Re: socket debug
Re: socket debug
- Subject: Re: socket debug
- From: Quinn <email@hidden>
- Date: Fri, 6 Dec 2002 18:08:24 +0000
At 16:23 +0000 6/12/02, Michael Marti wrote:
I believe this means that I have to recompile the kernel (sigh). Well I
have to do so anyway in order to use ktrace. I just don't know, how to get
the source of the kernel (the tag given by uname -a does not exist on the
cvs server) and I don't know what config to change in order to use trpt.
There are two easy ways to do this.
1. If you go to the CVS Web interface for xnu, you'll find a popup
menu that lists all of the tags.
<
http://www.opensource.apple.com/cgi-bin/registered/cvs/src/notlive/xnu/>
2. Alternatively, if you go to the Darwin 6.0.1 projects page, you
can get download a .tar.gz file for the xnu sources.
<
http://www.opensource.apple.com/projects/darwin/6.0/projects.html>
I'm using a normal tcp socket to connect to a remote host. The connection
works fine, just sometimes it takes about one minute to establish. If I look
at the packages with tcpdump, I can see that the client tries to connect:
(see below the connection requests)
This makes me think that the problem is with the server. On the other hand
it is possible to connect to the server, during the time another connection
is blocked and sends the packages below. This even works from the same host
(epp02). Now I don't know if it's the server or the client.
Oh and after about one or two minutes the hanging connection sometimes
establishes and everything is OK (except for the 2 minute delay).
Any idea where the problem is?
------------------------------------------------------------------
15:53:56.381263 epp02.epp.ist.utl.pt.1023 > agamemnon.epp.ist.utl.pt.15001:
S 1879446430:1879446430(0) win 32768 <mss 1460,nop,wscale
0,nop,nop,timestamp 2612369 0> (DF)
15:53:59.174780 epp02.epp.ist.utl.pt.1023 > agamemnon.epp.ist.utl.pt.15001:
S 1879446430:1879446430(0) win 32768 <mss 1460,nop,wscale
0,nop,nop,timestamp 2612374 0> (DF)
15:54:02.175034 epp02.epp.ist.utl.pt.1023 > agamemnon.epp.ist.utl.pt.15001:
S 1879446430:1879446430(0) win 32768 <mss 1460,nop,wscale
0,nop,nop,timestamp 2612380 0> (DF)
----------------------------------------------------------------------------
Given that you're only ever seeing SYN packets from the client to the
server, this doesn't seem like a client problem. More likely the SYN
packets are being dropped or the SYN-ACK coming back from the server
are. So the Mac just keeps resending the SYN packets every couple of
seconds, which is what it's supposed.
My guess is that some hardware between the client and server is
dropping the packets, most likely a firewall or some broken packet
shaper. Can you get a packet trace from the server side? If so, you
can see whether the Mac's SYN is being dropped, or whether it's the
server's reply SYN-ACK that's going astray. Given that both machines
are on your network, it should be feasible to get traces from every
hop along the way to see where the problem is.
S+E
--
Quinn "The Eskimo!" <
http://www.apple.com/developer/>
Apple Developer Technical Support * Networking, Communications, Hardware
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