- FTP, TCP

apps/ftp_server.c

@@ -1,6 +1,7 @@
 #include "ftp_server.h"
 
 #include <stdbool.h>
+#include <stdlib.h>
 
 #include <etherlib/prefab/conn_blocks/tcp_connblock.h>
 
@@ -8,10 +9,21 @@
 
 /* FTP response messages */
 
-static char ftpGreeting[] = "220 Service ready for new user.\r\n";
+static const char ftpOpeningDataConn[] = "150 Opening data connection.\r\n";
-static char ftpNotImplemented[] = "502 Command not implemented.\r\n";
+static const char ftpCmdOk[] = "200 Command OK.\r\n";
-static char ftpLoginOK[] = "230 User logged in, proceed.\r\n";
+static const char ftpGreeting[] = "220 Service ready for new user.\r\n";
-static char ftpRootDirName[] = "257 \"/\" is the current directory\r\n";
+static const char ftpClosingDataConn[] = "226 Closing data connection.\r\n";
+static const char ftpEnteringPassivePrefix[] = "227 Entering passive mode ";
+static const char ftpLoginOK[] = "230 User logged in, proceed.\r\n";
+static const char ftpFileActionCplt[] = "250 Requested file action complete.\r\n";
+static const char ftpRootDirName[] = "257 \"/\" is the current directory\r\n";
+static const char ftpSyntaxError[] = "501 Syntax error in command or parameters\r\n";
+static const char ftpNotImplemented[] = "502 Command not implemented.\r\n";
+static const char ftpCmdNotImplForParam[] = "504 Command not implemented for that parameter\r\n";
+
+#define FTPS_DYNAMIC_RESPONSE_MAXLEN (63)
+
+static char ftpsDynResp[FTPS_DYNAMIC_RESPONSE_MAXLEN + 1] = {0};
 
 /* Implemented commands */
 
@@ -29,6 +41,9 @@ static char *ftpImplementedCmdsStr[] = {
 
     // ------ additional commands
     "PWD",
+    "CWD",
+    "PASV",
+    "LIST",
     "\0" // SENTRY!
 };
 
@@ -45,7 +60,10 @@ typedef enum { // ordering must be the same as in the string version above
     NOOP,
 
     // ------ additional commands
-    PWD
+    PWD,
+    CWD,
+    PASV,
+    LIST
 } Ftp_ImplementedCmds;
 
 // -----------
@@ -61,7 +79,7 @@ int ftps_ctrl_recv(cbd d) {
     return 0;
 }
 
-int ftps_accept_cb(cbd d) {
+int ftps_ctrl_accept_cb(cbd d) {
     s.connCtrl = d;
     uint32_t event = FTPEVT_NEW_CONNECTION;
     ETHLIB_OS_QUEUE_PUSH(s.eventQ, &event);
@@ -73,12 +91,36 @@ void ftps_thread(void *param);
 void ftps_init() {
     osThreadAttr_t attr;
     memset(&attr, 0, sizeof(osThreadAttr_t));
-    attr.stack_size = 2048;
+    attr.stack_size = 3072;
     attr.priority = osPriorityNormal;
     attr.name = "ftp";
     osThreadNew(ftps_thread, NULL, &attr);
 }
 
+char *ftps_get_word(char *word, char *str, uint32_t maxLen) {
+    char *iter = str;
+    uint32_t len = 0;
+
+    // skip leading whitespaces
+    while ((*iter <= ' ') && (*iter != '\0')) {
+        iter++;
+    }
+
+    // look for end of word, and copy until copy size is reached
+    while (*iter > ' ') {
+        if (len < maxLen) {
+            word[len] = *iter;
+        }
+
+        len++;
+        iter++;
+    }
+    word[len] = '\0'; // insert null termination
+
+    // return the position of the next whitespace
+    return iter;
+}
+
 bool ftps_is_command_implemented(char *cmd, uint32_t len, uint32_t *cmdCode) {
     char *iter = ftpImplementedCmdsStr[0];
     bool ret = false;
@@ -109,14 +151,29 @@ bool ftps_is_command_implemented(char *cmd, uint32_t len, uint32_t *cmdCode) {
     return ret;
 }
 
