Merge branch 'feature/vtop-fix' into feature/tcp

Add full TCP/IP stack implementation at L4 alongside UDP and ICMP.

Core Protocol Engine:
- TCP types in nettypes.pas (header, TCB, state enum, error codes,
  callbacks, OOO entry, socket structures)
- 3-way handshake (active & passive OPEN)
- Reliable data transfer with ACK and sequence number tracking
- Graceful close (FIN_WAIT, CLOSE_WAIT, LAST_ACK, TIME_WAIT)
- RST send/receive handling
- Retransmission with exponential backoff (max 5 attempts)
- Pseudo-header based checksum (RFC 793)

Server Support:
- LISTEN → SYN_RECEIVED → ESTABLISHED passive open path
- Listen backlog enforcement (configurable per-socket)
- accept() to retrieve established child connections

Robustness & Hardening:
- Delayed ACK timer (~200ms)
- Nagle's algorithm (buffer small sends while unACKed data pending)
- Jacobson/Karels RTT estimation with adaptive RTO
- Congestion control (slow start / congestion avoidance)
- Zero-window probing with exponential backoff
- MSS option negotiation in SYN/SYN-ACK (Kind=2, Len=4)
- Keep-alive (30s idle, 10s interval, 5 probes)
- Out-of-order segment reassembly (4-slot buffer)

Terminal & Testing:
- tcpconnect: active open + send "Hello, World!"
- tcplisten: passive open with syslog output
- tcphttp: HTTP/1.0 GET client

Also add push_trace() instrumentation to net, eth2, arp, ipv4,
icmp, udp, and dhcp entry points for call tracing, and register
tcp in net.init.

src/driver/net/l1/net.pas

@@ -100,8 +100,8 @@ end;
 
 procedure send(p_data : void; p_len : uint16);
 begin
-    //push_trace('net.send');
-    //writeToLogLn('L1: net.send');
+    push_trace('net.send');
+    writeToLogLn('L1/NET: send');
     if CBSend <> nil then CBSend(p_data, p_len);
     pop_trace;
 end;
@@ -111,8 +111,7 @@ var
     context : PPacketContext;
 
 begin
-    //push_trace('net.recv');
-    //writeToLogLn('L1: net.recv');
+    push_trace('net.recv');
     context:= newPacketContext;
     if CBNext <> nil then CBNext(p_data, p_len, context);
     freePacketContext(context);
@@ -129,6 +128,7 @@ end;
 procedure init;
 begin
     push_trace('net.init');
+    writeToLogLn('L1/NET: init');
     //l2
     eth2.register;
     //l3
@@ -136,6 +136,7 @@ begin
     ipv4.register;
     //l4
     icmp.register;
+    tcp.register;
     udp.register;
     //l5
     dhcp.register;

src/driver/net/l2/eth2.pas

@@ -46,6 +46,7 @@ var
 
 procedure registerTypePromisc(eType : uint16; RecvCB : TRecvCallback);
 begin
+    push_trace('eth2.registerTypePromisc');
     register;
     if EthTypes[eType] = nil then EthTypes[eType]:= RecvCB;
     Promisc[eType]:= true;
@@ -53,6 +54,7 @@ end;
 
 procedure registerType(eType : uint16; RecvCB : TRecvCallback);
 begin
+    push_trace('eth2.registerType');
     register;
     if EthTypes[eType] = nil then EthTypes[eType]:= RecvCB;
 end;
@@ -93,7 +95,7 @@ var
     buf        : puint8;
 
 begin
-    //writeToLogLn('    L2: eth2.recv');
+    push_trace('eth2.recv');
     buf:= puint8(p_data);
     
