Why ipset module fails to load with iptables service during boot or when restarting the iptables service in RHEL 6?

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux (RHEL) 6
  • ipset.
  • iptables.

Issue

  • ipset module not loaded on system boot.
  • iptables is failing to start with error "Kernel module ip_set is not loaded in."
# /etc/init.d/iptables restart
iptables: Setting chains to policy ACCEPT: filter          [  OK  ]
iptables: Flushing firewall rules:                         [  OK  ]
iptables: Unloading modules:                               [  OK  ]
iptables: Applying firewall rules: iptables-restore v1.4.7: Kernel module ip_set is not loaded in.

                                                           [FAILED]

Resolution

  • It is an expected behaviour for the iptables service to fail when an undefined ipset is used with iptables rules.

  • If ipset is used make sure that etc/sysconfig/ipset is not empty. But If ipset is not used then remove the --match set option in the iptables rules.

Root Cause

The use of an undefined ipset in the iptables rule set is an issue, which prevents to apply the rule set. The failure intends to warn/alert admins about blank rule sets. Every error in the rule set has this effect. This is expected behaviour.

Diagnostic Steps

  • Create an ipset with no set rules defined and use in theiptables` rule:

    • Create a rule set with ipset:

          # ipset create ip-blacklist hash:ip timeout 7200
    # ipset list
    Name: ip-blacklist
    Type: hash:ip

    • Add the rule set with --match-set option in iptables:

           # iptables -I INPUT 4 -m set --match-set ip-blacklist src -p tcp --dport 80 -j REJECT
     # iptables -nvL
     Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
      pkts bytes target     prot opt in     out     source               destination         
      552 52734 ACCEPT     all  --  *      *       0.0.0.0/0            0.0.0.0/0           state RELATED,ESTABLISHED 
     0     0 ACCEPT     icmp --  *      *       0.0.0.0/0            0.0.0.0/0           
     0     0 ACCEPT     all  --  lo     *       0.0.0.0/0            0.0.0.0/0           
     0     0 REJECT     tcp  --  *      *       0.0.0.0/0            0.0.0.0/0           match-set ip-blacklist src tcp dpt:80 reject-with  icmp-port-unreachable 
     0     0 ACCEPT     tcp  --  *      *       0.0.0.0/0            0.0.0.0/0           state NEW tcp dpt:22 
     0     0 ACCEPT     tcp  --  *      *       0.0.0.0/0            0.0.0.0/0           state NEW tcp dpt:80 
     0     0 ACCEPT     tcp  --  *      *       0.0.0.0/0            0.0.0.0/0           state NEW tcp dpt:25 
     0     0 REJECT     all  --  *      *       0.0.0.0/0            0.0.0.0/0           reject-with icmp-host-prohibited

    • Save the iptables rule:

           # service iptables save
      iptables: Saving firewall rules to /etc/sysconfig/iptables:[  OK  ]

     # service iptables restart
     iptables: Setting chains to policy ACCEPT: filter          [  OK  ]
     iptables: Flushing firewall rules:                         [  OK  ]
     iptables: Unloading modules:                               [  OK  ]
     iptables: Applying firewall rules:                         [  OK  ]

    • After reboot the iptables fails to start and manual restart yields following error:

          iptables: Setting chains to policy ACCEPT: filter          [  OK  ]
    iptables: Flushing firewall rules:                         [  OK  ]
    iptables: Unloading modules:                               [  OK  ]
    iptables: Applying firewall rules: iptables-restore v1.4.7: Kernel module ip_set is not loaded in.      [FAILED]

  # service iptables status
    Table: filter
    Chain INPUT (policy ACCEPT)
    num  target     prot opt source               destination         

    Chain FORWARD (policy ACCEPT)
    num  target     prot opt source               destination         

    Chain OUTPUT (policy ACCEPT)
    num  target     prot opt source               destination

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