-void ftps_rtrim(char * str) {
+void ftps_rtrim(char *str) {
-    char * iter = str + strlen(str) - 1;
+    char *iter = str + strlen(str) - 1;
     while ((*iter <= ' ') && (iter >= str)) {
         *iter = '\0';
         iter--;
     }
 }
 
+// data reception on data port
+int ftps_data_recv(cbd d) {
+    return 0;
+}
+
+// accept new data connection
+int ftps_data_accept_cb(cbd d) {
+    s.connData = d;                          // set data connection ID
+    ETHLIB_OS_SEM_POST(s.dataConnHasOpened); // release data connection semaphore
+    return 0;
+}
+
+#define FTPS_TYPE_ASCII 'A'
+#define FTPS_TYPE_IMAGE 'I'
+
 void ftps_process_event(uint32_t event) {
     const char *resp = NULL; // response towards the FTP client
     char *cmdArg = NULL;     // command argument
@@ -169,12 +226,71 @@ void ftps_process_event(uint32_t event) {
             s.connState = FTPS_ESTABLISHED;
         }
     } else if (s.connState == FTPS_ESTABLISHED) {
-        switch (cmdCode)
+        switch (cmdCode) {
-        {
         case PWD: // print working directory name
             resp = ftpRootDirName;
             break;
-        case TYPE: // 
+        case CWD:
+            resp = ftpFileActionCplt;
+            break;
+        case TYPE: {                            // set transfer format
+            char typeChar[2];                   // get type character
+            ftps_get_word(typeChar, cmdArg, 1); // (first parameter)
+
+            // if no parameter was defined
+            if (typeChar[0] == '\0') {
+                goto syntax_error;
+            }
+
+            // if parameter is defined, then act accordingly
+            switch (typeChar[0]) {
+            case FTPS_TYPE_ASCII: // ASCII
+            case FTPS_TYPE_IMAGE: // Image (binary)
+                // I don't know if there's any difference between ASCII and Image transfers, since bytes are 8-bit long
+                goto cmd_ok;
+                break;
+            default: // other formats are not implemented
+                goto cmd_param_not_implemented;
+                break;
+            }
+
+        } break;
+        case PASV: { // enter passive mode
+            if (!s.passiveMode) {
+                // start data connection listener socket
+                uint16_t port;
+                do {                                          // randomize a port number not in use currently
+                    port = (rand() % (0xFFFF - 1024)) + 1024; // it's a nice practice if we pick a port number greater than 1024
+                    s.connDataS = tcp_new_connblock(s.intf, IPv4_IF_ADDR, port, ftps_data_recv);
+                } while (s.connDataS == 0); // retry if connection block could not be opened
+
+                // convert to server socket
+                tcp_set_accept_callback(s.connDataS, ftps_data_accept_cb);
+                tcp_listen(s.connDataS);
+
+                MSG("port: %u\n", port);
+
+                // turn passive mode on and save passive mode port
+                s.passiveMode = true;
+                s.passiveModePort = port;
+            }
+
+            // compile response message
+            SNPRINTF(ftpsDynResp, FTPS_DYNAMIC_RESPONSE_MAXLEN, "%s (%u,%u,%u,%u,%u,%u)\r\n", // no space in the whole address-port compound
+                     ftpEnteringPassivePrefix, EXPLODE_IPv4(s.intf->ip), (s.passiveModePort >> 8) & 0xFF, s.passiveModePort & 0xFF);
+
+            // set response
+            resp = ftpsDynResp;
+        } break;
+        case LIST: {                                                                               // list files
+            ETHLIB_OS_SEM_WAIT(s.dataConnHasOpened);                                               // wait for data connection to establish
+            tcp_send(s.connCtrl, (const uint8_t *)ftpOpeningDataConn, strlen(ftpOpeningDataConn)); // opening data connection
+            tcp_send(s.connData, (const uint8_t *)"\r\n", 2);                                                       // sending listing data
+            tcp_send(s.connCtrl, (const uint8_t *)ftpClosingDataConn, strlen(ftpClosingDataConn)); // closing data connection
+            close_connection(s.connData);                                                          // actually close connection
+            s.connData = 0;                                                                        // clear data connection CBD
+            break;
+        }
         default:
             break;
         }
@@ -187,19 +303,41 @@ resp_and_return:
     if (resp != NULL) {
         tcp_send(s.connCtrl, (const uint8_t *)resp, strlen(resp));
     }
+    return;
+
+// -----
+syntax_error:
+    resp = ftpSyntaxError;
+    goto resp_and_return;
+
+cmd_param_not_implemented:
+    resp = ftpCmdNotImplForParam;
+    goto resp_and_return;
+
+cmd_ok:
+    resp = ftpCmdOk;
+    goto resp_and_return;
 }
 
