force client into character mode

telnet.c

@@ -0,0 +1,145 @@
+#include "moxerver.h"
+
+
+/* structure for holding telnet option name and value */
+struct telnet_option_t {
+	const char *name;
+	char value;
+};
+
+/* supported telnet option values */
+struct telnet_option_t telnet_options[] = {
+	{"WILL", 251},
+	{"WONT", 252},
+	{"DO", 253},
+	{"DONT", 254},
+	{"IAC", 255},
+	{"ECHO", 1},
+	{"SGA", 3},
+	{"LINEMODE", 34},
+	{"SLE", 45}
+};
+#define TELNET_OPTIONS_COUNT 9 /* keep this up with the number of supported options */
+
+/* Returns telnet option name based on the value. */
+static const char* telnet_option_name(int value) {
+	int i;
+	for (i = 0; i < TELNET_OPTIONS_COUNT; i ++)
+		if (telnet_options[i].value == value)
+			return telnet_options[i].name;
+	return '\0';
+}
+
+/* Returns telnet option value based on the name. */
+static char telnet_option_value(const char* name) {
+	int i;
+	for (i = 0; i < TELNET_OPTIONS_COUNT; i ++)
+		if (!strcmp(telnet_options[i].name, name))
+			return telnet_options[i].value;
+	return 0;
+}
+
+/* Sends telnet option command. */
+int telnet_send_command(struct client_t *client, const char* option, const char* command) {
+	
+	char data[3];
+	
+	/* pack command */
+	data[0] = telnet_option_value("IAC");
+	data[1] = telnet_option_value(option);
+	data[2] = telnet_option_value(command);
+	
+	/* send command */
+	if (client_write(client, data, 3) <= 0) {
+		fprintf(stderr, "[%s:%d] failed sending %s %s\n", __func__, __LINE__, option, command);
+		return -1;
+	}
+	
+	fprintf(stderr, "[%s]: sent %s %s\n", __func__, option, command);
+	return 0;
+}
+
+/* Handles received telnet option command. */
+int telnet_handle_command(char *databuf, int datalen) {
+	
+	if (databuf[0] == telnet_option_value("IAC")) {
+		fprintf(stderr, "[%s]: received %s %s\n", __func__,
+				telnet_option_name(databuf[1]), telnet_option_name(databuf[2]));
+	}
+	
+	return 0;
+}
+
+/* Tells client to go into "character" mode. */
+int telnet_set_character_mode(struct client_t *client) {
+	
+	int err = 0;
+	
+	/* send predefined commands and add up their return vaules */
+	err += telnet_send_command(client, "WILL", "ECHO");
+	err += telnet_send_command(client, "WILL", "SGA");
+	err += telnet_send_command(client, "WONT", "LINEMODE"); /* this depends on telnet client */
+		
+	//TODO Do we verify client response? What do we do if the response is not how we expected?
+	
+	return err;
+}
+
+/* Handles special characters in data buffer after receiving them from client. */
+int telnet_handle_client_read(char *databuf, int *datalen) {	
+	
+	int i;
+	char newdata[DATA_BUFLEN];
+	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 data with new buffer */
+	for (i = 0; i < newlen; i++) databuf[i] = newdata[i];
+	*datalen = newlen;
+	
+	return 0;
+}
+
+/* Handles special characters in data buffer before sending to client. */
+int telnet_handle_client_write(char *databuf, int *datalen) {
+	
+	int i;
+	char newdata[DATA_BUFLEN];
+	int newlen = 0;
+	
+	/* process data using a new buffer */
+	for (i = 0; i < *datalen; i++) {
+		/* pressed ENTER */
+		if (databuf[i] == 13) {
+			fprintf(stderr, "[%s]: handling ENTER\n", __func__);
+			newdata[newlen++] = '\r';
+			newdata[newlen++] = '\n';
+		}
+		/* pressed BACKSPACE */
+		if (databuf[i] == 127) {
+			fprintf(stderr, "[%s]: handling BACKSPACE\n", __func__);
+			newdata[newlen++] = 8;
+			newdata[newlen++] = ' ';
+			newdata[newlen++] = 8;
+		}
+		else {
+			newdata[newlen++] = databuf[i];
+		}
+	}
+	/* overwrite data with new buffer */
+	for (i = 0; i < newlen; i++) databuf[i] = newdata[i];
+	*datalen = newlen;
+	
+	return 0;
+}