Home » General » Support » ip_conntrack: CT 0: table full, dropping packet. (server gets unavailable due to this error)  
	
		
		
			| ip_conntrack: CT 0: table full, dropping packet. [message #37827] | 
			Tue, 27 October 2009 01:55   | 
		 
		
			
				
				
				
					
						  
						mavines
						 Messages: 4 Registered: October 2009 
						
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					Junior Member  | 
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		Hi, 
 
I have the major problem with networking - /var/log/messages reports this: 
ip_conntrack: CT 0: table full, dropping packet. 
 
And I have CentOS 5.4, kernel: 
 
Linux  2.6.18-128.2.1.el5.028stab064.7xen #1 SMP Wed Aug 26 16:41:55 MSD 2009 x86_64 x86_64 x86_64 GNU/Linux 
 
# ip rule list 
0:      from all lookup 255 
32766:  from all lookup main 
32767:  from all lookup default 
 
 
the iptables rules are attached, tcpdump is attached as well. 
 
here is the lsmod of main server: 
Module                  Size  Used by 
iptable_nat            43532  0 
tun                    47872  2 
xt_physdev             35984  0 
bridge                 94384  1 xt_physdev 
netloop                40324  0 
netbk                 129984  0 [permanent] 
blktap                151460  2 [permanent] 
blkbk                  54712  0 [permanent] 
vzethdev               47520  0 
vznetdev               56848  8 
simfs                  38296  4 
vzrst                 172968  0 
ip_nat                 53392  2 iptable_nat,vzrst 
vzcpt                 150840  0 
vzdquota               78320  4 [permanent] 
vzmon                  83864  8 vzethdev,vznetdev,vzrst,vzcpt 
vzdev                  36872  4 vzethdev,vznetdev,vzdquota,vzmon 
xt_tcpmss              35328  0 
ipt_tos                34560  0 
xt_tcpudp              36224  245 
xt_conntrack           36352  0 
ip_conntrack_irc       41168  0 
xt_state               35200  23 
ip_conntrack_ftp       42192  0 
xt_multiport           36224  4 
xt_length              34944  0 
xt_mac                 34944  0 
xt_limit               36352  46 
ipt_TCPMSS             37248  1 
iptable_mangle         37888  5 
iptable_filter         37760  6 
ipt_TOS                35200  14 
ipt_ULOG               42504  0 
ip_conntrack          100884  8  iptable_nat,vzrst,ip_nat,vzcpt,xt_conntrack,ip_conntrack_irc ,xt_state,ip_conntrack_ftp 
ipt_recent             43404  45 
ipt_ecn                35200  0 
ipt_owner              34944  0 
ip_tables              57440  3 iptable_nat,iptable_mangle,iptable_filter 
ipt_ttl                34816  0 
ipt_REJECT             39684  42 
ipt_LOG                39808  40 
nfnetlink              40392  2 ip_nat,ip_conntrack 
x_tables               52616  21  iptable_nat,xt_physdev,xt_tcpmss,ipt_tos,xt_tcpudp,xt_conntr ack,xt_state,xt_multiport,xt_length,xt_mac,xt_limit,ipt_TCPM SS,ipt_TOS,ipt_ULOG,ipt_recent,ipt_ecn,ipt_owner,ip_tables,i pt_ttl,ipt_REJECT,ipt_LOG 
autofs4                57480  2 
hidp                   83584  2 
rfcomm                104872  0 
l2cap                  89216  10 hidp,rfcomm 
bluetooth             118916  5 hidp,rfcomm,l2cap 
lockd                 101776  0 
sunrpc                201416  2 lockd 
ipv6                  456124  435 vzrst,vzcpt,vzmon 
xfrm_nalgo             43268  1 ipv6 
crypto_api             42880  1 xfrm_nalgo 
ib_iser                66936  0 
rdma_cm                67092  1 ib_iser 
ib_cm                  67752  1 rdma_cm 
iw_cm                  43400  1 rdma_cm 
ib_sa                  74760  2 rdma_cm,ib_cm 
ib_mad                 70820  2 ib_cm,ib_sa 
ib_core                93700  6 ib_iser,rdma_cm,ib_cm,iw_cm,ib_sa,ib_mad 
ib_addr                42128  1 rdma_cm 
iscsi_tcp              57856  0 
libiscsi               63488  2 ib_iser,iscsi_tcp 
scsi_transport_iscsi    66960  5 ib_iser,iscsi_tcp,libiscsi 
loop                   48656  4 
dm_mirror              54280  0 
dm_multipath           55192  0 
scsi_dh                41600  1 dm_multipath 
raid0                  40448  1 
video                  53004  0 
hwmon                  36488  0 
backlight              39808  1 video 
sbs                    49856  0 
i2c_ec                 38528  1 sbs 
container              37760  0 
button                 40480  0 
battery                43784  0 
asus_acpi              50724  0 
ac                     38664  0 
lp                     47056  0 
snd_hda_intel         481584  0 
snd_seq_dummy          36996  0 
snd_seq_oss            65408  0 
snd_seq_midi_event     40960  1 snd_seq_oss 
snd_seq                87968  5 snd_seq_dummy,snd_seq_oss,snd_seq_midi_event 
snd_seq_device         41492  3 snd_seq_dummy,snd_seq_oss,snd_seq 
snd_pcm_oss            77440  0 
snd_mixer_oss          49920  1 snd_pcm_oss 
snd_pcm               116872  2 snd_hda_intel,snd_pcm_oss 
snd_timer              57224  2 snd_seq,snd_pcm 
snd_page_alloc         43920  2 snd_hda_intel,snd_pcm 
r8169                  71172  0 
snd_hwdep              43528  1 snd_hda_intel 
snd                    99496  9  snd_hda_intel,snd_seq_oss,snd_seq,snd_seq_device,snd_pcm_oss ,snd_mixer_oss,snd_pcm,snd_timer,snd_hwdep 
mii                    38784  1 r8169 
i2c_i801               41620  0 
soundcore              41760  1 snd 
parport_pc             62248  1 
pcspkr                 36224  0 
i2c_core               56064  2 i2c_ec,i2c_i801 
ohci1394               67928  0 
shpchp                 70572  0 
parport                73868  2 lp,parport_pc 
ieee1394              390648  1 ohci1394 
r8168                  95000  0 
sg                     69544  0 
serial_core            56192  0 
dm_raid45              98704  0 
dm_message             36096  1 dm_raid45 
dm_region_hash         46336  1 dm_raid45 
dm_log                 44800  3 dm_mirror,dm_raid45,dm_region_hash 
dm_mod                100560  4 dm_mirror,dm_multipath,dm_raid45,dm_log 
dm_mem_cache           39424  1 dm_raid45 
ahci                   68744  4 
libata                208784  1 ahci 
sd_mod                 56448  7 
scsi_mod              197528  8  ib_iser,iscsi_tcp,libiscsi,scsi_transport_iscsi,scsi_dh,sg,l ibata,sd_mod 
ext3                  168848  2 
jbd                   102512  1 ext3 
uhci_hcd               57496  0 
ohci_hcd               55988  0 
ehci_hcd               65676  0 
 