 void ftps_thread(void *param) {
+    // set interface
+    s.intf = get_default_interface();
+
     // initialize event queue
     s.eventQ = ETHLIB_OS_QUEUE_CREATE(FTPS_EVENT_QUEUE_LENGTH, uint32_t);
 
     // initialize control connection
-    s.connCtrlS = tcp_new_connblock(get_default_interface(), IPv4_IF_ADDR, FTPS_CTRL_PORT, ftps_ctrl_recv);
+    s.connCtrlS = tcp_new_connblock(s.intf, IPv4_IF_ADDR, FTPS_CTRL_PORT, ftps_ctrl_recv);
+    tcp_set_accept_callback(s.connCtrlS, ftps_ctrl_accept_cb); // set callback for accepting an incoming connection
     tcp_listen(s.connCtrlS);                                   // make it listen for incoming connections
-    tcp_set_accept_callback(s.connCtrlS, ftps_accept_cb); // set callback for accepting an incoming connection
 
     // initialize connection state
     s.connState = FTPS_IDLE;
+    s.passiveMode = false; // at the beginning we disable passive mode
+    s.passiveModePort = 0;
+
+    // initialize semaphore which synchronizes data connection state
+    s.dataConnHasOpened = ETHLIB_OS_SEM_CREATE(1);
 
     // process loop
     for (;;) {

apps/ftp_server.h

@@ -10,8 +10,6 @@
 
 #define FTPS_LINEBUF_LEN (63)
 
-#define FTPS_ROOT_DIR_NAME "ftp_root"
-
 /**
  * FTP connection state machine states.
 */
@@ -30,13 +28,20 @@ typedef enum {
     FTPEVT_CTRL_RECVD, // a control message has been received
 } Ftps_ConnEvents;
 
+/**
+ * FTP server state.
+*/
 typedef struct {
+    EthInterface * intf; // pointer to associated Ethernet interface
+    bool passiveMode; // indicates whether the server is operating in passive mode
+    uint16_t passiveModePort; // passive mode port once the passive mode is activated
     cbd connCtrlS; // control connection server
     cbd connCtrl; // established control connection
     cbd connDataS; // data connection server
     cbd connData; // established data connection
     Ftps_ConnState connState; // connection state
     ETHLIB_OS_QUEUE_TYPE eventQ; // event queue
+    ETHLIB_OS_SEM_TYPE dataConnHasOpened; // semaphore synchronizing data connection opening
     char lineBuffer[FTPS_LINEBUF_LEN + 1]; // line buffer
 } Ftps_State;
 

connection_block.h

@@ -11,12 +11,12 @@ typedef int (*ConnBlockTransmitFn)(struct EthInterface_ * intf, const uint8_t *
  * Connection block.
  */
 typedef struct ConnBlock_ {
-    PcktSieve * sieve; ///< Ethernet interface
+    PcktSieve * sieve; ///< Pointer to the packet sieve
     PcktSieveLayer * sieveLayer; ///< Sieve layer
 } ConnBlock;
 
 typedef struct ConstConnBlock_ {
-    const PcktSieve * sieve; ///< Ethernet interface
+    const PcktSieve * sieve; ///< Pointer to the packet sieve
     const PcktSieveLayer * sieveLayer; ///< Sieve layer
 } ConstConnBlock;
 

