[PATCH v2 1/4] tests/vm: Set UseDNS=no in the sshd configuration

[Ilya Leoshkevich <iii@linux.ibm.com>]

make vm-build-freebsd sometimes fails with "Connection timed out during
banner exchange". The client strace shows:

    13:59:30 write(3, "SSH-2.0-OpenSSH_9.3\r\n", 21) = 21
    13:59:30 getpid()                       = 252655
    13:59:30 poll([{fd=3, events=POLLIN}], 1, 5000) = 1 ([{fd=3, revents=POLLIN}])
    13:59:32 read(3, "S", 1)                = 1
    13:59:32 poll([{fd=3, events=POLLIN}], 1, 3625) = 1 ([{fd=3, revents=POLLIN}])
    13:59:32 read(3, "S", 1)                = 1
    13:59:32 poll([{fd=3, events=POLLIN}], 1, 3625) = 1 ([{fd=3, revents=POLLIN}])
    13:59:32 read(3, "H", 1)                = 1

There is a 2s delay during connection, and ConnectTimeout is set to 1.
Raising it makes the issue go away, but we can do better. The server
truss shows:

    888: 27.811414714 socket(PF_INET,SOCK_DGRAM|SOCK_CLOEXEC,0) = 5 (0x5)
    888: 27.811765030 connect(5,{ AF_INET 10.0.2.3:53 },16) = 0 (0x0)
    888: 27.812166941 sendto(5,"\^Z/\^A\0\0\^A\0\0\0\0\0\0\^A2"...,39,0,NULL,0) = 39 (0x27)
    888: 29.363970743 poll({ 5/POLLRDNORM },1,5000) = 1 (0x1)

So the delay is due to a DNS query. Disable DNS queries in the server
config.

Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 tests/vm/basevm.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tests/vm/basevm.py b/tests/vm/basevm.py
index 61725b83254..c0d62c08031 100644
--- a/tests/vm/basevm.py
+++ b/tests/vm/basevm.py
@@ -396,60 +396,62 @@ def console_consume(self):
             self.console_log(output)
         vm.console_socket.setblocking(1)
 
     def console_send(self, command):
         vm = self._guest
         if self.debug:
             logline = re.sub("\n", "<enter>", command)
             logline = re.sub("[\x00-\x1f]", ".", logline)
             sys.stderr.write("con send: %s\n" % logline)
         for char in list(command):
             vm.console_socket.send(char.encode("utf-8"))
             time.sleep(0.01)
 
     def console_wait_send(self, wait, command):
         self.console_wait(wait)
         self.console_send(command)
 
     def console_ssh_init(self, prompt, user, pw):
         sshkey_cmd = "echo '%s' > .ssh/authorized_keys\n" \
                      % self._config['ssh_pub_key'].rstrip()
         self.console_wait_send("login:",    "%s\n" % user)
         self.console_wait_send("Password:", "%s\n" % pw)
         self.console_wait_send(prompt,      "mkdir .ssh\n")
         self.console_wait_send(prompt,      sshkey_cmd)
         self.console_wait_send(prompt,      "chmod 755 .ssh\n")
         self.console_wait_send(prompt,      "chmod 644 .ssh/authorized_keys\n")
 
     def console_sshd_config(self, prompt):
         self.console_wait(prompt)
         self.console_send("echo 'PermitRootLogin yes' >> /etc/ssh/sshd_config\n")
+        self.console_wait(prompt)
+        self.console_send("echo 'UseDNS no' >> /etc/ssh/sshd_config\n")
         for var in self.envvars:
             self.console_wait(prompt)
             self.console_send("echo 'AcceptEnv %s' >> /etc/ssh/sshd_config\n" % var)
 
     def print_step(self, text):
         sys.stderr.write("### %s ...\n" % text)
 
     def wait_ssh(self, wait_root=False, seconds=300, cmd="exit 0"):
         # Allow more time for VM to boot under TCG.
         if not kvm_available(self.arch):
             seconds *= self.tcg_timeout_multiplier
         starttime = datetime.datetime.now()
         endtime = starttime + datetime.timedelta(seconds=seconds)
         cmd_success = False
         while datetime.datetime.now() < endtime:
             if wait_root and self.ssh_root(cmd) == 0:
                 cmd_success = True
                 break
             elif self.ssh(cmd) == 0:
                 cmd_success = True
                 break
             seconds = (endtime - datetime.datetime.now()).total_seconds()
             logging.debug("%ds before timeout", seconds)
             time.sleep(1)
         if not cmd_success:
             raise Exception("Timeout while waiting for guest ssh")
 
     def shutdown(self):
         self._guest.shutdown(timeout=self._shutdown_timeout)
 
-- 
2.43.0