From RDB: a patch to allow special keys (^C, ^Z, Delete, Return) to

send Telnet special sequences (Interrupt Process, Suspend, Erase
Char, End Of Line) instead of their ASCII equivalents. In particular
Return -> Telnet End Of Line is _always_ enabled irrespective of the
configuration, while the others are optional. Also in this patch, an
entertainingly ghastly use of `switch' to allow literal ^M^J to do
the same thing as magic-^M (the Return key) when in Raw protocol.

[originally from svn r1109]

ldisc.c

@@ -59,9 +59,11 @@ static void bsb(int n)
 }
 
 #define CTRL(x) (x^'@')
+#define KCTRL(x) ((x^'@') | 0x100)
 
 void ldisc_send(char *buf, int len)
 {
+    int keyflag = 0;
     /*
      * Called with len=0 when the options change. We must inform
      * the front end in case it needs to know.
@@ -70,13 +72,20 @@ void ldisc_send(char *buf, int len)
 	void ldisc_update(int echo, int edit);
 	ldisc_update(ECHOING, EDITING);
     }
+    /*
+     * Less than zero means null terminated special string.
+     */
+    if (len < 0) {
+	len = strlen(buf);
+	keyflag = KCTRL('@');
+    }
     /*
      * Either perform local editing, or just send characters.
      */
     if (EDITING) {
 	while (len--) {
-	    char c;
+	    int c;
-	    c = *buf++;
+	    c = *buf++ + keyflag;
 	    switch (term_quotenext ? ' ' : c) {
 		/*
 		 * ^h/^?: delete one char and output one BSB
@@ -92,8 +101,8 @@ void ldisc_send(char *buf, int len)
 		 * else send line and reset to BOL
 		 * ^m: send line-plus-\r\n and reset to BOL
 		 */
-	      case CTRL('H'):
+	      case KCTRL('H'):
-	      case CTRL('?'):	       /* backspace/delete */
+	      case KCTRL('?'):	       /* backspace/delete */
 		if (term_buflen > 0) {
 		    if (ECHOING)
 			bsb(plen(term_buf[term_buflen - 1]));
@@ -147,17 +156,51 @@ void ldisc_send(char *buf, int len)
 		    term_buflen = 0;
 		}
 		break;
-	      case CTRL('M'):	       /* send with newline */
+		/*
+		 * This particularly hideous bit of code from RDB
+		 * allows ordinary ^M^J to do the same thing as
+		 * magic-^M when in Raw protocol. The line `case
+		 * KCTRL('M'):' is _inside_ the if block. Thus:
+		 * 
+		 *  - receiving regular ^M goes straight to the
+		 *    default clause and inserts as a literal ^M.
+		 *  - receiving regular ^J _not_ directly after a
+		 *    literal ^M (or not in Raw protocol) fails the
+		 *    if condition, leaps to the bottom of the if,
+		 *    and falls through into the default clause
+		 *    again.
+		 *  - receiving regular ^J just after a literal ^M
+		 *    in Raw protocol passes the if condition,
+		 *    deletes the literal ^M, and falls through
+		 *    into the magic-^M code
+		 *  - receiving a magic-^M empties the line buffer,
+		 *    signals end-of-line in one of the various
+		 *    entertaining ways, and _doesn't_ fall out of
+		 *    the bottom of the if and through to the
+		 *    default clause because of the break.
+		 */
+	      case CTRL('J'):
+		if (cfg.protocol == PROT_RAW &&
+		    term_buflen > 0 && term_buf[term_buflen - 1] == '\r') {
+		    if (ECHOING)
+			bsb(plen(term_buf[term_buflen - 1]));
+		    term_buflen--;
+		    /* FALLTHROUGH */
+	      case KCTRL('M'):	       /* send with newline */
 		    if (term_buflen > 0)
 			back->send(term_buf, term_buflen);
 		    if (cfg.protocol == PROT_RAW)
 			back->send("\r\n", 2);
+		    else if (cfg.protocol == PROT_TELNET)
+			back->special(TS_EOL);
 		    else
 			back->send("\r", 1);
 		    if (ECHOING)
 			c_write("\r\n", 2);
 		    term_buflen = 0;
 		    break;
+		}
+		/* FALLTHROUGH */
 	      default:		       /* get to this label from ^V handler */
 		if (term_buflen >= term_bufsiz) {
 		    term_bufsiz = term_buflen + 256;
@@ -165,7 +208,7 @@ void ldisc_send(char *buf, int len)
 		}
 		term_buf[term_buflen++] = c;
 		if (ECHOING)
-		    pwrite(c);
+		    pwrite((unsigned char) c);
 		term_quotenext = FALSE;
 		break;
 	    }
@@ -181,6 +224,33 @@ void ldisc_send(char *buf, int len)
 	if (len > 0) {
 	    if (ECHOING)
 		c_write(buf, len);
+	    if (keyflag && cfg.protocol == PROT_TELNET && len == 1) {
+		switch (buf[0]) {
+		  case CTRL('M'):
+		    back->special(TS_EOL);
+		    break;
+		  case CTRL('?'):
+		  case CTRL('H'):
+		    if (cfg.telnet_keyboard) {
+			back->special(TS_EC);
+			break;
+		    }
+		  case CTRL('C'):
+		    if (cfg.telnet_keyboard) {
+			back->special(TS_IP);
+			break;
+		    }
+		  case CTRL('Z'):
+		    if (cfg.telnet_keyboard) {
+			back->special(TS_SUSP);
+			break;
+		    }
+
+		  default:
+		    back->send(buf, len);
+		    break;
+		}
+	    } else
 		back->send(buf, len);
 	}
     }

