Путь: Toys/Pending, команды версии: Ver.4 Ver.9 telnet Комментарии в файле telnet.c :
Исходный текст в файле telnet.c #define FOR_telnet
#include "toys.h"
#include <arpa/telnet.h>
GLOBALS(
int sock;
char buf[2048]; // Half sizeof(toybuf) allows a buffer full of IACs.
struct termios old_term;
struct termios raw_term;
uint8_t mode;
int echo, sga;
int state, request;
)
#define NORMAL 0
#define SAW_IAC 1
#define SAW_WWDD 2
#define SAW_SB 3
#define SAW_SB_TTYPE 4
#define WANT_IAC 5
#define WANT_SE 6
#define SAW_CR 10
#define CM_TRY 0
#define CM_ON 1
#define CM_OFF 2
static void raw(int raw)
{
tcsetattr(0, TCSADRAIN, raw ? &TT.raw_term : &TT.old_term);
}
static void slc(int line)
{
TT.mode = line ? CM_OFF : CM_ON;
xprintf("Entering %s mode\r\nEscape character is '^%c'.\r\n",
line ? "line" : "character", line ? 'C' : ']');
raw(!line);
}
static void set_mode(void)
{
if (TT.echo) {
if (TT.mode == CM_TRY) slc(0);
} else if (TT.mode != CM_OFF) slc(1);
}
static void handle_esc(void)
{
char input;
if (toys.signal) raw(1);
// This matches busybox telnet, not BSD telnet.
xputsn("\r\n"
"Console escape. Commands are:\r\n"
"\r\n"
" l go to line mode\r\n"
" c go to character mode\r\n"
" z suspend telnet\r\n"
" e exit telnet\r\n"
"\r\n"
"telnet> ");
// In particular, the boxes only read a single character, not a line.
if (read(0, &input, 1) <= 0 || input == 4 || input == 'e') {
xprintf("Connection closed.\r\n");
xexit();
}
if (input == 'l') {
if (!toys.signal) {
TT.mode = CM_TRY;
TT.echo = TT.sga = 0;
set_mode();
dprintf(TT.sock,"%c%c%c%c%c%c",IAC,DONT,TELOPT_ECHO,IAC,DONT,TELOPT_SGA);
goto ret;
}
} else if (input == 'c') {
if (toys.signal) {
TT.mode = CM_TRY;
TT.echo = TT.sga = 1;
set_mode();
dprintf(TT.sock,"%c%c%c%c%c%c",IAC,DO,TELOPT_ECHO,IAC,DO,TELOPT_SGA);
goto ret;
}
} else if (input == 'z') {
raw(0);
kill(0, SIGTSTP);
raw(1);
}
xprintf("telnet %s %s\r\n", toys.optargs[0], toys.optargs[1] ?: "23");
if (toys.signal) raw(0);
ret:
toys.signal = 0;
}
// Handle WILL WONT DO DONT requests from the server.
static void handle_wwdd(char opt)
{
if (opt == TELOPT_ECHO) {
if (TT.request == DO) dprintf(TT.sock, "%c%c%c", IAC, WONT, TELOPT_ECHO);
if (TT.request == DONT) return;
if (TT.echo) {
if (TT.request == WILL) return;
} else if (TT.request == WONT) return;
if (TT.mode != CM_OFF) TT.echo ^= 1;
dprintf(TT.sock, "%c%c%c", IAC, TT.echo ? DO : DONT, TELOPT_ECHO);
set_mode();
} else if (opt == TELOPT_SGA) { // Suppress Go Ahead
if (TT.sga) {
if (TT.request == WILL) return;
} else if (TT.request == WONT) return;
TT.sga ^= 1;
dprintf(TT.sock, "%c%c%c", IAC, TT.sga ? DO : DONT, TELOPT_SGA);
} else if (opt == TELOPT_TTYPE) { // Terminal TYPE
dprintf(TT.sock, "%c%c%c", IAC, WILL, TELOPT_TTYPE);
} else if (opt == TELOPT_NAWS) { // Negotiate About Window Size
unsigned cols = 80, rows = 24;
terminal_size(&cols, &rows);
dprintf(TT.sock, "%c%c%c%c%c%c%c%c%c%c%c%c", IAC, WILL, TELOPT_NAWS,
IAC, SB, TELOPT_NAWS, cols>>8, cols, rows>>8, rows,
IAC, SE);
} else {
// Say "no" to anything we don't understand.
