RoCE v2.0 UDP source port is used to provide per-conversation
entropy for Network Routers (ECMP), load balancers and 802.3ad Link
Aggregation Switching that are not aware of RoCE headers.
We will use the following hash functions definition to calculate the
RoCE UDP src_port according to the service type (QP Type) and Service ID
(SID), or according to the source and destination QPN values where CM
services are not used.
UDP source port selection must adhere IANA port allocation ranges. Thus
we will be using IANA recommendation for Ephemeral port range of:
49152-65535, or in hex: 0xC000-0xFFFF.
As this RFC does not modify any wire format nor does it change any protocol,
I don't think it requires IBTA specification.
The below calculations take into account the importance of producing a
symmetric hash result so we can support symmetric hash calculation of
network elements.
Hash Calculation for RDMA IP CM Service
=======================================
For RDMA IP CM Services, based on QP1 usage and connected RC QPs using
the
RDMA IP CM SID, the RoCEv2 UDP source port will be calculated according
to IBTA CM REQ private data info and Service ID.
Hash Function Calculations:
Extract the following fields from the CM IP REQ:
CM_REQ.ServiceID.DstPort [2 Bytes]
CM_REQ.PrivateData.SrcPort [2 Bytes]
RoCE.UDP.src_port = (DstPort[0..1] XOR SrcPort[0..1]) OR 0xC000
Result of the above hash will be kept in the CM connection context and
will be used all across his vitality for all preceding CM messages on
both ends of the connection (including REP, REJ, DREQ, DREP, ..).
Once connection is established, the corresponding Connected RC QPs on
both ends of the connection will update their context with the
calculated RDMA IP CM Service based UDP src_port hash at the Connect
phase of the active side and Accept phase of the passive side of the
connection.
CM will provide to the calculated value of the hash RoCEv2 UDP src_port
(16 bit) result in the 'uint16_t dlid' field of 'struct ibv_ah_attr'.
The 'struct ibv_ah_attr' is passed to the provider library when calling
ibv_modify_qp(qp, ah_attr, attr_mask |= IBV_QP_AV), so that providers
supporting RoCEv2 will use the 'dlid' value to update the RoCEv2 UDP
src_port in the QP context.
Hash Calculation for non-RDMA CM Service ID
===========================================
For non CM QP's we'll use input arguments: src.QP[24bit], dst.QP[24bit].
As QP[] is an array of 3 bytes, we'll define a 'Folded QP' value of:
For src.QP and dst.QP perform: QP[0] ^= QP[2];
Folded.QP now resides in QP[0..15].
Desired hash functions is:
UDP src_port = (s.QP[0..15] XOR d.QP[0..15]) OR 0xC000;
RoCEv2 UDP source port set scenario is dependent on QP type:
For RC QP:
Set on QP creation in QP Context through the provider library.
If (s.QP != d.QP)
QPC.entropy = Folded.s.QP XOR Folded.d.QP OR 0xC000
Else
QPC.entropy = Folded.s.QP OR 0xC000
For UD QP:
Set per post send scenario by the provider library into the WQ Element.
If (s.QP != d.QP) && (d.QP != 0xFFFFFF)
WQE.entropy = Folded.s.QP XOR Folded.d.QP AND 0xC000
Else
WQE.entropy = Folded.s.QP AND 0xC000
Based on feedback and agreement we will submit patches to Kernel and
rdma_core for review on the ML.
Signed-off-by: Alex Rosenbaum <alexr@xxxxxxxxxxxx>
