Public bug reported: * Summary (Bug title): keep it small, possibly one line.
When ipv6_ra_mode is dhcpv6-stateful, both M flag and O flag should be 1, but actually only M flag is 1 and O flag is 0 in router advertisement packets. ml2/OVS and ml2/OVN have the same behavior. * High level description: provide a brief sentence (a couple of lines) of what are you trying to accomplish, or would like to accomplish differently. According to the following document, both M flag and O flag will be 1 when ipv6_ra_mode is dhcpv6-stateful. https://docs.openstack.org/neutron/latest/admin/config-ipv6.html > Setting DHCPv6-stateless for ipv6_ra_mode configures the neutron router with an radvd agent to send > Router Advertisements. The list below captures the values set for the address configuration > flags in the Router Advertisement messages in this scenario. Similarly, setting DHCPv6- > stateless for ipv6_address_mode configures neutron DHCP implementation to provide the additional network information. > - Autonomous Address Configuration Flag = 1 > - Managed Address Configuration Flag = 0 > - Other Configuration Flag = 1 But actually only M flag is 1 and O flag is 0. This behavior comes from the following implementations: ML2/OVS https://github.com/openstack/neutron/blob/f545c002dc699f849026ccd1bad403b2933373aa/neutron/agent/linux/ra.py#L53-L55 ML2/OVN https://github.com/ovn-org/ovn/blob/a5238e6234d17e119dca952d9e43c36dce057d5e/controller/pinctrl.c#L3733-L3734 https://github.com/ovn-org/ovn/blob/a5238e6234d17e119dca952d9e43c36dce057d5e/lib/actions.c#L3349-L3350 I tested a RHEL 8 instance and the instance could obtain DNS server information from DHCPv6 even though O flag is 0. Therefore some kind of operating system is not affected even if O flag is 0. But actually there is a difference between the document and actual behavior. Which one is correct and which should I modify? * Pre-conditions: what is the initial state of your system? Please consider enumerating resources available in the system, if useful in diagnosing the problem. Who are you? A regular tenant or a super-user? Are you describing service-to-service interaction? ml2/OVS or ml2/OVN * Step-by-step reproduction steps: CLI commands or API requests are great; please, consider using http://paste.openstack.org for long outputs. I confirmed this behavior on Train-based-OpenStack (Red Hat OpenStack Platform 16.2) 1. Deploy OpenStack with ml2/OVS or ml2/OVN 2. Create a router and a tenant network/subnet with ipv6_stateful by the following commands openstack network create ipv6_stateful openstack subnet create --ip-version 6 --ipv6-address-mode dhcpv6-stateful --ipv6-ra-mode dhcpv6-stateful --network ipv6_stateful --subnet-range fc00:2::/64 ipv6_stateful --gateway fc00:2::1 --dns-nameserver 2001:4860:4860::8888 openstack router create router1 openstack router add subnet router1 ipv6_stateful 3. Create an instance on the network openstack server create --flavor flavor --image rhel-8.2-290 --network ipv6_stateful --security-group sg --key-name keypair ipv6_stateful 4. Take packet capture of Router Advertisement packets on the instance * Expected output: what did you hope to see? Both M flag and O flag are 1, * Actual output: did the system silently fail (in this case log traces are useful)? Only M flag is 1 and O flag is 0. * Version: I confirmed this behavior on Train-based-OpenStack (Red Hat OpenStack Platform 16.2) But as far as I checked the implementation, the latest version should have the same behavior. * Perceived severity: is this a blocker for you? Serverity is low. I just wander why there is the difference between document and actual behavior. * Attachments: consider attaching logs, truncated log snippets are rarely useful. The following is the excerpt of actual packet captures. <ML2/OVN> ~~~ Internet Control Message Protocol v6 Type: Router Advertisement (134) Code: 0 Checksum: 0x2a73 [correct] [Checksum Status: Good] Cur hop limit: 255 Flags: 0x80, Managed address configuration, Prf (Default Router Preference): Medium 1... .... = Managed address configuration: Set .0.. .... = Other configuration: Not set ..0. .... = Home Agent: Not set ...0 0... = Prf (Default Router Preference): Medium (0) .... .0.. = Proxy: Not set .... ..0. = Reserved: 0 Router lifetime (s): 65535 Reachable time (ms): 0 Retrans