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telnetd: some simplifications and better error hadling.

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telnetd: don't SIGKILL child when closing the session.
kernel will seng SIGHUP for us.

static.iacs_to_send                                    -      15     +15
.rodata                                           123418  123429     +11
make_new_session                                     549     525     -24
send_iac                                              26       -     -26
free_session                                         144     118     -26
telnetd_main                                        1303    1261     -42
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 1/3 up/down: 26/-118)           Total: -92 bytes
   text    data     bss     dec     hex filename
 676341    2538   12104  690983   a8b27 busybox_old
 676234    2538   12104  690876   a8abc busybox_unstripped
This commit is contained in:
Denis Vlasenko 2007-10-15 15:19:36 +00:00
parent d898b8600c
commit 59d7c43dbe
1 changed files with 167 additions and 137 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

300
networking/telnetd.c
View File

@ -33,22 +33,18 @@
#include <sys/syslog.h> #include <sys/syslog.h>
#if ENABLE_LOGIN /* Structure that describes a session */
static const char *loginpath = "/bin/login";
#else
static const char *loginpath = DEFAULT_SHELL;
#endif
static const char *issuefile = "/etc/issue.net";
/* structure that describes a session */
struct tsession { struct tsession {
struct tsession *next; struct tsession *next;
int sockfd_read, sockfd_write, ptyfd; int sockfd_read, sockfd_write, ptyfd;
int shell_pid; /*int shell_pid;*/
/* two circular buffers */ /* two circular buffers */
char *buf1, *buf2; /*char *buf1, *buf2;*/
/*#define TS_BUF1 ts->buf1*/
/*#define TS_BUF2 TS_BUF2*/
#define TS_BUF1 ((char*)(ts + 1))
#define TS_BUF2 (((char*)(ts + 1)) + BUFSIZE)
int rdidx1, wridx1, size1; int rdidx1, wridx1, size1;
int rdidx2, wridx2, size2; int rdidx2, wridx2, size2;
}; };
@ -57,39 +53,31 @@ struct tsession {
* Make whole thing fit in 4k */ * Make whole thing fit in 4k */
enum { BUFSIZE = (4 * 1024 - sizeof(struct tsession)) / 2 }; enum { BUFSIZE = (4 * 1024 - sizeof(struct tsession)) / 2 };
/*
This is how the buffers are used. The arrows indicate the movement
of data.
+-------+ wridx1++ +------+ rdidx1++ +----------+
| | <-------------- | buf1 | <-------------- | |
| | size1-- +------+ size1++ | |
| pty | | socket |
| | rdidx2++ +------+ wridx2++ | |
| | --------------> | buf2 | --------------> | |
+-------+ size2++ +------+ size2-- +----------+
Each session has got two buffers.
*/
/* Globals */
static int maxfd; static int maxfd;
static struct tsession *sessions; static struct tsession *sessions;
#if ENABLE_LOGIN
static const char *loginpath = "/bin/login";
#else
static const char *loginpath = DEFAULT_SHELL;
#endif
static const char *issuefile = "/etc/issue.net";
/* /*
Remove all IAC's from the buffer pointed to by bf (received IACs are ignored Remove all IAC's from buf1 (received IACs are ignored and must be removed
and must be removed so as to not be interpreted by the terminal). Make an so as to not be interpreted by the terminal). Make an uninterrupted
uninterrupted string of characters fit for the terminal. Do this by packing string of characters fit for the terminal. Do this by packing
all characters meant for the terminal sequentially towards the end of bf. all characters meant for the terminal sequentially towards the end of buf.
Return a pointer to the beginning of the characters meant for the terminal. Return a pointer to the beginning of the characters meant for the terminal.
and make *num_totty the number of characters that should be sent to and make *num_totty the number of characters that should be sent to
the terminal. the terminal.
Note - If an IAC (3 byte quantity) starts before (bf + len) but extends Note - If an IAC (3 byte quantity) starts before (bf + len) but extends
past (bf + len) then that IAC will be left unprocessed and *processed will be past (bf + len) then that IAC will be left unprocessed and *processed
less than len. will be less than len.
