[Dnsmasq-discuss] dnsmasq 2.86 crash

Eloy Paris peloy at chapus.net
Wed Oct 13 02:55:22 UTC 2021


I am experiencing crashes in dnsmasq (2.86). I am able to reproduce it
though I am not sure about the exact sequence of events -- it happens
when I enable/disable my Ethernet NIC and disable/enable my wireless

In this use case, dnsmasq provides DNS and DHCP for a virtual machine
(VM) running on KVM. Something like this:

   +-- (Ethernet)-+
   |              |
Internet          + Hypervisor (virbr0) --- VM
   |              |
   +--- (Wi-fi)---+

The interfaces I am enabling and disabling are on the hypervisor
("Ethernet" and "Wi-fi" above; virbr0 never goes down).

I guess dnsmasq does not handle gracefully receiving a DNS request from
the VM when the external interfaces of the hypervisor (Ethernet or
wi-fi) go down?

Some details below; happy to provide more information if that's not
enough to get to the bottom of it.


Eloy Paris.-


elparis at chapilu[0]:~$ sudo coredumpctl debug dnsmasq
[sudo] Mot de passe de elparis : 
           PID: 46002 (dnsmasq)
           UID: 65534 (nobody)
           GID: 65534 (nobody)
        Signal: 11 (SEGV)
     Timestamp: Tue 2021-10-12 22:17:33 EDT (11min ago)
  Command Line: /usr/bin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/default.conf --leasefile-ro --dhcp-script=/usr/lib/libvirt/libvirt_leaseshelper
    Executable: /usr/bin/dnsmasq
 Control Group: /system.slice/libvirtd.service
          Unit: libvirtd.service
         Slice: system.slice
       Boot ID: a42fe0fbd18649ad8a6951687e2855d8
    Machine ID: 3d34409507634591951da9abb51a3942
      Hostname: chapilu
       Storage: /var/lib/systemd/coredump/core.dnsmasq.65534.a42fe0fbd18649ad8a6951687e2855d8.46002.1634091453000000.zst (present)
     Disk Size: 204.6K
       Message: Process 46002 (dnsmasq) of user 65534 dumped core.
                Found module linux-vdso.so.1 with build-id: c6d7bcf242640b81aef03f231535fa4c2486c744
                Found module libffi.so.7 with build-id: de60e99f39569d11d09160bbdcd486cedc87d2b6
                Found module libp11-kit.so.0 with build-id: 5314ec746546ada6f442b6fdfae15eab9f6d3cdc
                Found module libcrypto.so.1.1 with build-id: 6d23f0a3f354825868d044684fad31d482cc9210
                Found module libdl.so.2 with build-id: 5abc547e7b0949f89f3c0e21ab0c8331a7440a8a
                Found module libcrypt.so.2 with build-id: 3743451bdaf36f951f926927633fd964813025d0
                Found module libnss_systemd.so.2 with build-id: 22990ff716d182c427e26b7a3cf94048b55b3e75
                Found module libnss_files.so.2 with build-id: 1a36dfc01d3a1010b2ee79766a24a8090a3266d5
                Found module libgpg-error.so.0 with build-id: ba85170c2d9343ea05eea8fa2048c212ff4ef552
                Found module libgcrypt.so.20 with build-id: db45f5d5e0f7af1e77324fea1885f974619ad268
                Found module libcap.so.2 with build-id: c1674f9082fedd415876b9f7d9712269163259b5
                Found module liblz4.so.1 with build-id: e63600ab23b2f6997f42fac2fa56e1f02ce159a1
                Found module libzstd.so.1 with build-id: 4b10444c1560ebc574af4d5f488b7408b22d450e
                Found module liblzma.so.5 with build-id: 8b615460aa230708c5183f16bede67aa0437d95e
                Found module librt.so.1 with build-id: 75484da2d6f1515189eefa076e0a40328834cd16
                Found module ld-linux-x86-64.so.2 with build-id: 040cc3dd10461562f177df39e3be2f3704258c3c
                Found module libmnl.so.0 with build-id: fdf3a318247060fa3e451d511ebaf23a7396d1dd
                Found module libnfnetlink.so.0 with build-id: 273cc877c7b2ff41e88753edda777d7f1c4017ca
                Found module libunistring.so.2 with build-id: 015ac6d6bcb60b7d8bea31a80d1941b06e8636ab
                Found module libsystemd.so.0 with build-id: f776aaa16b4e2ba7056d01d928e4b2726ffe2b8b
                Found module libpthread.so.0 with build-id: 07c8f95b4f3251d08550217ad8a1f31066229996
                Found module libc.so.6 with build-id: 4b406737057708c0e4c642345a703c47a61c73dc
                Found module libgmp.so.10 with build-id: e58d34ab389d1b649c24195c2d145e3ff2e58290
                Found module libhogweed.so.6 with build-id: 2d70cff7b1841b4d9ca4e8e7726cd4b944c07fdc
                Found module libnettle.so.8 with build-id: 9a878e513c02007598fcf1e2e286c2203f13536e
                Found module libnetfilter_conntrack.so.3 with build-id: 0ad526380b1a1986a1e471a84d88d5f2a7fedd80
                Found module libidn2.so.0 with build-id: 1ce2b50ad9f9821c2c629b521cf5a3c99593d332
                Found module libdbus-1.so.3 with build-id: 74f2ab9c60512f3a93c932c3f627564d42e0b11e
                Found module dnsmasq with build-id: 17b49d0999133997748526c51d99bf8b932fb79d
                Stack trace of thread 46002:
                #0  0x0000561772564d46 lookup_domain (dnsmasq + 0x55d46)
                #1  0x0000561772532b1e forward_query (dnsmasq + 0x23b1e)
                #2  0x000056177253387e receive_query (dnsmasq + 0x2487e)
                #3  0x0000561772538b7c check_dns_listeners (dnsmasq + 0x29b7c)
                #4  0x000056177251888b main (dnsmasq + 0x988b)
                #5  0x00007f85147e4b25 __libc_start_main (libc.so.6 + 0x27b25)
                #6  0x00005617725197ae _start (dnsmasq + 0xa7ae)

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Reading symbols from /usr/bin/dnsmasq...
[New LWP 46002]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".
Core was generated by `/usr/bin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/default.conf --leasefile-'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x0000561772564d46 in lookup_domain (domain=0x561772b1d7a0 "enterprise.activity.windows.com", flags=flags at entry=128, 
    lowout=lowout at entry=0x7ffe8a4b63ac, highout=highout at entry=0x7ffe8a4b63b0) at domain-match.c:234
234	domain-match.c: Aucun fichier ou dossier de ce type.

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