global_state.c

@@ -91,6 +91,13 @@ void close_connection(cbd d) {
 
     cbdt_release(E.cbdt, d); // release from CBD table
 
+    // connb_remove() calls pcktsieve_remove_layer() which does not guarantee 
+    // that the layer is instantaneously removed, since some protocols (like TCP)
+    // must gracefully shutdown the connection and the protocol implementation
+    // will then remove the layer. As long as the protocol implementation does
+    // not attempt to use the CBD released above, the cleanup actions will 
+    // execute silently in the background without raising errors.
+
     connb_remove(&connBlock); // remove connection block
 }
 

packet_sieve.c

@@ -257,6 +257,7 @@ PcktSieveLayer* packsieve_new_layer(PcktSieveLayer *parent, const PcktSieveFilte
         layer->tag = tag;
         layer->connBReportFn = NULL;
         layer->txTsCb = NULL;
+        layer->mgmtCb = NULL;
         return layer;
     }
 }
@@ -267,6 +268,13 @@ bool packsieve_remove_layer(const PcktSieveLayer *layer) {
         return true;
     }
 
+    // dispath management message if callback is defined
+    if (layer->mgmtCb != NULL) {
+        if (layer->mgmtCb(layer, PSLEVT_REMOVE) == PSMGMT_RET_ABORT) {
+            return false;
+        }
+    }
+
     // remove parent elements if their only subnode is the one we're deleting
     PcktSieveLayer *parent;
     while (layer != NULL && layer->nodes == NULL) {

packet_sieve.h

@@ -78,8 +78,28 @@ typedef int (*SieveCallBackFn)(const Pckt *pckt, PcktSieveLayerTag tag);
 struct ConnBlock_;
 typedef void (*ConnBlockReportFn)(const struct ConnBlock_ *connBlock);
 
+/**
+ * Timestamp callback function.
+*/
 typedef void(*TxTimeStampCBFn)(uint32_t ts_s, uint32_t ts_ns, uint32_t tag);
 
+/**
+ * Management event types.
+*/
+typedef enum {
+    PSLEVT_NONE, ///< No event.
+    PSLEVT_REMOVE ///< The sievele layer is about to get deleted.
+} PcktSieveLayerMgmtEvent;
+
+// Management callback return values
+#define PSMGMT_RET_PROCEED (0) // proceed with processing
+#define PSMGMT_RET_ABORT (1) // abort processing
+
+/**
+ * Packet sieve layer management function.
+*/
+typedef int(*MgmtCBFn)(const struct PcktSieveLayer_ * layer, PcktSieveLayerMgmtEvent event);
+
 #define PCKT_SIEVE_INFOTAG_LEN (24)
 
 /**
@@ -97,6 +117,7 @@ typedef struct PcktSieveLayer_ {
     struct PcktSieveLayer_ *next, *prev; ///< Next and previous sieve layer on the same level
     struct PcktSieveLayer_ *nodes; ///< Subnodes in the sieve tree
     ConnBlockReportFn connBReportFn; ///< Connection block report function pointer
+    MgmtCBFn mgmtCb; ///< Management callback function
 } PcktSieveLayer;
 
 /**

prefab/conn_blocks/tcp/tcp_window.c

@@ -27,7 +27,7 @@ void tcpw_set_seqnum_offset(TcpWindow * tcpw, uint32_t offset) {
     tcpw->firstUnACK = offset;
 }
 
-static inline uint32_t tcpw_get_occupied_size(TcpWindow * tcpw) {
+uint32_t tcpw_get_occupied_size(TcpWindow * tcpw) {
     return tcpw->nextWritten - tcpw->firstUnACK;
 }
 

prefab/conn_blocks/tcp/tcp_window.h

@@ -44,6 +44,15 @@ void tcpw_set_seqnum_offset(TcpWindow * tcpw, uint32_t offset);
  */
 uint32_t tcpw_get_max_window_size(TcpWindow * tcpw);
 
+/**
+ * TODO: rename function
+ * Get used area size of this window.
+ * @param tcpw pointer to TCP Window object
+ * @return used area size in bytes
+ * 
+*/
+uint32_t tcpw_get_occupied_size(TcpWindow * tcpw);
+
 /** TODO: rename function
  * Store TCP segment
  * @param tcpw pointer to TCP Window object

prefab/conn_blocks/tcp_connblock.c

@@ -45,7 +45,7 @@ static bool filtTcp(const PcktSieveFilterCondition *filtCond, const PcktProps *c
                            (remote_addr == ipProps->SourceIPAddr)) || // the packet has come from the known origin
                           (remote_addr == 0));                        // the latter conditions only matter if the control block is connected to a remote station
 
