handle server list ping

include/globals.h

@@ -62,6 +62,9 @@ extern uint32_t rng_seed;
 
 extern uint16_t world_time;
 
+extern char motd[];
+extern uint8_t motd_len;
+
 extern uint16_t client_count;
 
 #pragma pack(push, 1)

include/packets.h

@@ -23,6 +23,7 @@ int cs_playerInput (int client_fd);
 int cs_playerCommand (int client_fd);
 
 // Clientbound packets
+int sc_statusResponse (int client_fd);
 int sc_loginSuccess (int client_fd, uint8_t *uuid, char *name);
 int sc_knownPacks (int client_fd);
 int sc_finishConfiguration (int client_fd);

src/globals.c

@@ -31,6 +31,9 @@ uint32_t rng_seed = 0xE2B9419;
 
 uint16_t world_time = 0;
 
+char motd[] = { "A bareiron server" };
+uint8_t motd_len = sizeof(motd) - 1;
+
 uint16_t client_count;
 
 BlockChange block_changes[20000];

src/main.c

@@ -32,9 +32,8 @@
 #include "registries.h"
 #include "procedures.h"
 
-void handlePacket (int client_fd, int length, int packet_id) {
+void handlePacket (int client_fd, int length, int packet_id, int state) {
 
-  int state = getClientState(client_fd);
   uint64_t bytes_received_start = total_bytes_received;
 
   switch (packet_id) {
@@ -42,7 +41,9 @@ void handlePacket (int client_fd, int length, int packet_id) {
     case 0x00:
       if (state == STATE_NONE) {
         if (cs_handshake(client_fd)) break;
-      } else if (state == STATE_LOGIN) {
+      } else if (state == STATE_STATUS) {
+        if (sc_statusResponse(client_fd)) break;
+      } if (state == STATE_LOGIN) {
         uint8_t uuid[16];
         char name[16];
         if (cs_loginStart(client_fd, uuid, name)) break;
@@ -55,6 +56,19 @@ void handlePacket (int client_fd, int length, int packet_id) {
       }
       break;
 
+    case 0x01:
+      // Handle status ping
+      if (state == STATE_STATUS) {
+        // No need for a packet handler, just echo back the long verbatim
+        writeByte(client_fd, 9);
+        writeByte(client_fd, 0x01);
+        writeUint64(client_fd, readUint64(client_fd));
+        // Close connection after this
+        recv_count = 0;
+        return;
+      }
+      break;
+
     case 0x02:
       if (state == STATE_CONFIGURATION) cs_pluginMessage(client_fd);
       break;
@@ -526,7 +540,7 @@ int main () {
     int client_fd = clients[client_index];
 
     // Check if at least 2 bytes are available for reading
-    ssize_t recv_count = recv(client_fd, &recv_buffer, 2, MSG_PEEK);
+    recv_count = recv(client_fd, &recv_buffer, 2, MSG_PEEK);
     if (recv_count < 2) {
       if (recv_count == 0 || (recv_count < 0 && errno != EAGAIN && errno != EWOULDBLOCK)) {
         disconnectClient(&clients[client_index], 1);
@@ -546,8 +560,15 @@ int main () {
       disconnectClient(&clients[client_index], 3);
       continue;
     }
+    // Get client connection state
+    int state = getClientState(client_fd);
+    // Disconnect on legacy server list ping
+    if (state == STATE_NONE && length == 254 && packet_id == 122) {
+      disconnectClient(&clients[client_index], 5);
+      continue;
+    }
     // Handle packet data
-    handlePacket(client_fd, length - sizeVarInt(packet_id), packet_id);
+    handlePacket(client_fd, length - sizeVarInt(packet_id), packet_id, state);
     if (recv_count == 0 || (recv_count == -1 && errno != EAGAIN && errno != EWOULDBLOCK)) {
       disconnectClient(&clients[client_index], 4);
       continue;

src/packets.c

@@ -20,6 +20,28 @@
 #include "procedures.h"
 #include "packets.h"
 
+// S->C Status Response (server list ping)
+int sc_statusResponse (int client_fd) {
+
+  char header[] = "{"
+    "\"version\":{\"name\":\"1.21.8\",\"protocol\":772},"
+    "\"enforcesSecureChat\":false,"
+    "\"description\":{\"text\":\"";
+  char footer[] = "\"}}";
+
+  uint16_t string_len = sizeof(header) + sizeof(footer) + motd_len - 2;
+
+  writeVarInt(client_fd, 1 + string_len + sizeVarInt(string_len));
+  writeByte(client_fd, 0x00);
+
+  writeVarInt(client_fd, string_len);
+  send_all(client_fd, header, sizeof(header) - 1);
+  send_all(client_fd, motd, motd_len);
+  send_all(client_fd, footer, sizeof(footer) - 1);
+
+  return 0;
+}
+
 // C->S Handshake
 int cs_handshake (int client_fd) {
   printf("Received Handshake:\n");
@@ -1071,6 +1093,7 @@ int cs_playerInput (int client_fd) {
   return 0;
 }
 
+// C->S Player Command
 int cs_playerCommand (int client_fd) {
 
   readVarInt(client_fd); // Ignore entity ID