Add Prototype Pseudocode

include/psuedocode.md

@@ -0,0 +1,115 @@
+The follow outlines some psuedocode for how to implement the logic for a prototype QEO solution.
+
+```csharp
+struct offload_info {
+    uint operation;
+    uint direction;
+    ulong next_packet_number;
+    addr ip_address;
+    byte cid[];
+    key_info key;
+}
+
+offload_info[] rx_offload_table;
+offload_info[] tx_offload_table;
+
+int rx_cid_length = -1;
+int tx_cid_length = -1;
+
+void update_offload(offload_info offloads[]) {
+    foreach (auto offload in offloads) {
+        if (offload.operation == "add") {
+            if (offload.direction == "tx") {
+                if (tx_cid_length == -1) tx_cid_length = offload.cid.length;
+                tx_offload_table.add(offload); // eventually will support update too, but simplifying things for now
+            } else {
+                if (rx_cid_length == -1) rx_cid_length = offload.cid.length;
+                rx_offload_table.add(offload); // eventually will support update too, but simplifying things for now
+            }
+        } else {
+            if (offload.direction == "tx") {
+                tx_offload_table.remove(offload);
+            } else {
+                rx_offload_table.remove(offload);
+            }
+        }
+    }
+}
+
+// Based on https://github.com/microsoft/msquic/blob/main/src/core/packet.h#L372
+void decompress_packet_number(ulong expected_packet_number, uint compressed_packet_number) {
+    ulong Mask = 0xFFFFFFFF00000000;
+    ulong PacketNumberInc = (~Mask) + 1;
+    ulong PacketNumber = (Mask & expected_packet_number) | compressed_packet_number;
+    if (PacketNumber < expected_packet_number) {
+        ulong High = expected_packet_number - PacketNumber;
+        ulong Low = PacketNumberInc - High;
+        if (Low < High) {
+            PacketNumber += PacketNumberInc;
+        }
+
+    } else {
+        ulong Low = PacketNumber - expected_packet_number;
+        ulong High = PacketNumberInc - Low;
+        if (High <= Low && PacketNumber >= PacketNumberInc) {
+            PacketNumber -= PacketNumberInc;
+        }
+    }
+    return PacketNumber;
+}
+
+void encrypt_quic_packet(packet packet, offload_info offload) {
+    // Decompress the full packet number
+    ulong packet_number =
+        decompress_packet_number(
+            offload.next_packet_number,
+            packet.udp_payload[tx_cid_length+1 .. tx_cid_length+4]); // 4 bytes after the CID
+
+    // Update the next full packet number for the next TX/encrypt call
+    offload.next_packet_number = packet_number + 1;
+
+    // TODO - Encrypt the packet payload
+    // TODO - Encrypt the packet header
+}
+
+void on_packet_tx(packet packet) {
+    if (packet.udp_payload[0] == "long header") return;
+
+    // Find the offload info based on the destination IP:port and CID.
+    offload_info offload =
+        rx_offload_table.find(
+            packet.dest_ip_address,
+            packet.udp_payload[1 .. tx_cid_length]); // tx_cid_length bytes after the first byte
+
+    encrypt_quic_packet(packet, offload);
+}
+
+void decrypt_quic_packet(packet packet, offload_info offload) {
+    // TODO - Decrypt packet header
+
+    // Decompress the full packet number
+    ulong packet_number =
+        decompress_packet_number(
+            offload.next_packet_number,
+            packet.udp_payload[rx_cid_length+1 .. rx_cid_length+4]); // 4 bytes after the CID
+
+    // Update the next full packet number for the next RX/decrypt call
+    if (packet_number >= offload.next_packet_number) {
+        offload.next_packet_number = packet_number + 1;
+    }
+
+    // TODO - Decrypt packet payload
+}
+
+void on_packet_rx(packet packet) {
+    if (packet.udp_payload[0] == "long header") return;
+
+    // Find the offload info based on the destination IP:port and CID.
+    offload_info offload =
+        rx_offload_table.find(
+            packet.dest_ip_address,
+            packet.udp_payload[1 .. rx_cid_length]); // rx_cid_length bytes after the first byte
+
+    decrypt_quic_packet(packet, offload);
+}
+```