-    return ipProps->Protocol == ETH_TCP_PACKET_CLASS && references_us;
+    return (ipProps->Protocol == ETH_TCP_PACKET_CLASS) && references_us;
 }
 
 #define MAX_TCP_WINDOW_SIZE (1200)
@@ -57,15 +57,16 @@ static inline TcpState *tcps_create() {
     tcps->txBufNotFull = ETHLIB_OS_SEM_CREATE(1);         // create transmit buffer not full semaphore
     ETHLIB_OS_SEM_POST(tcps->txBufNotFull);               // post the tx buffer semaphore
     tcps->txInProgress = ETHLIB_OS_SEM_CREATE(1);         // create transmission in progress semaphore
-    ETHLIB_OS_SEM_POST(tcps->txInProgress);
+    ETHLIB_OS_SEM_POST(tcps->txInProgress);               // post the TX in progress, since no transmission is in progress
-
+    tcps->eventFlags = osEventFlagsNew(NULL);             // create event flags for internal event synchronization
+    osEventFlagsSet(tcps->eventFlags, EVTFLAG_ALL_ACKED); // everything is ACKed in the beginning
+    tcps->processMtx = ETHLIB_OS_RECMTX_CREATE();         // create mutex protecting the internal state
     return tcps;
 }
 
 static inline void tcps_release_client_related_objects(TcpState *tcps) {
     tcpw_destroy(tcps->txWin);
     ETHLIB_OS_SEM_DESTROY(tcps->txBufNotFull);
-    ETHLIB_OS_SEM_DESTROY(tcps->txInProgress);
     eth_bfifo_destroy(tcps->rxFifo);
 }
 
@@ -78,6 +79,10 @@ static inline void tcps_remove_and_cleanup(TcpState *tcps) {
         tcps_release_client_related_objects(tcps);
     }
 
+    ETHLIB_OS_SEM_DESTROY(tcps->txInProgress); // TODO: ezt a szerver bezárásakor nem kell vizsgálni
+    osEventFlagsDelete(tcps->eventFlags);
+    ETHLIB_OS_MTX_DESTROY(tcps->processMtx);
+
     dynmem_free(tcps);
 }
 
@@ -147,10 +152,76 @@ static inline cbd tcps_create_based_on_listening(const TcpState *source, uint16_
     return d;
 }
 
+// ----------------------------
+
+static bool tcp_close(TcpState *tcps) {
+    TcpConnectionState cs = tcps->connState;
+
+    // a closed connection cannot be more closed...
+    if (cs == TCP_STATE_CLOSED) {
+        return true;
+    }
+
+    // act according to the current state
+    switch (cs) {
+    case TCP_STATE_ESTAB: // close connecion from established state
+        // take send semaphore
+        ETHLIB_OS_SEM_WAIT(tcps->txInProgress);
+
+        MSG("TX SEM\n");
+
+        // wait for the TX FIFO contents to get transmitted
+        osEventFlagsWait(tcps->eventFlags, EVTFLAG_ALL_ACKED, osFlagsWaitAll | osFlagsNoClear, osWaitForever); // FIXME: ez így nem lesz jó, mert, ha valamiért nem kapjuk meg az ACK-t, akkor itt ragadunk
+
+        MSG("FLAG\n");
+
+        // lock the mutex -----
+        ETHLIB_OS_MTX_LOCK(tcps->processMtx);
+        // --------------------
+
+        // send a FIN-ACK segment
+        tcp_send_segment(&(tcps->connBlock), TCP_FLAG_FIN | TCP_FLAG_ACK, NULL, NULL, 0);
+        tcps->txSeqNum++; // increase own sequence number
+
+        // step into FIN WAIT-1 state
+        tcps->connState = TCP_STATE_FIN_WAIT_1;
+
+        // unlock the mutex -----
+        ETHLIB_OS_MTX_UNLOCK(tcps->processMtx);
+        // --------------------
+
+        break;
+    default:
+        break;
+    }
+
+    return false;
+}
+
+int tcp_mgmt_cb(const PcktSieveLayer *layer, PcktSieveLayerMgmtEvent event) {
+    TcpState *tcps = TCP_FETCH_STATE_FROM_SIEVE_LAYER(layer);
+
+    switch (event) {
+    case PSLEVT_REMOVE: {                                               // connection removal is in progress
+        return tcp_close(tcps) ? PSMGMT_RET_PROCEED : PSMGMT_RET_ABORT; // abort further removal processing if further steps are required to close the connection
+    } break;
+    default:
+        break;
+    }
+
+    return PSMGMT_RET_PROCEED;
+}
+
+// ----------------------------
+
 int tcp_receive_segment_cb(const Pckt *pckt, PcktSieveLayerTag tag) {
     TcpState *tcps = (TcpState *)tag.p;                              // pointer to state is stored in sieve layer tag
     TcpProps *tcpProps = HEADER_FETCH_PROPS(TcpProps, pckt->header); // fetch header
 