     Header:= PEthernetHeader(buf);
@@ -120,6 +122,7 @@ var
 begin
     push_trace('eth2.register');
     if not Registered then begin
+        writeToLogLn('    L2/ETH: register');
         for i:=0 to 65535 do begin
             EthTypes[i]:= nil;
             Promisc[i]:= false;

src/driver/net/l3/arp.pas

@@ -96,6 +96,7 @@ var
     hSize, pSize : uint8;
 
 begin
+    push_trace('arp.send');
     if p_context <> nil then begin
         buf:= kalloc(sizeof(TARPHeader));
         hdr:= PARPHeader(buf);
@@ -135,6 +136,8 @@ var
     context : PPacketContext;
 
 begin
+     push_trace('arp.sendGratuitous');
+     writeToLogLn('      L3/ARP: sendGratuitous');
      context:= newPacketContext;
      CopyIPv4(@getIPv4Config^.Address[0], @context^.IP.Destination[0]);
      CopyIPv4(@getIPv4Config^.Address[0], @context^.IP.Source[0]);
@@ -150,6 +153,7 @@ var
     CacheRecord : PARPCacheRecord;
 
 begin
+     push_trace('arp.sendRequestGateway');
      context:= newPacketContext;
      CacheRecord:= findCacheRecordByIP(@getIPv4Config^.Gateway[0]);
      if CacheRecord <> nil then begin
@@ -168,6 +172,8 @@ var
     CacheRecord : PARPCacheRecord;
 
 begin
+     push_trace('arp.sendRequest');
+     writeToLogLn('      L3/ARP: sendRequest');
      context:= newPacketContext;
      CopyIPv4(ip, @context^.IP.Destination[0]);
      CopyIPv4(@getIPv4Config^.Address[0], @context^.IP.Source[0]);
@@ -184,6 +190,7 @@ var
     CacheRecord : PARPCacheRecord;
 
 begin
+    push_trace('arp.resolveIP');
     CacheRecord:= findCacheRecordByIP(ip);
     resolveIP:= nil;
     if CacheRecord = nil then begin
@@ -203,6 +210,7 @@ var
     context      : PPacketContext;
 
 begin
+    push_trace('arp.recv');
     { Get our converted Header }
     Header:= PARPHeader(p_data);
     AHeader.Hardware_Type:= (Header^.Hardware_Type_Hi SHL 8) + Header^.Hardware_Type_Lo;
@@ -298,6 +306,7 @@ procedure register;
 begin
     push_trace('arp.register');
     if not Registered then begin
+        writeToLogLn('      L3/ARP: register');
         Cache:= LL_New(sizeof(TARPCacheRecord));
         eth2.registerTypePromisc($0806, @recv);
         stdio.registerCommand('ARP', @terminal_command_arp, 'Get ARP Table.');

src/driver/net/l3/ipv4.pas

@@ -46,7 +46,9 @@ var
 
 function  getIPv4Config : PIPv4Configuration;
 begin
+    push_trace('ipv4.getIPv4Config');
     getIPv4Config:= @Config;
+    pop_trace;
 end;
 
 procedure send(p_data : void; p_len : uint16; p_context : PPacketContext);
@@ -57,6 +59,7 @@ var
     buffer : void;
 
 begin
+    push_trace('ipv4.send');
     inc(CurrentID);
     Header.version:= 4;
     Header.header_len:= 5;
@@ -84,6 +87,7 @@ begin
     memcpy(uint32(p_data), uint32(Buffer) + (Header.header_len * 4), p_len);
     eth2.send(Buffer, (Header.header_len * 4) + p_len, $0800, p_context);
     kfree(Buffer);
+    pop_trace;
 end;
 
 procedure recv(p_data : void; p_len : uint16; p_context : PPacketContext);
@@ -95,6 +99,7 @@ var
     len     : uint16;
 
 begin
+    push_trace('ipv4.recv');
     Header:= PIPV4Header(p_data);
     AHeader.version:= Header^.version;
     AHeader.header_len:= Header^.header_len;
@@ -195,6 +200,7 @@ var
 begin
     push_trace('ipv4.register');
     if not Registered then begin
+        writeToLogLn('      L3/IPv4: register');
         for i:=0 to 255 do begin
             Protocols[i]:= nil;
         end;
@@ -213,6 +219,7 @@ end;
 
