** Tags added: sts
** Description changed:
[Environment]
# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04.2 LTS
Release: 16.04
Codename: xenial
# uname -a
Linux juju-niedbalski-xenial-machine-12 4.8.0-46-generic
#49~16.04.1-Ubuntu SMP Fri Mar 31 14:51:03 UTC 2017 x86_64 x86_64 x86_64
GNU/Linux
+
[Description]
+
+ We identified a bug in one of the utilities provided by dnsmasq, the
'dhcp_release' utility which
+ is executed as part of the DHCP lease cleanup mechanism by Neutron once a
network resource is freed.
+ We noticed that some packets were discarded by the DHCP server (dnsmasq) in
Ubuntu systems
+ running a kernel >= 4.7. The reason was the ipi_ifindex field on the pktinfo
was incorrectly assumed to be 1 (loopback),
+ this causes the message to be ignored by the dnsmasq daemon since isn't the
interface on which dnsmasq is bind to.
+
+ (gdb) p *p.p
+ $4 = {
+ ipi_ifindex = 1,
+ ipi_spec_dst = {
+ s_addr = 34973888
+ },
+ ipi_addr = {
+ s_addr = 34973888
+ }
+ }
+
+ (gdb) p ifr
+ $8 = {ifr_ifrn = {ifrn_name = "lo", '\000' <repeats 13 times>},
+
+
+ [Fix]
+
+ Upstream commit:
+
https://github.com/torvalds/linux/commit/f0c16ba8933ed217c2688b277410b2a37ba81591
+
+ [Test Case]
+
+ 1) Configure a dnsmasq instance to server DHCP
+
+ (Example):
+
+ $ sudo dnsmasq --no-hosts --no-resolv --strict-order --except-interface=lo
--pid-file=/var/lib/neutron/dhcp/860b0cbb-37c3-4bcb-8345-52b942518dca/pid
--dhcp-hostsfile=/var/lib/neutron/dhcp/860b0cbb-37c3-4bcb-8345-52b942518dca/host
-
+
-addn-hosts=/var/lib/neutron/dhcp/860b0cbb-37c3-4bcb-8345-52b942518dca/addn_hosts
--dhcp-optsfile=/var/lib/neutron/dhcp/860b0cbb-37c3-4bcb-8345-52b942518dca/opts
--dhcp-leasefile=/var/lib/neutron/dhcp/860b0cbb-37c3-4bcb-8345-52b942
+ 518dca/leases --dhcp-match=set:ipxe,175 --bind-interfaces
--interface=ns-1cb1b7c7-c0 --dhcp-range=set:tag0,192.168.21.0,static,86400s
--dhcp-option-force=option:mtu,1458 --dhcp-lease-max=256
--conf-file=/etc/neutron/dnsmasq.conf --
+ domain=openstacklocal
+
+ 2) Boot a VM or container on the bridge/interface on which dnsmasq is bind to.
+ 2) Use the dhcp_release utility to release the lease.
+
+ (Example):
+ $ sudo dhcp_release ns-1cb1b7c7-c0 192.168.21.8 fa:16:3e:f3:b2:fe
+
+ The expected result: The lease is freed.
+ Current results: dnsmasq ignored the DHCP Release message.
+
+ [Fix]
When we send a packet for our own local address on a non-loopback
interface (e.g. eth0), due to the change had been introduced from
commit 0b922b7 ("net: original ingress device index in PKTINFO"), the
original ingress device index would be set as the loopback interface.
- [Fix]
-
*
https://github.com/torvalds/linux/commit/f0c16ba8933ed217c2688b277410b2a37ba81591
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https://bugs.launchpad.net/bugs/1683982
Title:
net/ipv4: original ingress device index set as the loopback interface.
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