+    // lock the mutex -----
+    ETHLIB_OS_MTX_LOCK(tcps->processMtx);
+    // --------------------
+
     TcpConnectionState beginState = tcps->connState;
 
     IPv4Props *ipProps = HEADER_FETCH_PROPS(IPv4Props, pckt->header->prev);
@@ -175,6 +246,8 @@ int tcp_receive_segment_cb(const Pckt *pckt, PcktSieveLayerTag tag) {
             // store rxAckNum
             tcps->rxAckNum = tcpProps->SequenceNumber + 1;
 
+            // MSG("SYN ACK\n");
+
             // get MSS
             TcpOption *mss = tcp_get_option_by_kind(tcpProps->options, TCP_OPT_KIND_MSS);
             if (mss != NULL) {                                // if MSS is included in the segment
@@ -205,6 +278,9 @@ int tcp_receive_segment_cb(const Pckt *pckt, PcktSieveLayerTag tag) {
 
                 // step into next state
                 tcps->connState = TCP_STATE_ESTAB;
+
+                // set event flags
+                osEventFlagsSet(tcps->eventFlags, EVTFLAG_ESTAB);
             }
         }
 
@@ -247,8 +323,7 @@ int tcp_receive_segment_cb(const Pckt *pckt, PcktSieveLayerTag tag) {
             }
         }
 
-        break;
+    } break;
-    }
 
     case TCP_STATE_ESTAB: /* Connection established */
         // if the other end tries to close down the connection
@@ -282,6 +357,13 @@ int tcp_receive_segment_cb(const Pckt *pckt, PcktSieveLayerTag tag) {
                 // release segment from retransmit window
                 tcpw_acknowledge(tcps->txWin, tcpProps->AcknowledgementNumber);
 
+                // set or clear all ACKed flag according to TX window state
+                if (tcpw_get_occupied_size(tcps->txWin) == 0) {
+                    osEventFlagsSet(tcps->eventFlags, EVTFLAG_ALL_ACKED);
+                } else {
+                    osEventFlagsClear(tcps->eventFlags, EVTFLAG_ALL_ACKED);
+                }
+
                 // release the transmit semaphore
                 ETHLIB_OS_SEM_POST(tcps->txBufNotFull);
 
@@ -296,12 +378,51 @@ int tcp_receive_segment_cb(const Pckt *pckt, PcktSieveLayerTag tag) {
     case TCP_STATE_LAST_ACK: /* last ACK received */
         if (tcpProps->Flags & TCP_FLAG_ACK) {
             tcps->connState = TCP_STATE_CLOSED;
-            //ETHLIB_OS_SEM_POST(tcps->txBufNotFull); FIXME!
+            // ETHLIB_OS_SEM_POST(tcps->txBufNotFull); FIXME!
-            //ETHLIB_OS_SEM_WAIT(tcps->txInProgress);
+            // ETHLIB_OS_SEM_WAIT(tcps->txInProgress);
             ret = SIEVE_LAYER_REMOVE_THIS; // if peer closed the connection, remove sieve layer
         }
         break;
 
