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Fuzzy Fox writes:
> I guess I have a question to ask, before I get into this: What do you
> really *expect* to happen, when the PPP link is down? If the link is
> down, then no connection is possible, and yet you are attempting to
> initiate a connection anyway! Why? Shouldn't you bring up the link,
> and then initiate contact?
>
> It seems to me that you might expect one of two activities to occur:
>
> 1. The connection fails with an error immediately on the attempting
> client.
>
> 2. The connection is brought up automatically by the masq box.
>
> instead, you're getting
>
> 3. The connection just hangs forever, then eventually times out.
>
> I believe that you can configure your masq box to do any of these three
> things, and apparently you have it set up to do #3. :)
I would like to have 1 to happen, because I prefer initiating the connection manually
with wvdial or kppp to automatic connection with diald. So I can prevent connections
to the internet by programms which and at moments when I do not want being connected.
3 would
not hurt me too much if it would not cause netscape to crash. For example I start
netscape to read some local html-files, and it immediately crashes on the masqued
mashine if I have the default route set to the linux box.
> > The problem is that when there is no connection to my ISP, when the
> > masqued machine is trying to reach a machine outside my LAN, the
> > program originating the demand hangs,
>
> It sounds like the masq box isn't replying with any sort of "destination
> unreachable" ICMP packet, which is what it really should do, if it is
> attempting to forward a packet, and cannot find a suitable route. When
> the PPP connection is down, is there still a default route pointing
> someplace, on the masq box? If so, where? And why?
[ cut ]
> If there is no default route on the masq box, then I'm rather puzzled as
> to why the connection doesn't get cut short. Do you filter ICMP
> messages? If you watch the connection attempt, from the masq box, with
> tcpdump, do you see any ICMP replies being sent? Are they ignored by
> the client? Interesting...
I retried the situation with my earlier set-up (without a DNS caching on the masq
box) and watched with tcpdump. (There is no default route on the masq box.)
The result is that the masq box sends an ICMP reply
back to the masqued box 16 times (8 times concerning the first DNS server, 8 times
concerning the second DNS server, which are set up on the masqued machine), for
example (x.x.x.x being the adress of one of the DNS servers.)
16:11:00.390347 my.masqued.box.1024 > x.x.x.x.domain: 20749+ (39)
16:11:00.390410 my.masq.box > my.masqued.box: icmp: net x.x.x.x unreachable [tos 0xc0]
the intervals of the replies are either 5, 10 or 20 seconds.
16:11:00.390410 ...
16:11:05.397198 ...
16:11:10.406392 ...
16:11:15.415731 ...
16:11:20.424989 ...
16:11:30.433605 ...
16:11:40.442106 ...
16:12:00.449253 ...
16:12:20.456425 ...
16:12:25.465691 ...
16:12:30.474878 ...
16:12:35.484160 ...
16:12:40.493441 ...
16:12:50.501982 ...
16:13:00.510573 ...
16:13:20.517766 ...
Then the programm on the masqued machine (e.g. ping foo) returns with: unknown host
Apparently the masqued machine is retrying 8 times to contact each DNS server, but is
waiting between each retry. After experimenting also with dnsquery I assume that it
is 4 times querying for foo, and 4 times for foo.my.domain.
I will retry to install the DNS caching (after reading the DNS-Howto ;) ), but maybe
in the meantime you can help me interpret this situation? Is there a way to have DNS
lookups fail immediately instead of retrying that often. Thanks,
Michael
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