Security Identities

Security identities are generated from labels. They are stored as uint32, which means the maximum limit for a security identity is 2^32 - 1. The minimum security identity is 1.

Note

Identity 0 is not a valid value. If it shows up in Hubble output, this means the identity was not found. In the eBPF datapath, it has a special role where it denotes “any identity”, i.e. as a wildcard allow in policy maps.

Security identities span over several ranges, depending on the context:

  1. Cluster-local
  2. ClusterMesh
  3. Identities generated from CIDR-based policies

Cluster-local identities (1) range from 1 to 2^16 - 1. The lowest values, from 1 to 255, correspond to the reserved identity range. See the internal code documentation for details.

For ClusterMesh (2), 8 bits are used as the cluster-id which identifies the cluster in the ClusterMesh, into the 3rd octet as shown by 0x00FF0000. The 4th octet (uppermost bits) must be set to 0 as well. Neither of these constraints apply CIDR identities however, see (3).

CIDR identities (3) are local to each node. CIDR identities begin from 1 and end at 16777215, however since they’re shifted by 24, this makes their effective range 1 | (1 << 24) to 16777215 | (1 << 24) or from 16777217 to 33554431. When CIDR policies are applied, the identity generated is local to each node. In other words, the identity may not be the same for the same CIDR policy across two nodes.

CIDR identities are never used for traffic between Cilium-managed nodes, so they do not need to fit inside of a VXLAN or Geneve virtual network field. Non-CIDR identities are limited to 24 bits so that they will fit in these fields on the wire, but since CIDR identities will not be encoded in these packets, they can start with a higher value. Hence, the minimum value for a CIDR identity is 2^24 + 1.

Overall, the following represents the different ranges:

0x00000001 - 0x0000FFFF (1           to 2^16 - 1)        => cluster-local identities
0x00010000 - 0x00FFFFFF (2^16        to 2^24 - 1)        => identities for remote clusters
0x01000000 - 0x0100FFFF (2^24        to 2^24 + 2^16 - 1) => identities for CIDRs (node-local)
0x01010000 - 0xFFFFFFFF (2^24 + 2^16 to 2^32 - 1)        => reserved for future use