like file data PDUs can only be used by CFDP source entities.
+pub struct PacketInfo<'raw_packet> {
+    pdu_type: PduType,
+    pdu_directive: Option<FileDirectiveType>,
+    target: PacketTarget,
+    raw_packet: &'raw_packet [u8],
+}
+
+impl<'raw> PacketInfo<'raw> {
+    pub fn new(raw_packet: &'raw [u8]) -> Result<Self, PduError> {
+        let (pdu_header, header_len) = PduHeader::from_bytes(raw_packet)?;
+        if pdu_header.pdu_type() == PduType::FileData {
+            return Ok(Self {
+                pdu_type: pdu_header.pdu_type(),
+                pdu_directive: None,
+                target: PacketTarget::DestEntity,
+                raw_packet,
+            });
+        }
+        if pdu_header.pdu_datafield_len() < 1 {
+            return Err(PduError::FormatError);
+        }
+        // Route depending on PDU type and directive type if applicable. Retrieve directive type
+        // from the raw stream for better performance (with sanity and directive code check).
+        // The routing is based on section 4.5 of the CFDP standard which specifies the PDU forwarding
+        // procedure.
+        let directive = FileDirectiveType::try_from(raw_packet[header_len]).map_err(|_| {
+            PduError::InvalidDirectiveType {
+                found: raw_packet[header_len],
+                expected: None,
+            }
+        })?;
+        let packet_target = match directive {
+            // Section c) of 4.5.3: These PDUs should always be targeted towards the file sender a.k.a.
+            // the source handler
+            FileDirectiveType::NakPdu
+            | FileDirectiveType::FinishedPdu
+            | FileDirectiveType::KeepAlivePdu => PacketTarget::SourceEntity,
+            // Section b) of 4.5.3: These PDUs should always be targeted towards the file receiver a.k.a.
+            // the destination handler
+            FileDirectiveType::MetadataPdu
+            | FileDirectiveType::EofPdu
+            | FileDirectiveType::PromptPdu => PacketTarget::DestEntity,
+            // Section a): Recipient depends of the type of PDU that is being acknowledged. We can simply
+            // extract the PDU type from the raw stream. If it is an EOF PDU, this packet is passed to
+            // the source handler, for a Finished PDU, it is passed to the destination handler.
+            FileDirectiveType::AckPdu => {
+                let acked_directive = FileDirectiveType::try_from(raw_packet[header_len + 1])
+                    .map_err(|_| PduError::InvalidDirectiveType {
+                        found: raw_packet[header_len],
+                        expected: None,
+                    })?;
+                if acked_directive == FileDirectiveType::EofPdu {
+                    PacketTarget::SourceEntity
+                } else if acked_directive == FileDirectiveType::FinishedPdu {
+                    PacketTarget::DestEntity
+                } else {
+                    // TODO: Maybe a better error? This might be confusing..
+                    return Err(PduError::InvalidDirectiveType {
+                        found: raw_packet[header_len + 1],
+                        expected: None,
+                    });
+                }
+            }
+        };
+        Ok(Self {
+            pdu_type: pdu_header.pdu_type(),
+            pdu_directive: Some(directive),
+            target: packet_target,
+            raw_packet,
+        })
+    }
+
+    pub fn pdu_type(&self) -> PduType {
+        self.pdu_type
+    }
+
+    pub fn pdu_directive(&self) -> Option<FileDirectiveType> {
+        self.pdu_directive
+    }
+
+    pub fn target(&self) -> PacketTarget {
+        self.target
+    }
+
+    pub fn raw_packet(&self) -> &[u8] {
+        self.raw_packet
+    }
+}
+
 #[cfg(test)]
 mod tests {
     #[test]