source:
MondoRescue/tags/3.2.2/mindi-busybox/networking/telnetd.ctrlSQ.patch@
3858
Last change on this file since 3858 was 2725, checked in by , 13 years ago | |
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File size: 6.5 KB |
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busybox-1.13.2/networking/telnetd.c
From: "Doug Graham" <dgraham@nortel.com> Date: 2009-01-22 07:20 Hello, Busybox's telnetd does not disable local (client-side) flow control properly. It does not put the pty into packet mode and then notify the client whenever flow control is disabled by an application running under its control. The result is that ^S/^Q are not passed through to the application, which is painful when the application is an emacs variant. I suppose that support for this might be considered bloat, but the included patch only adds about 200 bytes of text to x86 busybox and 300 bytes to mipsel busybox. Please consider applying. ============================= NB: the patch doesn't work as-is because we now have iac_safe_write() which quotes IACs on output. ============================= Docs: The following ioctl(2) calls apply only to pseudo terminals: TIOCSTOP Stops output to a terminal (e.g. like typing ^S). Takes no parameter. TIOCSTART Restarts output (stopped by TIOCSTOP or by typing ^S). Takes no parameter. TIOCPKT Enable/disable packet mode. When applied to the master side of a pseudo terminal, each subsequent read(2) from the terminal will return data written on the slave part of the pseudo terminal preceded by a zero byte (symbolically defined as TIOCPKT_DATA), or a single byte reflecting control status information. In the latter case, the byte is an inclusive-or of zero or more of the bits: TIOCPKT_FLUSHREAD whenever the read queue for the terminal is flushed. TIOCPKT_FLUSHWRITE whenever the write queue for the terminal is flushed. TIOCPKT_STOP whenever output to the terminal is stopped a la ^S. TIOCPKT_START whenever output to the terminal is restarted. TIOCPKT_DOSTOP whenever t_stopc is ^S and t_startc is ^Q. TIOCPKT_NOSTOP whenever the start and stop characters are not ^S/^Q. While this mode is in use, the presence of control status information to be read from the master side may be detected by a select(2) for exceptional conditions. This mode is used by rlogin(1) and rlogind(8) to implement a remote-echoed, locally ^S/^Q flow-controlled remote login with proper back-flushing of output; it can be used by other similar programs. TIOCUCNTL Enable/disable a mode that allows a small number of simple user ioctl(2) commands to be passed through the pseudo-terminal, using a protocol similar to that of TIOCPKT. The TIOCUCNTL and TIOCPKT modes are mutually exclusive. This mode is enabled from the master side of a pseudo terminal. Each subsequent read(2) from the master side will return data written on the slave part of the pseudo terminal preceded by a zero byte, or a single byte reflecting a user control operation on the slave side. A user control command consists of a special ioctl(2) operation with no data; the command is given as UIOCCMD (n), where n is a number in the range 1-255. The operation value n will be received as a single byte on the next read(2) from the master side. The ioctl(2) UIOCCMD (0) is a no-op that may be used to probe for the existence of this facility. As with TIOCPKT mode, command operations may be detected with a select(2) for exceptional conditions.
38 38 int sockfd_read, sockfd_write, ptyfd; 39 39 int shell_pid; 40 40 41 #ifdef TIOCPKT 42 int flowstate; 43 #endif 41 44 /* two circular buffers */ 42 45 /*char *buf1, *buf2;*/ 43 46 /*#define TS_BUF1 ts->buf1*/ … … 170 173 int fd, pid; 171 174 char tty_name[GETPTY_BUFSIZE]; 172 175 struct tsession *ts = xzalloc(sizeof(struct tsession) + BUFSIZE * 2); 176 #ifdef TIOCPKT 177 int on = 1; 178 #endif 173 179 174 180 /*ts->buf1 = (char *)(ts + 1);*/ 175 181 /*ts->buf2 = ts->buf1 + BUFSIZE;*/ … … 180 186 maxfd = fd; 181 187 ts->ptyfd = fd; 182 188 ndelay_on(fd); 189 #ifdef TIOCPKT 190 ioctl(fd, TIOCPKT, &on); 191 ts->flowstate = TIOCPKT_DOSTOP; 192 #endif 183 193 #if ENABLE_FEATURE_TELNETD_STANDALONE 184 194 ts->sockfd_read = sock; 185 195 /* SO_KEEPALIVE by popular demand */ … … 385 395 portnbr = 23, 386 396 }; 387 397 #endif 398 #ifdef TIOCPKT 399 int control; 400 static const char lflow_on[] = 401 {IAC, SB, TELOPT_LFLOW, LFLOW_ON, IAC, SE}; 402 static const char lflow_off[] = 403 {IAC, SB, TELOPT_LFLOW, LFLOW_OFF, IAC, SE}; 404 # define RESERVED sizeof(lflow_on) 405 #else 406 # define RESERVED 0 407 #endif 388 408 /* Even if !STANDALONE, we accept (and ignore) -i, thus people 389 409 * don't need to guess whether it's ok to pass -i to us */ 390 410 opt = getopt32(argv, "f:l:Ki" IF_FEATURE_TELNETD_STANDALONE("p:b:F"), … … 475 495 FD_SET(ts->sockfd_read, &rdfdset); 476 496 if (ts->size2 > 0) /* can write to socket */ 477 497 FD_SET(ts->sockfd_write, &wrfdset); 478 if (ts->size2 < BUFSIZE) /* can read from pty */498 if (ts->size2 < (BUFSIZE - RESERVED)) /* can read from pty */ 479 499 FD_SET(ts->ptyfd, &rdfdset); 480 500 } 481 501 ts = next; … … 593 613 goto skip4; 594 614 goto kill_session; 595 615 } 616 #ifdef TIOCPKT 617 control = TS_BUF2[ts->rdidx2]; 618 if (--count > 0 && control == TIOCPKT_DATA) { 619 /* 620 * If we are in packet mode, and we have 621 * just read a chunk of actual data from 622 * the pty, then there is the TIOCPKT_DATA 623 * byte (zero) that we have got to remove 624 * somehow. If there were no chars in 625 * TS_BUF2 before we did this read, then 626 * we can optimize by just advancing wridx2. 627 * Otherwise we have to copy the new data down 628 * to close the gap (Could use readv() instead). 629 */ 630 if (ts->size2 == 0) 631 ts->wridx2++; 632 else { 633 memmove(TS_BUF2 + ts->rdidx2, 634 TS_BUF2 + ts->rdidx2 + 1, count); 635 } 636 } 637 638 /* 639 * If the flow control state changed, notify 640 * the client. If "control" is not TIOCPKT_DATA, 641 * then there are no data bytes to worry about. 642 */ 643 if ((control & (TIOCPKT_DOSTOP|TIOCPKT_NOSTOP)) != 0 644 && ts->flowstate != (control & TIOCPKT_DOSTOP)) { 645 const char *p = ts->flowstate ? lflow_off : lflow_on; 646 647 /* 648 * We know we have enough free slots available 649 * (see RESERVED) but they are not necessarily 650 * contiguous; we may have to wrap. 651 */ 652 for (count = sizeof(lflow_on); count > 0; count--) { 653 TS_BUF2[ts->rdidx2++] = *p++; 654 if (ts->rdidx2 >= BUFSIZE) 655 ts->rdidx2 = 0; 656 ts->size2++; 657 } 658 659 ts->flowstate = control & TIOCPKT_DOSTOP; 660 } 661 #endif /* TIOCPKT */ 596 662 ts->size2 += count; 597 663 ts->rdidx2 += count; 598 664 if (ts->rdidx2 >= BUFSIZE) /* actually == BUFSIZE */
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