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    Contents of /trunk/mkinitrd-magellan/busybox/networking/telnetd.ctrlSQ.patch

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    Revision 984 - (show annotations) (download)
    Sun May 30 11:32:42 2010 UTC (13 years, 11 months ago) by niro
    File size: 6625 byte(s) 
    -updated to busybox-1.16.1 and enabled blkid/uuid support in default config
    1 From: "Doug Graham" <dgraham@nortel.com>
    2 Date: 2009-01-22 07:20
    3
    4 Hello,
    5
    6 Busybox's telnetd does not disable local (client-side) flow control
    7 properly. It does not put the pty into packet mode and then notify the
    8 client whenever flow control is disabled by an application running under
    9 its control. The result is that ^S/^Q are not passed through to the
    10 application, which is painful when the application is an emacs variant.
    11
    12 I suppose that support for this might be considered bloat, but the
    13 included patch only adds about 200 bytes of text to x86 busybox and 300
    14 bytes to mipsel busybox. Please consider applying.
    15
    16 =============================
    17
    18 NB: the patch doesn't work as-is because we now have iac_safe_write()
    19 which quotes IACs on output.
    20
    21 =============================
    22 Docs:
    23
    24 The following ioctl(2) calls apply only to pseudo terminals:
    25
    26 TIOCSTOP Stops output to a terminal (e.g. like typing ^S). Takes no parameter.
    27
    28 TIOCSTART Restarts output (stopped by TIOCSTOP or by typing ^S). Takes no parameter.
    29
    30 TIOCPKT Enable/disable packet mode. When applied to the master side of a pseudo terminal, each
    31 subsequent read(2) from the terminal will return data written on the slave part of the pseudo terminal preceded by a
    32 zero byte (symbolically defined as TIOCPKT_DATA), or a single byte reflecting control status information.
    33 In the latter case, the byte is an inclusive-or of zero or more of the bits:
    34
    35 TIOCPKT_FLUSHREAD whenever the read queue for the terminal is flushed.
    36 TIOCPKT_FLUSHWRITE whenever the write queue for the terminal is flushed.
    37 TIOCPKT_STOP whenever output to the terminal is stopped a la ^S.
    38 TIOCPKT_START whenever output to the terminal is restarted.
    39 TIOCPKT_DOSTOP whenever t_stopc is ^S and t_startc is ^Q.
    40 TIOCPKT_NOSTOP whenever the start and stop characters are not ^S/^Q.
    41
    42 While this mode is in use, the presence of control status information to be read from the master side may be detected
    43 by a select(2) for exceptional conditions.
    44
    45 This mode is used by rlogin(1) and rlogind(8) to implement a remote-echoed, locally ^S/^Q flow-controlled remote login
    46 with proper back-flushing of output; it can be used by other similar programs.
    47
    48 TIOCUCNTL Enable/disable a mode that allows a small number of simple user ioctl(2) commands to be passed through
    49 the pseudo-terminal, using a protocol similar to that of TIOCPKT. The TIOCUCNTL and TIOCPKT modes are mutually
    50 exclusive. This mode is enabled from the master side of a pseudo terminal. Each subsequent read(2) from the master side
    51 will return data written on the slave part of the pseudo terminal preceded by a zero byte, or a single byte reflecting a
    52 user control operation on the slave side. A user control command consists of a special ioctl(2) operation with no data;
    53 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
    54 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
    55 for the existence of this facility. As with TIOCPKT mode, command operations may be detected with a select(2) for
    56 exceptional conditions.