FIXME - if we mean to send 0xFF to the terminal then it will be escaped, FIXME - if we mean to send 0xFF to the terminal then it will be escaped,
what is the escape character? We aren't handling that situation here. what is the escape character? We aren't handling that situation here.
@ -99,7 +87,7 @@ static struct tsession *sessions;
static char * static char *
remove_iacs(struct tsession *ts, int *pnum_totty) remove_iacs(struct tsession *ts, int *pnum_totty)
{ {
unsigned char *ptr0 = (unsigned char *)ts->buf1 + ts->wridx1; unsigned char *ptr0 = (unsigned char *)TS_BUF1 + ts->wridx1;
unsigned char *ptr = ptr0; unsigned char *ptr = ptr0;
unsigned char *totty = ptr; unsigned char *totty = ptr;
unsigned char *end = ptr + MIN(BUFSIZE - ts->wridx1, ts->size1); unsigned char *end = ptr + MIN(BUFSIZE - ts->wridx1, ts->size1);
@ -210,19 +198,6 @@ getpty(char *line, int size)
} }
static void
send_iac(struct tsession *ts, unsigned char command, int option)
{
/* We rely on that there is space in the buffer for now. */
char *b = ts->buf2 + ts->rdidx2;
*b++ = IAC;
*b++ = command;
*b++ = option;
ts->rdidx2 += 3;
ts->size2 += 3;
}
static struct tsession * static struct tsession *
make_new_session( make_new_session(
USE_FEATURE_TELNETD_STANDALONE(int sock_r, int sock_w) USE_FEATURE_TELNETD_STANDALONE(int sock_r, int sock_w)
@ -234,25 +209,28 @@ make_new_session(
char tty_name[32]; char tty_name[32];
struct tsession *ts = xzalloc(sizeof(struct tsession) + BUFSIZE * 2); struct tsession *ts = xzalloc(sizeof(struct tsession) + BUFSIZE * 2);
ts->buf1 = (char *)(&ts[1]); /*ts->buf1 = (char *)(ts + 1);*/
ts->buf2 = ts->buf1 + BUFSIZE; /*ts->buf2 = ts->buf1 + BUFSIZE;*/
/* Got a new connection, set up a tty. */ /* Got a new connection, set up a tty. */
fd = getpty(tty_name, 32); fd = getpty(tty_name, 32);
if (fd < 0) { if (fd < 0) {
bb_error_msg("all terminals in use"); bb_error_msg("can't create pty");
return NULL; return NULL;
} }
if (fd > maxfd) maxfd = fd; if (fd > maxfd) maxfd = fd;
ndelay_on(ts->ptyfd = fd); ts->ptyfd = fd;
ndelay_on(fd);
#if ENABLE_FEATURE_TELNETD_STANDALONE #if ENABLE_FEATURE_TELNETD_STANDALONE
if (sock_w > maxfd) maxfd = sock_w; if (sock_w > maxfd) maxfd = sock_w;
ts->sockfd_write = sock_w;
ndelay_on(sock_w);
if (sock_r > maxfd) maxfd = sock_r; if (sock_r > maxfd) maxfd = sock_r;
ndelay_on(ts->sockfd_write = sock_w); ts->sockfd_read = sock_r;
ndelay_on(ts->sockfd_read = sock_r); ndelay_on(sock_r);
#else #else
ts->sockfd_write = 1; ts->sockfd_write = 1;
/* xzalloc: ts->sockfd_read = 0; */ /* ts->sockfd_read = 0; - done by xzalloc */
ndelay_on(0); ndelay_on(0);
ndelay_on(1); ndelay_on(1);
#endif #endif
@ -260,26 +238,36 @@ make_new_session(
* should not do it locally. We don't tell the client to run linemode, * should not do it locally. We don't tell the client to run linemode,
* because we want to handle line editing and tab completion and other * because we want to handle line editing and tab completion and other
* stuff that requires char-by-char support. */ * stuff that requires char-by-char support. */
send_iac(ts, DO, TELOPT_ECHO); {
send_iac(ts, DO, TELOPT_NAWS); static const char iacs_to_send[] ALIGN1 = {
