[Bug 1947099] Re: ipconfig does not honour user-requested timeouts in some cases

[Eric Desrochers]

Khaled El Mously (kmously),

Thanks for the update. I'll review this and talk with sil2100, an SRU
verification member.

Could you please help to fill the SRU template in the description above.
Extra documentations can be found here: https://wiki.ubuntu.com/StableReleaseUpdates#SRU_Bug_Template

What make Bionic more susceptible to this particular problem ? Bionic
kernel version in use ? else ?

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https://bugs.launchpad.net/bugs/1947099

Title:
  ipconfig does not honour user-requested timeouts in some cases

Status in klibc package in Ubuntu:
  New
Status in klibc source package in Bionic:
  New

Bug description:
  ** SRU TEMPLATE DRAFT **

  [Impact]

  
  [Test Plan]

  
  [Where problems could occur]

  
  [Other Info]

  
  [Original Description]

  In some cases, ipconfig can take longer than the user-specified
  timeouts, causing unexpected delays.

  in main.c, in function loop(), the process can go into
  process_timeout_event() (or process_receive_event() ) and if it
  encounters an error situation, will set an attempt to "try again
  later" at time equal now + 10 seconds by setting

  s->expire = now + 10;

  This can happen at any time during the main event loop, which can end
  up extending the user-specified timeout if "now + 10" is greater than
  "start_time + user-specified-timeout".

  I believe a patch like the following is needed to avoid this problem:

  --- a/usr/kinit/ipconfig/main.c
  +++ b/usr/kinit/ipconfig/main.c
  @@ -437,6 +437,13 @@ static int loop(void)

                          if (timeout > s->expire - now.tv_sec)
                                  timeout = s->expire - now.tv_sec;
  +
  +                       /* Compensate for already-lost time */
  +                       gettimeofday(&now, NULL);
  +                       if (now.tv_sec + timeout > start + loop_timeout) {
  +                               timeout = loop_timeout - (now.tv_sec - start);
  +                               printf("Lowered timeout to match user request = (%d s) \n", timeout);
  +                       }
                  }

  I believe the current behaviour is buggy. This is confirmed when the
  following line is executed:

                          if (loop_timeout >= 0 &&
                              now.tv_sec - start >= loop_timeout) {
                                  printf("IP-Config: no response after %d "
                                         "secs - giving up\n", loop_timeout);
                                  rc = -1;
                                  goto bail;
                          }

  'loop_timeout' is the user-specified time-out. With a value of 2, in
  case of error, this line prints:

  IP-Config: no response after 2 secs - giving up

  So it thinks that it waited 2 seconds - however, in reality it had
  actually waited for 10 seconds.

  The suggested code-change ensures that the timeout that is actually
  used never exceeds the user-specified timeout.

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