datapath: link-local unicast addresses can be "host" #25298
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This is a fix for a regression in the local addresses logic, introduced in 080857b as part of the implementation for AddressScopeMax. Addresses with the form of link-local unicast addresses began to be filtered out of the local address aggregation, causing them to labeled with the "world" identity for the sake of policy enforcement. Examples of such addresses include: 169.254.10.10 fe80::1234 This caused issues for a variety of users, whose policies allowing "host" traffic would no longer allow traffic to these addresses, forcing the use of workarounds involving CIDR policies, which is not the intended behavior for this type of address. This was a regression as of Cilium 1.12.0-rc2. One reason for this regression was that logic prior to the change looked at the address scope, whereas logic after the change looked at the address bytes, and it was found that many users had assigned addresses of the forms above but with scope global, causing them to again be filtered unconditionally. This patch factors out the local address filtering logic into a function, removes the skip over IsLinkLocalUnicast(), and adds a variety of unit tests for that function. fixes: #25242 fixes: #23910 fixes: #16308 fixes: #20055 Signed-off-by: Andrew Sauber <andrew.sauber@isovalent.com>
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Background
This is a fix for a regression in the local addresses logic, introduced in 080857b as part of the implementation for AddressScopeMax. Addresses with the form of a link-local unicast address began to be filtered out of the local address aggregation, causing them to labeled with the "world" identity for the sake of policy enforcement. Examples of such addresses include:
169.254.10.10
fe80::1234
This caused issues for a variety of users, whose policies allowing "host" traffic would no longer allow traffic to these addresses, forcing the use of workarounds involving CIDR policies, which is not the intended behavior for this type of address. This was a regression as of Cilium 1.12.0-rc2. One reason for this regression was that logic prior to the change looked at the address scope, whereas logic after the change looked at the address bytes, and it was found that many users had assigned addresses of the forms above but with scope global, causing them to again be filtered out unconditionally.
Implementation
This patch factors out the local address filtering logic into a function, removes the skip over IsLinkLocalUnicast(), and adds a variety of unit tests for that function.
Important Note
This change has no effect on link-local services such as the AWS Metadata service which operates on
169.254.169.254/32because that address is not assigned to any interface of the local host and thus is not enumerated by rnetlink. The address is still labeled with the "world" identity as usual. This has been tested on EKS and kind.Fixes
fixes: #25242
fixes: #23910
fixes: #16308
fixes: #20055