** Summary changed:

- dnsmasq often using 100% of CPU 
+ dnsmasq often using 100% of CPU if the upstream nameserver is unreachable

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https://bugs.launchpad.net/bugs/1980146

Title:
  dnsmasq often using 100% of CPU if the upstream nameserver is
  unreachable

Status in dnsmasq package in Ubuntu:
  Triaged
Status in dnsmasq source package in Focal:
  Triaged
Status in dnsmasq source package in Jammy:
  Triaged
Status in dnsmasq source package in Kinetic:
  Triaged

Bug description:
  Release:      22.04
  Codename:     jammy
  Kernel:         Linux 5.15.0-40-generic x86_64

  ⏵ apt-cache policy dnsmasq
    Installed: 2.86-1.1ubuntu0.1

  dnsmasq is caught in a loop after every dns request, resulting in 100%
  CPU usage for several minutes each time.  This leads to a hot and
  lethargic computer.  During this time thousands of the following
  messages (see below) are printed from strace.

  The loop tends to obsess on denied connections, but there are so many
  I'm not 100% sure.

  systemd-resolved is _not_ running, some bugs refer to that.

  ⏵ head /etc/dnsmasq.d/foo.conf

  address=/#/127.0.0.2
  port=53
  resolv-file=/var/run/NetworkManager/resolv.conf

  ⏵ sudo strace -p 3519  (dnsmasq)

  poll([{fd=3, events=POLLIN}, {fd=4, events=POLLIN}, {fd=5,
  events=POLLIN}, {fd=6, events=POLLIN}, {fd=7, events=POLLIN}, {fd=8,
  events=POLLIN}, {fd=9, events=POLLIN}, {fd=13, events=POLLIN}, {fd=14,
  events=POLLIN}], 9, -1) = 1 ([{fd=4, revents=POLLIN}])

  recvmsg(4, {msg_name={sa_family=AF_INET, sin_port=htons(60224),
  sin_addr=inet_addr("127.0.0.1")}, msg_namelen=28 => 16,
  msg_iov=[{iov_base="\302\221\1\0\0\1\0\0\0\0\0\0\17classify-
  client\10ser"..., iov_len=4096}], msg_iovlen=1,
  msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO,
  cmsg_data={ipi_ifindex=if_nametoindex("lo"),
  ipi_spec_dst=inet_addr("127.0.0.53"),
  ipi_addr=inet_addr("127.0.0.53")}}], msg_controllen=32, msg_flags=0},
  0) = 54

  ioctl(4, SIOCGIFNAME, {ifr_ifindex=1, ifr_name="lo"}) = 0

  sendto(14, "\302\221\1\0\0\1\0\0\0\0\0\0\17classify-client\10ser"...,
  54, 0, {sa_family=AF_INET, sin_port=htons(53),
  sin_addr=inet_addr("127.0.0.53")}, 16) = 54

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