dprintf(TT.sock, "%c%c%c", IAC, (TT.request == WILL) ? DONT : WONT, opt);
}
}
static void handle_server_output(int n)
{
char *p = TT.buf, *end = TT.buf + n, ch;
int i = 0;
// Possibilities:
//
// 1. Regular character
// 2. IAC [WILL|WONT|DO|DONT] option
// 3. IAC SB option arg... IAC SE
//
// The only subnegotiation we support is IAC SB TTYPE SEND IAC SE, so we just
// hard-code that into our state machine rather than having a more general
// "collect the subnegotation into a buffer and handle it after we've seen
// the IAC SE at the end". It's 2021, so we're unlikely to need more.
while (p < end) {
ch = *p++;
if (TT.state == SAW_IAC) {
if (ch >= WILL && ch <= DONT) {
TT.state = SAW_WWDD;
TT.request = ch;
} else if (ch == SB) {
TT.state = SAW_SB;
} else {
TT.state = NORMAL;
}
} else if (TT.state == SAW_WWDD) {
handle_wwdd(ch);
TT.state = NORMAL;
} else if (TT.state == SAW_SB) {
if (ch == TELOPT_TTYPE) TT.state = SAW_SB_TTYPE;
else TT.state = WANT_IAC;
} else if (TT.state == SAW_SB_TTYPE) {
if (ch == TELQUAL_SEND) {
dprintf(TT.sock, "%c%c%c%c%s%c%c", IAC, SB, TELOPT_TTYPE, TELQUAL_IS,
getenv("TERM") ?: "NVT", IAC, SE);
}
TT.state = WANT_IAC;
} else if (TT.state == WANT_IAC) {
if (ch == IAC) TT.state = WANT_SE;
} else if (TT.state == WANT_SE) {
if (ch == SE) TT.state = NORMAL;
} else if (ch == IAC) {
TT.state = SAW_IAC;
} else {
if (TT.state == SAW_CR && ch == '\0') {
// CR NUL -> CR
} else toybuf[i++] = ch;
if (ch == '\r') TT.state = SAW_CR;
TT.state = NORMAL;
}
}
if (i) xwrite(0, toybuf, i);
}
static void handle_user_input(int n)
{
char *p = TT.buf, ch;
int i = 0;
while (n--) {
ch = *p++;
if (ch == 0x1d) {
handle_esc();
return;
}
toybuf[i++] = ch;
if (ch == IAC) toybuf[i++] = IAC; // IAC -> IAC IAC
else if (ch == '\r') toybuf[i++] = '\n'; // CR -> CR LF
else if (ch == '\n') { // LF -> CR LF
toybuf[i-1] = '\r';
toybuf[i++] = '\n';
}
}
if (i) xwrite(TT.sock, toybuf, i);
}
static void reset_terminal(void)
{
raw(0);
}
void telnet_main(void)
{
struct pollfd pfds[2];
int n = 1;
tcgetattr(0, &TT.old_term);
TT.raw_term = TT.old_term;
cfmakeraw(&TT.raw_term);
TT.sock = xconnectany(xgetaddrinfo(*toys.optargs, toys.optargs[1] ?: "23", 0,
SOCK_STREAM, IPPROTO_TCP, 0));
xsetsockopt(TT.sock, SOL_SOCKET, SO_KEEPALIVE, &n, sizeof(n));
xprintf("Connected to %s.\r\n", *toys.optargs);
sigatexit(reset_terminal);
signal(SIGINT, generic_signal);
pfds[0].fd = 0;
pfds[0].events = POLLIN;
pfds[1].fd = TT.sock;
pfds[1].events = POLLIN;
for (;;) {
if (poll(pfds, 2, -1) < 0) {
if (toys.signal) handle_esc();
else perror_exit("poll");
}
if (pfds[0].revents) {
if ((n = read(0, TT.buf, sizeof(TT.buf))) <= 0) xexit();
handle_user_input(n);
}
if (pfds[1].revents) {
if ((n = read(TT.sock, TT.buf, sizeof(TT.buf))) <= 0)
error_exit("Connection closed by foreign host\r");
handle_server_output(n);
}
}
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