On 2/19/2020 8:06 AM, Jason Gunthorpe wrote:
On Wed, Feb 19, 2020 at 02:06:28AM +0000, Mark Zhang wrote:
The symmetry is important when calculate flow_label with DstQPn/SrcQPn
for non-RDMA CM Service ID (check the first mail), so that the server
and client will have same flow_label and udp_sport. But looks like it is
not important in this case.
If the application needs a certain flow label it should not rely on
auto-generation, IMHO.
I expect most networks will not be reversible anyhow, even with the
same flow label?
These are network flow labels, not under application control. If they
are under application control, that's a security issue.
But I agree, if the symmetric behavior is not needed, it should be
ignored and a better (more uniformly distributed) hash should be chosen.
I definitely like the simplicity and perfect flatness of the newly
proposed (src * 31) + dst. But that "31" causes overflow into bit 21,
doesn't it? (31 * 0xffff == 0x1f0000)
Tom.
