Date: 10 May 2002 11:09:17 +1000 From: Andrew Reilly <areilly@bigpond.net.au> To: bugs@bugs.au.freebsd.org, freebsd-questions@freebsd.org Cc: Archie Cobbs <archie@dellroad.org> Subject: Network problems in recent -stable Message-ID: <1020992958.18920.113.camel@gurney.reilly.home>
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Hi, I follow -stable on a more-or-less weekly basis, and this has it's ups and downs, because sometimes things change, and it's not clear whether the change is the result of the system upgrade, a port upgrade, or something external. All good fun, anyway. I maintain an MS-PPTP VPN link between my FreeBSD system and my office network, using the mpd port and netgraph. This has, historically, been really reliable, and works well. Lately, I've been having problems, though: Often, mail sent _to_ the office mail server will hang, and qmail-send will note a time-out. Mail from the server is almost never a problem (fetchmail), and messages sent manually, by typing SMTP through a telnet session also always work fine. I've recently noticed CVS update, diff and commit commands failing. Turning on logging (cvs -t) shows that a hang occurs when sending files to the server (another FreeBSD-4.something box). Checking out whole project directories works fine, though. Only sent data is the problem. Yesterday I tried running some X clients across the VPN, with apparently similar results. xev would run, but xv and xterm would hang. Both would run nicely through an ssh proxy connection, rather than over the VPN. I've run tcpdump on ng0, the netgraph VPN interface, and these hangs show my system sending an ACK packet over and over again, with no reply or progress from the other end. In summary: it sounds to me like a fragmentation/MTU problem on packets sent from my machine to machines on the office network. Little packets get through fine, but large ones that have to fragment get lost in the works. Seemingly. Trouble is, I know only enough TCP/IP networking juju to get myself into trouble. I don't know how to tweak MTUs, or even to determine whether that is indeed the problem. Are there network trouble-shooting diagnostic tools in the system, or in the ports collection? I need to get to the bottom of this, but don't know where to start. Any help would be greatly appreciated. -- Andrew To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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