> However, Focal (which uses klibc 2.0.7) uses dhclient for networking initialization instead of ipconfig...
If no users in Focal could be affected by the bug then I'm fine with accepting the fix to Bionic only. But could you please expand on the above statement? Under what conditions does Focal use dhclient instead of ipconfig? Presumably through initramfs-tools and ip=/ip6=? Are there any other situations where users could reasonably be using klibc/ipconfig on Focal? Is it possible for them to be doing this but not using initramfs-tools? It would help me understand if you could present a complete user story to explain the user impact. Right now the bug description doesn't explain the full scenario under which they would be impacted by this bug. > [Where problems could occur] I don't think you've really answered this question. What different scenarios, from a user perspective (ie. user stories), can reasonably be predicted that will hit this ipconfig DHCP-related timeout case? -- You received this bug notification because you are a member of STS Sponsors, which is subscribed to the bug report. 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: In Progress Bug description: [Impact] In some cases, ipconfig can take a longer time than the user-specified timeouts, causing unexpected delays. [Test Plan] 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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/klibc/+bug/1947099/+subscriptions -- Mailing list: https://launchpad.net/~sts-sponsors Post to : sts-sponsors@lists.launchpad.net Unsubscribe : https://launchpad.net/~sts-sponsors More help : https://help.launchpad.net/ListHelp
