I have been experiencing problems running a nfs server and iptables on the same machine.The problem was also reported almost a year ago by Paul Raines http://lists.netfilter.org/pipermail/netfilter/2002-January/030002.html but it seems no solution has been found yet. The problem is this: A machine running linux 2.4.18 or 2.4.19 works just fine when running just the kernel nfsd. A single client connected to the server with 100Mbit ethernet sees throughput of 5-10MByte/sec even after an hour or two of continous transfers. If the nfs server is also running iptables the throughput is initially the same (5-10MByte/sec) but after a while (200MByte-500MByte total transfer) the client starts reporting "nfs server not responding" followed after a while by "nfs server OK" and of course the transfer rate goes way down (< 1MByte/sec). Using tcpdump on the client seems to indicate that some packets have their headers garbled - wrong fragment ids being the typical error. Having iptables compiled as modules and simply loading or unloading the ipt_conntrack module is sufficient for causing/removing the problem. Having iptables support compiled into the kernel causes the problem allways. The problem has been verified on 4 different machines with a variety of different ethernet cards. In all cases the network continues to work without problems for all other types of traffic - i.e a telnet connection from client to server works with no delay and a ftp transfer goes at >5MByte/sec even when nfs throughput is suffering. \Lars Knudsen
