Messages in this thread |  | | | Date | Wed, 19 Dec 2007 19:03:27 +0100 | | From | Eric Dumazet <> | | Subject | Re: After many hours all outbound connections get stuck in SYN_SENT |
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James Nichols a écrit : > On 12/19/07, Eric Dumazet <dada1@cosmosbay.com> wrote: >> James Nichols a écrit : >>>> So you see outgoing SYN packets, but no SYN replies coming from the remote >>>> peer ? (you mention ACKS, but the first packet received from the remote >>>> peer should be a SYN+ACK), >>> Right, I meant to say SYN+ACK. I don't see them coming back. >> So... Really unlikely a linux problem, but ... >> > > > I don't know how you can be so sure. Turning tcp_sack off instantly > resovles the problem and all connections are succesful. I can't > imagine even the most far-fetched scenario where a router or every > single remote endpoints would suddenly stop causing the problem just > by removing a single TCP option. > > >>> I can take these captures and take a look at the results. >>> Unfortunately, I don't think I'll be able to make the captures >>> available to the general public. >> I dont understand, why dont you change IPs to mask them with 192.168.X.Y, or >> just ME, and peer1, peer2, peer... > > I will see if I can do that, but it's major pain with 2000 hosts. > Plus, there is application data in the packets that I can't allow into > the public domain. I really don't think I can pull it off... I > literally would have to go through our legal department.
I still dont understand.
"tcpdump -p -n -s 1600 -c 10000" doesnt reveal User data at all. Without any exact data from you, I am afraid nobody can help.
> >> Random ideas : >> >> 1) Is your server behind a NET router or something ? > > What's a NET router? I am behind a Cisco router and a firewall, but > these network components have completely been replaced/rebuilt several > times in the 4+ years that we've had this problem. I've looked at the > logs there and neither are doing anything other than passing the > traffic along.
Typo error, I meant NAT. Most routers doing NAT have some limits, timers, hacks...
> >> 2) Are you sure you are not using connection tracking, and hit a limit on it ? > > I'm using ip_conntrack, but the limit I have for max entries is 65K. > The most I've seen in there are a couple thousand- that was one of the > first things I monitored very closely.
Now please try without conn tracking module. I saw many failures in the past that were trigered by conntrack.
Do you have some firewall rules, using some netfilter modules like hashlimit ?
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