Due to lack of any activity in this RFE since more than 1 year, I'm
going to close it for now. If You would be still interested in
implementing this and would like to continue discussion on that, feel
free to reopen it and ping me (slaweq) on irc.
** Changed in: neutron
Status: New => Opinion
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https://bugs.launchpad.net/bugs/1755414
Title:
VR replaces connected routes
Status in neutron:
Opinion
Bug description:
Hi colleagues,
The idea behind this design is to easily switch VM between different
address scopes (e.g. "grey" addresses in Subnet-1 and "white" in
Subnet-2), using same port/MAC (which always is in E-Network).
If VR connected to subnets belonging to same network (preformatted
scheme also is at https://pastebin.com/AesqkcXa) :
E-Network
+------------------------------------------+
Subnet-1 Subnet-2
+---+----+--+ +----+------+
| | +----+ |
VM-+ | | | |
+--------+ VR +------------+
/| |\
qr-64.. -/ 0----+ \- qg-16..
using Subnet-1 as LAN connection and Subnet-2 as external gateway
connection, then Neutron swaps connected route to Subnet-1 with same
route but through Subnet-2 interface (3rd entry in the following
sequence):
14:45:18.043 Running command: ['ip', 'netns', 'exec', 'qrouter-UUID', 'ip',
'-4', 'addr', 'add', '25.0.0.1/8', 'scope', 'global', 'dev', 'qr-64c53cf8-d9',
'brd', '25.255.255.255']
14:45:19.815 Running command: ['ip', 'netns', 'exec', 'qrouter-UUID', 'ip',
'-4', 'addr', 'add', '51.x.x.x/24', 'scope', 'global', 'dev', 'qg-16bdddb1-d5',
'brd', '51.x.x.255']
14:45:20.283 Running command: ['ip', 'netns', 'exec', 'qrouter-UUID', 'ip',
'-4', 'route', 'replace', '25.0.0.0/8', 'dev', 'qg-16bdddb1-d5', 'scope',
'link']
14:45:20.919 Running command: ['ip', 'netns', 'exec', 'qrouter-UUID', 'ip',
'-4', 'route', 'replace', 'default', 'via', '51.x.x.254', 'dev',
'qg-16bdddb1-d5']
which makes it impossible to communicate between VMs in Subnet-1 with
the VR.
Proposed solution:
When creating VR, use "ip route add ... metric <LOWER>" for extra subnets of
the interfaces. To achieve this:
- function add_route() in ip_lib.py contain unconditional arg "replace" and
add other args from function's parameters. If, finally, var "args" contains
keyword "metric", then change keyword "replace" with "add".
- when creating VR, add keyword "metric 20" (can be anything lower than
connected metric) to all extra subnets.
This will fix routing in case of conflict, will preserve routing model
if there is no conflict and will preserve compatibility with other
functions calling add_route (no keyword "metric" - no changes in
behavior).
Openstack: Pike
Neutron: 11.0.2
Ubuntu: 16.04
Thank you.
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