Method of using bit vectors to allow expansion and collapse of header layers within packets for enabling flexible modifications and an apparatus thereof
Embodiments of the apparatus for modifying packet headers relate to a use of bit vectors to allow expansion and collapse of protocol headers within packets for enabling flexible modification. A rewrite engine expands each protocol header into a generic format and applies various commands to modify the generalized protocol header. The rewrite engine maintains a bit vector for the generalized protocol header with each bit in the bit vector representing a byte of the generalized protocol header. A bit marked as 0 in the bit vector corresponds to an invalid byte, while a bit marked as 1 in the bit vector corresponds to a valid byte. The rewrite engine uses the bit vector to remove all the invalid bytes after all commands have been operated on the generalized protocol header to thereby form a new protocol header.
1. A method of a network device, the method comprising:
for each protocol of a plurality of protocols:
maintaining a generic protocol layer format associated with the protocol; and
maintaining a set of one or more generic commands associated with the protocol;
receiving a packet having a header including a plurality of protocol layers; and
for at least one protocol layer of the plurality of protocol layers:
converting the protocol layer to the generic protocol layer format associated with the protocol of the protocol layer by adding one or more fields to the protocol layer increasing a size of the protocol layer, wherein the one or more fields added to the protocol layer are dependent on the protocol of the protocol layer; and
modifying the protocol layer as converted using the set of generic commands associated with the protocol of the protocol layer regardless of which variant of the protocol the protocol layer is.
2. The method of claim 1 , further comprising maintaining a protocol table including a plurality of entries, wherein each entry of the plurality of entries is associated with a unique identifier and stores data associated with a different combination of protocol layers.
3. The method of claim 1 , wherein the header of the packet includes a body that is a portion of the header that is not modified by the set of generic commands, the method further comprising:
maintaining a pointer structure for the packet that includes an end pointer, a plurality of layer pointers and a total size of the header of the packet, wherein each of the layer pointers point to a start position of a different one of the protocol layers of the header of the packet and the end pointer points to the start of the body of the header.
4. The method of claim 1 , further comprising, for each protocol layer of the protocol layers that is converted, storing a bit vector including a plurality of values that each represent a different portion of the converted protocol layer.
5. The method of claim 1 , wherein the generic format includes all supported fields of the protocol.
6. The method of claim 1 , wherein converting each of the protocol layers includes:
of fields supported by the protocol of the protocol layer, detecting which of the fields are missing from the protocol layer; and
based on the detection, expanding the protocol layer to the generic format by including the missing fields.
7. A network switch comprising:
an input port for receiving a packet having a header including one or more protocol layers each corresponding to a different one of a plurality of protocols;
a memory storing, for each protocol of a plurality of protocols, a generic protocol layer format associated with the protocol and a set of one or more generic commands associated with the protocol; and
a rewrite engine that, for at least one protocol layer of the plurality of protocol layers, converts the protocol layer to the generic protocol layer format associated with the protocol of the protocol layer by adding one or more fields to the protocol layer increasing a size of the protocol layer and modifies the protocol layer as converted using the set of generic commands associated with the protocol of the protocol layer regardless of which variant of the protocol the protocol layer is, wherein the one or more fields added to the protocol layer are dependent on the protocol of the protocol layer.
8. The network of claim 7 , wherein the memory stores a protocol table including a plurality of entries, wherein each entry of the plurality of entries is associated with a unique identifier and stores data associated with a different combination of protocol layers.
9. The network of claim 7 , wherein the header of the packet includes a body that is a portion of the header that is not modified by the set of generic commands, and further wherein the memory stores a pointer structure for the packet that includes an end pointer, a plurality of layer pointers and a total size of the header of the packet, wherein each of the layer pointers point to a start position of a different one of the protocol layers of the header of the packet and the end pointer points to the start of the body of the header.
10. The network of claim 7 , wherein, for each protocol layer of the protocol layers that is converted, the memory stores a bit vector including a plurality of values that each represent a different portion of the converted protocol layer.
11. The network of claim 7 , wherein the generic format includes all supported fields of the protocol.
12. The network of claim 7 , wherein converting each of the protocol layers includes:
of fields supported by the protocol of the protocol layer, detecting which of the fields are missing from the protocol layer; and
based on the detection, expanding the protocol layer to the generic format by including the missing fields.
13. A non-transitory computer-readable medium storing a rewrite engine for receiving a packet having a header including one or more protocol layers each corresponding to a different one of a plurality of protocols, the rewrite engine configure to, for at least one protocol layer of the plurality of protocol layers, convert the protocol layer to a generic protocol layer format associated with the protocol of the protocol layer by adding one or more fields to the protocol layer increasing a size of the protocol layer and modify the protocol layer as converted using a set of generic commands associated with the protocol of the protocol layer regardless of which variant of the protocol the protocol layer is, wherein the one or more fields added to the protocol layer are dependent on the protocol of the protocol layer.
14. The non-transitory computer-readable medium of claim 13 , wherein the rewrite engine is configured to access a protocol table including a plurality of entries, wherein each entry of the plurality of entries is associated with a unique identifier and stores data associated with a different combination of protocol layers.
15. The non-transitory computer-readable medium of claim 13 , wherein the header of the packet includes a body that is a portion of the header that is not modified by the set of generic commands, and further wherein the rewrite ending is configured to access a pointer structure for the packet that includes an end pointer, a plurality of layer pointers and a total size of the header of the packet, wherein each of the layer pointers point to a start position of a different one of the protocol layers of the header of the packet and the end pointer points to the start of the body of the header.
16. The non-transitory computer-readable medium of claim 13 , wherein, for each protocol layer of the protocol layers that is converted, the rewrite engine is configured to generate a bit vector including a plurality of values that each represent a different portion of the converted protocol layer.
17. The non-transitory computer-readable medium of claim 13 , wherein the generic format includes all supported fields of the protocol.
18. The non-transitory computer-readable medium of claim 13 , wherein converting each of the protocol layers includes:
of fields supported by the protocol of the protocol layer, detecting which of the fields are missing from the protocol layer; and
based on the detection, expanding the protocol layer to the generic format by including the missing fields.