machine-os: install netcat

[vrutkovs]

Discussed in #1521

^{Originally posted by dsevost February 22, 2023}
Describe the bug
Hello dear OKD Team.
Startup script /usr/local/bin/configure-ovs.sh tries to bind to some port while config IPv6 (line 557, see below)

[root@worker2-rs1 ~]# cat -n /usr/local/bin/configure-ovs.sh | grep ' nc ' -B 14 -A 12
   543  # This function waits for ip address of br-ex to be bindable only in case of ipv6
   544  # This is workaround for OCPBUGS-673 as it will not allow starting crio
   545  # before address is bindable
   546  try_to_bind_ipv6_address() {
   547    # Retry for 1 minute
   548    retries=60
   549    until [[ ${retries} -eq 0 ]]; do
   550      ip=$(ip -6 -j addr | jq -r "first(.[] | select(.ifname==\"br-ex\") | .addr_info[] | select(.scope==\"global\") | .local)")
   551      if [[ "${ip}" == "" ]]; then
   552        echo "No ipv6 ip to bind was found"
   553        break
   554      fi
   555      random_port=$(shuf -i 50000-60000 -n 1)
   556      echo "Trying to bind ${ip} on port ${random_port}"
   557      exit_code=$(timeout 2s **nc** -l "${ip}" ${random_port}; echo $?)
   558      if [[ exit_code -eq 124 ]]; then
   559        echo "Address bound successfully"
   560        break
   561      fi
   562      sleep 1
   563      (( retries-- ))
   564    done
   565    if [[ ${retries} -eq 0 ]]; then
   566      echo "Failed to bind ip"
   567      exit 1
   568    fi
   569  }

Version
4.12.0-0.okd-2023-01-21-055900

How reproducible
Enable IPv6 RA on subnet

[vrutkovs]

Fixed in amd64.origin.releases.ci.openshift.org/releasestream/4-stable/release/4.12.0-0.okd-2023-03-05-022504

[vrutkovs]

Somehow despite installing the package still no /usr/bin/nc on the machine os content

[vrutkovs]

Expected:

ls -la /usr/bin/nc                                                                             
lrwxrwxrwx. 1 root root 20 Mar 15 20:33 /usr/bin/nc -> /etc/alternatives/nc

but we get

bash-5.2# rpm -ql netcat
/usr/bin/nc
/usr/bin/netcat
/usr/lib/.build-id
/usr/lib/.build-id/5e
/usr/lib/.build-id/5e/2cf9a27e870b9c05dba3677208e6ae1afd2fdc
/usr/share/man/man1/nc.1.gz
/usr/share/man/man1/netcat.1.gz
bash-5.2# /usr/bin/nc
bash: /usr/bin/nc: No such file or directory
bash-5.2# /usr/bin/netcat
usage: nc [-46cDdFhklNnrStUuvz] [-C certfile] [-e name] [-H hash] [-I length]
	  [-i interval] [-K keyfile] [-M ttl] [-m minttl] [-O length]
	  [-o staplefile] [-P proxy_username] [-p source_port] [-R CAfile]
	  [-s sourceaddr] [-T keyword] [-V rtable] [-W recvlimit] [-w timeout]
	  [-X proxy_protocol] [-x proxy_address[:port]] [-Z peercertfile]
	  [destination] [port]

which is an rpm-ostree bug - coreos/rpm-ostree#1614

[ibotty]

Can't https://docs.fedoraproject.org/en-US/fedora-coreos/alternatives/ be used?

[vrutkovs]

OKD 4.12+ stables should have it for some time - openshift/okd-machine-os#565 added the right nc, working around the rpm-ostree bug for alternatives