Something in a recent dnsmasq update broke KVM. I hit the same and found
a workaround that gets me rolling again wtih KVM guests at least....
here's a quick shell summary:
bladernr@galactica:~$ sudo virsh net-start default
error: Failed to start network default
error: internal error: Child process (VIR_BRIDGE_NAME=virbr0 /usr/sbin/dnsmasq
--conf-file=/var/lib/libvirt/dnsmasq/default.conf --leasefile-ro
--dhcp-script=/usr/lib/libvirt/libvirt_leaseshelper) unexpected exit status 2:
dnsmasq: failed to create listening socket for 192.168.123.1: Address already
in use
bladernr@galactica:~$ sudo virsh net-list
Name State Autostart Persistent
----------------------------------------
bladernr@galactica:~$ sudo apt-cache policy dnsmasq-base
dnsmasq-base:
Installed: 2.90-0ubuntu0.23.10.1
Candidate: 2.90-0ubuntu0.23.10.1
Version table:
*** 2.90-0ubuntu0.23.10.1 500
500 http://archive.ubuntu.com/ubuntu mantic-updates/main amd64 Packages
500 http://security.ubuntu.com/ubuntu mantic-security/main amd64
Packages
100 /var/lib/dpkg/status
2.89-1 500
500 http://archive.ubuntu.com/ubuntu mantic/main amd64 Packages
bladernr@galactica:~$ sudo apt install dnsmasq-base=2.89-1
bladernr@galactica:~$ sudo virsh net-start default
Network default started
bladernr@galactica:~$ sudo virsh net-list
Name State Autostart Persistent
--------------------------------------------
default active yes yes
as you can see, as a workaround, reverting to the original Mantic
version allows the NAT network to start and I can once again launch KVM
guests on my machine.
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Touch seeded packages, which is subscribed to dnsmasq in Ubuntu.
https://bugs.launchpad.net/bugs/2055776
Title:
After updating ubuntu, the network to which the subnet address is
assigned does not become active in KVM.
Status in dnsmasq package in Ubuntu:
Confirmed
Bug description:
phenomenon:
After updating ubuntu, the network to which the subnet address is assigned
does not become active in KVM.
Cause:
This is because the following dnsmasq update operation performed by apt's
automatic update causes an error. It worked properly with dnsmasq 2.80, but
does not work properly with 2.90.
$ cat /var/log/apt/history.log
(snip)
Start-Date: 2024-02-27 06:17:31
Commandline: /usr/bin/unattended-upgrade
Upgrade: dnsmasq-base:amd64 (2.80-1.1ubuntu1.7, 2.90-0ubuntu0.20.04.1)
End-Date: 2024-02-27 06:17:44
(snip)
$
Cause details:
As a premise, bind-dynamic is set in the dnsmasq config file for KVM. Below
is an example.
$ cat default.conf
##WARNING: THIS IS AN AUTO-GENERATED FILE. CHANGES TO IT ARE LIKELY TO BE
##OVERWRITTEN AND LOST. Changes to this configuration should be made using:
## virsh net-edit default
## or other application using the libvirt API.
##
## dnsmasq conf file created by libvirt
strict-order
user=libvirt-dnsmasq
pid-file=/run/libvirt/network/default.pid
except-interface=lo
bind-dynamic
interface=virbr0
dhcp-range=192.168.122.2,192.168.122.254,255.255.255.0
dhcp-no-override
dhcp-authoritative
dhcp-lease-max=253
dhcp-hostsfile=/var/lib/libvirt/dnsmasq/default.hostsfile
addn-hosts=/var/lib/libvirt/dnsmasq/default.addnhosts
$
When starting the network with KVM (virsh net-start), dnsmasq started from
KVM executes the make_sock function twice as shown below.
$ cat network.c
(snip)
1087 static struct listener *create_listeners(union mysockaddr *addr, int
do_
1087 tftp, int dienow)
1088 {
1089 struct listener *l = NULL;
1090 int fd = -1, tcpfd = -1, tftpfd = -1;
1091
1092 (void)do_tftp;
1093
1094 if (daemon->port != 0)
1095 {
1096 fd = make_sock(addr, SOCK_DGRAM, dienow);
1097 tcpfd = make_sock(addr, SOCK_STREAM, dienow);
1098 }
(snip)
The following code causes an issue with the update made in dnsmasq
2.90.
$ cat network.c
(snip)
895 static int make_sock(union mysockaddr *addr, int type, int dienow)
896 {
(snip)
934 if (!option_bool(OPT_CLEVERBIND) || errno != EADDRNOTAVAIL)
935 {
936 if (dienow)
937 die(s, daemon->addrbuff, EC_BADNET);
938 else
939 my_syslog(LOG_WARNING, s, daemon->addrbuff,
strerror(errno)) 939 ;
940 }
(snip)
function "make_sock" in network.c:1096 binds the socket to 192.168.122.1/24,
and then make_sock in network.c:1097 tries to bind to the same address.
However, in network.c:934, when errno==98 occurs, network.c:937 is executed, so
dnsmasq does not cause a startup error. As a result, virsh net-start fails.
As a temporary workaround, it will work if you try not to die.
$ diff -u network_c_back network.c
--- network_c_back 2024-02-29 15:36:05.156467935 +0000
+++ network.c 2024-02-29 15:36:38.733324350 +0000
@@ -934,7 +934,8 @@
if (!option_bool(OPT_CLEVERBIND) || errno != EADDRNOTAVAIL)
{
if (dienow)
- die(s, daemon->addrbuff, EC_BADNET);
+ my_syslog(LOG_WARNING, s, daemon->addrbuff, strerror(errno));
+ //die(s, daemon->addrbuff, EC_BADNET);
else
my_syslog(LOG_WARNING, s, daemon->addrbuff, strerror(errno));
}
$
If bind-dynamic is set, it should be modified so that it works even if
errno==98.
For reference, in the case of dnsmasq 2.80, the code is as follows, so
no error occurs.
network.c
699 static int make_sock(union mysockaddr *addr, int type, int dienow)
700 {
701 int family = addr->sa.sa_family;
702 int fd, rc, opt = 1;
(snip)
715 err:
716 errsave = errno;
717 port = prettyprint_addr(addr, daemon->addrbuff);
718 if (!option_bool(OPT_NOWILD) && !option_bool(OPT_CLEVERBIND))
719 sprintf(daemon->addrbuff, "port %d", port);
720 s = _("failed to create listening socket for %s: %s");
721
722 if (fd != -1)
723 close (fd);
724
725 errno = errsave;
726
727 if (dienow)
728 {
729 /* failure to bind addresses given by --listen-address at
this
729 point
730 is OK if we're doing bind-dynamic */
731 if (!option_bool(OPT_CLEVERBIND))
732 die(s, daemon->addrbuff, EC_BADNET);
733 }
734 else
735 my_syslog(LOG_WARNING, s, daemon->addrbuff, strerror(errno));
736
737 return -1;
738 }
If bind-dynamic is set (option_bool(OPT_CLEVERBIND)==true), it will
not die.
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https://bugs.launchpad.net/ubuntu/+source/dnsmasq/+bug/2055776/+subscriptions
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