[Bug 300151] [NEW] ssh slow during logon, when ENTERING INTERACTIVE SESSION

[ichudov]

Public bug reported:

I am using a Ubuntu Intrepid 32 bit server with all latest patches.

Logging on via ssh (USING KEYS) is incredibly, painfully slow.

I have done some investigation.

1. Slowness is mild after a reboot and, as time goes on, it becomes
progressively slower and sloowweerr and ssslllooowwweeerrrr.

2. If I run ssh -v, then I can see that the ssh process is stuck for
many seconds after saying "entering interactive session".

3. This even happens if I do, from that server, a command "ssh
localhost".

4. Disabling GSSAPI authentication, as well as saying "UseDNS no", in
sshd_config, does not help.

5. A similar problems applies to use of "su" and can be more easily
debugged. If, as root, I say "su - <username> date", it is also
incredibly slow. If I debug that with

  strace -o q -f su - <myuserid> date

then I see that su tries to connect to UNIX socket
/var/run/dbus/system_bus_socket, and then it is stuck doing poll(),
which remains <unfinished>. Not sure if it is related, but it could be.

munmap(0x7f21ab91a000, 2970)            = 0
close(4)                                = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 4
connect(4, {sa_family=AF_FILE, path="/var/run/dbus/system_bus_socket"}, 33) = 0
fcntl(4, F_GETFL)                       = 0x2 (flags O_RDWR)
fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK)    = 0
fcntl(4, F_GETFD)                       = 0
fcntl(4, F_SETFD, FD_CLOEXEC)           = 0
geteuid()                               = 0
poll([{fd=4, events=POLLOUT, revents=POLLOUT}], 1, 0) = 1
write(4, "\0", 1)                       = 1
write(4, "AUTH EXTERNAL 30\r\n", 18)    = 18
poll([{fd=4, events=POLLIN, revents=POLLIN}], 1, -1) = 1
read(4, "OK 951631a86cc350048c747bce491f8"..., 2048) = 37
poll([{fd=4, events=POLLOUT, revents=POLLOUT}], 1, -1) = 1
write(4, "BEGIN\r\n", 7)                = 7
poll([{fd=4, events=POLLIN|POLLOUT, revents=POLLOUT}], 1, -1) = 1
writev(4, [{"l\1\0\1\0\0\0\0\1\0\0\0n\0\0\0\1\1o\0\25\0\0\0/org/fre"..., 128}, {"", 0}], 2) = 128
gettimeofday({1227143564, 211248}, NULL) = 0
poll([{fd=4, events=POLLIN, revents=POLLIN}], 1, 25000) = 1
read(4, "l\2\1\1\r\0\0\0\1\0\0\0E\0\0\0\6\1s\0\10\0\0\0:1.28259"..., 2048) = 282
read(4, 0x24686e0, 2048)                = -1 EAGAIN (Resource temporarily unavailable)
writev(4, [{"l\1\0\1\304\0\0\0\2\0\0\0\273\0\0\0\1\1o\0#\0\0\0/org/"..., 208}, {"\274\0\0\0\0\0\0\0\t\0\0\0unix-user\0\1i\0\0\0\0\350\3"..., 196}], 2) = 404
gettimeofday({1227143564, 213048}, NULL) = 0
poll(

** Affects: openssh (Ubuntu)
     Importance: Undecided
         Status: New

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ssh slow during logon, when ENTERING INTERACTIVE SESSION
https://bugs.launchpad.net/bugs/300151
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