1  /*
       2   * Check decoding of SCM_PIDFD control messages.
       3   *
       4   * Copyright (c) 2023 Dmitry V. Levin <ldv@strace.io>
       5   * All rights reserved.
       6   *
       7   * SPDX-License-Identifier: GPL-2.0-or-later
       8   */
       9  
      10  #include "tests.h"
      11  #include <assert.h>
      12  #include <stdio.h>
      13  #include <string.h>
      14  #include <unistd.h>
      15  #include <sys/socket.h>
      16  
      17  #define XLAT_MACROS_ONLY
      18  # include "xlat/sock_options.h"
      19  # include "xlat/scmvals.h"
      20  #undef XLAT_MACROS_ONLY
      21  
      22  static void
      23  print_pidfd(const struct cmsghdr *c)
      24  {
      25  	const void *cmsg_header = c;
      26  	const void *cmsg_data = CMSG_DATA(c);
      27  	int pidfd;
      28  	const unsigned int expected_len = sizeof(pidfd);
      29  	const unsigned int data_len = c->cmsg_len - (cmsg_data - cmsg_header);
      30  
      31  	if (expected_len != data_len)
      32  		perror_msg_and_fail("sizeof(pidfd) = %u, data_len = %u\n",
      33  				    expected_len, data_len);
      34  
      35  	memcpy(&pidfd, cmsg_data, sizeof(pidfd));
      36  	printf("%d<anon_inode:[pidfd]>", pidfd);
      37  }
      38  
      39  int
      40  main(void)
      41  {
      42  	skip_if_unavailable("/proc/self/fd/");
      43  
      44  	int sv[2];
      45  	if (socketpair(AF_UNIX, SOCK_STREAM, 0, sv))
      46                  perror_msg_and_skip("socketpair AF_UNIX SOCK_STREAM");
      47  
      48  	int one = 1;
      49  	if (setsockopt(sv[0], SOL_SOCKET, SO_PASSPIDFD, &one, sizeof(one)))
      50  		perror_msg_and_skip("setsockopt SO_PASSPIDFD");
      51  
      52  	char sym = 'A';
      53  	if (send(sv[1], &sym, 1, 0) != 1)
      54  		perror_msg_and_fail("send");
      55  	if (close(sv[1]))
      56  		perror_msg_and_fail("close send");
      57  
      58  	int pidfd;
      59  	unsigned int cmsg_size = CMSG_SPACE(sizeof(pidfd));
      60  	struct cmsghdr *cmsg = tail_alloc(cmsg_size);
      61  	memset(cmsg, 0, cmsg_size);
      62  
      63  	struct iovec iov = {
      64  		.iov_base = &sym,
      65  		.iov_len = sizeof(sym)
      66  	};
      67  	struct msghdr mh = {
      68  		.msg_iov = &iov,
      69  		.msg_iovlen = 1,
      70  		.msg_control = cmsg,
      71  		.msg_controllen = cmsg_size
      72  	};
      73  
      74  	if (recvmsg(sv[0], &mh, 0) != 1)
      75  		perror_msg_and_fail("recvmsg");
      76  
      77  	printf("recvmsg(%d<socket:[%lu]>, {msg_name=NULL, msg_namelen=0"
      78  	       ", msg_iov=[{iov_base=\"A\", iov_len=1}], msg_iovlen=1",
      79  	       sv[0], inode_of_sockfd(sv[0]));
      80  
      81  	bool found = false;
      82  	if (mh.msg_controllen) {
      83  		printf(", msg_control=[");
      84  		for (struct cmsghdr *c = CMSG_FIRSTHDR(&mh); c;
      85  		     c = CMSG_NXTHDR(&mh, c)) {
      86  			printf("%s{cmsg_len=%lu, cmsg_level=",
      87  			       (c == cmsg ? "" : ", "),
      88  			       (unsigned long) c->cmsg_len);
      89  			if (c->cmsg_level == SOL_SOCKET) {
      90  				printf("SOL_SOCKET");
      91  			} else {
      92  				printf("%d /* expected SOL_SOCKET == %d */",
      93  				       c->cmsg_level, (int) SOL_SOCKET);
      94  			}
      95  			printf(", cmsg_type=");
      96  			if (c->cmsg_type == SCM_PIDFD) {
      97  				printf("SCM_PIDFD, cmsg_data=");
      98  				print_pidfd(c);
      99  				found = true;
     100  			} else {
     101  				printf("%d /* expected SCM_PIDFD == %d */",
     102  				       c->cmsg_type, (int) SCM_PIDFD);
     103  			}
     104  			printf("}");
     105  		}
     106  		printf("]");
     107  	}
     108  	printf(", msg_controllen=%lu, msg_flags=0}, 0) = 1\n",
     109  	       (unsigned long) mh.msg_controllen);
     110  
     111  	if (!found)
     112  		error_msg_and_fail("SCM_PIDFD not found");
     113  
     114  	puts("+++ exited with 0 +++");
     115  	return 0;
     116  }