338 lines
9 KiB
C
Executable file
338 lines
9 KiB
C
Executable file
#define _GNU_SOURCE 1
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#include <errno.h>
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#include <fcntl.h>
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#include <signal.h>
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#include <stdarg.h>
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#include <stdbool.h>
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#include <stddef.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stropts.h>
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#include <sys/ioctl.h>
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#include <sys/stat.h>
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#include <sys/time.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <sys/socket.h>
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#include <sys/un.h>
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#include <termios.h>
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#include <unistd.h>
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static void
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fail_io (const char *msg, ...)
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__attribute__ ((noreturn))
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__attribute__ ((format (printf, 1, 2)));
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/* Prints MSG, formatting as with printf(),
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plus an error message based on errno,
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and exits. */
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static void
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fail_io (const char *msg, ...)
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{
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va_list args;
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va_start (args, msg);
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vfprintf (stderr, msg, args);
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va_end (args);
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if (errno != 0)
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fprintf (stderr, ": %s", strerror (errno));
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putc ('\n', stderr);
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exit (EXIT_FAILURE);
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}
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/* If FD is a terminal, configures it for noncanonical input mode
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with VMIN and VTIME set as indicated.
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If FD is not a terminal, has no effect. */
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static void
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make_noncanon (int fd, int vmin, int vtime)
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{
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if (isatty (fd))
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{
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struct termios termios;
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if (tcgetattr (fd, &termios) < 0)
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fail_io ("tcgetattr");
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termios.c_lflag &= ~(ICANON | ECHO);
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termios.c_cc[VMIN] = vmin;
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termios.c_cc[VTIME] = vtime;
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if (tcsetattr (fd, TCSANOW, &termios) < 0)
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fail_io ("tcsetattr");
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}
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}
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/* Make FD non-blocking if NONBLOCKING is true,
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or blocking if NONBLOCKING is false. */
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static void
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make_nonblocking (int fd, bool nonblocking)
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{
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int flags = fcntl (fd, F_GETFL);
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if (flags < 0)
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fail_io ("fcntl");
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if (nonblocking)
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flags |= O_NONBLOCK;
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else
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flags &= ~O_NONBLOCK;
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if (fcntl (fd, F_SETFL, flags) < 0)
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fail_io ("fcntl");
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}
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/* Handle a read or write on *FD, which is the socket if
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FD_IS_SOCK is true, that returned end-of-file or error
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indication RETVAL. The system call is named CALL, for use in
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error messages. Returns true if processing may continue,
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false if we're all done. */
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static bool
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handle_error (ssize_t retval, int *fd, bool fd_is_sock, const char *call)
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{
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if (retval == 0)
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{
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if (fd_is_sock)
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return false;
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else
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{
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*fd = -1;
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return true;
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}
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}
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else
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fail_io (call);
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}
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/* Copies data from stdin to SOCK and from SOCK to stdout until no
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more data can be read or written. */
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static void
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relay (int sock)
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{
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struct pipe
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{
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int in, out;
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char buf[BUFSIZ];
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size_t size, ofs;
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bool active;
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};
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struct pipe pipes[2];
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/* In case stdin is a file, go back to the beginning.
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This allows replaying the input on reset. */
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lseek (STDIN_FILENO, 0, SEEK_SET);
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/* Make SOCK, stdin, and stdout non-blocking. */
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make_nonblocking (sock, true);
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make_nonblocking (STDIN_FILENO, true);
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make_nonblocking (STDOUT_FILENO, true);
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/* Configure noncanonical mode on stdin to avoid waiting for
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end-of-line. */
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make_noncanon (STDIN_FILENO, 1, 0);
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memset (pipes, 0, sizeof pipes);
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pipes[0].in = STDIN_FILENO;
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pipes[0].out = sock;
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pipes[1].in = sock;
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pipes[1].out = STDOUT_FILENO;
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while (pipes[0].in != -1 || pipes[1].in != -1
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|| (pipes[1].size && pipes[1].out != -1))
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{
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fd_set read_fds, write_fds;
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sigset_t empty_set;
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int retval;
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int i;
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FD_ZERO (&read_fds);
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FD_ZERO (&write_fds);
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for (i = 0; i < 2; i++)
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{
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struct pipe *p = &pipes[i];
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/* Don't do anything with the stdin->sock pipe until we
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have some data for the sock->stdout pipe. If we get
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too eager, vmplayer will throw away our input. */
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if (i == 0 && !pipes[1].active)
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continue;
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if (p->in != -1 && p->size + p->ofs < sizeof p->buf)
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FD_SET (p->in, &read_fds);
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if (p->out != -1 && p->size > 0)
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FD_SET (p->out, &write_fds);
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}
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sigemptyset (&empty_set);
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retval = pselect (FD_SETSIZE, &read_fds, &write_fds, NULL, NULL,
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&empty_set);
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if (retval < 0)
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{
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if (errno == EINTR)
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{
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/* Child died. Do final relaying. */
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struct pipe *p = &pipes[1];
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if (p->out == -1)
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exit (0);
