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moxerver/telnet.c

@@ -0,0 +1,153 @@
+#include <telnet.h>
+
+/* structure for holding telnet option name and value */
+typedef struct
+{
+	const char *name;
+	char value;
+} telnet_option_t;
+
+/* supported telnet option values */
+telnet_option_t telnet_options[] =
+{
+	{"WILL", 251},
+	{"WONT", 252},
+	{"DO", 253},
+	{"DONT", 254},
+	{"IAC", 255},
+	{"ECHO", 1},
+	{"SGA", 3},
+	{"LINEMODE", 34},
+	{NULL, 0}
+	/* this list must end with {NULL, 0} */
+};
+
+/* Returns the name of a telnet option based on the value. */
+static const char* telnet_option_name(int value)
+{
+	int i;
+	for (i = 0; telnet_options[i].name != NULL; i++)
+	{
+		if (telnet_options[i].value == value)
+		{
+			return telnet_options[i].name;
+		}
+	}
+	/* default value */
+	return '\0';
+}
+
+/* Returns the value of a telnet option based on the name. */
+static char telnet_option_value(const char* name)
+{
+	int i;
+	for (i = 0; telnet_options[i].name != NULL; i++)
+	{
+		if (strcmp(telnet_options[i].name, name) == 0)
+		{
+			return telnet_options[i].value;
+		}
+	}
+	/* default value */
+	return 0;
+}
+
+/* Handles a received telnet option command. */
+static void telnet_handle_command(char *databuf, int datalen)
+{
+	/* just print received commands:
+	 * we set the client, we don't adapt to client commands */
+	if (databuf[0] == telnet_option_value("IAC"))
+	{
+		LOG("received %s %s",
+			telnet_option_name(databuf[1]),
+			telnet_option_name(databuf[2]));
+	}
+}
+
+void telnet_message_set_character_mode(char *databuf)
+{
+	/* send a predefined set of commands proven to work */
+
+	databuf[0] = telnet_option_value("IAC");
+	databuf[1] = telnet_option_value("WILL");
+	databuf[2] = telnet_option_value("ECHO");
+
+	databuf[3] = telnet_option_value("IAC");
+	databuf[4] = telnet_option_value("WILL");
+	databuf[5] = telnet_option_value("SGA");
+
+	/* this one really depends on telnet client */
+	databuf[6] = telnet_option_value("IAC");
+	databuf[7] = telnet_option_value("WONT");
+	databuf[8] = telnet_option_value("LINEMODE");
+		
+	//TODO Do we verify client response? What do we do if the response is not how we expected?
+}
+
+void telnet_filter_client_read(char *databuf, int *datalen)
+{
+	int i;
+	char newdata[BUFFER_LEN];
+	int newlen = 0;
+	
+	/* process data using a new buffer */
+	for (i = 0; i < *datalen; i++)
+	{
+		/* handle and discard telnet commands */
+		if (databuf[i] == telnet_option_value("IAC"))
+		{
+			telnet_handle_command((databuf+i), 3);
+			i += 2;
+		}
+		/* let other data pass through */
+		else
+		{
+			newdata[newlen++] = databuf[i];
+		}
+	}
+	/* overwrite the data with the new buffer */
+	for (i = 0; i < newlen; i++)
+	{
+		databuf[i] = newdata[i];
+	}
+	/* update data length */
+	*datalen = newlen;
+}
+
+void telnet_filter_client_write(char *databuf, int *datalen)
+{
+	int i;
+	char newdata[BUFFER_LEN]; // TODO: maybe use realloc, this is risky
+	int newlen = 0;
+	
+	/* process data using a new buffer */
+	for (i = 0; i < *datalen; i++)
+	{
+		/* pressed ENTER */
+		if (databuf[i] == 13)
+		{
+			LOG("handling ENTER");
+			newdata[newlen++] = '\r';
+			newdata[newlen++] = '\n';
+		}
+		/* pressed BACKSPACE */
+		if (databuf[i] == 127)
+		{
+			LOG("handling BACKSPACE");
+			newdata[newlen++] = 8;
+			newdata[newlen++] = ' ';
+			newdata[newlen++] = 8;
+		}
+		else {
+			newdata[newlen++] = databuf[i];
+		}
+	}
+	/* overwrite the data with the new buffer */
+	for (i = 0; i < newlen; i++)
+	{
+		databuf[i] = newdata[i];
+	}
+	/* update data length */
+	*datalen = newlen;
+}