There are two possible utilizations so far: - Switch devices that don't support a native insertion/extraction header on the CPU port may still enjoy the benefits of port isolation with a custom VLAN tag. For this, they need to have a customizable TPID in hardware and a new Ethertype to distinguish between real 802.1Q traffic and the private tags used for port separation. - Switches that don't support the deactivation of VLAN awareness, but still want to have a mode in which they accept all traffic, including frames that are tagged with a VLAN not configured on their ports, may use this as a fake to trick the hardware into thinking that the TPID for VLAN is something other than 0x8100. What follows after the ETH_P_DSA_8021Q EtherType is a regular VLAN header (TCI), however there is no other EtherType that can be used for this purpose and doesn't already have a well-defined meaning. ETH_P_8021AD, ETH_P_QINQ1, ETH_P_QINQ2 and ETH_P_QINQ3 expect that another follow-up VLAN tag is present, which is not the case here.
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| @@ -109,6 +109,7 @@ · 108 unmodified lines | ||
| 109 | 109 | #define ETH_P_QINQ2 0x9200 /* deprecated QinQ VLAN [ NOT AN OFFICIALLY REGISTERED ID ] */ |
| 110 | 110 | #define ETH_P_QINQ3 0x9300 /* deprecated QinQ VLAN [ NOT AN OFFICIALLY REGISTERED ID ] */ |
| 111 | 111 | #define ETH_P_EDSA 0xDADA /* Ethertype DSA [ NOT AN OFFICIALLY REGISTERED ID ] */ |
| 112 | +#define ETH_P_DSA_8021Q 0xDADB /* Fake VLAN Header for DSA [ NOT AN OFFICIALLY REGISTERED ID ] */ | |
| 112 | 113 | #define ETH_P_IFE 0xED3E /* ForCES inter-FE LFB type */ |
| 113 | 114 | #define ETH_P_AF_IUCV 0xFBFB /* IBM af_iucv [ NOT AN OFFICIALLY REGISTERED ID ] */ |
| 114 | 115 | |