- FTP basics

apps/ftp_server.c

@@ -0,0 +1,213 @@
+#include "ftp_server.h"
+
+#include <stdbool.h>
+
+#include <etherlib/prefab/conn_blocks/tcp_connblock.h>
+
+// ----------
+
+/* FTP response messages */
+
+static char ftpGreeting[] = "220 Service ready for new user.\r\n";
+static char ftpNotImplemented[] = "502 Command not implemented.\r\n";
+static char ftpLoginOK[] = "230 User logged in, proceed.\r\n";
+static char ftpRootDirName[] = "257 \"/\" is the current directory\r\n";
+
+/* Implemented commands */
+
+static char *ftpImplementedCmdsStr[] = {
+    // this is the smallest standard set of implemented FTP commands
+    "USER",
+    "QUIT",
+    "PORT",
+    "TYPE",
+    "MODE",
+    "STRU",
+    "RETR",
+    "STOR",
+    "NOOP",
+
+    // ------ additional commands
+    "PWD",
+    "\0" // SENTRY!
+};
+
+// THIS MUST REMAIN LOCAL!
+typedef enum { // ordering must be the same as in the string version above
+    USER,
+    QUIT,
+    PORT,
+    TYPE,
+    MODE,
+    STRU,
+    RETR,
+    STOR,
+    NOOP,
+
+    // ------ additional commands
+    PWD
+} Ftp_ImplementedCmds;
+
+// -----------
+
+static Ftps_State s; // TODO: dynamically allocate this later
+
+// TODO deinit!
+// TODO ambiguous naming between server and client connections
+
+int ftps_ctrl_recv(cbd d) {
+    uint32_t event = FTPEVT_CTRL_RECVD;
+    ETHLIB_OS_QUEUE_PUSH(s.eventQ, &event);
+    return 0;
+}
+
+int ftps_accept_cb(cbd d) {
+    s.connCtrl = d;
+    uint32_t event = FTPEVT_NEW_CONNECTION;
+    ETHLIB_OS_QUEUE_PUSH(s.eventQ, &event);
+    return 0;
+}
+
+void ftps_thread(void *param);
+
+void ftps_init() {
+    osThreadAttr_t attr;
+    memset(&attr, 0, sizeof(osThreadAttr_t));
+    attr.stack_size = 2048;
+    attr.priority = osPriorityNormal;
+    attr.name = "ftp";
+    osThreadNew(ftps_thread, NULL, &attr);
+}
+
+bool ftps_is_command_implemented(char *cmd, uint32_t len, uint32_t *cmdCode) {
+    char *iter = ftpImplementedCmdsStr[0];
+    bool ret = false;
+    uint8_t index = 0;
+    while (*iter != '\0') {
+        // compare passed command with the iterator value
+        if (len == 0) {
+            if (!strcmp(iter, cmd)) {
+                ret = true;
+                break;
+            }
+        } else {
+            if (!strncmp(iter, cmd, len)) {
+                ret = true;
+                break;
+            }
+        }
+
+        // select next command
+        iter = ftpImplementedCmdsStr[++index];
+    }
+
+    // if cmdCode pointer is provided, then write back the command code
+    if (ret && (cmdCode != NULL)) {
+        *cmdCode = index;
+    }
+
+    return ret;
+}
+
+void ftps_rtrim(char * str) {
+    char * iter = str + strlen(str) - 1;
+    while ((*iter <= ' ') && (iter >= str)) {
+        *iter = '\0';
+        iter--;
+    }
+}
+
+void ftps_process_event(uint32_t event) {
+    const char *resp = NULL; // response towards the FTP client
+    char *cmdArg = NULL;     // command argument
+    int cmdCode = -1;        // command code fetched from the string command
+
+    // is something is received, then read it
+    if (event == FTPEVT_CTRL_RECVD) {
+        // read into the linebuffer
+        uint32_t recvLen = tcp_recv(s.connCtrl, (uint8_t *)s.lineBuffer, FTPS_LINEBUF_LEN);
+        s.lineBuffer[recvLen] = '\0';
+
+        // right trim the line
+        ftps_rtrim(s.lineBuffer);
+
+        MSG("%s\n", s.lineBuffer);
+
+        // get first word: get pointer to first space and calculate compare length
+        char *spacePos = strchr(s.lineBuffer, ' ');
+        uint32_t compareLen = (spacePos == NULL) ? 0 : (spacePos - s.lineBuffer);
+
+        // determine if we support this command or not
+        bool cmdImpl = ftps_is_command_implemented(s.lineBuffer, compareLen, (uint32_t *)&cmdCode);
+
+        // if command is not implemented, then send the "not implemented" answer and return from this function
+        if (!cmdImpl) {
+            resp = ftpNotImplemented;
+            goto resp_and_return; // yes, goto, but it's efficient
+        }
+
+        // if command is implemented, then set the argument pointer
+        cmdArg = spacePos + 1; // the argument begins right after the first space
+    }
+
+    // ------
+
+    if (s.connState == FTPS_IDLE) {           // IDLE...
+        if (event == FTPEVT_NEW_CONNECTION) { // ...and there's an incoming connection
+            // send greeting to the client
+            resp = ftpGreeting;
+
+            // set state to logging in
+            s.connState = FTPS_LOGGING_IN;
+        }
+    } else if (s.connState == FTPS_LOGGING_IN) {
+        if (cmdCode == USER) { // if user command is issued, the login, no username or password checking
+            // send login ok
+            resp = ftpLoginOK;
+
+            // switch to established state
+            s.connState = FTPS_ESTABLISHED;
+        }
+    } else if (s.connState == FTPS_ESTABLISHED) {
+        switch (cmdCode)
+        {
+        case PWD: // print working directory name
+            resp = ftpRootDirName;
+            break;
+        case TYPE: // 
+        default:
+            break;
+        }
+    }
+
+    // ------
+
+resp_and_return:
+    // send response if instructed
+    if (resp != NULL) {
+        tcp_send(s.connCtrl, (const uint8_t *)resp, strlen(resp));
+    }
+}
+
+void ftps_thread(void *param) {
+    // 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);
+    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;
+
+    // process loop
+    for (;;) {
+        // wait for some connection event
+        uint32_t event = FTPEVT_NONE;
+        ETHLIB_OS_QUEUE_POP(s.eventQ, &event);
+
+        // execute event process
+        ftps_process_event(event);
+    }
+}

