I've tested the package from -proposed and I can confirm it fixes the
problem:
Installed from -proposed:
root@ubuntu:~# apt-cache policy klibc-utils
klibc-utils:
Installed: 2.0.4-9ubuntu2.2
Candidate: 2.0.4-9ubuntu2.18.04.1
Version table:
2.0.4-9ubuntu2.18.04.1 500
500 http://ppa.launchpad.net/mfo/lp1947099/ubuntu bionic/main amd64
Packages
*** 2.0.4-9ubuntu2.2 500
500 http://archive.ubuntu.com/ubuntu bionic-proposed/main amd64 Packages
100 /var/lib/dpkg/status
2.0.4-9ubuntu2.1 500
500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
500 http://security.ubuntu.com/ubuntu bionic-security/main amd64
Packages
2.0.4-9ubuntu2 500
500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages
Working well without timeout:
root@ubuntu:~# ip l set dev ens9 down
root@ubuntu:~# date; /usr/lib/klibc/bin/ipconfig ens9; date
Thu May 12 12:54:48 UTC 2022
IP-Config: ens9 hardware address 52:54:00:f3:4e:0e mtu 1500 DHCP RARP
IP-Config: ens9 complete (dhcp from 192.168.150.2):
address: 192.168.150.105 broadcast: 192.168.150.255 netmask: 255.255.255.0
gateway: 192.168.150.1 dns0 : 192.168.150.2 dns1 : 0.0.0.0
domain : sts.lab
rootserver: 192.168.150.2 rootpath:
filename :
Thu May 12 12:55:01 UTC 2022
Timeout being honored:
root@ubuntu:~# ip l set dev ens9 down
root@ubuntu:~# date; /usr/lib/klibc/bin/ipconfig -t 2 ens9; date
Thu May 12 12:55:44 UTC 2022
IP-Config: ens9 hardware address 52:54:00:f3:4e:0e mtu 1500 DHCP RARP
Lowered timeout to match user request = (2 s)
IP-Config: no response after 2 secs - giving up
Thu May 12 12:55:46 UTC 2022
Testing the original issue (timeout being ignored when not receiving any reply
from a DHCP Server), which is now also getting honored:
root@ubuntu:~# ip l set dev ens9 down
root@ubuntu:~# date; /usr/lib/klibc/bin/ipconfig -t 2 ens9; date
Thu May 12 12:56:32 UTC 2022
IP-Config: ens9 hardware address 52:54:00:f3:4e:0e mtu 1500 DHCP RARP
Lowered timeout to match user request = (2 s)
IP-Config: no response after 2 secs - giving up
Thu May 12 12:56:34 UTC 2022
root@ubuntu:~# ip l set dev ens9 down
root@ubuntu:~# date; /usr/lib/klibc/bin/ipconfig -t 5 ens9; date
Thu May 12 12:56:43 UTC 2022
IP-Config: ens9 hardware address 52:54:00:f3:4e:0e mtu 1500 DHCP RARP
Lowered timeout to match user request = (5 s)
IP-Config: no response after 5 secs - giving up
Thu May 12 12:56:48 UTC 2022
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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:
Won't Fix
Status in klibc source package in Bionic:
Fix Committed
Bug description:
[Impact]
In some cases, ipconfig can take a longer time than the user-specified
timeouts, causing unexpected delays.
[Test Plan]
[racb: pending agreement with the SRU team; please see comment 37]
Any situation where ipconfig encounters an error sending the DHCP
packet, it will automatically set a delay of 10 seconds, which could
be longer than the user-specified timeout. It can be reproduced by
creating a dummy interface and attempting to run ipconfig on it with a
timeout value of less than 10:
# ip link add eth1 type dummy
# date; /usr/lib/klibc/bin/ipconfig -t 2 eth1; date
Thu Nov 18 04:46:13 EST 2021
IP-Config: eth1 hardware address ae:e0:f5:9d:7e:00 mtu 1500 DHCP RARP
IP-Config: no response after 2 secs - giving up
Thu Nov 18 04:46:23 EST 2021
^ Notice above, ipconfig thinks that it waited 2 seconds, but the
timestamps show an actual delay of 10 seconds.
[Where problems could occur]
Please see reproduction steps above. We are seeing this in production too
(see comment #2).
[Other Info]
A patch to fix the issue is being proposed here. It is a safe fix - it only
checks before going into sleep that the timeout never exceeds the
user-requested value.
[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.
[ Regression potential ]
This change ensures that user-specified timeouts are never exceeded, which is
a problem that appears to happen only in case of interface errors.
It may be that someone is relying on current behaviour where they receive
DHCP offers after their specified timeout (but within the 10-second error
timeout). However, 1) that is buggy behaviour and should be exposed. Such a
user would need to update their specified timeout to make it long enough to
receive the DHCP offer (setting the timeout to 10 would keep the existing
behaviour). 2) I think it is unlikely that such a scenario exists at all. The
10-second timeout problem happens when there are problems with the interface
that prevent it from even sending out the DHCP request. I think it is very
unlikely (or even, impossible) that DHCP offers would be received on a dead
interface.
Based on the above points, I consider the regression potential to be
very low for this change. I do not expect anyone who is currently
using ipconfig successfully to notice this change.
I believe the only difference introduced by this is the reduction of
delays caused by dead or problematic network interfaces. Those error
delays are shortened such that they never exceeed user-specified
timeouts.
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https://bugs.launchpad.net/ubuntu/+source/klibc/+bug/1947099/+subscriptions
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