send_iac(ts, DO, TELOPT_LFLOW); IAC, DO, TELOPT_ECHO,
send_iac(ts, WILL, TELOPT_ECHO); IAC, DO, TELOPT_NAWS,
send_iac(ts, WILL, TELOPT_SGA); IAC, DO, TELOPT_LFLOW,
IAC, WILL, TELOPT_ECHO,
IAC, WILL, TELOPT_SGA
};
memcpy(TS_BUF2, iacs_to_send, sizeof(iacs_to_send));
ts->rdidx2 = sizeof(iacs_to_send);
ts->size2 = sizeof(iacs_to_send);
}
pid = fork(); fflush(NULL); /* flush all streams */
pid = vfork(); /* NOMMU-friendly */
if (pid < 0) { if (pid < 0) {
free(ts); free(ts);
close(fd); close(fd);
bb_perror_msg("fork"); /* sock_r and sock_w will be closed by caller */
bb_perror_msg("vfork");
return NULL; return NULL;
} }
if (pid > 0) { if (pid > 0) {
/* parent */ /* Parent */
ts->shell_pid = pid; /*ts->shell_pid = pid;*/
return ts; return ts;
} }
/* child */ /* Child */
/* Careful - we are after vfork! */
/* make new session and process group */ /* make new session and process group */
setsid(); setsid();
@ -304,14 +292,18 @@ make_new_session(
/*termbuf.c_lflag &= ~ICANON;*/ /*termbuf.c_lflag &= ~ICANON;*/
tcsetattr(0, TCSANOW, &termbuf); tcsetattr(0, TCSANOW, &termbuf);
/* Uses FILE-based I/O to stdout, but does fflush(stdout),
* so should be safe with vfork.
* I fear, though, that some users will have ridiculously big
* issue files, and they may block writing to fd 1. */
print_login_issue(issuefile, NULL); print_login_issue(issuefile, NULL);
/* exec shell / login /whatever */ /* Exec shell / login / whatever */
login_argv[0] = loginpath; login_argv[0] = loginpath;
login_argv[1] = NULL; login_argv[1] = NULL;
execv(loginpath, (char **)login_argv); execvp(loginpath, (char **)login_argv);
/* Hmmm... this gets sent to the client thru fd#2! Is it ok?? */ /* Safer with vfork, and we shouldn't send this to the client anyway */
bb_perror_msg_and_die("execv %s", loginpath); _exit(1); /*bb_perror_msg_and_die("execv %s", loginpath);*/
} }
#if ENABLE_FEATURE_TELNETD_STANDALONE #if ENABLE_FEATURE_TELNETD_STANDALONE
@ -321,7 +313,7 @@ free_session(struct tsession *ts)
{ {
struct tsession *t = sessions; struct tsession *t = sessions;
/* unlink this telnet session from the session list */ /* Unlink this telnet session from the session list */
if (t == ts) if (t == ts)
sessions = ts->next; sessions = ts->next;
else { else {
@ -330,15 +322,18 @@ free_session(struct tsession *ts)
t->next = ts->next; t->next = ts->next;
} }
kill(ts->shell_pid, SIGKILL); /* It was said that "normal" telnetd just closes ptyfd,
wait4(ts->shell_pid, NULL, 0, NULL); * doesn't send SIGKILL. When we close ptyfd,
* kernel sends SIGHUP to processes having slave side opened. */
/*kill(ts->shell_pid, SIGKILL);
wait4(ts->shell_pid, NULL, 0, NULL);*/
close(ts->ptyfd); close(ts->ptyfd);
close(ts->sockfd_read); close(ts->sockfd_read);
/* error if ts->sockfd_read == ts->sockfd_write. So what? ;) */ /* error if ts->sockfd_read == ts->sockfd_write. So what? ;) */
close(ts->sockfd_write); close(ts->sockfd_write);
free(ts); free(ts);
/* scan all sessions and find new maxfd */ /* Scan all sessions and find new maxfd */
ts = sessions; ts = sessions;
maxfd = 0; maxfd = 0;
while (ts) { while (ts) {
@ -369,7 +364,7 @@ int telnetd_main(int argc, char **argv)
struct tsession *ts; struct tsession *ts;