 procedure registerProtocol(Protocol_ID : uint8; recv_callback : TRecvCallback);
 begin
+    push_trace('ipv4.registerProtocol');
     register;
     if Protocols[Protocol_ID] = nil then Protocols[Protocol_ID]:= recv_callback;
     pop_trace;

src/driver/net/l4/icmp.pas

@@ -23,7 +23,7 @@ interface
 
 uses
     bios_data_area,
-    lmemorymanager,
+    lmemorymanager, tracer,
     net, nettypes, netutils, ipv4, arp, util;
 
 type
@@ -55,6 +55,7 @@ var
     i : uint8;
 
 begin
+    push_trace('icmp.nextInactiveHandler');
     nextInactiveHandler:= 0;
     for i:=1 to 255 do begin
         if not Handlers[i].Active then begin
@@ -80,6 +81,8 @@ var
     Size     : uint32;
 
 begin
+    push_trace('icmp.sendICMPRequest');
+    writeToLogLn('        L4/ICMP: sendICMPRequest');
     handle:= nextInactiveHandler;
     Handlers[handle].Active:= true;
     Handlers[handle].OnReply:= OnRep;
@@ -135,6 +138,8 @@ var
     Handle : uint8;
 
 begin
+    push_trace('icmp.recv');
+    writeToLogLn('        L4/ICMP: recv');
     Header:= PICMPHeader(p_data);
     //writehexlnWND(Header^.ICMP_Type, getTerminalHWND); 
     case Header^.ICMP_Type of
@@ -243,6 +248,8 @@ var
     i : uint32;
 
 begin
+    push_trace('icmp.register');
+    writeToLogLn('        L4/ICMP: register');
     for i:=0 to 255 do begin
         Handlers[i].Active:= false;
         Handlers[i].OnError:= nil;

src/driver/net/l4/udp.pas

@@ -25,7 +25,7 @@ uses
     lmemorymanager,
     nettypes, netutils,
     ipv4, net,
-    util;
+    tracer, util;
 
 procedure register();
 function bind(bindContext : PUDPBindContext) : TUDPError;
@@ -71,6 +71,7 @@ begin
             nullend:= true;
         end;
         pseudoBuffer:= kalloc(sizeof(TUDPPseudoHeader) + pseudoSize);
+        push_trace('udp.CalculateChecksum');
         pseudoBuffer8:= puint8(pseudoBuffer);
         pseudoBuffer16:= puint16(pseudoBuffer);
         pseudoBuffer32:= puint32(pseudoBuffer);
@@ -118,6 +119,7 @@ var
 
 
 begin
+    push_trace('udp.send');
     if udpContext <> nil then begin
         size:= p_len + sizeof(TUDPHeader);
         buffer:= kalloc(size);
@@ -152,6 +154,7 @@ var
     context : PUDPBindContext;
 
 begin
+    push_trace('udp.bind');
     result:= tueGenericError;
     if bindContext <> nil then begin
         if Ports[bindContext^.port] = nil then begin
@@ -174,6 +177,7 @@ var
     context : PUDPBindContext;
 
 begin
+    push_trace('udp.unbind');
     result:= tueGenericError;
     if bindContext <> nil then begin
         context:= Ports[bindContext^.port];
@@ -203,6 +207,7 @@ var
     size    : uint16;
 
 begin
+    push_trace('udp.ProcessPacket');
     header:= PUDPHeader(p_data);
     if Ports[switchendian16(header^.DstPort)] <> nil then begin
         context:= PUDPPacketContext(kalloc(sizeof(TUDPPacketContext)));
@@ -245,6 +250,8 @@ var
     Checksum      : uint32;
 
 begin
+    push_trace('udp.register');
+    writeToLogLn('        L4/UDP: register');
     for i:=0 to 65535 do begin
         Ports[i]:= nil;
     end;

src/driver/net/l5/dhcp.pas

@@ -415,7 +415,7 @@ end;
 
