From owner-freebsd-net  Thu Feb  3 22:17:34 2000
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Subject: Non-blocking sockets and network outages
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Date: Thu, 03 Feb 2000 22:17:31 -0800
From: Gene Kan <genehkan@scam.xcf.berkeley.edu>
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I've got an interesting problem involving non-blocking sockets and network
outages.  In all cases, SO_KEEPALIVE is on, and
net.inet.tcp.always_keepalive: 1.  The problem manifests itself when
there is a net partition, the other endpoint loses power, or something of
that sort.  Basically, when a connection dies without first notifying with
RST or FIN.

If I mark a socket for reading, the fd will just never become active, and
I have an ESTABLISHED connection (verified with netstat) forever.

If I do a non-blocking write, the write will return -1 with errno==EAGAIN.
Obviously, since it just looks like the other side isn't slurping up the
data because I'm not getting a window update.

Finally...I can't figure out why the keepalives aren't taking care of all
this for me, and discovering the connections are dead.  I waited for hours,
which surely should have been more than all timeouts...

Thanks for any help.

Gene


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