Clear DNS configuration received from DHCP during networking reconfiguration in Linux. #13516

oleksandrivantsiv · 2023-01-25T19:03:04Z

Why I did it

When the management interface IP address configuration changes from dynamic to static the DNS configuration (retrieved from the DHCP server) in /etc/resolv.conf remains uncleared. This leads to a DNS configuration pointing to the wrong nameserver. To make the behavior clear DNS configuration received from DHCP should be cleared.

How I did it

Use resolvconf package for managing DNS configuration. It is capable of tracking the source of DNS configuration and puts the configuration retrieved from the DHCP servers into a separate file. This allows the implementation of DNS configuration cleanup retrieved from DHCP during networking reconfiguration.

How to verify it

Ensure that the management interface has no static configuration.
Check that /etc/resolv.conf has DNS configuration.
Configure a static IP address on the management interface.
Verify that /etc/resolv.conf has no DNS configuration.
Remove the static IP address from the management interface.
Verify that /etc/resolv.conf has DNS configuration retrieved form DHCP server.

Which release branch to backport (provide reason below if selected)

Description for the changelog

Ensure to add label/tag for the feature raised. example - PR#2174 under sonic-utilities repo. where, Generic Config and Update feature has been labelled as GCU.

Link to config_db schema for YANG module changes

A picture of a cute animal (not mandatory but encouraged)

…n to static.

liat-grozovik · 2023-01-30T07:06:07Z

@qiluo-msft could you please review or assign someone?

mssonicbld · 2023-02-02T19:28:36Z

@oleksandrivantsiv PR conflicts with 202205 branch

Go's runtime (and dockerd inherits this) uses own DNS resolver implementation by default on Linux. It has been observed that there are some DNS resolution issues when executing ```docker pull``` after first boot. Consider the following script: ``` admin@r-boxer-sw01:~$ while :; do date; cat /etc/resolv.conf; ping -c 1 harbor.mellanox.com; docker pull harbor.mellanox.com/sonic/cpu-report:1.0.0 ; sleep 1; done Fri 03 Feb 2023 10:06:22 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.99 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.989/5.989/5.989/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:57245->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:23 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.56 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.561/5.561/5.561/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:53299->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:24 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.78 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.783/5.783/5.783/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:55765->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:25 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=7.17 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 7.171/7.171/7.171/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:44877->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:26 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.66 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.656/5.656/5.656/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:54604->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:27 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=8.22 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 8.223/8.223/8.223/0.000 ms 1.0.0: Pulling from sonic/cpu-report 004f1eed87df: Downloading [===================> ] 19.3MB/50.43MB 5d6f1e8117db: Download complete 48c2faf66abe: Download complete 234b70d0479d: Downloading [=========> ] 9.363MB/51.84MB 6fa07a00e2f0: Downloading [==> ] 9.51MB/192.4MB 04a31b4508b8: Waiting e11ae5168189: Waiting 8861a99744cb: Waiting d59580d95305: Waiting 12b1523494c1: Waiting d1a4b09e9dbc: Waiting 99f41c3f014f: Waiting ``` While /etc/resolv.conf has the correct content and ping (and any other utility that uses libc's DNS resolution implementation) works correctly docker is unable to resolve the hostname and falls back to default [::1]:53. This started to happen after PR sonic-net#13516 has been merged. As you can see from the log, dockerd is able to pick up the correct /etc/resolv.conf only after 5 sec since first try. This seems to be somehow related to the logic in Go's DNS resolver https://github.com/golang/go/blob/master/src/net/dnsclient_unix.go#L385. There have been issues like that reported in docker like: - docker/cli#2299 - docker/cli#2618 - moby/moby#22398 Since this starts to happen after inclusion of resolvconf package by above mentioned PR and the fact I can't see any problem with that (ping, nslookup, etc. works) the choice is made to force dockerd to use cgo (libc) resolver. Signed-off-by: Stepan Blyschak <[email protected]>

