Infer subnet for node /128 IPv6 addresses #2338
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jcaamano
changed the title
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@jcaamano yeah I'd un-draft this one. Clever workaround. Can you make sure a bug is filed against OVN to handle on-link static routes? Listening to RAs gets complicated fast but could be a future enchancement too. |
When node addresses are allocated through DHCPv6 IA_NA, they might get a /128 prefix address. These node addresses are set on the gateway router port as well. OVN routers infers on-link routes from subnet information on the address itself. Since /128 addresses are not on a subnet, cluster traffic is routed through the node gatway instead of directly. Note that OVN does not support learning routes from ICMPv6 route advertisement and does not support adding on-link static routes. This patch infers the subnet of the interface looking at the node routing information and replaces the /128 prefix with the subnet prefix. Signed-off-by: Jaime Caamaño Ruiz <jcaamano@redhat.com>
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/retest |
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/retest |
trozet
approved these changes
Jul 15, 2021
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OK I was very confused on this PR for a while, but I think I understand now and lgtm. Feel free to confirm/deny if my understanding and thought process is correct:
- I didn't understand how with /128 prefix we didn't listen to RA for on link routes, but somehow OVN listened for gateway route from RA.
- Now I realize OVN doesn't listen to any RA, and we statically configure the gateway route for ipv6:
// Add static routes in GR with gateway router as the default next hop.
for _, nextHop := range l3GatewayConfig.NextHops {
var allIPs string
if utilnet.IsIPv6(nextHop) {
allIPs = "::/0"
} else {
allIPs = "0.0.0.0/0"
}
- Since we determine the things anyway from the host and manually configure them in OVN because it does not listen to RA, I dont see any reason determining the prefix from the host should be an issue either.
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- What this PR does and why is it needed
When node addresses are allocated through DHCPv6 IA_NA, they might get
a /128 prefix address. These node addresses are set on the gateway
router port as well. OVN routers infers on-link routes from subnet
information on the address itself. Since /128 addresses are not on a
subnet, cluster traffic is routed through the node gatway instead of
directly.
Note that OVN does not support learning routes from ICMPv6 route
advertisement and does not support adding on-link static routes.
This patch infers a subnet for the interface looking at the node
routing information and replaces the /128 prefix with the subnet
prefix.
- How to verify it
Added unit tests
- Description for the changelog
Infer subnet for /128 IPv6 addresses allocated through DHCPv6 IA_NA