putty.h

@@ -107,7 +107,8 @@ GLOBAL HWND logbox;
 
 typedef enum {
     TS_AYT, TS_BRK, TS_SYNCH, TS_EC, TS_EL, TS_GA, TS_NOP, TS_ABORT,
-    TS_AO, TS_IP, TS_SUSP, TS_EOR, TS_EOF, TS_LECHO, TS_RECHO, TS_PING
+    TS_AO, TS_IP, TS_SUSP, TS_EOR, TS_EOF, TS_LECHO, TS_RECHO, TS_PING,
+    TS_EOL
 } Telnet_Special;
 
 typedef enum {
@@ -206,6 +207,7 @@ typedef struct {
     int app_cursor;
     int app_keypad;
     int nethack_keypad;
+    int telnet_keyboard;
     int alt_f4;			       /* is it special? */
     int alt_space;		       /* is it special? */
     int alt_only;		       /* is it special? */

settings.c

@@ -100,6 +100,7 @@ void save_settings(char *section, int do_host, Config * cfg)
     write_setting_i(sesskey, "AltOnly", cfg->alt_only);
     write_setting_i(sesskey, "ComposeKey", cfg->compose_key);
     write_setting_i(sesskey, "CtrlAltKeys", cfg->ctrlaltkeys);
+    write_setting_i(sesskey, "TelnetKey", cfg->telnet_keyboard);
     write_setting_i(sesskey, "LocalEcho", cfg->localecho);
     write_setting_i(sesskey, "LocalEdit", cfg->localedit);
     write_setting_s(sesskey, "Answerback", cfg->answerback);
@@ -263,6 +264,7 @@ void load_settings(char *section, int do_host, Config * cfg)
     gppi(sesskey, "AltOnly", 0, &cfg->alt_only);
     gppi(sesskey, "ComposeKey", 0, &cfg->compose_key);
     gppi(sesskey, "CtrlAltKeys", 1, &cfg->ctrlaltkeys);
+    gppi(sesskey, "TelnetKey", 0, &cfg->telnet_keyboard);
     gppi(sesskey, "LocalEcho", LD_BACKEND, &cfg->localecho);
     gppi(sesskey, "LocalEdit", LD_BACKEND, &cfg->localedit);
     gpps(sesskey, "Answerback", "PuTTY", cfg->answerback,

telnet.c

@@ -653,7 +653,9 @@ static void telnet_send(char *buf, int len)
     char *p;
     static unsigned char iac[2] = { IAC, IAC };
     static unsigned char cr[2] = { CR, NUL };
+#if 0
     static unsigned char nl[2] = { CR, LF };
+#endif
 
     if (s == NULL)
 	return;
@@ -667,7 +669,7 @@ static void telnet_send(char *buf, int len)
 	sk_write(s, q, p - q);
 
 	while (p < buf + len && !iswritable((unsigned char) *p)) {
-	    sk_write(s, (unsigned char) *p == IAC ? iac : nl, 2);
+	    sk_write(s, (unsigned char) *p == IAC ? iac : cr, 2);
 	    p++;
 	}
     }
@@ -759,6 +761,9 @@ static void telnet_special(Telnet_Special code)
 	b[1] = xEOF;
 	sk_write(s, b, 2);
 	break;
+      case TS_EOL:
+	sk_write(s, "\r\n", 2);
+	break;
       case TS_SYNCH:
 	b[1] = DM;
 	sk_write(s, b, 1);

windlg.c

@@ -291,6 +291,7 @@ enum { IDCX_ABOUT =
     IDC_CURAPPLIC,
     IDC_COMPOSEKEY,
     IDC_CTRLALTKEYS,
+    IDC_TELNETKEY,
     keyboardpanelend,
 
