Increase usefulness of telnet(1) as a protocol tester. By prepending

"+" to the port number, disable option negotiation and allow
transferring of data with high bit set.

OKed by:	markm (maintainer)
PR:		52032
Submitted by:	Valentin Nechayev <netch maybe-at netch stop kiev stop ua>
MFC After:	2 weeks

3 files changed, 23 insertions, 4 deletions

diff --git a/contrib/telnet/telnet/commands.c b/contrib/telnet/telnet/commands.c
index a8a3a44..a64d763 100644
--- a/contrib/telnet/telnet/commands.c
+++ b/contrib/telnet/telnet/commands.c
@@ -2299,6 +2299,9 @@ tn(int argc, char *argv[])
     } else if (*portp == '-') {
       portp++;
       telnetport = 1;
+    } else if (*portp == '+') {
+      portp++;
+      telnetport = -1;
     } else
       telnetport = 0;
 
diff --git a/contrib/telnet/telnet/telnet.1 b/contrib/telnet/telnet/telnet.1
index 06a9274..2e0181c 100644
--- a/contrib/telnet/telnet/telnet.1
+++ b/contrib/telnet/telnet/telnet.1
@@ -591,9 +591,10 @@ Prints out help information for the
 command.
 .El
 .It Xo
-.Ic open Ar host
+.Ic open
 .Op Fl l Ar user
-.Op Oo Fl Oc Ns Ar port
+.Op Ar host
+.Op Oo Fl /+ Oc Ns Ar port
 .Xc
 Open a connection to the named host.
 If no port number
@@ -620,6 +621,13 @@ omits any automatic initiation of
 options.
 When the port number is preceded by a minus sign,
 the initial option negotiation is done.
+When, however, the port number
+is preceded by a plus sign,
+any option negotiation and understanding is prohibited,
+making telnet dumb client for POP3/SMTP/NNTP/HTTP-like
+protocols with any data including
+.Tn TELNET
+IAC character (0xff).
 After establishing a connection, the file
 .Pa \&.telnetrc
 in the
diff --git a/contrib/telnet/telnet/telnet.c b/contrib/telnet/telnet/telnet.c
index 82ee464..692fb49 100644
--- a/contrib/telnet/telnet/telnet.c
+++ b/contrib/telnet/telnet/telnet.c
@@ -217,6 +217,8 @@ send_do(int c, int init)
 	set_my_want_state_do(c);
 	do_dont_resp[c]++;
     }
+    if (telnetport < 0)
+	return;
     NET2ADD(IAC, DO);
     NETADD(c);
     printoption("SENT", DO, c);
@@ -232,6 +234,8 @@ send_dont(int c, int init)
 	set_my_want_state_dont(c);
 	do_dont_resp[c]++;
     }
+    if (telnetport < 0)
+	return;
     NET2ADD(IAC, DONT);
     NETADD(c);
     printoption("SENT", DONT, c);
@@ -247,6 +251,8 @@ send_will(int c, int init)
 	set_my_want_state_will(c);
 	will_wont_resp[c]++;
     }
+    if (telnetport < 0)
+	return;
     NET2ADD(IAC, WILL);
     NETADD(c);
     printoption("SENT", WILL, c);
@@ -262,6 +268,8 @@ send_wont(int c, int init)
 	set_my_want_state_wont(c);
 	will_wont_resp[c]++;
     }
+    if (telnetport < 0)
+	return;
     NET2ADD(IAC, WONT);
     NETADD(c);
     printoption("SENT", WONT, c);
@@ -1651,7 +1659,7 @@ telrcv(void)
 	    /* FALLTHROUGH */
 
 	case TS_DATA:
-	    if (c == IAC) {
+	    if (c == IAC && telnetport >= 0) {
 		telrcv_state = TS_IAC;
 		break;
 	    }
@@ -2069,7 +2077,7 @@ telnet(char *user __unusedhere)
     }
 #endif
 #endif
-    if (telnetport) {
+    if (telnetport > 0) {
 #ifdef	AUTHENTICATION
 	if (autologin)
 		send_will(TELOPT_AUTHENTICATION, 1);