 
 
 
So, firstly I had a problem with orphaned sockets (it persisted about 6 months, but I did not paid enough attention), then server started to fail and I somehow fixed the problem with orphaned sockets at CT300. But instead I've got the problem with ip_conntrack which lasts for 2 weeks already and I am not able to figure out why.  
 
sysctl -A output is also attached. 
 
So, my server for now gets overflowed at least once by day and I have to increase max value for ip_conntrack, but this helps only for few hours, then I have to reboot the server or it just hangs without response.  
 
I was suspecting that this is an attack (like DDoS) but even when the server has very few connections, it gets overflowed. And that is really nasty.  
 
 
Can you please help with that?  
 
Yes, another detail - I have 4 OpenVZ VPSs and 2 XEN VPSs running on the same server. It has 8 GB RAM and 1.5 TB HDD - Core Quad Intel CPU.
		
		
		
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		ip_conntrack: CT 0: table full, dropping packet.
		By:  mavines on Tue, 27 October 2009 01:55  
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		Re: ip_conntrack: CT 0: table full, dropping packet.
		By:  kir on Tue, 27 October 2009 09:33  
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		Re: ip_conntrack: CT 0: table full, dropping packet.
		By:  mavines on Tue, 27 October 2009 10:59  
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		Re: ip_conntrack: CT 0: table full, dropping packet.
		By:  mavines on Tue, 27 October 2009 11:13  
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		Re: ip_conntrack: CT 0: table full, dropping packet.
		By:  kir on Tue, 27 October 2009 12:54  
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		Re: ip_conntrack: CT 0: table full, dropping packet.
		By:  mavines on Tue, 27 October 2009 14:04  
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