How to diagnose a hung ppp connection.

svn path=/head/; revision=4159

FAQ/network.sgml

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-<!-- $Id: network.sgml,v 1.20 1999-01-27 10:01:08 mbarkah Exp $ -->
+<!-- $Id: network.sgml,v 1.21 1999-01-31 18:58:22 brian Exp $ -->
 <!-- The FreeBSD Documentation Project -->
 
   <sect>
@@ -317,6 +317,82 @@ default            10.0.0.2           UGSc        0        0      tun0
 
         <p>Refer to your modem manual for details.
 
+      <sect2>
+        <heading>My connection hangs after a random amount of time</heading>
+
+        <p>Many people experience hung connections with no apparent
+        explaination.  The first thing to establish is which side of the
+        link is hung.
+
+        <p>If you are using an external modem, you can simply try using
+        <tt/ping/ to see if the <tt/TD/ light is flashing when you
+        transmit data.  If it flashes (and the <tt/RD/ light doesn't), the
+        problem is with the remote end.  If <tt/TD/ doesn't flash, the problem
+        is local.  With an internal modem, you'll need to use the <tt/set
+        server/ command in your <tt/ppp.conf/ file.  When the hang occurs,
+        connect to ppp using pppctl.  If your network connection suddenly
+        revives (ppp was revived due to the activity on the diagnostic socket)
+        or if you can't connect (assuming the <tt/set socket/ command
+        succeeded at startup time), the problem is local.  If you can connect
+        and things are still hung, enable local async logging with <tt/set log
+        local async/ and use <tt/ping/ from another window or terminal to make
+        use of the link.  The async logging will show you the data being
+        transmitted and received on the link.  If data is going out and not
+        coming back, the problem is remote.
+
+        <p>Having established whether the problem is local or remote,
+        you now have to possibilities:
+
+        <sect3>
+          <heading>The remote end isn't responding</heading>
+
+          <p>There's very little you can do about this.  Most ISPs will
+          refuse to help if you're not running a Microsoft OS.  You can
+          <tt/enable lqr/ in your <tt/ppp.conf/ file, allowing ppp to
+          detect the remote failure and hang up, but this detection is
+          relatively slow and therefore not that useful.  You may want
+          to avoid telling your ISP that you're running user-ppp....
+
+          <p>First, try disabling all local compression by adding the
+          following to your configuration:
+
+          <verb>
+            disable pred1 deflate deflate24 protocomp acfcomp shortseq vj
+            deny pred1 deflate deflate24 protocomp acfcomp shortseq vj
+          </verb>
+
+          <p>Then reconnect to ensure that this makes no difference.
+          If things improve or if the problem is solved completely,
+          determine which setting makes the difference through trial
+          and error.  This will provide good amunition when you contact
+          your ISP (although it may make it apparent that you're not
+          running a Microsoft product).
+
+          <p>Before contacting your ISP, enable async logging locally
+          and wait until the connection hangs again.  This may use up
+          quite a bit of disk space.  The last data read from the port
+          may be of interest.  It is usually ascii data, and may even
+          describe the problem (``Memory fault, core dumped'' ?).
+
+          <p>If your ISP is helpful, they should be able to enable logging
+          on their end, then when the next link drop occurs, they may be
+          able to tell you why their side is having a problem.  Feel free
+          to send the details to <url url="mailto:brian@Awfulhak.org"
+          name="brian@Awfulhak.org">, or even to ask your ISP to
+          contact me directly.
+
+        <sect3>
+          <heading>Ppp is hung</heading>
+          <p>Your best bet here is to rebuild ppp by adding <tt/CFLAGS+=-g/
+          and <tt/STRIP=/ to the end of the Makefile, then doing a
+          <tt/make clean &amp;&amp; make &amp;&amp; make install/.  When
+          ppp hangs, find the ppp process id with <tt/ps ajxww | fgrep ppp/
+          and run <tt/gdb ppp PID/.  From the gdb prompt, you can then use
+          <tt/bt/ to get a stack trace.
+
+          <p>Send the results to <url url="mailto:brian@Awfulhak.org"
+          name="brian@Awfulhak.org">.
+
       <sect2>
         <heading>Nothing happens after the Login OK! message</heading>