func partitionInterfaces()

in google_guest_agent/network/manager/dhclient_linux.go [407:454]
35 lines of code
13 McCabe index (conditional complexity)

func partitionInterfaces(ctx context.Context, interfaces, ipv6Interfaces []string) ([]string, []string, []string, error) {
	var obtainIpv4Interfaces []string
	var obtainIpv6Interfaces []string
	var releaseIpv6Interfaces []string

	for i, iface := range interfaces {
		if !shouldManageInterface(i == 0) {
			// Do not setup anything for this interface to avoid duplicate processes.
			logger.Debugf("ManagePrimaryNIC is disabled, skipping dhclient launch for %s", iface)
			continue
		}
		if isInvalid(iface) {
			continue
		}
		// On 18.04 we fallback to dhclient as networkctl is very old and has not reload support for example.
		// Default netplan config will take care of it, do not launch dhclient for primary NIC on 18.04.
		if (i == 0) && isUbuntu1804() {
			logger.Debugf("ManagePrimaryNIC is enabled, but skipping primary nic as its managed by default OS config")
			continue
		}

		// Check for IPv4 interfaces for which to obtain a lease.
		processExists, err := dhclientProcessExists(ctx, iface, ipv4)
		if err != nil {
			return nil, nil, nil, err
		}
		if !processExists {
			obtainIpv4Interfaces = append(obtainIpv4Interfaces, iface)
		}

		// Check for IPv6 interfaces for which to obtain a lease.
		processExists, err = dhclientProcessExists(ctx, iface, ipv6)
		if err != nil {
			return nil, nil, nil, err
		}

		if slices.Contains(ipv6Interfaces, iface) && !processExists {
			// Obtain a lease and spin up the DHClient process.
			obtainIpv6Interfaces = append(obtainIpv6Interfaces, iface)
		} else if !slices.Contains(ipv6Interfaces, iface) && processExists {
			// Release the lease since the DHClient IPv6 process is running,
			// but the interface is no longer IPv6.
			releaseIpv6Interfaces = append(releaseIpv6Interfaces, iface)
		}
	}

	return obtainIpv4Interfaces, obtainIpv6Interfaces, releaseIpv6Interfaces, nil
}