linux/net/core
Ulrich Drepper 4a19542e5f O_CLOEXEC for SCM_RIGHTS
Part two in the O_CLOEXEC saga: adding support for file descriptors received
through Unix domain sockets.

The patch is once again pretty minimal, it introduces a new flag for recvmsg
and passes it just like the existing MSG_CMSG_COMPAT flag.  I think this bit
is not used otherwise but the networking people will know better.

This new flag is not recognized by recvfrom and recv.  These functions cannot
be used for that purpose and the asymmetry this introduces is not worse than
the already existing MSG_CMSG_COMPAT situations.

The patch must be applied on the patch which introduced O_CLOEXEC.  It has to
remove static from the new get_unused_fd_flags function but since scm.c cannot
live in a module the function still hasn't to be exported.

Here's a test program to make sure the code works.  It's so much longer than
the actual patch...

#include <errno.h>
#include <error.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>

#ifndef O_CLOEXEC
# define O_CLOEXEC 02000000
#endif
#ifndef MSG_CMSG_CLOEXEC
# define MSG_CMSG_CLOEXEC 0x40000000
#endif

int
main (int argc, char *argv[])
{
  if (argc > 1)
    {
      int fd = atol (argv[1]);
      printf ("child: fd = %d\n", fd);
      if (fcntl (fd, F_GETFD) == 0 || errno != EBADF)
        {
          puts ("file descriptor valid in child");
          return 1;
        }
      return 0;

    }

  struct sockaddr_un sun;
  strcpy (sun.sun_path, "./testsocket");
  sun.sun_family = AF_UNIX;

  char databuf[] = "hello";
  struct iovec iov[1];
  iov[0].iov_base = databuf;
  iov[0].iov_len = sizeof (databuf);

  union
  {
    struct cmsghdr hdr;
    char bytes[CMSG_SPACE (sizeof (int))];
  } buf;
  struct msghdr msg = { .msg_iov = iov, .msg_iovlen = 1,
                        .msg_control = buf.bytes,
                        .msg_controllen = sizeof (buf) };
  struct cmsghdr *cmsg = CMSG_FIRSTHDR (&msg);

  cmsg->cmsg_level = SOL_SOCKET;
  cmsg->cmsg_type = SCM_RIGHTS;
  cmsg->cmsg_len = CMSG_LEN (sizeof (int));

  msg.msg_controllen = cmsg->cmsg_len;

  pid_t child = fork ();
  if (child == -1)
    error (1, errno, "fork");
  if (child == 0)
    {
      int sock = socket (PF_UNIX, SOCK_STREAM, 0);
      if (sock < 0)
        error (1, errno, "socket");

      if (bind (sock, (struct sockaddr *) &sun, sizeof (sun)) < 0)
        error (1, errno, "bind");
      if (listen (sock, SOMAXCONN) < 0)
        error (1, errno, "listen");

      int conn = accept (sock, NULL, NULL);
      if (conn == -1)
        error (1, errno, "accept");

      *(int *) CMSG_DATA (cmsg) = sock;
      if (sendmsg (conn, &msg, MSG_NOSIGNAL) < 0)
        error (1, errno, "sendmsg");

      return 0;
    }

  /* For a test suite this should be more robust like a
     barrier in shared memory.  */
  sleep (1);

  int sock = socket (PF_UNIX, SOCK_STREAM, 0);
  if (sock < 0)
    error (1, errno, "socket");

  if (connect (sock, (struct sockaddr *) &sun, sizeof (sun)) < 0)
    error (1, errno, "connect");
  unlink (sun.sun_path);

  *(int *) CMSG_DATA (cmsg) = -1;

  if (recvmsg (sock, &msg, MSG_CMSG_CLOEXEC) < 0)
    error (1, errno, "recvmsg");

  int fd = *(int *) CMSG_DATA (cmsg);
  if (fd == -1)
    error (1, 0, "no descriptor received");

  char fdname[20];
  snprintf (fdname, sizeof (fdname), "%d", fd);
  execl ("/proc/self/exe", argv[0], fdname, NULL);
  puts ("execl failed");
  return 1;
}

[akpm@linux-foundation.org: Fix fastcall inconsistency noted by Michael Buesch]
[akpm@linux-foundation.org: build fix]
Signed-off-by: Ulrich Drepper <drepper@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Michael Buesch <mb@bu3sch.de>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-16 09:05:45 -07:00
..
datagram.c [NET]: Revert sk_buff walker cleanups. 2007-04-27 15:21:23 -07:00
dev_mcast.c [NET]: dev_mcast: add multicast list synchronization helpers 2007-07-14 18:52:02 -07:00
dev.c [NET]: Add macvlan driver 2007-07-14 18:55:06 -07:00
dst.c [NET]: Merge dst_discard_in and dst_discard_out. 2007-06-07 13:39:46 -07:00
ethtool.c [NET]: Add ethtool support for NETIF_F_IPV6_CSUM devices. 2007-07-14 19:07:52 -07:00
fib_rules.c [RTNETLINK]: Remove unnecessary locking in dump callbacks 2007-04-25 22:29:05 -07:00
filter.c [SK_BUFF]: Convert skb->tail to sk_buff_data_t 2007-04-25 22:26:28 -07:00
flow.c Add suspend-related notifications for CPU hotplug 2007-05-09 12:30:56 -07:00
gen_estimator.c [NET]: Fix gen_estimator timer removal race 2007-07-10 22:19:03 -07:00
gen_stats.c [SK_BUFF]: Convert skb->tail to sk_buff_data_t 2007-04-25 22:26:28 -07:00
iovec.c [PATCH] remove many unneeded #includes of sched.h 2007-02-14 08:09:54 -08:00
kmap_skb.h [PATCH] severing skbuff.h -> highmem.h 2006-12-04 02:00:29 -05:00
link_watch.c [NET] link_watch: Always schedule urgent events 2007-05-10 23:45:28 -07:00
Makefile [WEXT]: Move to net/wireless 2007-04-26 20:42:51 -07:00
neighbour.c [NETLINK]: Mark netlink policies const 2007-06-07 13:40:10 -07:00
net-sysfs.c [NET]: Fix race condition about network device name allocation. 2007-05-19 15:39:25 -07:00
netevent.c [NET]: net/core/netevent.c should #include <net/netevent.h> 2007-07-05 17:40:27 -07:00
netpoll.c [NET]: Fix races in net_rx_action vs netpoll. 2007-07-11 19:32:02 -07:00
pktgen.c [PKTGEN]: IPSEC support 2007-07-10 22:16:36 -07:00
request_sock.c [NET]: Size listen hash tables using backlog hint 2006-12-02 21:21:44 -08:00
rtnetlink.c [RTNETLINK]: rtnl_link: allow specifying initial device address 2007-07-11 19:45:36 -07:00
scm.c O_CLOEXEC for SCM_RIGHTS 2007-07-16 09:05:45 -07:00
skbuff.c [NETFILTER]: x_tables: add TRACE target 2007-07-10 22:17:14 -07:00
sock.c [NET]: "wrong timeout value in sk_wait_data()": cleanups 2007-07-10 22:18:50 -07:00
stream.c [NET] CORE: Fix whitespace errors. 2007-02-10 23:19:25 -08:00
sysctl_net_core.c [XFRM]: Allow XFRM_ACQ_EXPIRES to be tunable via sysctl. 2007-05-31 01:23:23 -07:00
user_dma.c [NET]: Revert sk_buff walker cleanups. 2007-04-27 15:21:23 -07:00
utils.c [NET]: parse ip:port strings correctly in in4_pton 2007-05-31 01:23:27 -07:00