[Dnsmasq-discuss] rr_on_list stuck in infinite loop, dnsmasq unresponsive

[Clayton Craft]

On Mon, 19 Feb 2024 13:29:44 -0800 Clayton Craft <clayton at craftyguy.net> wrote:

> The conditions to trigger this aren't well understood by me... it seems to
> happen when we use dnsmasq's dbus interface to toggle filtering ("set_filter A
> bool"). But I've had trouble reproducing it manually. We hit it a lot when using
> a NetworkManager dispatcher script to apply filtering in dnsmasq conditionally.

Ok I've been able to reproduce this with a simple script that interacts with
dnsmasq over dbus. The CNAME lookup at the end hangs dnsmasq pretty consistently
on the second iteration on one device I have (OnePlus 6, aarch64 running
postmarketOS), and it does not trigger a hang on another aarch64 system I
have (same OS).

I also forgot to mention this earlier, but I'm using dnsmasq 2.90 :)


    #!/bin/sh
    
    dnsmasq -p 5353 --enable-dbus=uk.org.thekelleys.dnsmasq
    
    trap cleanup SIGINT
    
    cleanup () {
            pkill -9 -f "dnsmasq -p 5353"
            exit
    }
    
    while true; do
            echo "Trying..."
    
            busctl call uk.org.thekelleys.dnsmasq \
                /uk/org/thekelleys/dnsmasq \
                uk.org.thekelleys.dnsmasq \
                SetFilterA b false
            busctl call uk.org.thekelleys.dnsmasq \
                /uk/org/thekelleys/dnsmasq \
                uk.org.thekelleys.dnsmasq \
                SetFilterAAAA b false
            busctl call uk.org.thekelleys.dnsmasq \
                /uk/org/thekelleys/dnsmasq \
                uk.org.thekelleys.dnsmasq \
                ClearCache
    
            dig @127.0.0.1 -p 5353 +nocmd mirror.postmarketos.org cname +noall +answer
    
            echo "Done"
    done
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