     terminalpanelstart,
@@ -588,6 +589,7 @@ static void init_dlg_ctrls(HWND hwnd)
     CheckDlgButton(hwnd, IDC_ALTONLY, cfg.alt_only);
     CheckDlgButton(hwnd, IDC_COMPOSEKEY, cfg.compose_key);
     CheckDlgButton(hwnd, IDC_CTRLALTKEYS, cfg.ctrlaltkeys);
+    CheckDlgButton(hwnd, IDC_TELNETKEY, cfg.telnet_keyboard);
     CheckRadioButton(hwnd, IDC_ECHOBACKEND, IDC_ECHONO,
 		     cfg.localecho == LD_BACKEND ? IDC_ECHOBACKEND :
 		     cfg.localecho == LD_YES ? IDC_ECHOYES : IDC_ECHONO);
@@ -1098,6 +1100,11 @@ static void create_controls(HWND hwnd, int dlgtype, int panel)
 	    staticedit(&cp, "Auto-login &username", IDC_LOGSTATIC,
 		       IDC_LOGEDIT, 50);
 	    endbox(&cp);
+	} else {
+	    beginbox(&cp, "Adjust telnet session.", IDC_BOX_CONNECTION1);
+	    checkbox(&cp, "Keyboard sends telnet Backspace and Interrupt",
+		     IDC_TELNETKEY);
+	    endbox(&cp);
 	}
 	beginbox(&cp, "Sending of null packets to keep session active",
 		 IDC_BOX_CONNECTION2);
@@ -1107,7 +1114,7 @@ static void create_controls(HWND hwnd, int dlgtype, int panel)
     }
 
     if (panel == telnetpanelstart) {
-	/* The Telnet panel. Accelerators used: [acgo] svldr bft */
+	/* The Telnet panel. Accelerators used: [acgo] svldr bftk */
 	struct ctlpos cp;
 	ctlposinit(&cp, hwnd, 80, 3, 13);
 	if (dlgtype == 0) {
@@ -1128,6 +1135,8 @@ static void create_controls(HWND hwnd, int dlgtype, int panel)
 	    radioline(&cp, "&Telnet negotiation mode:", IDC_ACTSTATIC, 2,
 		      "Passive", IDC_TPASSIVE, "Active",
 		      IDC_TACTIVE, NULL);
+	    checkbox(&cp, "&Keyboard sends telnet Backspace and Interrupt",
+		     IDC_TELNETKEY);
 	    endbox(&cp);
 	}
     }
@@ -1698,6 +1707,12 @@ static int GenericMainDlgProc(HWND hwnd, UINT msg,
 			cfg.ctrlaltkeys =
 			IsDlgButtonChecked(hwnd, IDC_CTRLALTKEYS);
 		break;
+	      case IDC_TELNETKEY:
+		if (HIWORD(wParam) == BN_CLICKED ||
+		    HIWORD(wParam) == BN_DOUBLECLICKED)
+			cfg.telnet_keyboard =
+			IsDlgButtonChecked(hwnd, IDC_TELNETKEY);
+		break;
 	      case IDC_WRAPMODE:
 		if (HIWORD(wParam) == BN_CLICKED ||
 		    HIWORD(wParam) == BN_DOUBLECLICKED)

window.c

@@ -2554,7 +2554,8 @@ static int TranslateKey(UINT message, WPARAM wParam, LPARAM lParam,
 
 	if (wParam == VK_BACK && shift_state == 0) {	/* Backspace */
 	    *p++ = (cfg.bksp_is_delete ? 0x7F : 0x08);
-	    return p - output;
+	    *p++ = 0;
+	    return -2;
 	}
 	if (wParam == VK_TAB && shift_state == 1) {	/* Shift tab */
 	    *p++ = 0x1B;
@@ -2572,7 +2573,8 @@ static int TranslateKey(UINT message, WPARAM wParam, LPARAM lParam,
 	}
 	if (wParam == VK_CANCEL && shift_state == 2) {	/* Ctrl-Break */
 	    *p++ = 3;
-	    return p - output;
+	    *p++ = 0;
+	    return -2;
 	}
 	if (wParam == VK_PAUSE) {      /* Break/Pause */
 	    *p++ = 26;
@@ -2786,7 +2788,8 @@ static int TranslateKey(UINT message, WPARAM wParam, LPARAM lParam,
 	 */
 	if (wParam == VK_RETURN) {     /* Return */
 	    *p++ = 0x0D;
-	    return p - output;
+	    *p++ = 0;
+	    return -2;
 	}
     }