+    case TCP_STATE_FIN_WAIT_1: { /* our FIN has been sent, waiting for the peer's one */
+        uint16_t flags = tcpProps->Flags;
+        bool rxACKok = tcpProps->AcknowledgementNumber == tcps->txSeqNum; // check if received ACK was correct
+        bool sendACK = false;                                             // set if we want to emit an ACK
+
+        if ((flags & TCP_FLAG_ACK) && (!(flags & TCP_FLAG_FIN))) {        // only ACK received
+            tcps->connState = TCP_STATE_FIN_WAIT_2;                       // this case don't send ACK
+        } else if ((!(flags & TCP_FLAG_ACK)) && (flags & TCP_FLAG_FIN)) { // only FIN received
+            tcps->connState = TCP_STATE_CLOSING;
+            sendACK = true;
+        } else if ((flags & TCP_FLAG_ACK) && (flags & TCP_FLAG_FIN)) { // received ACK and FIN
+            tcps->connState = TCP_STATE_CLOSED;
+            ret = SIEVE_LAYER_REMOVE_THIS;
+            sendACK = true;
+        }
+
+        // send ACK if required and received ACK was correct
+        if (sendACK && rxACKok) {
+            tcps->rxAckNum++; // acknowledge the FIN-ACK packet
+            tcp_send_segment(&(tcps->connBlock), TCP_FLAG_ACK, NULL, NULL, 0);
+        }
+    } break;
+
+    case TCP_STATE_FIN_WAIT_2: { /* waiting on peer's FIN */
+        if (tcpProps->Flags & TCP_FLAG_FIN) {
+            tcps->rxAckNum++; // acknowledge the FIN packet
+            tcp_send_segment(&(tcps->connBlock), TCP_FLAG_ACK, NULL, NULL, 0);
+            tcps->connState = TCP_STATE_CLOSED;
+            ret = SIEVE_LAYER_REMOVE_THIS;
+        }
+    } break;
+
+    case TCP_STATE_CLOSING: /* waiting on arrival of ACK sent by the peer against our FIN */           /* connection is closing waiting on peers ACK */
+        if ((tcpProps->Flags & TCP_FLAG_ACK) && (tcpProps->AcknowledgementNumber == tcps->txSeqNum)) { // ACK received
+            tcps->connState = TCP_STATE_CLOSED;
+            ret = SIEVE_LAYER_REMOVE_THIS;
+        }
+        break;
+
     case TCP_STATE_CLOSED: /* connection is CLOSED */
     default:
         break;
@@ -323,8 +444,13 @@ int tcp_receive_segment_cb(const Pckt *pckt, PcktSieveLayerTag tag) {
         tcpopt_chain_free(tcpProps->options);
     }
 
+    // unlock the mutex -----
+    ETHLIB_OS_MTX_UNLOCK(tcps->processMtx);
+    // --------------------
+
     // release descriptor if not meaningful anymore
     if (ret == SIEVE_LAYER_REMOVE_THIS) {
+        tcps->connBlock.sieveLayer->mgmtCb = NULL;
         cbdt_release(E.cbdt, tcps->d); // release descriptor
         tcps_remove_and_cleanup(tcps); // release TCP state
     }
@@ -332,6 +458,7 @@ int tcp_receive_segment_cb(const Pckt *pckt, PcktSieveLayerTag tag) {
     return ret;
 }
 
+// TODO: mindent egy függvénybe kellene tenni, mert így nagyon sok versenyhelyet alakulhat ki
 void tcp_bind(cbd d, ip4_addr remoteAddr, uint16_t remotePort) {
     ConnBlock connBlock;
     if (!cbdt_get_connection_block(E.cbdt, d, &connBlock)) {
@@ -339,8 +466,14 @@ void tcp_bind(cbd d, ip4_addr remoteAddr, uint16_t remotePort) {
         return;
     }
 
-    // store remote station data
+    // fetch TCP state
     TcpState *tcps = TCP_FETCH_STATE_FROM_CONNBLOCK(&connBlock);
+
+    // lock the mutex -----
+    ETHLIB_OS_MTX_LOCK(tcps->processMtx);
+    // --------------------
+
+    // set peer address and port
     tcps->remoteAddr = remoteAddr;
     tcps->remotePort = remotePort;
 