timer (ms): 0 ICMPv6 Option (Source link-layer address : fa:16:3e:de:92:07) Type: Source link-layer address (1) Length: 1 (8 bytes) Link-layer address: fa:16:3e:de:92:07 (fa:16:3e:de:92:07) ICMPv6 Option (MTU : 1442) Type: MTU (5) Length: 1 (8 bytes) Reserved MTU: 1442 ICMPv6 Option (Prefix information : fc00:2::/64) Type: Prefix information (3) Length: 4 (32 bytes) Prefix Length: 64 Flag: 0x80, On-link flag(L) 1... .... = On-link flag(L): Set .0.. .... = Autonomous address-configuration flag(A): Not set ..0. .... = Router address flag(R): Not set ...0 0000 = Reserved: 0 Valid Lifetime: Infinity (4294967295) Preferred Lifetime: Infinity (4294967295) Reserved Prefix: fc00:2:: ~~~ <ml2/OVS> ~~~ Internet Control Message Protocol v6 Type: Router Advertisement (134) Code: 0 Checksum: 0x986a [correct] [Checksum Status: Good] Cur hop limit: 64 Flags: 0x80, Managed address configuration, Prf (Default Router Preference): Medium 1... .... = Managed address configuration: Set .0.. .... = Other configuration: Not set ..0. .... = Home Agent: Not set ...0 0... = Prf (Default Router Preference): Medium (0) .... .0.. = Proxy: Not set .... ..0. = Reserved: 0 Router lifetime (s): 300 Reachable time (ms): 0 Retrans timer (ms): 0 ICMPv6 Option (Prefix information : fc00:2::/64) Type: Prefix information (3) Length: 4 (32 bytes) Prefix Length: 64 Flag: 0x80, On-link flag(L) 1... .... = On-link flag(L): Set .0.. .... = Autonomous address-configuration flag(A): Not set ..0. .... = Router address flag(R): Not set ...0 0000 = Reserved: 0 Valid Lifetime: 86400 Preferred Lifetime: 14400 Reserved Prefix: fc00:2:: ICMPv6 Option (MTU : 1450) Type: MTU (5) Length: 1 (8 bytes) Reserved MTU: 1450 ICMPv6 Option (Source link-layer address : fa:16:3e:a6:2f:3d) Type: Source link-layer address (1) Length: 1 (8 bytes) Link-layer address: fa:16:3e:a6:2f:3d (fa:16:3e:a6:2f:3d) ~~~ ** Affects: neutron Importance: Undecided Status: New -- You received this bug notification because you are a member of Yahoo! Engineering Team, which is subscribed to neutron. https://bugs.launchpad.net/bugs/2011687 Title: O flag is not enabled when ipv6_ra_mode is dhcpv6-stateful Status in neutron: New Bug description: * Summary (Bug title): keep it small, possibly one line. When ipv6_ra_mode is dhcpv6-stateful, both M flag and O flag should be 1, but actually only M flag is 1 and O flag is 0 in router advertisement packets. ml2/OVS and ml2/OVN have the same behavior. * High level description: provide a brief sentence (a couple of lines) of what are you trying to accomplish, or would like to accomplish differently. According to the following document, both M flag and O flag will be 1 when ipv6_ra_mode is dhcpv6-stateful. https://docs.openstack.org/neutron/latest/admin/config-ipv6.html > Setting DHCPv6-stateless for ipv6_ra_mode configures the neutron router with an radvd agent to send > Router Advertisements. The list below captures the values set for the address configuration > flags in the Router Advertisement messages in this scenario. Similarly, setting DHCPv6- > stateless for ipv6_address_mode configures neutron DHCP implementation to provide the additional network information. > - Autonomous Address Configuration Flag = 1 > - Managed Address Configuration Flag = 0 > - Other Configuration Flag = 1 But actually only M flag is 1 and O flag is 0. This behavior comes from the following implementations: ML2/OVS https://github.com/openstack/neutron/blob/f545c002dc699f849026ccd1bad403b2933373aa/neutron/agent/linux/ra.py#L53-L55 ML2/OVN https://github.com/ovn-org/ovn/blob/a5238e6234d17e119dca952d9e43c36dce057d5e/controller/pinctrl.c#L3733-L3734 https://github.com/ovn-org/ovn/blob/a5238e6234d17e119dca952d9e43c36dce057d5e/lib/actions.c#L3349-L3350 I tested a RHEL 8 instance and the instance could obtain DNS server information from DHCPv6 even though O flag is 0. Therefore some kind of operating system is not affected even if O flag is 0. But actually there is a difference between the document and actual behavior. Which one is correct and which should I modify? * Pre-conditions: what is the initial state of your system? Please consider enumerating resources available in the system, if useful in diagnosing the problem. Who are you? A regular tenant or a super-user? Are you describing service-to-service interaction? ml2/OVS