[dpdk-users] How to use .last and .spec fields in the Generic Flow API?

[Andrew Bainbridge <andbain@microsoft.com>]

Hi

How should I specify a range of UDP ports in the generic flow API? Here's what I've tried...

I'm trying to create a flow to move packets with UDP dest ports from 1234 to 1244 into a specified queue. It works fine if I specify a single port of 1234, instead of the range. Here's how I set the flow item for that:

    struct rte_flow_item_udp udp_spec = { 0 };
    struct rte_flow_item_udp udp_mask = { 0 };
    udp_spec.hdr.dst_port = htons(udp_dst_port);
    udp_mask.hdr.dst_port = 0xffff;
    pattern[2].type = RTE_FLOW_ITEM_TYPE_UDP;
    pattern[2].spec = &udp_spec;
    pattern[2].mask = &udp_mask;

But if I attempt to specify the range, I believe I have to use the .last field. When I do that, I get this error, 'range between "spec" and "last" is larger than "mask"'. Here's how I set that flow item:

    struct rte_flow_item_udp udp_spec = { 0 };
    struct rte_flow_item_udp udp_last = { 0 };
    struct rte_flow_item_udp udp_mask = { 0 };
    udp_spec.hdr.dst_port = htons(1234);
    udp_last.hdr.dst_port = htons(1244);
    udp_mask.hdr.dst_port = 0xffff;
    pattern[2].type = RTE_FLOW_ITEM_TYPE_UDP;
    pattern[2].spec = &udp_spec;
    pattern[2].last = &udp_last;
    pattern[2].mask = &udp_mask;

I don't understand the error message. The range between spec and last is 10. The mask is 0xffff. The error message seems wrong. But probably I just misunderstood something.

More details:

I'm using the mlx4 PMD. The source of the error message is in mlx4_flow_item_check(), where the code appears goes through each byte of the spec and last and checks that:

    (((const uint8_t *)item->spec)[i] & mask[i]) != (((const uint8_t *)item->last)[i] & mask[i]))

Which makes no sense to me. That appears to require that spec and last are equal wherever mask is not zero.

Any ideas?

Thanks,
Andy