 procedure processPacket_NAK(Header : PDHCPHeader; Options : PDHCPOptions);
 begin
-    syslog.logln('DHCP', 'Process NAK.'); 
+    writeToLogLn('          L5/DHCP: Process NAK.');
     { Server provided a NAK, NULL configuration ready for next DISCOVER/Request } 
     nullConfiguration();  
 end;
@@ -429,7 +429,7 @@ var
     cfgopt : void;
 
 begin
-    syslog.logln('DHCP', 'Process ACK.');
+    writeToLogLn('          L5/DHCP: Process ACK.');
     getIPv4Config^.UP:= false;
     
     //Copy new address
@@ -484,7 +484,7 @@ Var
 
 begin
     syslog.logln('DHCP', 'Process OFFER.');  
-
+    writeToLogLn('          L5/DHCP: Process OFFER.');
     { Check the Transaction ID matches our stored ID, discard if not. }
     if Header^.Transaction_ID = Configuration^.Transaction then begin
         syslog.logln('DHCP', 'XID Match');
@@ -566,6 +566,7 @@ var
 
 begin
     tracer.push_trace('dhcp.processPacket.enter');
+    writeToLogLn('          L5/DHCP: processPacket');
     syslog.logln('DHCP','processPacket');
     
     { Give access to header values & process to correct endianness. }
@@ -636,6 +637,7 @@ var
 
 begin
     tracer.push_trace('dhcp.DHCPDiscover.begin');
+    writeToLogLn('          L5/DHCP: DHCPDiscover');
     { Ensure we have a socket bound. }
     if Socket <> nil then begin    
         { Clear any current configuration }
@@ -711,6 +713,7 @@ var
 
 begin
     tracer.push_trace('dhcp.register');
+    writeToLogLn('          L5/DHCP: register');
     syslog.logln('DHCP', 'Register begin.');
     
     { Kalloc our Configuration Data }

src/kernel.pas

@@ -73,6 +73,23 @@ procedure kmain(mbinfo: Pmultiboot_info_t; mbmagic: uint32); stdcall;
  
 implementation
 
+procedure terminal_command_meminfo(params : PParamList; stdin_buf, stdout_buf, stderr_buf : POutBuf);
+begin
+    push_trace('kernel.terminal_command_meminfo');
+
+    stdio.bufWriteStr(stdout_buf, 'Lower Memory = ');
+    stdio.bufWriteInt(stdout_buf, multibootinfo^.mem_lower);
+    stdio.bufWriteStrLn(stdout_buf, 'KB');
+    stdio.bufWriteStr(stdout_buf, 'Higher Memory = ');
+    stdio.bufWriteInt(stdout_buf, multibootinfo^.mem_upper);
+    stdio.bufWriteStrLn(stdout_buf, 'KB');
+    stdio.bufWriteStr(stdout_buf, 'Total Memory = ');
+    stdio.bufWriteInt(stdout_buf, ((multibootinfo^.mem_upper + 1000) div 1024) + 1);
+    stdio.bufWriteStrLn(stdout_buf, 'MB');
+
+    pop_trace;
+end;
+
 procedure terminal_command_bsod(params : PParamList; stdin_buf, stdout_buf, stderr_buf : POutBuf);
 begin
     push_trace('kernel.terminal_command_bsod');
@@ -165,6 +182,7 @@ begin
 
      { Stdio Init }
      stdio.init();
+     stdio.registerCommand('MEMINFO', @terminal_command_meminfo, 'Print Simple Memory Information.');
      stdio.registerCommand('BSOD', @terminal_command_bsod, 'Force a Panic Screen.');
 
      tss.init();