…uration in Linux. (sonic-net#13516) - Why I did it fixes sonic-net#12907 When the management interface IP address configuration changes from dynamic to static the DNS configuration (retrieved from the DHCP server) in /etc/resolv.conf remains uncleared. This leads to a DNS configuration pointing to the wrong nameserver. To make the behavior clear DNS configuration received from DHCP should be cleared. - How I did it Use resolvconf package for managing DNS configuration. It is capable of tracking the source of DNS configuration and puts the configuration retrieved from the DHCP servers into a separate file. This allows the implementation of DNS configuration cleanup retrieved from DHCP during networking reconfiguration. - How to verify it Ensure that the management interface has no static configuration. Check that /etc/resolv.conf has DNS configuration. Configure a static IP address on the management interface. Verify that /etc/resolv.conf has no DNS configuration. Remove the static IP address from the management interface. Verify that /etc/resolv.conf has DNS configuration retrieved form DHCP server.

mssonicbld · 2023-02-06T13:10:11Z

Cherry-pick PR to 202211: #13686

…uration in Linux. (sonic-net#13516) - Why I did it fixes sonic-net#12907 When the management interface IP address configuration changes from dynamic to static the DNS configuration (retrieved from the DHCP server) in /etc/resolv.conf remains uncleared. This leads to a DNS configuration pointing to the wrong nameserver. To make the behavior clear DNS configuration received from DHCP should be cleared. - How I did it Use resolvconf package for managing DNS configuration. It is capable of tracking the source of DNS configuration and puts the configuration retrieved from the DHCP servers into a separate file. This allows the implementation of DNS configuration cleanup retrieved from DHCP during networking reconfiguration. - How to verify it Ensure that the management interface has no static configuration. Check that /etc/resolv.conf has DNS configuration. Configure a static IP address on the management interface. Verify that /etc/resolv.conf has no DNS configuration. Remove the static IP address from the management interface. Verify that /etc/resolv.conf has DNS configuration retrieved form DHCP server.

…uration in Linux. (#13516) (#13695) - Why I did it fixes #12907 When the management interface IP address configuration changes from dynamic to static the DNS configuration (retrieved from the DHCP server) in /etc/resolv.conf remains uncleared. This leads to a DNS configuration pointing to the wrong nameserver. To make the behavior clear DNS configuration received from DHCP should be cleared. - How I did it Use resolvconf package for managing DNS configuration. It is capable of tracking the source of DNS configuration and puts the configuration retrieved from the DHCP servers into a separate file. This allows the implementation of DNS configuration cleanup retrieved from DHCP during networking reconfiguration. - How to verify it Ensure that the management interface has no static configuration. Check that /etc/resolv.conf has DNS configuration. Configure a static IP address on the management interface. Verify that /etc/resolv.conf has no DNS configuration. Remove the static IP address from the management interface. Verify that /etc/resolv.conf has DNS configuration retrieved form DHCP server.

Go's runtime (and dockerd inherits this) uses own DNS resolver implementation by default on Linux. It has been observed that there are some DNS resolution issues when executing ```docker pull``` after first boot. Consider the following script: ``` admin@r-boxer-sw01:~$ while :; do date; cat /etc/resolv.conf; ping -c 1 harbor.mellanox.com; docker pull harbor.mellanox.com/sonic/cpu-report:1.0.0 ; sleep 1; done Fri 03 Feb 2023 10:06:22 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.99 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.989/5.989/5.989/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:57245->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:23 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.56 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.561/5.561/5.561/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:53299->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:24 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.78 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.783/5.783/5.783/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:55765->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:25 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=7.17 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 7.171/7.171/7.171/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:44877->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:26 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.66 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.656/5.656/5.656/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:54604->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:27 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=8.22 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 8.223/8.223/8.223/0.000 ms 1.0.0: Pulling from sonic/cpu-report 004f1eed87df: Downloading [===================> ] 19.3MB/50.43MB 5d6f1e8117db: Download complete 48c2faf66abe: Download complete 234b70d0479d: Downloading [=========> ] 9.363MB/51.84MB 6fa07a00e2f0: Downloading [==> ] 9.51MB/192.4MB 04a31b4508b8: Waiting e11ae5168189: Waiting 8861a99744cb: Waiting d59580d95305: Waiting 12b1523494c1: Waiting d1a4b09e9dbc: Waiting 99f41c3f014f: Waiting ``` While /etc/resolv.conf has the correct content and ping (and any other utility that uses libc's DNS resolution implementation) works correctly docker is unable to resolve the hostname and falls back to default [::1]:53. This started to happen after PR #13516 has been merged. As you can see from the log, dockerd is able to pick up the correct /etc/resolv.conf only after 5 sec since first try. This seems to be somehow related to the logic in Go's DNS resolver https://github.com/golang/go/blob/master/src/net/dnsclient_unix.go#L385. There have been issues like that reported in docker like: - docker/cli#2299 - docker/cli#2618 - moby/moby#22398 Since this starts to happen after inclusion of resolvconf package by above mentioned PR and the fact I can't see any problem with that (ping, nslookup, etc. works) the choice is made to force dockerd to use cgo (libc) resolver. Signed-off-by: Stepan Blyschak <[email protected]>