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make_nonblocking (STDOUT_FILENO, false);
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for (;;)
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{
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ssize_t n;
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/* Write buffer. */
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while (p->size > 0)
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{
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n = write (p->out, p->buf + p->ofs, p->size);
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if (n < 0)
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fail_io ("write");
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else if (n == 0)
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fail_io ("zero-length write");
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p->ofs += n;
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p->size -= n;
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}
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p->ofs = 0;
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p->size = n = read (p->in, p->buf, sizeof p->buf);
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if (n <= 0)
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exit (0);
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}
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}
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fail_io ("select");
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}
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for (i = 0; i < 2; i++)
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{
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struct pipe *p = &pipes[i];
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if (p->in != -1 && FD_ISSET (p->in, &read_fds))
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{
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ssize_t n = read (p->in, p->buf + p->ofs + p->size,
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sizeof p->buf - p->ofs - p->size);
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if (n > 0)
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{
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p->active = true;
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p->size += n;
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if (p->size == BUFSIZ && p->ofs != 0)
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{
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memmove (p->buf, p->buf + p->ofs, p->size);
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p->ofs = 0;
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}
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}
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else if (!handle_error (n, &p->in, p->in == sock, "read"))
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return;
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}
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if (p->out != -1 && FD_ISSET (p->out, &write_fds))
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{
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ssize_t n = write (p->out, p->buf + p->ofs, p->size);
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if (n > 0)
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{
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p->ofs += n;
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p->size -= n;
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if (p->size == 0)
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p->ofs = 0;
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}
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else if (!handle_error (n, &p->out, p->out == sock, "write"))
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return;
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}
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}
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}
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}
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static void
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sigchld_handler (int signo __attribute__ ((unused)))
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{
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/* Nothing to do. */
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}
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int
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main (int argc __attribute__ ((unused)), char *argv[])
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{
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pid_t pid;
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struct itimerval zero_itimerval;
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struct sockaddr_un sun;
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sigset_t sigchld_set;
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int sock;
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if (argc < 3)
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{
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fprintf (stderr,
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"usage: squish-unix SOCKET COMMAND [ARG]...\n"
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"Squishes both stdin and stdout into a single Unix domain\n"
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"socket named SOCKET, and runs COMMAND as a subprocess.\n");
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return EXIT_FAILURE;
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}
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/* Create socket. */
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sock = socket (PF_LOCAL, SOCK_STREAM, 0);
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if (sock < 0)
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fail_io ("socket");
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/* Configure socket. */
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sun.sun_family = AF_LOCAL;
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strncpy (sun.sun_path, argv[1], sizeof sun.sun_path);
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sun.sun_path[sizeof sun.sun_path - 1] = '\0';
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if (unlink (sun.sun_path) < 0 && errno != ENOENT)
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fail_io ("unlink");
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if (bind (sock, (struct sockaddr *) &sun,
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(offsetof (struct sockaddr_un, sun_path)
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+ strlen (sun.sun_path) + 1)) < 0)
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fail_io ("bind");
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/* Listen on socket. */
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if (listen (sock, 1) < 0)
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fail_io ("listen");
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/* Block SIGCHLD and set up a handler for it. */
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sigemptyset (&sigchld_set);
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sigaddset (&sigchld_set, SIGCHLD);
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if (sigprocmask (SIG_BLOCK, &sigchld_set, NULL) < 0)
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fail_io ("sigprocmask");
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if (signal (SIGCHLD, sigchld_handler) == SIG_ERR)
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fail_io ("signal");
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/* Save the virtual interval timer, which might have been set
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by the process that ran us. It really should be applied to
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our child process. */
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memset (&zero_itimerval, 0, sizeof zero_itimerval);
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if (setitimer (ITIMER_VIRTUAL, &zero_itimerval, NULL) < 0)
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fail_io ("setitimer");
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pid = fork ();
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if (pid < 0)
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fail_io ("fork");
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else if (pid != 0)
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{
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/* Running in parent process. */
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make_nonblocking (sock, true);
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for (;;)
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{
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fd_set read_fds;
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sigset_t empty_set;
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int retval;
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int conn;
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/* Wait for connection. */
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FD_ZERO (&read_fds);
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FD_SET (sock, &read_fds);
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sigemptyset (&empty_set);
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retval = pselect (sock + 1, &read_fds, NULL, NULL, NULL, &empty_set);
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if (retval < 0)
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{
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if (errno == EINTR)
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break;
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fail_io ("select");
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}
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/* Accept connection. */
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conn = accept (sock, NULL, NULL);
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if (conn < 0)
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fail_io ("accept");
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/* Relay connection. */
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relay (conn);
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close (conn);
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}
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return 0;
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}
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else
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{
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/* Running in child process. */
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if (close (sock) < 0)
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fail_io ("close");
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execvp (argv[2], argv + 2);
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fail_io ("exec");
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}
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}
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