adding UDP packet fragmentation

tuic/src/protocol/address.rs

@@ -1,5 +1,6 @@
 use std::{
     fmt::{Display, Formatter, Result as FmtResult},
+    mem,
     net::SocketAddr,
 };
 
@@ -56,6 +57,10 @@ impl Address {
         }
     }
 
+    pub fn take(&mut self) -> Self {
+        mem::take(self)
+    }
+
     pub fn is_none(&self) -> bool {
         matches!(self, Self::None)
     }
@@ -82,3 +87,9 @@ impl Display for Address {
         }
     }
 }
+
+impl Default for Address {
+    fn default() -> Self {
+        Self::None
+    }
+}

tuic/src/protocol/packet.rs

@@ -35,6 +35,10 @@ impl Packet {
             addr,
         }
     }
+
+    pub const fn len_without_addr() -> usize {
+        2 + 2 + 1 + 1 + 2
+    }
 }
 
 impl Command for Packet {

tuic/src/prototype/authenticate.rs

@@ -13,4 +13,8 @@ impl Authenticate {
             _task_reg: task_reg,
         }
     }
+
+    pub fn header(&self) -> &Header {
+        &self.header
+    }
 }

tuic/src/prototype/connect.rs

@@ -13,4 +13,8 @@ impl Connect {
             _task_reg: task_reg,
         }
     }
+
+    pub fn header(&self) -> &Header {
+        &self.header
+    }
 }

tuic/src/prototype/dissociate.rs

@@ -13,4 +13,8 @@ impl Dissociate {
             _task_reg: task_reg,
         }
     }
+
+    pub fn header(&self) -> &Header {
+        &self.header
+    }
 }

tuic/src/prototype/heartbeat.rs

@@ -10,4 +10,8 @@ impl Heartbeat {
             header: Header::Heartbeat(HeartbeatHeader::new()),
         }
     }
+
+    pub fn header(&self) -> &Header {
+        &self.header
+    }
 }

tuic/src/prototype/mod.rs

@@ -1,8 +1,11 @@
 use crate::protocol::Address;
 use parking_lot::Mutex;
 use std::{
-    collections::{hash_map::Entry, HashMap},
-    sync::{Arc, Weak},
+    collections::HashMap,
+    sync::{
+        atomic::{AtomicU16, Ordering},
+        Arc, Weak,
+    },
 };
 
 mod authenticate;
@@ -102,14 +105,10 @@ impl UdpSessions {
         payload: &'a [u8],
         frag_len: usize,
     ) -> Packet<'a> {
-        match self.sessions.entry(assoc_id) {
-            Entry::Occupied(_) => {}
-            Entry::Vacant(entry) => {
-                entry.insert(UdpSession::new(self.local_active_task_count.reg()));
-            }
-        }
-
-        Packet::new(assoc_id, addr, payload, frag_len)
+        self.sessions
+            .entry(assoc_id)
+            .or_insert_with(|| UdpSession::new(self.local_active_task_count.reg()))
+            .send(assoc_id, addr, payload, frag_len)
     }
 
     fn dissociate(&mut self, assoc_id: u16) -> Dissociate {
@@ -119,13 +118,31 @@ impl UdpSessions {
 }
 
 struct UdpSession {
+    next_pkt_id: AtomicU16,
     _task_reg: TaskRegister,
 }
 
 impl UdpSession {
     fn new(task_reg: TaskRegister) -> Self {
         Self {
+            next_pkt_id: AtomicU16::new(0),
             _task_reg: task_reg,
         }
     }
+
+    fn send<'a>(
+        &self,
+        assoc_id: u16,
+        addr: Address,
+        payload: &'a [u8],
+        frag_len: usize,
+    ) -> Packet<'a> {
+        Packet::new(
+            assoc_id,
+            self.next_pkt_id.fetch_add(1, Ordering::AcqRel),
+            addr,
+            payload,
+            frag_len,
+        )
+    }
 }

tuic/src/prototype/packet.rs

@@ -1,19 +1,79 @@
-use crate::protocol::Address;
+use crate::protocol::{Address, Header, Packet as PacketHeader};
 
 pub struct Packet<'a> {
     assoc_id: u16,
+    pkt_id: u16,
     addr: Address,
     payload: &'a [u8],
-    frag_len: usize,
+    max_pkt_size: usize,
+    frag_total: u8,
+    next_frag_id: u8,
+    next_frag_start: usize,
 }
 
 impl<'a> Packet<'a> {
-    pub(super) fn new(assoc_id: u16, addr: Address, payload: &'a [u8], frag_len: usize) -> Self {
+    pub(super) fn new(
+        assoc_id: u16,
+        pkt_id: u16,
+        addr: Address,
+        payload: &'a [u8],
+        max_pkt_size: usize,
+    ) -> Self {
+        let first_frag_size = max_pkt_size - PacketHeader::len_without_addr() - addr.len();
+        let frag_size_addr_none =
+            max_pkt_size - PacketHeader::len_without_addr() - Address::None.len();
+
+        let frag_total = if first_frag_size < payload.len() {
+            (1 + (payload.len() - first_frag_size) / frag_size_addr_none + 1) as u8
+        } else {
+            1u8
+        };
+
         Self {
             assoc_id,
+            pkt_id,
             addr,
             payload,
-            frag_len,
+            max_pkt_size,
+            frag_total,
+            next_frag_id: 0,
+            next_frag_start: 0,
         }
     }
 }
+
+impl<'a> Iterator for Packet<'a> {
+    type Item = (Header, &'a [u8]);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.next_frag_id < self.frag_total {
+            let payload_size =
+                self.max_pkt_size - PacketHeader::len_without_addr() - self.addr.len();
+            let next_frag_end = (self.next_frag_start + payload_size).min(self.payload.len());
+
+            let header = Header::Packet(PacketHeader::new(
+                self.assoc_id,
+                self.pkt_id,
+                self.frag_total,
+                self.next_frag_id,
+                (next_frag_end - self.next_frag_start) as u16,
+                self.addr.take(),
+            ));
+
+            let payload = &self.payload[self.next_frag_start..next_frag_end];
+
+            self.next_frag_id += 1;
+            self.next_frag_start = next_frag_end;
+
+            Some((header, payload))
+        } else {
+            None
+        }
+    }
+}
+
+impl ExactSizeIterator for Packet<'_> {
+    fn len(&self) -> usize {
+        self.frag_total as usize
+    }
+}