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   1 #include "config.h"
   2 #include <stdio.h>
   3 #include <string.h>
   4
   5 /**
   6  * io/fdpass - IO helper for passing file descriptors across local sockets
   7  *
   8  * This code adds the ability to pass file descriptors to ccan/io.
   9  *
  10  * License: LGPL (v2.1 or any later version)
  11  * Author: Rusty Russell <rusty@rustcorp.com.au>
  12  *
  13  * Example:
  14  *      // Given "hello" outputs hello
  15  *      #include <ccan/io/fdpass/fdpass.h>
  16  *      #include <sys/types.h>
  17  *      #include <sys/socket.h>
  18  *      #include <sys/un.h>
  19  *      #include <stdio.h>
  20  *      #include <stdlib.h>
  21  *      #include <unistd.h>
  22  *
  23  *      // Child reads stdin into the buffer, prints it out.
  24  *      struct buf {
  25  *              size_t used;
  26  *              char c[100];
  27  *      };
  28  *      static struct io_plan *read_more(struct io_conn *conn, struct buf *buf)
  29  *      {
  30  *              printf("%.*s", (int)buf->used, buf->c);
  31  *              return io_read_partial(conn, buf->c, sizeof(buf->c), &buf->used,
  32  *                                      read_more, buf);
  33  *      }
  34  *
  35  *      // Clean up allocation so -fsanitize=address doesn't see leak!
  36  *      static void free_buf(struct io_conn *c, struct buf *buf)
  37  *      {
  38  *              free(buf);
  39  *      }
  40  *
  41  *      // Child has received fd, start reading loop.
  42  *      static struct io_plan *got_infd(struct io_conn *conn, int *infd)
  43  *      {
  44  *              struct buf *buf = calloc(1, sizeof(*buf));
  45  *              struct io_conn *new_conn;
  46  *
  47  *              new_conn = io_new_conn(NULL, *infd, read_more, buf);
  48  *              io_set_finish(new_conn, free_buf, buf);
  49  *              return io_close(conn);
  50  *      }
  51  *      // Child is receiving the fd to read into.
  52  *      static struct io_plan *recv_infd(struct io_conn *conn, int *infd)
  53  *      {
  54  *              return io_recv_fd(conn, infd, got_infd, infd);
  55  *      }
  56  *
  57  *      // Gets passed fd (stdin), which it reads from.
  58  *      static void child(int sockfd)
  59  *      {
  60  *              int infd;
  61  *
  62  *              io_new_conn(NULL, sockfd, recv_infd, &infd);
  63  *              io_loop(NULL, NULL);
  64  *              exit(0);
  65  *      }
  66  *
  67  *      static struct io_plan *send_stdin(struct io_conn *conn, void *unused)
  68  *      {
  69  *              return io_send_fd(conn, STDIN_FILENO, false, io_close_cb, NULL);
  70  *      }
  71  *
  72  *      static void parent(int sockfd)
  73  *      {
  74  *              io_new_conn(NULL, sockfd, send_stdin, NULL);
  75  *              io_loop(NULL, NULL);
  76  *              exit(0);
  77  *      }
  78  *
  79  *      int main(void)
  80  *      {
  81  *              int sv[2];
  82  *
  83  *              socketpair(AF_UNIX, SOCK_STREAM, 0, sv);
  84  *              if (fork() == 0)
  85  *                      child(sv[0]);
  86  *              else
  87  *                      parent(sv[1]);
  88  *      }
  89  */
  90 int main(int argc, char *argv[])
  91 {
  92         /* Expect exactly one argument */
  93         if (argc != 2)
  94                 return 1;
  95
  96         if (strcmp(argv[1], "depends") == 0) {
  97                 printf("ccan/fdpass\n");
  98                 printf("ccan/io\n");
  99                 return 0;
 100         }
 101
 102         return 1;
 103 }