UDP Packet Header Formats
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Load Balancer Header
- Following is the C routine to write the header that the LB reads, and eventually strips off, in order to direct the packet to the proper destination.
- Currently using version = 2 and protocol = 1.
/**
* Set the Load Balancer header data.
* The first four bytes go as ordered.
* The entropy goes as a single, network byte ordered, 16-bit int.
* The tick goes as a single, network byte ordered, 64-bit int.
*
* Bit#
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | L | B | Version | Protocol |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* 3 4 5 6
* 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Rsvd | Entropy |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* 6 12
* 4 5 ... ... ... 0 1 2 3 4 5 6 7
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | |
* + Tick +
* | |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*
* @param buffer buffer in which to write the header.
* @param tick unsigned 64 bit tick number used to tell the load balancer
* which backend host to direct the packet to.
* @param version version of this software.
* @param protocol protocol this software uses.
* @param entropy entropy field used to determine destination port.
*/
static void setLbMetadata(char* buffer, uint64_t tick, int version, int protocol, int entropy) {
*buffer = 'L';
*(buffer+1) = 'B';
*(buffer+2) = version;
*(buffer+3) = protocol;
// Put the data in network byte order (big endian)
*((uint16_t *)(buffer + 6)) = htons(entropy);
*((uint64_t *)(buffer + 8)) = htonll(tick);
}
Reassembly Header
- Following is the C routine to write the header that passes through the LB and is used by the receiving software to reassemble UDP packets into their original buffer.
- Currently using version = 2.
/**
* Set the Reassembly Header data.
* The first 16 bits go as ordered. The dataId is put in network byte order.
* The offset, length and tick are also put into network byte order.</p>
*
* Bit#
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |Version| Rsvd | Data-ID |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Buffer Offset |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Buffer Length |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | |
* + Tick +
* | |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*
* @param buffer buffer in which to write the header.
* @param offset byte offset into full buffer payload.
* @param length total length in bytes of full buffer payload.
* @param tick 64 bit tick number used to tell the load balancer
* which backend host to direct the packet to. Necessary to
* disentangle packets from different ticks at one destination
* as there may be overlap in time.
* @param version the version of this software.
* @param dataId the data source id number.
*/
static void setReMetadata(char* buffer, uint32_t offset, uint32_t length,
uint64_t tick, int version, uint16_t dataId) {
buffer[0] = version << 4;
*((uint16_t *)(buffer + 2)) = htons(dataId);
*((uint32_t *)(buffer + 4)) = htonl(offset);
*((uint32_t *)(buffer + 8)) = htonl(length);
*((uint64_t *)(buffer + 12)) = htonll(tick);
}
Format of Sync Packet to Control Plane
- Following is the C routine to write the packet send to the LB's control plane to inform it of the latest event number that was sent to the data plane.
- Currently using version = 2.
/**
* Set the data for a synchronization message sent directly to the load balancer's control plane.
* The first 3 fields go as ordered. The src id, event number, event rate and time are all
* put into network byte order.</p>
*
* Bit#
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | L | C | Version | Rsvd |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | EventSrcId |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | |
* + EventNumber +
* | |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | AvgEventRateHz |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | |
* + UnixTimeNano +
* | |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*
* @param buffer buffer in which to write the data.
* @param version version of this software.
* @param srcId id number of this data source.
* @param evtNum unsigned 64 bit event number used to tell the load balancer
* which backend host to direct the packet to. This message
* is telling the load balancer that this application has
* already sent this, latest, event.
* @param evtRate in Hz, the rate this application is sending events
* to the load balancer (0 if unknown).
* @param nanos at what unix time in nanoseconds was this message sent (0 if unknown).
*/
static void setSyncData(char* buffer, int version, uint32_t srcId,
uint64_t evtNum, uint32_t evtRate, uint64_t nanos) {
buffer[0] = 'L';
buffer[1] = 'C';
buffer[2] = version;
// Put the data in network byte order (big endian)
*((uint32_t *)(buffer + 4)) = htonl(srcId);
*((uint64_t *)(buffer + 8)) = htonll(evtNum);
*((uint32_t *)(buffer + 16)) = htonl(evtRate);
*((uint64_t *)(buffer + 20)) = htonll(nanos);
}