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[Uqbar <1593657@xxxxxxxxxxxxxxxxxx>]

I added a couple of extra debugging lines in mux.c, recompiled and ran
it.

debug3: link( "/tmp/sshcontrol-f1b458a85cd2aa9d5c115abc12afee9f485ad6b0.XSLUj2BsBSDnTkhZ","/tmp/sshcontrol-f1b458a85cd2aa9d5c115abc12afee9f485ad6b0" ): 0
debug3: unlink( "/tmp/sshcontrol-f1b458a85cd2aa9d5c115abc12afee9f485ad6b0.XSLUj2BsBSDnTkhZ" ): 0

The ": 0" is the value of the int returned by the two calls. They are
successful according to LINK(3POSIX) and UNLINK(3POSIX).

Seth Arnold is right. OpenSSH is doing the things in the right way.

But somehow the kernel (or could it be the libc?) is messing stuff
around with link() and/or unlink().

** Changed in: linux (Ubuntu)
       Status: Opinion => Confirmed

** Changed in: openssh (Ubuntu)
       Status: Opinion => Invalid

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https://bugs.launchpad.net/bugs/1593657

Title:
  ControlPath unix socket is created in a weird way

Status in linux package in Ubuntu:
  Confirmed
Status in openssh package in Ubuntu:
  Invalid

Bug description:
  STEPS.

  1. Create a ControlPath socket with something like "-o ControlPath=/tmp/sshcontrol-%C" during an SSH connection.
  2. Check with ls the socket is there. I am getting

  srw------- 1 enzo enzo  0 2016-06-17 10:17:21 sshcontrol-
  369d1187d3900c559f063f947218528001d0e705

  3. Ask lsof who's that socket belonging to:

  lsof /tmp/sshcontrol-369d1187d3900c559f063f947218528001d0e705

  4. Ask lsof the same but with grep

  lsof | grep /tmp/sshcontrol-369d1187d3900c559f063f947218528001d0e705

  ACTUAL RESULTS.
  For step no. 3 I am getting nothing (but the WARNING about /sys/kernel/debug/tracing)
  For step no. 4 I am getting:

  [enzo@Feynman ~] lsof | grep /tmp/sshcontrol-369d1187d3900c559f063f947218528001d0e705
  lsof: WARNING: can't stat() tracefs file system /sys/kernel/debug/tracing
        Output information may be incomplete.
  ssh       10667             enzo    4u     unix 0x0000000000000000       0t0     173813 /tmp/sshcontrol-369d1187d3900c559f063f947218528001d0e705.NDScoG3mgs0mWc4q type=STREAM

  Where you can see clearly that the socket name has a trailing part
  ".NDScoG3mgs0mWc4q".

  EXTRA STEP.
  5. Ask lsof about the socket with the extended name

  EXTRA RESULT

  [enzo@Feynman ~] lsof /tmp/sshcontrol-369d1187d3900c559f063f947218528001d0e705.NDScoG3mgs0mWc4q
  lsof: WARNING: can't stat() tracefs file system /sys/kernel/debug/tracing
        Output information may be incomplete.
  lsof: status error on /tmp/sshcontrol-369d1187d3900c559f063f947218528001d0e705.NDScoG3mgs0mWc4q: No such file or directory
  lsof 4.89
   latest revision: ftp://lsof.itap.purdue.edu/pub/tools/unix/lsof/
   latest FAQ: ftp://lsof.itap.purdue.edu/pub/tools/unix/lsof/FAQ
   latest man page: ftp://lsof.itap.purdue.edu/pub/tools/unix/lsof/lsof_man
   usage: [-?abhKlnNoOPRtUvVX] [+|-c c] [+|-d s] [+D D] [+|-E] [+|-e s] [+|-f[gG]]
   [-F [f]] [-g [s]] [-i [i]] [+|-L [l]] [+m [m]] [+|-M] [-o [o]] [-p s]
   [+|-r [t]] [-s [p:s]] [-S [t]] [-T [t]] [-u s] [+|-w] [-x [fl]] [--] [names]
  Use the ``-h'' option to get more help information.

  
  EXPECTED RESULT
  A reasonable output from lsof detailing the real and actual unix socket.

  SOURCES

  man 5 ssh_config at the section "ControlPath"

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: openssh-client 1:7.2p2-4ubuntu1
  Uname: Linux 4.4.13-040413-lowlatency x86_64
  NonfreeKernelModules: rfcomm ipt_REJECT nf_reject_ipv4 pci_stub vboxpci vboxnetadp vboxnetflt vboxdrv bnep btusb btrtl btbcm btintel xt_multiport iptable_filter ip_tables x_tables 8812au ath3k cfg80211 bluetooth uas usb_storage input_leds hp_wmi sparse_keymap snd_hda_codec_realtek snd_hda_codec_generic intel_rapl x86_pkg_temp_thermal intel_powerclamp snd_hda_intel coretemp snd_hda_codec kvm_intel snd_hda_core kvm snd_hwdep snd_pcm irqbypass crct10dif_pclmul crc32_pclmul aesni_intel snd_seq_midi aes_x86_64 snd_seq_midi_event lrw snd_rawmidi gf128mul glue_helper ablk_helper cryptd snd_seq snd_seq_device serio_raw snd_timer mei_me snd mei soundcore shpchp lpc_ich 8250_fintek mac_hid parport_pc ppdev lp parport autofs4 xfs raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 multipath linear hid_generic usbhid hid raid0 i915 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimgblt psmouse ahci fb_sys_fops libahci drm r8169 mii wmi fjes video
  ApportVersion: 2.20.1-0ubuntu2.1
  Architecture: amd64
  CurrentDesktop: KDE
  Date: Fri Jun 17 11:49:04 2016
  InstallationDate: Installed on 2016-04-22 (55 days ago)
  InstallationMedia: Kubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
  RelatedPackageVersions:
   ssh-askpass       N/A
   libpam-ssh        N/A
   keychain          N/A
   ssh-askpass-gnome N/A
  SSHClientVersion: OpenSSH_7.2p2 Ubuntu-4ubuntu1, OpenSSL 1.0.2g-fips  1 Mar 2016
  SourcePackage: openssh
  UpgradeStatus: No upgrade log present (probably fresh install)

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