src/prog/meminfo.pas

@@ -1,83 +0,0 @@
-//  Copyright 2021 Kieron Morris
-//
-//  Licensed under the Apache License, Version 2.0 (the "License");
-//  you may not use this file except in compliance with the License.
-//  You may obtain a copy of the License at
-//
-//  http://www.apache.org/licenses/LICENSE-2.0
-//
-//  Unless required by applicable law or agreed to in writing, software
-//  distributed under the License is distributed on an "AS IS" BASIS,
-//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-//  See the License for the specific language governing permissions and
-//  limitations under the License.
-
-{ 
-	Prog->meminfo - Print memory statistics (PMM / LMM).
-	
-	@author(Kieron Morris <[email protected]>)
-}
-unit meminfo;
-
-interface
-
-uses
-    stdio, multiboot, pmemorymanager, lmemorymanager, tracer;
-
-procedure init();
-
-implementation
-
-procedure run(Params : PParamList; stdin_buf, stdout_buf, stderr_buf : POutBuf);
-var
-    pmm_total, pmm_free, pmm_used : uint32;
-    lmm_pages, lmm_free           : uint32;
-begin
-    { Multiboot memory info }
-    stdio.bufWriteStrLn(stdout_buf, '--- Multiboot ---');
-    stdio.bufWriteStr(stdout_buf, 'Lower Memory  : ');
-    stdio.bufWriteInt(stdout_buf, multibootinfo^.mem_lower);
-    stdio.bufWriteStrLn(stdout_buf, ' KB');
-    stdio.bufWriteStr(stdout_buf, 'Upper Memory  : ');
-    stdio.bufWriteInt(stdout_buf, multibootinfo^.mem_upper);
-    stdio.bufWriteStrLn(stdout_buf, ' KB');
-    stdio.bufWriteStr(stdout_buf, 'Total Memory  : ');
-    stdio.bufWriteInt(stdout_buf, ((multibootinfo^.mem_upper + 1000) div 1024) + 1);
-    stdio.bufWriteStrLn(stdout_buf, ' MB');
-
-    { PMM stats }
-    stdio.bufWriteStrLn(stdout_buf, '--- PMM (4 MB blocks) ---');
-    pmm_total := pmemorymanager.pmm_total_blocks;
-    pmm_free  := pmemorymanager.pmm_free_blocks;
-    pmm_used  := pmm_total - pmm_free;
-    stdio.bufWriteStr(stdout_buf, 'Total Blocks  : ');
-    stdio.bufWriteIntLn(stdout_buf, pmm_total);
-    stdio.bufWriteStr(stdout_buf, 'Free Blocks   : ');
-    stdio.bufWriteIntLn(stdout_buf, pmm_free);
-    stdio.bufWriteStr(stdout_buf, 'Used Blocks   : ');
-    stdio.bufWriteIntLn(stdout_buf, pmm_used);
-    stdio.bufWriteStr(stdout_buf, 'Free Physical : ');
-    stdio.bufWriteInt(stdout_buf, pmm_free * 4);
-    stdio.bufWriteStrLn(stdout_buf, ' MB');
-
-    { LMM heap stats }
-    stdio.bufWriteStrLn(stdout_buf, '--- LMM (Heap) ---');
-    lmm_pages := lmemorymanager.lmm_page_count;
-    lmm_free  := lmemorymanager.lmm_total_free;
-    stdio.bufWriteStr(stdout_buf, 'Heap Pages    : ');
-    stdio.bufWriteIntLn(stdout_buf, lmm_pages);
-    stdio.bufWriteStr(stdout_buf, 'Heap Size     : ');
-    stdio.bufWriteInt(stdout_buf, lmm_pages * 4);
-    stdio.bufWriteStrLn(stdout_buf, ' MB');
-    stdio.bufWriteStr(stdout_buf, 'Heap Free     : ');
-    stdio.bufWriteInt(stdout_buf, lmm_free div 1024);
-    stdio.bufWriteStrLn(stdout_buf, ' KB');
-end;
-
-procedure init();
-begin
-    tracer.push_trace('meminfo.init');
-    stdio.registerCommand('MEMINFO', @Run, 'Print memory statistics (PMM/LMM).');
-end;
-
-end.

