sbr: Add rule for outbound interface when there is a single interface IP #1144
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Adding the outbound interface rule allows applications to bind to an interface name rather than only the interface IP. This allows applications in a multus environment to be configured with the interface name, which can be configured, rather than the interface IP address, which is not known in advance. The outbound interface rule is on;y added if the interface is configured with 1 IP address, because when there are multiple, only one will be selected, depending on the rule order, which is non-deterministic. Signed-off-by: Neil Cook <[email protected]>
Signed-off-by: Neil Cook <[email protected]>
Signed-off-by: Neil Cook <[email protected]>
Signed-off-by: Neil Cook <[email protected]>
Signed-off-by: Neil Cook <[email protected]>
Signed-off-by: Neil Cook <[email protected]>
The outbound interface rule does not reference anything from ipCfg so should not be in the loop. Signed-off-by: Neil Cook <[email protected]>
…able no is correct The previous commit moved the rule creation to after the ipCfg loop, but since the loop increments the table number, the rule gets added to the wrong table. Signed-off-by: Neil Cook <[email protected]>
Moving the outbound interface rule creation to before the ipCfg loop means that tests need to reflect the changed order of rules. Signed-off-by: Neil Cook <[email protected]>
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Any more thoughts on this PR? |
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So, this is intended for packets originating from applications that are bound to a device. After that, a table is selected to continue with the regular routing process. Is that right? I believe this should be a new parameter instead of applying with there is a single IP (no provided table ID case). It can take precedence over the IPs. Something like Also, why not using the VRF plugin instead? |
Yes. Because binding to IP addresses is problematic, as they are dynamically assigned.
Yes, probably setting this via a parameter is better.
Doesn't that require the application to be VRF aware? |
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as far as I know, for vrf, you only need to use SO_BINDTODEVICE which I guess you are already using |
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When using the sbr plugin with a CNI plugin such as multus, applications have to bind to the source IP address of the interface for the str plugin to work correctly. They cannot bind to the interface name, because the sbr plugin doesn't currently add a rule for the interface name.
This is problematic because it is straightforward to configure the name of a multus interface, however the IP address is usually assigned from a range, so the exact interface IP address to use is not known in advance unlike the interface name. It would thus be much easier for applications if the sbr plugin added a rule with the interface name in addition to the rule with the interface address.
This PR does exactly that - adds an additional rule with the outbound interface name, so that applications can configure the name of the interface to bind to, rather than having to know the interface IP address.
Obviously, this approach does not work if there are multiple IP addresses for the interface, so this change only adds the rule for the outbound interface name if there is a single IP address on that interface.
I have added tests for the new rule, which all pass.