…uration in Linux. (#13516) - Why I did it fixes #12907 When the management interface IP address configuration changes from dynamic to static the DNS configuration (retrieved from the DHCP server) in /etc/resolv.conf remains uncleared. This leads to a DNS configuration pointing to the wrong nameserver. To make the behavior clear DNS configuration received from DHCP should be cleared. - How I did it Use resolvconf package for managing DNS configuration. It is capable of tracking the source of DNS configuration and puts the configuration retrieved from the DHCP servers into a separate file. This allows the implementation of DNS configuration cleanup retrieved from DHCP during networking reconfiguration. - How to verify it Ensure that the management interface has no static configuration. Check that /etc/resolv.conf has DNS configuration. Configure a static IP address on the management interface. Verify that /etc/resolv.conf has no DNS configuration. Remove the static IP address from the management interface. Verify that /etc/resolv.conf has DNS configuration retrieved form DHCP server.

Go's runtime (and dockerd inherits this) uses own DNS resolver implementation by default on Linux. It has been observed that there are some DNS resolution issues when executing ```docker pull``` after first boot. Consider the following script: ``` admin@r-boxer-sw01:~$ while :; do date; cat /etc/resolv.conf; ping -c 1 harbor.mellanox.com; docker pull harbor.mellanox.com/sonic/cpu-report:1.0.0 ; sleep 1; done Fri 03 Feb 2023 10:06:22 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.99 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.989/5.989/5.989/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:57245->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:23 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.56 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.561/5.561/5.561/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:53299->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:24 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.78 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.783/5.783/5.783/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:55765->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:25 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=7.17 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 7.171/7.171/7.171/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:44877->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:26 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.66 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.656/5.656/5.656/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:54604->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:27 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=8.22 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 8.223/8.223/8.223/0.000 ms 1.0.0: Pulling from sonic/cpu-report 004f1eed87df: Downloading [===================> ] 19.3MB/50.43MB 5d6f1e8117db: Download complete 48c2faf66abe: Download complete 234b70d0479d: Downloading [=========> ] 9.363MB/51.84MB 6fa07a00e2f0: Downloading [==> ] 9.51MB/192.4MB 04a31b4508b8: Waiting e11ae5168189: Waiting 8861a99744cb: Waiting d59580d95305: Waiting 12b1523494c1: Waiting d1a4b09e9dbc: Waiting 99f41c3f014f: Waiting ``` While /etc/resolv.conf has the correct content and ping (and any other utility that uses libc's DNS resolution implementation) works correctly docker is unable to resolve the hostname and falls back to default [::1]:53. This started to happen after PR sonic-net#13516 has been merged. As you can see from the log, dockerd is able to pick up the correct /etc/resolv.conf only after 5 sec since first try. This seems to be somehow related to the logic in Go's DNS resolver https://github.com/golang/go/blob/master/src/net/dnsclient_unix.go#L385. There have been issues like that reported in docker like: - docker/cli#2299 - docker/cli#2618 - moby/moby#22398 Since this starts to happen after inclusion of resolvconf package by above mentioned PR and the fact I can't see any problem with that (ping, nslookup, etc. works) the choice is made to force dockerd to use cgo (libc) resolver. Signed-off-by: Stepan Blyschak <[email protected]>