or ml2/OVN * Step-by-step reproduction steps: CLI commands or API requests are great; please, consider using http://paste.openstack.org for long outputs. I confirmed this behavior on Train-based-OpenStack (Red Hat OpenStack Platform 16.2) 1. Deploy OpenStack with ml2/OVS or ml2/OVN 2. Create a router and a tenant network/subnet with ipv6_stateful by the following commands openstack network create ipv6_stateful openstack subnet create --ip-version 6 --ipv6-address-mode dhcpv6-stateful --ipv6-ra-mode dhcpv6-stateful --network ipv6_stateful --subnet-range fc00:2::/64 ipv6_stateful --gateway fc00:2::1 --dns-nameserver 2001:4860:4860::8888 openstack router create router1 openstack router add subnet router1 ipv6_stateful 3. Create an instance on the network openstack server create --flavor flavor --image rhel-8.2-290 --network ipv6_stateful --security-group sg --key-name keypair ipv6_stateful 4. Take packet capture of Router Advertisement packets on the instance * Expected output: what did you hope to see? Both M flag and O flag are 1, * Actual output: did the system silently fail (in this case log traces are useful)? Only M flag is 1 and O flag is 0. * Version: I confirmed this behavior on Train-based-OpenStack (Red Hat OpenStack Platform 16.2) But as far as I checked the implementation, the latest version should have the same behavior. * Perceived severity: is this a blocker for you? Serverity is low. I just wander why there is the difference between document and actual behavior. * Attachments: consider attaching logs, truncated log snippets are rarely useful. The following is the excerpt of actual packet captures. <ML2/OVN> ~~~ Internet Control Message Protocol v6 Type: Router Advertisement (134) Code: 0 Checksum: 0x2a73 [correct] [Checksum Status: Good] Cur hop limit: 255 Flags: 0x80, Managed address configuration, Prf (Default Router Preference): Medium 1... .... = Managed address configuration: Set .0.. .... = Other configuration: Not set ..0. .... = Home Agent: Not set ...0 0... = Prf (Default Router Preference): Medium (0) .... .0.. = Proxy: Not set .... ..0. = Reserved: 0 Router lifetime (s): 65535 Reachable time (ms): 0 Retrans timer (ms): 0 ICMPv6 Option (Source link-layer address : fa:16:3e:de:92:07) Type: Source link-layer address (1) Length: 1 (8 bytes) Link-layer address: fa:16:3e:de:92:07 (fa:16:3e:de:92:07) ICMPv6 Option (MTU : 1442) Type: MTU (5) Length: 1 (8 bytes) Reserved MTU: 1442 ICMPv6 Option (Prefix information : fc00:2::/64) Type: Prefix information (3) Length: 4 (32 bytes) Prefix Length: 64 Flag: 0x80, On-link flag(L) 1... .... = On-link flag(L): Set .0.. .... = Autonomous address-configuration flag(A): Not set ..0. .... = Router address flag(R): Not set ...0 0000 = Reserved: 0 Valid Lifetime: Infinity (4294967295) Preferred Lifetime: Infinity (4294967295) Reserved Prefix: fc00:2:: ~~~ <ml2/OVS> ~~~ Internet Control Message Protocol v6 Type: Router Advertisement (134) Code: 0 Checksum: 0x986a [correct] [Checksum Status: Good] Cur hop limit: 64 Flags: 0x80, Managed address configuration, Prf (Default Router Preference): Medium 1... .... = Managed address configuration: Set .0.. .... = Other configuration: Not set ..0. .... = Home Agent: Not set ...0 0... = Prf (Default Router Preference): Medium (0) .... .0.. = Proxy: Not set .... ..0. = Reserved: 0 Router lifetime (s): 300 Reachable time (ms): 0 Retrans timer (ms): 0 ICMPv6 Option (Prefix information : fc00:2::/64) Type: Prefix information (3) Length: 4 (32 bytes) Prefix Length: 64 Flag: 0x80, On-link flag(L) 1... .... = On-link flag(L): Set .0.. .... = Autonomous address-configuration flag(A): Not set ..0. .... = Router address flag(R): Not set ...0 0000 = Reserved: 0 Valid Lifetime: 86400 Preferred Lifetime: 14400 Reserved Prefix: fc00:2:: ICMPv6 Option (MTU : 1450) Type: MTU (5) Length: 1 (8 bytes) Reserved MTU: 1450 ICMPv6 Option (Source link-layer address : fa:16:3e:a6:2f:3d) Type: Source link-layer address (1) Length: 1 (8 bytes) Link-layer address: fa:16:3e:a6:2f:3d (fa:16:3e:a6:2f:3d) ~~~ To manage notifications about this bug go to: https://bugs.launchpad.net/neutron/+bug/2011687/+subscriptions -- Mailing list: https://launchpad.net/~yahoo-eng-team Post to : [email protected] Unsubscribe : https://launchpad.net/~yahoo-eng-team More help : https://help.launchpad.net/ListHelp
