Hi all,
Apologies if my question has been addressed already. I did search FAQ
and archives first, and found nothing that seemed related. My apologies also if this post is excessively long.
I have found on a number of installations that squid fails/ceases to work if the machine connects to the internet *after* boot time (and therefore, after squid has been started).
Basically, whenever I connect to the internet (in each case over ADSL), then access to web pages through squid will hang, and squid needs to be restarted before it will work again.
On my laptop, this situation occurs whenever I boot whilst disconnected from the office LAN, since squid is started before I connect to the internet. If I am in the office, then the LAN (eth0) is started before squid, and so squid works immediately. If I subsequently stop eth0, and connect to the internet using ADSL, then squid needs to be restarted before it will resume working.
On a friend's server, a similar situation occurs. Squid is started at boot time, but the ADSL is connected on demand. It appears that each time the ADSL is started, squid needs a restart before it is operational.
My laptop is running squid 2.5.STABLE1 (from RedHat 9.0), and my friend's server is running whatever version comes with Fedora Core 2.
On my laptop: * the connection to ADSL is made using PPPoE, running under linux (roaring penguin).
* I need to restart squid every time I change my path to the internet (eg, switch between eth0 and ADSL (ppp0)).
* my browser is configured to use squid as a proxy (since squid and browser are running on the same machine, so I can see no way to make squid a transparent proxy).
* I can successfully telnet to a remote web server before squid has been restarted, so I am confident the problem is specific to squid.
* the contents of resolv.conf change whenever I switch between LAN and WAN.
* The logs show nothing is amiss. /var/log/messages shows no errors from squid, and /var/log/squid/access.log shows no record of the hanging access.
On my friend's server:
* the connection is made using PPPoA which is built into the ADSL modem.
This means, among other things, that the linux network interface for the
ADSL connection is always up, and never changes address; and that no scripts are run on the linux box when connecting to or disconnecting from the internet.
* squid doesn't seem to require restarting every time the ADSL reconnected. There are times the it can be disconnected and then reconnected and squid is fine, and other times squid must be restarted after the ADSL has been reconnected.
* squid is configured to be a transparent caching proxy. The clients on the server's LAN are not configured to use squid as their proxy, and the server REDIRECTs the packets to squid.
* the contents of resolve.conf do not change when the ADSL connection is connected/disconnected. In addition, the server is running a caching DNS server.
* I haven't checked logs, or tried telnetting manually.
One possible theory is that the problem is related to DNS resolution. This could explain why squid shows different results to other applications (since I understand squid does its own DNS resolution). On my laptop, the DNS server addresses have changed whenever I switch network (in this case, resolve.conf has definitely changed). On my friend's server, the DNS server used by linux does not change (resolv.conf does not change, and the local DNS server is always available). However, I notice that squid can (usually does) check for available DNS servers, and that this test would normally fail when squid first starts.
So, my questions are:
1. How should I be trying to fix this? With a workaround, such as automating a squid restart whenever the ADSL is connected; or with a fix to squid, such as adjustment of config parameters, an upgrade, or changes in source code?
2. Can anyone explain what is causing the problem, or suggest further tests I could run to determine the actual cause?
All replies received with thanks.
Cheers! Nik.
