openssh bugs - May 2018 - [Bug 2864] New: ssh client 7.7p1: "Tunnel device open failed." (regression from 7.6p1)

https://bugzilla.mindrot.org/show_bug.cgi?id=2864

            Bug ID: 2864
           Summary: ssh client 7.7p1: "Tunnel device open failed."
                    (regression from 7.6p1)
           Product: Portable OpenSSH
           Version: 7.7p1
          Hardware: amd64
                OS: Linux
            Status: NEW
          Severity: major
          Priority: P5
         Component: ssh
          Assignee: unassigned-bugs at mindrot.org
          Reporter: calimeroteknik at free.fr

Created attachment 3148
  --> https://bugzilla.mindrot.org/attachment.cgi?id=3148&action=edit
ssh -vvv -w0:0 remotehost for 7.6p1 and 7.7p1

I have tun0 set up on the local and remote host.

Here is what happens with 7.7p1:

calimero at localhost ~ $ ssh -w0:0 remotehost
Tunnel device open failed.
Could not request tunnel forwarding.
calimero at remotehost ~ $

For the verbose (-vvv) output, which didn't seem extremely helpful, see
attachment.


Here are strace excerpts:


For 7.6p1:

openat(AT_FDCWD, "/dev/net/tun", O_RDWR) = 4
ioctl(4, TUNSETIFF, 0x7fffaeea8490)     = 0
fcntl(4, F_SETFD, FD_CLOEXEC)           = 0
fcntl(4, F_GETFL)                       = 0x8002 (flags
O_RDWR|O_LARGEFILE)
fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK|O_LARGEFILE) = 0
fcntl(4, F_GETFL)                       = 0x8802 (flags
O_RDWR|O_NONBLOCK|O_LARGEFILE)
getpid()                                = 4905
dup(0)                                  = 5
dup(1)                                  = 6
dup(2)                                  = 7


For 7.7p1:

openat(AT_FDCWD, "/dev/net/tun", O_RDWR) = 4
ioctl(4, TUNSETIFF, 0x7ffcb8813710)     = 0
close(4)                                = 0
write(2, "Tunnel device open failed.\r\n", 28Tunnel device open
failed.
) = 28
write(2, "Could not request tunnel forward"..., 38Could not request
tunnel forwarding.
) = 38
dup(0)                                  = 4
dup(1)                                  = 5
dup(2)                                  = 6

Reproducible at will on this box running arch linux with kernel 4.16.6
(same bug also experienced on 4.16.4).
Upgrading or downgrading openssh takes seconds.

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--- Comment #1 from calimeroteknik at free.fr ---
The problem disappears if I erase this block of code that was added.

In function sys_tun_open() for SSH_TUN_LINUX:

Location :
(absent)  openssh-7.6p1/openbsd-compat/port-tun.c:101
(present) openssh-7.7p1/openbsd-compat/port-net.c:188

if (ifname != NULL && (*ifname = strdup(ifr.ifr_name)))
        goto failed;


For some reason I have "Could not request tunnel forwarding." in the
console but that's spurious, everything works perfectly.


I replaced the above with :

printf("one, *ifname=%s, ifname=%p\n", *ifname, ifname);

if (ifname != NULL && (*ifname = strdup(ifr.ifr_name))) {
        printf("two, *ifname=%s, ifname=%p\n", *ifname, ifname);
        goto failed;
}

I get this in the output of ssh:
one, *ifname=(null), ifname=0x7ffec28c5dc0
two, *ifname=tun0, ifname=0x7ffec28c5dc0

I'm not sure what should be happening, but this cripples tunnel for me.

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Jakub Jelen <jjelen at redhat.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |jjelen at redhat.com
         Resolution|---                         |DUPLICATE

--- Comment #2 from Jakub Jelen <jjelen at redhat.com> ---
Already fixed in both master and the 7_7 branch:

https://github.com/openssh/openssh-portable/commit/b81b2d120e9c8a83489e241620843687758925ad

*** This bug has been marked as a duplicate of bug 2855 ***

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED

--- Comment #3 from Damien Miller <djm at mindrot.org> ---
Close RESOLVED bugs with the release of openssh-8.0

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