Reach keep alive state in 0.6

Author: ChillerDragon

src/data/logger.asm

@@ -43,10 +43,12 @@ l_s_logger equ $ - s_logger
 
 ; null terminated C strings
 
+c_invalid_length_ddnet_only db "error: got unexpected packet length for 0.6 connection. Only servers with ddnet security tokens are supported in 0.6", 0x00
 c_connect6 db "connecting using 0.6 ddnet protocol to ", 0x00
 c_connect7 db "connecting using 0.7 protocol to ", 0x00
 c_map_change db "got map change. new map: ", 0x00
 c_motd db "motd", 0x00
 c_chat db "chat", 0x00
 c_broadcast db "broadcast", 0x00
 c_client db "client", 0x00
+c_error db "error", 0x00

src/data/teeworlds.asm

@@ -11,7 +11,7 @@ MSG_CTRL_TOKEN equ 5
 MSG6_CTRL_KEEPALIVE equ 0
 MSG6_CTRL_CONNECT equ 1
 MSG6_CTRL_CONNECTACCEPT equ 2
-; MSG6_CTRL_ACCEPT equ 3 ; UNUSED!
+MSG6_CTRL_ACCEPT equ 3
 MSG6_CTRL_CLOSE equ 4
 
 MSG_SYSTEM_NULL equ 0

src/logger.asm

@@ -1,6 +1,17 @@
 ; vim: set tabstop=4:softtabstop=4:shiftwidth=4
 ; vim: set expandtab:
 
+throw_c_str:
+    ; throw_c_str [rax]
+    ;  rax = null terminated string with error message
+    ; logs with log level error and terminates the process
+    mov r9, rax
+    mov rax, c_error
+    mov rdi, r9
+    call log_error
+    exit 1
+    ret
+
 build_log_line:
     ; log_info [rax]
     ;  rax = null terminated label
@@ -78,6 +89,13 @@ log_info:
     pop_registers
     ret
 
+log_error:
+    ; log_error [rax]
+    ;  rax = null terminated label
+    ;  rdi = null terminated string
+    call log_info
+    ret
+
 log_debug:
     ; log_debug [rax]
     ;  rax = null terminated label

src/packet_packer.asm

@@ -75,7 +75,7 @@ send_packet6:
     call set_packet_header
 
     ; append ddnet security token at the end of all packet payloads
-    packet6_pack_raw token, 4
+    packet6_pack_raw peer_token, 4
 
     ; buf
     mov rax, udp_send_buf

src/receive_control6.asm

@@ -1,11 +1,25 @@
 on_ctrl6_msg_connect_accept:
-    ; ignore cursed token only ddnet servers send
-    ; https://github.com/ddnet/ddnet/issues/8805
+    ; in addition to checking the length
+    ; we could also check for the "TKEN"
+    ; magic in front of the token
 
-    ; mov rax, [udp_recv_buf + 8]
-    ; mov [peer_token], rax
+    mov eax, dword [udp_read_len]
+    cmp eax, 12
+    je .len_ok
+    mov rax, c_invalid_length_ddnet_only
+    call throw_c_str
+    .len_ok:
+
+    mov rax, [udp_recv6_buf + PACKET6_HEADER_LEN + 5]
+    mov [peer_token], eax
+    print_label s_got_peer_token
+    mov rax, peer_token
+    mov rdi, 4
+    call print_hexdump
+    call print_newline
 
     print_label s_got_accept
+    call send_ctrl6_msg_ack_accept
     ; call send_msg_info
 
     jmp on_ctrl6_message_end

src/send_control.asm

@@ -30,12 +30,8 @@ send_ctrl_close:
 send_ctrl_msg_connect6:
     push rax
 
-    mov byte [token+0], 0xff
-    mov byte [token+1], 0xff
-    mov byte [token+2], 0xff
-    mov byte [token+3], 0xff
 
-    packet6_pack_byte MSG_CTRL_CONNECT
+    packet6_pack_byte MSG6_CTRL_CONNECT
     packet6_pack_raw MAGIC_TKEN, 4
 
     mov byte [out_packet_header_flags], PACKETFLAG6_CONTROL
@@ -45,6 +41,19 @@ send_ctrl_msg_connect6:
     pop rax
     ret
 
+send_ctrl6_msg_ack_accept:
+    push rax
+
+    packet6_pack_byte MSG6_CTRL_ACCEPT
+    ; packet6_pack_raw [peer_token], 4
+
+    mov byte [out_packet_header_flags], PACKETFLAG6_CONTROL
+    mov byte [out_packet_header_num_chunks], 0
+    call send_packet
+
+    pop rax
+    ret
+
 send_ctrl_msg_connect:
     push rax
     mov al, byte [connection_version]