TCP outgoing problems in 2.0.X?
Allan Hsu (animate2@underworld.net)
Mon, 20 Jul 1998 01:45:00 -0400
I've got a 16MB 5x86WB-133 box running linux as a ip_masq for a lan, and it
works great, except for one problem; after anywhere from a few minutes to a
few hours of uptime, the box suddenly refuses to make any outgoing TCP
connections. One moment, I'll be able to telnet/ftp/browse out from the
box, and the next, nothing happens. When this problem occurs, it does not
affect any masqueraded traffic, only TCP connections originating from the
box itself. Strangely enough, the box will still make outoing icmp/udp
connections, so DNS and traceroutes still work. I've tried to remedy this
problem for quite a while now, and am beginning to wonder if anything is
happening in the tcp code in the kernel that would effect this. When this
problem hits, I am even unable to make connections to localhost via
ftp/telnet/etc. This problem seems to arise faster if the box is making a
rapid series of connects. A quick and easy way to trigger this was to use
wget to (try to) mirror a web directory on the local machine (wget -r
http://localhost/)... It takes a few seconds for the box make several
connects to itself, and then wget just stops at "connecting to
localhost:80..." and then just sits there until the connect times out. This
problem does not affect any existing, established connections, only new
ones. A "netstat" shows that the outgoing connections have statuses of
"SYN_SENT." If I am trying to make a connect to localhost, I also get a
connection with status "SYN_RECV," and that's that; nothing else happens. If
I don't deliberately try to trigger this behaviour, the box can sometimes go
for a day or two without doing it again, at which point I have to reboot
(and kick and scream a few times). Could this be a kernel problem in 2.0.X
kernels? I have yet to try a 2.1.X kernel on the box, but this behaviour has
been exihibited in at least the last couple 2.0.X kernels on this box.
Allan.
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