Poor throughput with natd
list at museum.rain.com
Tue Nov 24 00:06:13 UTC 2009
Please copy me on replies.
I am testing ipfw and natd on a gateway machine running FreeBSD
7.2-STABLE #0: Tue Oct 27 00:12:39 PDT 2009 with the generic
kernel. ipfw.ko and ipdivert.ko are loaded as modules, since
they're not part of the GENERIC kernel.
The symptom is that scp uploads from the gateway machine have
very poor throughput, often showing "stalled" status in the scp
Machines on the LAN do not suffer this problem, and can upload
their traffic via NAT with no observed degradation in throughput.
That's why I haven't noticed this problem until recently, when I
tried rsync-ing some files outbound from the gateway to a remote
I can work around the problem, but this problem has never cropped
up in the past. Is there a problem in my configuration, or in
Thanks for your time!
All commands below were executed on the gateway machine that is
running natd with very basic options:
15:07:37 /root# findps natd
root 480 0.0 0.1 3388 1252 ?? Ss 12Nov09 4:32.81 natd -n fxp1
Here are the ipfw rules:
14:55:41 /root# ipfw show
00100 949306 56746770 allow ip from any to any via lo0
00200 0 0 deny ip from any to 127.0.0.0/8
00300 0 0 deny ip from 127.0.0.0/8 to any
00400 77293 8699526 divert 8668 ip from any to any via fxp1
00500 35245946 28535731864 allow ip from any to any
65535 0 0 deny ip from any to any
Downloading, scp has no trouble:
14:55:59 /root# scp -p remote:public_html/video/tatra1.mpg .
tatra1.mpg 100% 85MB 559.4KB/s 02:36
But uploads stall. This scp process was killed after about 60 seconds:
14:58:40 /root# scp -p tatra1.mpg remote:/tmp/
tatra1.mpg 0% 320KB 1.8KB/s - stalled -^CKilled by signal 2.
Deleting the DIVERT rule eliminates the stalling:
14:59:54 /root# ipfw delete 400
15:00:04 /root# scp -p tatra1.mpg remote:/tmp/
tatra1.mpg 27% 23MB 248.2KB/s 04:14 ETA^CKilled by signal 2.
But of course, it also eliminates NAT.
15:01:14 /root# ipfw add 400 divert 8668 ip from any to any via fxp1
00400 divert 8668 ip from any to any via fxp1
Adding this rule works around the natd throughput problem:
15:01:29 /root# ipfw add 350 allow all from me to any via fxp1
00350 allow ip from me to any via fxp1
15:02:03 /root# scp -p tatra1.mpg remote:/tmp/
tatra1.mpg 100% 85MB 266.9KB/s 05:27
More information about the freebsd-questions