@@ -359,6 +492,13 @@ void tcp_bind(cbd d, ip4_addr remoteAddr, uint16_t remotePort) {
 
     // step into SYN SENT state
     tcps->connState = TCP_STATE_SYN_SENT;
+
+    // unlock the mutex -----
+    ETHLIB_OS_MTX_UNLOCK(tcps->processMtx);
+    // --------------------
+
+    // wait for getting into Established state
+    osEventFlagsWait(tcps->eventFlags, EVTFLAG_ESTAB, osFlagsWaitAll | osFlagsNoClear, osWaitForever);
 }
 
 void tcp_listen(cbd d) {
@@ -368,12 +508,22 @@ void tcp_listen(cbd d) {
         return;
     }
 
+    // fetch state
     TcpState *tcps = TCP_FETCH_STATE_FROM_CONNBLOCK(&connBlock);
+
+    // lock the mutex -----
+    ETHLIB_OS_MTX_LOCK(tcps->processMtx);
+    // --------------------
+
     if ((tcps->streamCb != NULL) && (tcps->connState == TCP_STATE_CLOSED)) { // step into listen state
         tcps->connState = TCP_STATE_LISTEN;
         tcps->isServer = true;
-        tcps_release_client_related_objects(tcps);
+        tcps_release_client_related_objects(tcps); // release client-only resources
     }
+
+    // unlock the mutex -----
+    ETHLIB_OS_MTX_UNLOCK(tcps->processMtx);
+    // --------------------
 }
 
 void tcp_set_accept_callback(cbd d, TcpAcceptCbFn acb) {
@@ -415,6 +565,7 @@ static inline cbd tcp_new_connblock_filtcond(EthInterface *intf, ip4_addr ipAddr
     tcpConnB.sieveLayer = packsieve_new_layer(ipConnB.sieveLayer, filtCond, false, filtTcp, tcp_receive_segment_cb, tag, ETH_TCP_PACKET_CLASS);
     ASSERT_NULL(tcpConnB.sieveLayer);
     tcpConnB.sieveLayer->connBReportFn = tcp_print_report;
+    tcpConnB.sieveLayer->mgmtCb = tcp_mgmt_cb;
 
     tcpConnB.sieve = &intf->sieve;
     tcpState->connBlock = tcpConnB; // also store connection block parameters
@@ -565,6 +716,9 @@ uint32_t tcp_send(cbd d, const uint8_t *data, uint32_t size) {
             // store segment for possible retransmission
             uint32_t txSize = tcpw_store(tcps->txWin, data, sizeLeft, tcps->txSeqNum);
 
+            // clear all ACK-ed flag
+            osEventFlagsClear(tcps->eventFlags, EVTFLAG_ALL_ACKED);
+
             // send segment with data (no options)
             tcp_send_segment(&connBlock, TCP_FLAG_ACK, NULL, data, txSize);
 

prefab/conn_blocks/tcp_connblock.h

@@ -52,6 +52,9 @@ typedef enum {
 typedef int (*StreamCallBackFn)(cbd d);
 typedef int (*TcpAcceptCbFn)(cbd d);
 
+#define EVTFLAG_ESTAB (0x00000001)
+#define EVTFLAG_ALL_ACKED (0x00000002)
+
 /**
  * TCP state.
  */
@@ -103,11 +106,20 @@ typedef struct {
 
     // ---------------
 
+    ETHLIB_OS_MTX_TYPE processMtx; ///< a mutex protecting TCP state changes (this is how we can manipulate the internal state without raising race conditions)
+
+    // ---------------
+
+    osEventFlagsId_t eventFlags; ///< Semaphore for synchronizing on getting into established state 
+
+    // ---------------
+
     EthBlockingFifo * rxFifo; ///< Receive FIFO
 
 } TcpState;
 
 #define TCP_FETCH_STATE_FROM_CONNBLOCK(connBlock) ((TcpState *) (connBlock)->sieveLayer->tag.p)
+#define TCP_FETCH_STATE_FROM_SIEVE_LAYER(layer) ((TcpState *) (layer)->tag.p)
 
 /**
  * Create new TCP connection block