    57
    58 --- busybox-1.13.2/networking/telnetd.c 2009/01/21 20:02:39 1.1
    59 +++ busybox-1.13.2/networking/telnetd.c 2009/01/22 00:35:28
    60 @@ -38,6 +38,9 @@
    61 int sockfd_read, sockfd_write, ptyfd;
    62 int shell_pid;
    63
    64 +#ifdef TIOCPKT
    65 + int flowstate;
    66 +#endif
    67 /* two circular buffers */
    68 /*char *buf1, *buf2;*/
    69 /*#define TS_BUF1 ts->buf1*/
    70 @@ -170,6 +173,9 @@
    71 int fd, pid;
    72 char tty_name[GETPTY_BUFSIZE];
    73 struct tsession *ts = xzalloc(sizeof(struct tsession) + BUFSIZE * 2);
    74 +#ifdef TIOCPKT
    75 + int on = 1;
    76 +#endif
    77
    78 /*ts->buf1 = (char *)(ts + 1);*/
    79 /*ts->buf2 = ts->buf1 + BUFSIZE;*/
    80 @@ -180,6 +186,10 @@
    81 maxfd = fd;
    82 ts->ptyfd = fd;
    83 ndelay_on(fd);
    84 +#ifdef TIOCPKT
    85 + ioctl(fd, TIOCPKT, &on);
    86 + ts->flowstate = TIOCPKT_DOSTOP;
    87 +#endif
    88 #if ENABLE_FEATURE_TELNETD_STANDALONE
    89 ts->sockfd_read = sock;
    90 /* SO_KEEPALIVE by popular demand */
    91 @@ -385,6 +395,16 @@
    92 portnbr = 23,
    93 };
    94 #endif
    95 +#ifdef TIOCPKT
    96 + int control;
    97 + static const char lflow_on[] =
    98 + {IAC, SB, TELOPT_LFLOW, LFLOW_ON, IAC, SE};
    99 + static const char lflow_off[] =
    100 + {IAC, SB, TELOPT_LFLOW, LFLOW_OFF, IAC, SE};
    101 +# define RESERVED sizeof(lflow_on)
    102 +#else
    103 +# define RESERVED 0
    104 +#endif
    105 /* Even if !STANDALONE, we accept (and ignore) -i, thus people
    106 * don't need to guess whether it's ok to pass -i to us */
    107 opt = getopt32(argv, "f:l:Ki" IF_FEATURE_TELNETD_STANDALONE("p:b:F"),
    108 @@ -475,7 +495,7 @@
    109 FD_SET(ts->sockfd_read, &rdfdset);
    110 if (ts->size2 > 0) /* can write to socket */
    111 FD_SET(ts->sockfd_write, &wrfdset);
    112 - if (ts->size2 < BUFSIZE) /* can read from pty */
    113 + if (ts->size2 < (BUFSIZE - RESERVED)) /* can read from pty */
    114 FD_SET(ts->ptyfd, &rdfdset);
    115 }
    116 ts = next;
    117 @@ -593,6 +613,52 @@
    118 goto skip4;
    119 goto kill_session;
    120 }
    121 +#ifdef TIOCPKT
    122 + control = TS_BUF2[ts->rdidx2];
    123 + if (--count > 0 && control == TIOCPKT_DATA) {
    124 + /*
    125 + * If we are in packet mode, and we have
    126 + * just read a chunk of actual data from
    127 + * the pty, then there is the TIOCPKT_DATA
    128 + * byte (zero) that we have got to remove
    129 + * somehow. If there were no chars in
    130 + * TS_BUF2 before we did this read, then
    131 + * we can optimize by just advancing wridx2.
    132 + * Otherwise we have to copy the new data down
    133 + * to close the gap (Could use readv() instead).
    134 + */
    135 + if (ts->size2 == 0)
    136 + ts->wridx2++;
    137 + else {
    138 + memmove(TS_BUF2 + ts->rdidx2,
    139 + TS_BUF2 + ts->rdidx2 + 1, count);
    140 + }
    141 + }
    142 +
    143 + /*
    144 + * If the flow control state changed, notify
    145 + * the client. If "control" is not TIOCPKT_DATA,
    146 + * then there are no data bytes to worry about.
    147 + */
    148 + if ((control & (TIOCPKT_DOSTOP|TIOCPKT_NOSTOP)) != 0
    149 + && ts->flowstate != (control & TIOCPKT_DOSTOP)) {
    150 + const char *p = ts->flowstate ? lflow_off : lflow_on;
    151 +
    152 + /*
    153 + * We know we have enough free slots available
    154 + * (see RESERVED) but they are not necessarily
    155 + * contiguous; we may have to wrap.
    156 + */
    157 + for (count = sizeof(lflow_on); count > 0; count--) {
    158 + TS_BUF2[ts->rdidx2++] = *p++;
    159 + if (ts->rdidx2 >= BUFSIZE)
    160 + ts->rdidx2 = 0;
    161 + ts->size2++;
    162 + }
    163 +
    164 + ts->flowstate = control & TIOCPKT_DOSTOP;
    165 + }
    166 +#endif /* TIOCPKT */
    167 ts->size2 += count;
    168 ts->rdidx2 += count;
    169 if (ts->rdidx2 >= BUFSIZE) /* actually == BUFSIZE */
    170
    171 --Doug
    172 _______________________________________________
    173 busybox mailing list
    174 busybox@busybox.net
    175 http://lists.busybox.net/mailman/listinfo/busybox