apps/ftp_server.h

@@ -0,0 +1,45 @@
+#ifndef APPS_FTP_SERVER
+#define APPS_FTP_SERVER
+
+#include <etherlib/etherlib.h>
+#include <etherlib/cbd_table.h>
+
+#define FTPS_CTRL_PORT (21) // FTP server control connection port
+
+#define FTPS_EVENT_QUEUE_LENGTH (8) // internal event queue length
+
+#define FTPS_LINEBUF_LEN (63)
+
+#define FTPS_ROOT_DIR_NAME "ftp_root"
+
+/**
+ * FTP connection state machine states.
+*/
+typedef enum {
+    FTPS_IDLE, // the server is IDLE
+    FTPS_LOGGING_IN, // the client is logging in
+    FTPS_ESTABLISHED // the connection is established
+} Ftps_ConnState;
+
+/**
+ * FTP connection events.
+*/
+typedef enum {
+    FTPEVT_NONE, // no action
+    FTPEVT_NEW_CONNECTION, // a new connection was recently initiated
+    FTPEVT_CTRL_RECVD, // a control message has been received
+} Ftps_ConnEvents;
+
+typedef struct {
+    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
+    char lineBuffer[FTPS_LINEBUF_LEN + 1]; // line buffer
+} Ftps_State;
+
+void ftps_init();
+
+#endif /* APPS_FTP_SERVER */