src/progmanager.pas

@@ -24,7 +24,7 @@ interface
 uses
     tracer,
     //progs
-    base64_prog, md5sum, dhclient, vbeinfo, meminfo;
+    base64_prog, md5sum, dhclient, vbeinfo;
 
 { Initialize all baked-in programs }
 procedure init();
@@ -40,7 +40,6 @@ begin
     tracer.push_trace('progmanager.dhclient.init');
     dhclient.init();
     vbeinfo.init();
-    meminfo.init();
 end;
 
 end.

src/vmemorymanager.pas

@@ -159,14 +159,20 @@ end;
 
 function map_page(page_number : uint16; block : uint16) : boolean;
 var
+    addr  : ubit20;
+    page  : uint16;
     rldpd : uint32;
 
 begin
     push_trace('vmemorymanager.map_page');
-    { Delegate to map_page_ex — no redundant direct PDE writes }
-    map_page := map_page_ex(page_number, block, PageDirectory);
-    { Reload CR3 to flush TLB }
-    rldpd := uint32(PageDirectory) - KERNEL_VIRTUAL_BASE;
+    map_page:= false; 
+    PageDirectory^[page_number].Present:= true;
+    addr:= block;
+    PageDirectory^[page_number].Address:= addr SHL 10;
+    PageDirectory^[page_number].PageSize:= true;
+    PageDirectory^[page_number].Writable:= true;
+    map_page:= map_page_ex(page_number, block, PageDirectory);
+    rldpd:= uint32(PageDirectory) - KERNEL_VIRTUAL_BASE;
     asm
         mov eax, rldpd
         mov CR3, eax
@@ -195,15 +201,14 @@ var
 
 begin
     push_trace('vmemorymanager.new_page');
-    new_page := false;
+    new_page:= false;
     if not PageDirectory^[page_number].Present then begin
         if not PageDirectory^[page_number].Reserved then begin
-            block := pmemorymanager.new_block(uint32(PageDirectory));
-            if block = 0 then begin
-                { OOM — PMM has no free blocks. Return false gracefully. }
-                syslog.logln('VMM', 'ERROR: new_page failed — PMM OOM.');
+            block:= pmemorymanager.new_block(uint32(PageDirectory));
+            if block < 2 then begin
+                GPF;
             end else begin
-                new_page := map_page(page_number, block);
+                new_page:= map_page(page_number, block);
             end;
         end;
     end;
@@ -211,15 +216,17 @@ begin
 end;
 
 function page_mappable(page_number : uint16) : boolean;
+var
+    block : uint16;
+
 begin
     push_trace('vmemorymanager.page_mappable');
-    page_mappable := false;
+    page_mappable:= false;
     if not PageDirectory^[page_number].Present then begin
         if not PageDirectory^[page_number].Reserved then begin
-            page_mappable := true;
+            page_mappable:= true;
         end;
     end;
-    pop_trace;
 end;
 
 function new_page_at_address(address : uint32) : boolean;
@@ -236,25 +243,14 @@ end;
 procedure free_page(page_number : uint16);
 var
     block : uint16;
-    vaddr : uint32;
 
 begin
     push_trace('vmemorymanager.free_page');
     if PageDirectory^[page_number].Present then begin
-        { Recover block index: Address stores (block SHL 10), so SHR 10 gives block }
-        block := PageDirectory^[page_number].Address SHR 10;
-        { Clear the PDE before invalidating }
-        PageDirectory^[page_number].Present    := false;
-        PageDirectory^[page_number].Writable   := false;
-        PageDirectory^[page_number].PageSize   := false;
-        PageDirectory^[page_number].Address    := 0;
-        { Invalidate TLB for this virtual address (invlpg needs a virtual addr) }
-        vaddr := uint32(page_number) SHL 22;
+        block:= PageDirectory^[page_number].Address;
         asm
-            mov eax, vaddr
-            invlpg [eax]
+            invlpg [page_number]
         end;
-        { Return physical block to PMM }
         pmemorymanager.free_block(block, uint32(PageDirectory));
     end else begin
         GPF;