Go's runtime (and dockerd inherits this) uses own DNS resolver implementation by default on Linux. It has been observed that there are some DNS resolution issues when executing ```docker pull``` after first boot. Consider the following script: ``` admin@r-boxer-sw01:~$ while :; do date; cat /etc/resolv.conf; ping -c 1 harbor.mellanox.com; docker pull harbor.mellanox.com/sonic/cpu-report:1.0.0 ; sleep 1; done Fri 03 Feb 2023 10:06:22 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.99 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.989/5.989/5.989/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:57245->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:23 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.56 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.561/5.561/5.561/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:53299->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:24 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.78 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.783/5.783/5.783/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:55765->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:25 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=7.17 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 7.171/7.171/7.171/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:44877->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:26 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=5.66 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 5.656/5.656/5.656/0.000 ms Error response from daemon: Get "https://harbor.mellanox.com/v2/": dial tcp: lookup harbor.mellanox.com on [::1]:53: read udp [::1]:54604->[::1]:53: read: connection refused Fri 03 Feb 2023 10:06:27 AM UTC nameserver 10.211.0.124 nameserver 10.211.0.121 nameserver 10.7.77.135 search mtr.labs.mlnx labs.mlnx mlnx lab.mtl.com mtl.com PING harbor.mellanox.com (10.7.1.117) 56(84) bytes of data. 64 bytes from harbor.mtl.labs.mlnx (10.7.1.117): icmp_seq=1 ttl=53 time=8.22 ms --- harbor.mellanox.com ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 8.223/8.223/8.223/0.000 ms 1.0.0: Pulling from sonic/cpu-report 004f1eed87df: Downloading [===================> ] 19.3MB/50.43MB 5d6f1e8117db: Download complete 48c2faf66abe: Download complete 234b70d0479d: Downloading [=========> ] 9.363MB/51.84MB 6fa07a00e2f0: Downloading [==> ] 9.51MB/192.4MB 04a31b4508b8: Waiting e11ae5168189: Waiting 8861a99744cb: Waiting d59580d95305: Waiting 12b1523494c1: Waiting d1a4b09e9dbc: Waiting 99f41c3f014f: Waiting ``` While /etc/resolv.conf has the correct content and ping (and any other utility that uses libc's DNS resolution implementation) works correctly docker is unable to resolve the hostname and falls back to default [::1]:53. This started to happen after PR #13516 has been merged. As you can see from the log, dockerd is able to pick up the correct /etc/resolv.conf only after 5 sec since first try. This seems to be somehow related to the logic in Go's DNS resolver https://github.com/golang/go/blob/master/src/net/dnsclient_unix.go#L385. There have been issues like that reported in docker like: - docker/cli#2299 - docker/cli#2618 - moby/moby#22398 Since this starts to happen after inclusion of resolvconf package by above mentioned PR and the fact I can't see any problem with that (ping, nslookup, etc. works) the choice is made to force dockerd to use cgo (libc) resolver. Signed-off-by: Stepan Blyschak <[email protected]>

…uration in Linux. (sonic-net#13516) - Why I did it fixes sonic-net#12907 When the management interface IP address configuration changes from dynamic to static the DNS configuration (retrieved from the DHCP server) in /etc/resolv.conf remains uncleared. This leads to a DNS configuration pointing to the wrong nameserver. To make the behavior clear DNS configuration received from DHCP should be cleared. - How I did it Use resolvconf package for managing DNS configuration. It is capable of tracking the source of DNS configuration and puts the configuration retrieved from the DHCP servers into a separate file. This allows the implementation of DNS configuration cleanup retrieved from DHCP during networking reconfiguration. - How to verify it Ensure that the management interface has no static configuration. Check that /etc/resolv.conf has DNS configuration. Configure a static IP address on the management interface. Verify that /etc/resolv.conf has no DNS configuration. Remove the static IP address from the management interface. Verify that /etc/resolv.conf has DNS configuration retrieved form DHCP server.

