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[OpenStack Infra <1896945@xxxxxxxxxxxxxxxxxx>]

Reviewed:  https://review.opendev.org/755356
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=704576e54e041340ed9c2964b110815e074239a6
Submitter: Zuul
Branch:    master

commit 704576e54e041340ed9c2964b110815e074239a6
Author: Dan Radez <dradez@xxxxxxxxxx>
Date:   Wed Sep 30 11:00:07 2020 -0400

    Default dnsmasq --conf-file to /dev/null
    
    Passing --conf-file= with no value has no effect on the dnsmasq
    process. Intended effect here is for the default system dnsmasq.conf
    file not to be read and included in configuring the process. For
    that to happen some value has to be passed to --conf-file. Passing
    /dev/null will invoke the desired outcome to skip the system
    default conf file.
    
    Closes-Bug: #1896945
    Change-Id: I22570a44f84d14a792633747c04d7426ab231009


** Changed in: neutron
       Status: In Progress => Fix Released

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https://bugs.launchpad.net/bugs/1896945

Title:
  dnsmasq >= 2.81 not responding to DHCP requests with current q-dhcp
  configs

Status in neutron:
  Fix Released

Bug description:
  * High level description:

  I've been attempting to enable Fedora 32 support in devstack and
  encountered the following issue where dnsmasq as configured by q-dhcp
  isn't responding to DHCP requests from clients:

  https://review.opendev.org/#/c/750292/

  Looking at tcpdump and strace it appears that dnsmasq can see the
  requests but doesn't reply suggesting a configuration issue either
  caused by q-dhcp *or* a regression in dnsmasq itself:

  $ openstack server reboot --hard test && sudo ip netns exec qdhcp-df64061e-0784-4bbe-909b-ae1c5f466981 tcpdump -i tapee679459-e1 -n port 67 or port 68
  dropped privs to tcpdump
  tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
  listening on tapee679459-e1, link-type EN10MB (Ethernet), capture size 262144 bytes
  18:40:24.070796 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from fa:16:3e:16:07:a0, length 300
  18:41:24.118961 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from fa:16:3e:16:07:a0, length 300
  18:42:24.192716 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from fa:16:3e:16:07:a0, length 300

  $ openstack server reboot --hard test && sudo ip netns exec qdhcp-df64061e-0784-4bbe-909b-ae1c5f466981 strace -p 196856
  strace: Process 196856 attached
  restart_syscall(<... resuming interrupted read ...>) = 1
  recvmsg(4, {msg_name={sa_family=AF_INET, sin_port=htons(68), sin_addr=inet_addr("0.0.0.0")}, msg_namelen=16, msg_iov=[{iov_base="\1\1\6\0\0041\326S\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\372\26>\26"..., iov_len=548}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={ipi_ifindex=if_nametoindex("tapee679459-e1"), ipi_spec_dst=inet_addr("10.0.0.2"), ipi_addr=inet_addr("255.255.255.255")}}], msg_controllen=32, msg_flags=0}, MSG_PEEK|MSG_TRUNC) = 300
  recvmsg(4, {msg_name={sa_family=AF_INET, sin_port=htons(68), sin_addr=inet_addr("0.0.0.0")}, msg_namelen=16, msg_iov=[{iov_base="\1\1\6\0\0041\326S\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\372\26>\26"..., iov_len=548}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={ipi_ifindex=if_nametoindex("tapee679459-e1"), ipi_spec_dst=inet_addr("10.0.0.2"), ipi_addr=inet_addr("255.255.255.255")}}], msg_controllen=32, msg_flags=0}, 0) = 300
  ioctl(4, SIOCGIFNAME, {ifr_index=9, ifr_name="tapee679459-e1"}) = 0
  ioctl(4, SIOCGIFFLAGS, {ifr_name="tapee679459-e1", ifr_flags=IFF_UP|IFF_BROADCAST|IFF_RUNNING|IFF_MULTICAST}) = 0
  ioctl(4, SIOCGIFADDR, {ifr_name="tapee679459-e1", ifr_addr={sa_family=AF_INET, sin_port=htons(0), sin_addr=inet_addr("10.0.0.2")}}) = 0
  poll([{fd=4, events=POLLIN}, {fd=5, events=POLLIN}, {fd=6, events=POLLIN}, {fd=7, events=POLLIN}, {fd=9, events=POLLIN}, {fd=10, events=POLLIN}, {fd=11, events=POLLIN}, {fd=14, events=POLLIN}], 8, -1

  The current configs are listed below:

  http://paste.openstack.org/show/798334/

  I was able to downgrade dnsmasq on f32 to 2.80 in order to workaround
  this:

  $ sudo dnf downgrade dnsmasq -y
  [..]
  $ rpm -qa | grep dnsmasq
  dnsmasq-2.80-14.fc32.x86_64
  $ sudo killall dnsmasq && sudo systemctl restart devstack@q-*
  $ openstack server reboot --hard test && sudo ip netns exec qdhcp-df64061e-0784-4bbe-909b-ae1c5f466981 tcpdump -i tapee679459-e1 -n port 67 or port 68
  dropped privs to tcpdump
  tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
  listening on tapee679459-e1, link-type EN10MB (Ethernet), capture size 262144 bytes
  12:06:57.028953 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from fa:16:3e:16:07:a0, length 300
  12:06:57.029994 IP 10.0.0.2.bootps > 10.0.0.49.bootpc: BOOTP/DHCP, Reply, length 328
  12:06:57.042300 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from fa:16:3e:16:07:a0, length 300
  12:06:57.047014 IP 10.0.0.2.bootps > 10.0.0.49.bootpc: BOOTP/DHCP, Reply, length 344

  * Pre-conditions:

  F32 with dnsmasq >= 2.81 installed.

  * Step-by-step reproduction steps:

  Deploy F32 with dnsmasq >= 2.81 installed, attempt to spawn an
  instance attached to a subnet with dhcp enabled.

  * Expected output:

  dnsmasq responds to DHCP request from instance.

  * Actual output:

  dnsmasq doesn't respond to DHCP request from instance.

  * Version:
    ** OpenStack version (Specific stable branch, or git hash if from trunk);

    Neutron @ 0fdcc4b1b63dc90fbc9f46f5947f84626f8e5b41

    ** Linux distro, kernel. For a distro, it’s also worth knowing
  specific versions of client and server;

    Fedora 32 with kernel 5.8.10-200.fc32.x86_64

    ** DevStack or other _deployment_ mechanism?

    Devstack @ https://review.opendev.org/#/c/750292/

  * Environment: what types of services are you running (core services
  like DB and AMQP broker, as well as Nova/hypervisor if it matters),
  and which type of deployment (clustered servers)? Multi-node or single
  node, etc.

    Single node devstack env.

  * Perceived severity: is this a blocker for you?

    High, assuming other distros will be impacted by this once they move
  to dnsmasq >= 2.81

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