#if ENABLE_FEATURE_TELNETD_STANDALONE #if ENABLE_FEATURE_TELNETD_STANDALONE
#define IS_INETD (opt & OPT_INETD) #define IS_INETD (opt & OPT_INETD)
int master_fd = -1; /* be happy, gcc */ int master_fd = master_fd; /* be happy, gcc */
unsigned portnbr = 23; unsigned portnbr = 23;
char *opt_bindaddr = NULL; char *opt_bindaddr = NULL;
char *opt_portnbr; char *opt_portnbr;
@ -381,12 +376,14 @@ int telnetd_main(int argc, char **argv)
}; };
#endif #endif
enum { enum {
OPT_PORT = 4 * ENABLE_FEATURE_TELNETD_STANDALONE, OPT_INETD = (1 << 2) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -i */
OPT_FOREGROUND = 0x10 * ENABLE_FEATURE_TELNETD_STANDALONE, OPT_PORT = (1 << 3) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -p */
OPT_INETD = 0x20 * ENABLE_FEATURE_TELNETD_STANDALONE, OPT_FOREGROUND = (1 << 5) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -F */
}; };
opt = getopt32(argv, "f:l:" USE_FEATURE_TELNETD_STANDALONE("p:b:Fi"), /* If !STANDALONE, we accept (and ignore) -i, thus people
* don't need to guess whether it's ok to pass -i to us */
opt = getopt32(argv, "f:l:i" USE_FEATURE_TELNETD_STANDALONE("p:b:F"),
&issuefile, &loginpath &issuefile, &loginpath
USE_FEATURE_TELNETD_STANDALONE(, &opt_portnbr, &opt_bindaddr)); USE_FEATURE_TELNETD_STANDALONE(, &opt_portnbr, &opt_bindaddr));
/* Redirect log to syslog early, if needed */ /* Redirect log to syslog early, if needed */
@ -410,19 +407,43 @@ int telnetd_main(int argc, char **argv)
#if ENABLE_FEATURE_TELNETD_STANDALONE #if ENABLE_FEATURE_TELNETD_STANDALONE
if (IS_INETD) { if (IS_INETD) {
sessions = make_new_session(0, 1); sessions = make_new_session(0, 1);
if (!sessions) /* pty opening or vfork problem, exit */
return 1; /* make_new_session prints error message */
} else { } else {
//vda: inform that we start in standalone mode?
master_fd = create_and_bind_stream_or_die(opt_bindaddr, portnbr); master_fd = create_and_bind_stream_or_die(opt_bindaddr, portnbr);
xlisten(master_fd, 1); xlisten(master_fd, 1);
if (!(opt & OPT_FOREGROUND)) if (!(opt & OPT_FOREGROUND))
//vda: NOMMU?
bb_daemonize(DAEMON_CHDIR_ROOT); bb_daemonize(DAEMON_CHDIR_ROOT);
} }
#else #else
sessions = make_new_session(); sessions = make_new_session();
if (!sessions) /* pty opening or vfork problem, exit */
return 1; /* make_new_session prints error message */
#endif #endif
/* We don't want to die if just one session is broken */ /* We don't want to die if just one session is broken */
signal(SIGPIPE, SIG_IGN); signal(SIGPIPE, SIG_IGN);
/*
This is how the buffers are used. The arrows indicate the movement
of data.
+-------+ wridx1++ +------+ rdidx1++ +----------+
| | <-------------- | buf1 | <-------------- | |
| | size1-- +------+ size1++ | |
| pty | | socket |
| | rdidx2++ +------+ wridx2++ | |
| | --------------> | buf2 | --------------> | |
+-------+ size2++ +------+ size2-- +----------+
size1: "how many bytes are buffered for pty between rdidx1 and wridx1?"
size2: "how many bytes are buffered for socket between rdidx2 and wridx2?"
Each session has got two buffers. Buffers are circular. If sizeN == 0,
buffer is empty. If sizeN == BUFSIZE, buffer is full. In both these cases
rdidxN == wridxN.
