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Active Diald does not work occasionally

Posted on 1997-06-17
Medium Priority
Last Modified: 2010-03-17
I have a typical setup with a local network and a Linux server on a single phone line. I have diald and IP masq installed. It works great, but once in a few days diald makes the connection completely, but no IP traffic is possible. Here is some output:

#ping (the other end of connection)
ping: sendto: Operation not permitted
PING ( 56 data bytes
ping: wrote 64 chars, ret=-1

#ifconfig ppp0
ppp0      Link encap:Point-Point Protocol  
          inet addr:  P-t-P:
          UP POINTOPOINT RUNNING  MTU:1500  Metric:1
          RX packets:193 errors:0 dropped:0 overruns:0
          TX packets:237 errors:0 dropped:0 overruns:0

I am not even sure if the problem is with diald or IP masq.
Any suggestions?

Question by:simonff
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Expert Comment

ID: 1584936
Try the above again, from both your masqueraded machine, and from your directly connected machine. This will tell you whether the problem is with the masquerading setup, or the PPP link.

The output from route -n on both machihnes when the problem manifests would also be useful in tracking this one down.

Author Comment

ID: 1584937
Alas, I cannot ping from other machines - UDP is not allowed through the masq setup, and I cannot use ifconfig because they are Win 95 machines. The above output applied to the directly connected machine.
I will monitor the 'route -n' output when this strange thing happens again, but I do not quite like what I have even under the normal conditions (note the multiple entries). Here is our local network.

Fresh after reboot:
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface UH    1      0        0 sl0   U     0      0        1 eth0       U     0      0        0 lo         U     1      0        0 sl0

While online:
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface UH    0      0        0 ppp0 UH    1      0        0 sl0 UH    0      0        1 ppp0   U     0      0      316 eth0       U     0      0      129 lo         U     0      0        3 ppp0         U     1      0      110 sl0

Accepted Solution

sauron earned 300 total points
ID: 1584938
After a reboot, you have a route to your local network, using eth0, a loopback route, a host route to, using sl0, and a default route over sl0.

The last 2 are set by diald, and monitored - when a packet is routed over the sl0 interface, it brings the link up, and adds the ppp0 routes you seen in the second table.

You can see that you only have a route to the remote end of your ppp link ( when the link is up - the fake sl0 route goes to - when the link comes up diald sets up this route over the ppp0 interface. I would guess that the route you have to (your real route) is negotiated by the remote end of your link, and if the negotiation goes a little slow sometimes, then this route may not get registered, leaving outgoing packets on the ppp link trying to reach - an address which is on a different class C network, and will be unreachable, thus your error message.

Check you diald.conf, and look for that bogus ip address - if you replace that with, it'll probably cure your problem. You might also want to look in the /etc/syconfig/network-scripts directory, and set up to be your default gateway, to tidy up your routing table.
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Author Comment

ID: 1584939
Silly me... :) I had this bogus IP address as remote_IP in diald.conf... Thanks. Say, do you know where I can get wildmat sources or the whole implementation of XPAT command?

Author Comment

ID: 1584940
Oops, it was premature. I have just had the same problem again. See the routing table, it is quite good now. What else can be wrong?

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface UH    0      0        1 ppp0 UH    1      0        0 sl0   U     0      0      263 eth0       U     0      0       77 lo         U     0      0        2 ppp0         U     1      0        4 sl0

Expert Comment

ID: 1584941
Routing table looks fine to me now - I have a very similar setup, and my routing table looks just like that, so I'd say your routing is set up right.

You're getting 'Operation not permitted' as well, so that seems to suggest that something else is up. What you might want to do, is , next time the problem occurs, try running tcpdump on the ppp0 interface, then trying to ping. See if any packets go out at all - if they don't, something is wrong with the logic somewhere, as opposed to the physical connection being at fault. You could put diald into debug mode - add 'debug 31' to the end of your diald.conf - this logs *loads* of stuff to syslog, and might give you some pointers.

Author Comment

ID: 1584942
OK, here is something that I have caught during the last trouble period.

Diald debug messages (debug flags at 255, rule 30 is the very last one - accept any):
Jul  5 19:01:18 rrg diald[216]: filter accepted rule 30 proto 89 len 64 packet,0 =>,0
Jul  5 19:01:18 rrg diald[216]: Adding connection 134680648 @ 868114878 - timeout 30

Tcpdump results:
22:21:06.090000 > OSPFv2-hello 44: backbone [tos 0xc0] [ttl 1]
22:21:16.090000 > OSPFv2-hello 44: backbone [tos 0xc0] [ttl 1]
And so on...

Does that help to diagnose the problem, or should I run tcpdump in a more verbose mode?

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