…reconfiguration in Linux. (sonic-net#13516) (sonic-net#13695)" This reverts commit d1fa414.

…reconfiguration in Linux. (sonic-net#13516)" This reverts commit 5ef488f.

…reconfiguration in Linux. (sonic-net#13516)" This reverts commit c7ecd92.

…reconfiguration in Linux. (#13516) (#13695)" (#14900) This reverts commit d1fa414.

…reconfiguration in Linux. (#13516)" (#14901) This reverts commit 5ef488f.

…reconfiguration in Linux. (#13516)" (#14902) This reverts commit c7ecd92.

…working reconfiguration in Linux. (sonic-net#13516)" (sonic-net#14902)" This reverts commit 72c52bc.

Clear /etc/resolv.conf after changing the mgmt interface configuratio…

08a84cd

…n to static.

oleksandrivantsiv requested a review from lguohan as a code owner January 25, 2023 19:03

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liat-grozovik merged commit c7ecd92 into sonic-net:master Jan 30, 2023

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[dockerd] Force usage of cgo DNS resolver stepanblyschak/sonic-buildimage#89

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[action] [PR:13516] Clear DNS configuration received from DHCP during networking reconfiguration in Linux. #13686

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oleksandrivantsiv mentioned this pull request Feb 6, 2023

[cherry-pick][202205] Clear DNS configuration received from DHCP during networking reconfiguration in Linux. (#13516) #13695

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Revert "Clear DNS configuration received from DHCP during networking …

ede6b70

…reconfiguration in Linux. (sonic-net#13516) (sonic-net#13695)" This reverts commit d1fa414.

yxieca added a commit to yxieca/sonic-buildimage that referenced this pull request May 1, 2023

Revert "Clear DNS configuration received from DHCP during networking …

35a7307

…reconfiguration in Linux. (sonic-net#13516)" This reverts commit 5ef488f.

yxieca added a commit to yxieca/sonic-buildimage that referenced this pull request May 1, 2023

Revert "Clear DNS configuration received from DHCP during networking …

0754a40

…reconfiguration in Linux. (sonic-net#13516)" This reverts commit c7ecd92.

yxieca added a commit that referenced this pull request May 1, 2023

Revert "Clear DNS configuration received from DHCP during networking …

9ac9908

…reconfiguration in Linux. (#13516) (#13695)" (#14900) This reverts commit d1fa414.

yxieca added a commit that referenced this pull request May 1, 2023

Revert "Clear DNS configuration received from DHCP during networking …

f621643

…reconfiguration in Linux. (#13516)" (#14901) This reverts commit 5ef488f.

yxieca added a commit that referenced this pull request May 2, 2023

Revert "Clear DNS configuration received from DHCP during networking …

72c52bc

…reconfiguration in Linux. (#13516)" (#14902) This reverts commit c7ecd92.

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Clear DNS configuration received from DHCP during networking reconfiguration in Linux. #13516

Clear DNS configuration received from DHCP during networking reconfiguration in Linux. #13516

oleksandrivantsiv commented Jan 25, 2023

liat-grozovik commented Jan 30, 2023

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mssonicbld commented Feb 6, 2023

Clear DNS configuration received from DHCP during networking reconfiguration in Linux. #13516

Clear DNS configuration received from DHCP during networking reconfiguration in Linux. #13516

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oleksandrivantsiv commented Jan 25, 2023

Why I did it

How I did it

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Ensure to add label/tag for the feature raised. example - PR#2174 under sonic-utilities repo. where, Generic Config and Update feature has been labelled as GCU.

Link to config_db schema for YANG module changes

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liat-grozovik commented Jan 30, 2023

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mssonicbld commented Feb 6, 2023