*/
again: again:
FD_ZERO(&rdfdset); FD_ZERO(&rdfdset);
FD_ZERO(&wrfdset); FD_ZERO(&wrfdset);
@ -435,12 +456,12 @@ int telnetd_main(int argc, char **argv)
maxfd = master_fd; maxfd = master_fd;
} }
/* select on the master socket, all telnet sockets and their /* Select on the master socket, all telnet sockets and their
* ptys if there is room in their session buffers. */ * ptys if there is room in their session buffers.
* NB: scalability problem: we recalculate entire bitmap
* before each select. Can be a problem with 500+ connections. */
ts = sessions; ts = sessions;
while (ts) { while (ts) {
/* buf1 is used from socket to pty
* buf2 is used from pty to socket */
if (ts->size1 > 0) /* can write to pty */ if (ts->size1 > 0) /* can write to pty */
FD_SET(ts->ptyfd, &wrfdset); FD_SET(ts->ptyfd, &wrfdset);
if (ts->size1 < BUFSIZE) /* can read from socket */ if (ts->size1 < BUFSIZE) /* can read from socket */
@ -452,9 +473,9 @@ int telnetd_main(int argc, char **argv)
ts = ts->next; ts = ts->next;
} }
selret = select(maxfd + 1, &rdfdset, &wrfdset, 0, 0); selret = select(maxfd + 1, &rdfdset, &wrfdset, NULL, NULL);
if (!selret) if (selret < 0)
return 0; goto again; /* EINTR or ENOMEM */
#if ENABLE_FEATURE_TELNETD_STANDALONE #if ENABLE_FEATURE_TELNETD_STANDALONE
/* First check for and accept new sessions. */ /* First check for and accept new sessions. */
@ -462,7 +483,7 @@ int telnetd_main(int argc, char **argv)
int fd; int fd;
struct tsession *new_ts; struct tsession *new_ts;
fd = accept(master_fd, NULL, 0); fd = accept(master_fd, NULL, NULL);
if (fd < 0) if (fd < 0)
goto again; goto again;
/* Create a new session and link it into our active list */ /* Create a new session and link it into our active list */
@ -481,83 +502,48 @@ int telnetd_main(int argc, char **argv)
while (ts) { /* For all sessions... */ while (ts) { /* For all sessions... */
struct tsession *next = ts->next; /* in case we free ts. */ struct tsession *next = ts->next; /* in case we free ts. */
if (ts->size1 && FD_ISSET(ts->ptyfd, &wrfdset)) { if (/*ts->size1 &&*/ FD_ISSET(ts->ptyfd, &wrfdset)) {
int num_totty; int num_totty;
char *ptr; char *ptr;
/* Write to pty from buffer 1. */ /* Write to pty from buffer 1. */
ptr = remove_iacs(ts, &num_totty); ptr = remove_iacs(ts, &num_totty);
w = safe_write(ts->ptyfd, ptr, num_totty); w = safe_write(ts->ptyfd, ptr, num_totty);
/* needed? if (w < 0 && errno == EAGAIN) continue; */
if (w < 0) { if (w < 0) {
if (errno == EAGAIN)
goto skip1;
if (IS_INETD) if (IS_INETD)
return 0; return 0;
free_session(ts); free_session(ts);
ts = next; ts = next;
continue; continue;
} }
ts->wridx1 += w;
ts->size1 -= w; ts->size1 -= w;
if (ts->wridx1 == BUFSIZE) ts->wridx1 += w;
if (ts->wridx1 >= BUFSIZE) /* actually == BUFSIZE */
ts->wridx1 = 0; ts->wridx1 = 0;
} }
skip1:
if (ts->size2 && FD_ISSET(ts->sockfd_write, &wrfdset)) { if (/*ts->size2 &&*/ FD_ISSET(ts->sockfd_write, &wrfdset)) {
