things

prudpv0/src/packet.rs

@@ -0,0 +1,187 @@
+use std::mem::transmute;
+
+use bytemuck::{Pod, Zeroable, try_from_bytes, try_from_bytes_mut};
+use log::error;
+use rnex_core::prudp::{
+    types_flags::{
+        TypesFlags,
+        flags::{HAS_SIZE, NEED_ACK},
+        types::{CONNECT, DATA, SYN},
+    },
+    virtual_port::VirtualPort,
+};
+
+use crate::crypto::{Crypto, CryptoInstance};
+
+#[repr(C, packed)]
+#[derive(Clone, Copy, Pod, Zeroable, Debug)]
+pub struct PRUDPV0Header {
+    pub source: VirtualPort,
+    pub destination: VirtualPort,
+    pub type_flags: TypesFlags,
+    pub session_id: u8,
+    pub packet_signature: [u8; 4],
+    pub sequence_id: u16,
+}
+#[repr(transparent)]
+pub struct PRUDPV0Packet<T: AsRef<[u8]>>(pub T);
+
+impl<T: AsRef<[u8]>> PRUDPV0Packet<T> {
+    #[inline(always)]
+    pub fn get_packet_specific_size(&self) -> Option<usize> {
+        Some(get_types_flags_size_from_types_flags(
+            self.header()?.type_flags,
+        ))
+    }
+
+    #[inline(always)]
+    pub fn header(&self) -> Option<&PRUDPV0Header> {
+        try_from_bytes(self.0.as_ref().get(..size_of::<PRUDPV0Header>())?).ok()
+    }
+    #[inline(always)]
+    pub fn header_mut(&mut self) -> Option<&mut PRUDPV0Header>
+    where
+        T: AsMut<[u8]>,
+    {
+        try_from_bytes_mut(self.0.as_mut().get_mut(..size_of::<PRUDPV0Header>())?).ok()
+    }
+
+    #[inline(always)]
+    pub fn connection_signature(&self) -> Option<&[u8; 4]> {
+        let offset = size_of::<PRUDPV0Header>();
+        Some(self.0.as_ref().get(offset..offset + 4)?.try_into().ok()?)
+    }
+    #[inline(always)]
+    pub fn connection_signature_mut(&mut self) -> Option<&mut [u8; 4]>
+    where
+        T: AsMut<[u8]>,
+    {
+        let offset = size_of::<PRUDPV0Header>();
+        Some(
+            self.0
+                .as_mut()
+                .get_mut(offset..offset + 4)?
+                .try_into()
+                .ok()?,
+        )
+    }
+
+    #[inline(always)]
+    fn get_payload_offset(&self) -> Option<usize> {
+        Some(size_of::<PRUDPV0Header>() + self.get_packet_specific_size()?)
+    }
+
+    #[inline(always)]
+    pub fn payload(&self) -> Option<&[u8]> {
+        self.0
+            .as_ref()
+            .get(self.get_payload_offset()?..(self.0.as_ref().len().saturating_sub(1)))
+    }
+    #[inline(always)]
+    pub fn payload_mut(&mut self) -> Option<&mut [u8]>
+    where
+        T: AsMut<[u8]>,
+    {
+        let start_offset = self.get_payload_offset()?;
+        let end_offset = self.0.as_ref().len().saturating_sub(1);
+        self.0.as_mut().get_mut(start_offset..end_offset)
+    }
+
+    #[inline(always)]
+    pub fn checksummed_data(&self) -> Option<&[u8]> {
+        self.0
+            .as_ref()
+            .get(..self.0.as_ref().len().saturating_sub(1))
+    }
+
+    #[inline(always)]
+    pub fn checksum(&self) -> Option<u8> {
+        self.0.as_ref().last().copied()
+    }
+    #[inline(always)]
+    pub fn checksum_mut(&mut self) -> Option<&mut u8>
+    where
+        T: AsMut<[u8]>,
+    {
+        self.0.as_mut().last_mut()
+    }
+
+    #[inline(always)]
+    pub fn check_checksum(&self, crypto: &impl Crypto) -> bool {
+        let Some(data) = self.checksummed_data() else {
+            return false;
+        };
+        let Some(checksum) = self.checksum() else {
+            return false;
+        };
+        checksum == crypto.calculate_checksum(data)
+    }
+
+    pub fn new(data: T) -> Self {
+        Self(data)
+    }
+}
+
+const DEFAULT_SIGNAT: [u8; 4] = [0x12, 0x34, 0x56, 0x78];
+#[inline(always)]
+const fn get_size_offset(tf: TypesFlags) -> usize {
+    size_of::<PRUDPV0Header>()
+        + (if tf.get_types() & (SYN | CONNECT) != 0 {
+            4
+        } else if tf.get_types() & DATA != 0 {
+            1
+        } else {
+            0
+        })
+}
+#[inline(always)]
+const fn get_type_specific_size(tf: TypesFlags) -> usize {
+    if tf.get_types() & (SYN | CONNECT) != 0 {
+        4
+    } else if tf.get_types() & DATA != 0 {
+        1
+    } else {
+        0
+    }
+}
+#[inline(always)]
+const fn get_types_flags_size_from_types_flags(tf: TypesFlags) -> usize {
+    get_type_specific_size(tf) + (if tf.get_flags() & HAS_SIZE != 0 { 2 } else { 0 })
+}
+#[inline(always)]
+pub const fn precalc_size(tf: TypesFlags, payload_size: usize) -> usize {
+    size_of::<PRUDPV0Header>() + get_types_flags_size_from_types_flags(tf) + payload_size + 1
+}
+pub fn new_syn_packet(
+    flags: u16,
+    source: VirtualPort,
+    destination: VirtualPort,
+    signat: [u8; 4],
+    crypto: &impl Crypto,
+) -> Vec<u8> {
+    let type_flags = TypesFlags::default().types(SYN).flags(flags);
+
+    let vec = vec![0; precalc_size(type_flags, 0)];
+    let mut packet = PRUDPV0Packet::new(vec);
+    let header = packet.header_mut().expect("packet malformed in creation");
+
+    *header = PRUDPV0Header {
+        destination,
+        source,
+        packet_signature: DEFAULT_SIGNAT,
+        sequence_id: 0,
+        session_id: 0,
+        type_flags,
+    };
+    *packet
+        .connection_signature_mut()
+        .expect("packet malformed in creation") = signat;
+
+    *packet.checksum_mut().expect("packet malformed in creation") = crypto.calculate_checksum(
+        packet
+            .checksummed_data()
+            .expect("packet malformed in creation"),
+    );
+
+    packet.0
+}