/* Write to socket from buffer 2. */ /* Write to socket from buffer 2. */
maxlen = MIN(BUFSIZE - ts->wridx2, ts->size2); maxlen = MIN(BUFSIZE - ts->wridx2, ts->size2);
w = safe_write(ts->sockfd_write, ts->buf2 + ts->wridx2, maxlen); w = safe_write(ts->sockfd_write, TS_BUF2 + ts->wridx2, maxlen);
/* needed? if (w < 0 && errno == EAGAIN) continue; */
if (w < 0) { if (w < 0) {
if (errno == EAGAIN)
goto skip2;
if (IS_INETD) if (IS_INETD)
return 0; return 0;
free_session(ts); free_session(ts);
ts = next; ts = next;
continue; continue;
} }
ts->wridx2 += w;
ts->size2 -= w; ts->size2 -= w;
if (ts->wridx2 == BUFSIZE) ts->wridx2 += w;
if (ts->wridx2 >= BUFSIZE) /* actually == BUFSIZE */
ts->wridx2 = 0; ts->wridx2 = 0;
} }
skip2:
if (ts->size1 < BUFSIZE && FD_ISSET(ts->sockfd_read, &rdfdset)) { #if 0
/* Read from socket to buffer 1. */ /* Not strictly needed, but allows for bigger reads in common case */
maxlen = MIN(BUFSIZE - ts->rdidx1, BUFSIZE - ts->size1);
r = safe_read(ts->sockfd_read, ts->buf1 + ts->rdidx1, maxlen);
if (r < 0 && errno == EAGAIN) continue;
if (r <= 0) {
if (IS_INETD)
return 0;
free_session(ts);
ts = next;
continue;
}
if (!ts->buf1[ts->rdidx1 + r - 1])
if (!--r)
continue;
ts->rdidx1 += r;
ts->size1 += r;
if (ts->rdidx1 == BUFSIZE)
ts->rdidx1 = 0;
}
if (ts->size2 < BUFSIZE && FD_ISSET(ts->ptyfd, &rdfdset)) {
/* Read from pty to buffer 2. */
maxlen = MIN(BUFSIZE - ts->rdidx2, BUFSIZE - ts->size2);
r = safe_read(ts->ptyfd, ts->buf2 + ts->rdidx2, maxlen);
if (r < 0 && errno == EAGAIN) continue;
if (r <= 0) {
if (IS_INETD)
return 0;
free_session(ts);
ts = next;
continue;
}
ts->rdidx2 += r;
ts->size2 += r;
if (ts->rdidx2 == BUFSIZE)
ts->rdidx2 = 0;
}
if (ts->size1 == 0) { if (ts->size1 == 0) {
ts->rdidx1 = 0; ts->rdidx1 = 0;
ts->wridx1 = 0; ts->wridx1 = 0;
@ -566,6 +552,50 @@ int telnetd_main(int argc, char **argv)
ts->rdidx2 = 0; ts->rdidx2 = 0;
ts->wridx2 = 0; ts->wridx2 = 0;
} }
#endif
if (/*ts->size1 < BUFSIZE &&*/ FD_ISSET(ts->sockfd_read, &rdfdset)) {
/* Read from socket to buffer 1. */
maxlen = MIN(BUFSIZE - ts->rdidx1, BUFSIZE - ts->size1);
r = safe_read(ts->sockfd_read, TS_BUF1 + ts->rdidx1, maxlen);
if (r <= 0) {
if (r < 0 && errno == EAGAIN)
goto skip3;
if (IS_INETD)
return 0;
free_session(ts);
ts = next;
continue;
}
/* Ignore trailing NUL if it is there */
if (!TS_BUF1[ts->rdidx1 + r - 1]) {
if (!--r)
goto skip3;
}
ts->size1 += r;
ts->rdidx1 += r;
if (ts->rdidx1 >= BUFSIZE) /* actually == BUFSIZE */
ts->rdidx1 = 0;
}
skip3:
if (/*ts->size2 < BUFSIZE &&*/ FD_ISSET(ts->ptyfd, &rdfdset)) {
/* Read from pty to buffer 2. */
maxlen = MIN(BUFSIZE - ts->rdidx2, BUFSIZE - ts->size2);
r = safe_read(ts->ptyfd, TS_BUF2 + ts->rdidx2, maxlen);
if (r <= 0) {
if (r < 0 && errno == EAGAIN)
goto skip4;
if (IS_INETD)
return 0;
free_session(ts);
ts = next;
continue;
}
ts->size2 += r;
ts->rdidx2 += r;
if (ts->rdidx2 >= BUFSIZE) /* actually == BUFSIZE */
ts->rdidx2 = 0;
}
skip4:
ts = next; ts = next;
} }
goto again; goto again;