Under the circumstance that `rx_tail` wrap back to zero
and the advance speed of `rx_tail` is greater than `rxrearm_start`,
`rx_tail` will catch up with `rxrearm_start` and surpass it.
This may cause some mbufs be reused by application.
So we need to make some restrictions to ensure that
`rx_tail` will not exceed `rxrearm_start`.
e.g.
RDH: 972 RDT: 991 rxrearm_nb: 991 rxrearm_start: 992 rx_tail: 959
RDH: 1004 RDT: 1023 rxrearm_nb: 991 rxrearm_start: 0 rx_tail: 991
RDH: 12 RDT: 31 rxrearm_nb: 991 rxrearm_start: 32 rx_tail: 1023
RDH: 31 RDT: 63 rxrearm_nb: 960 rxrearm_start: 64 rx_tail: 0
RDH: 95 RDT: 95 rxrearm_nb: 1016 rxrearm_start: 96 rx_tail: 88
RDH: 95 RDT: 127 rxrearm_nb: 991 rxrearm_start: 128 rx_tail: 95
...
RDH: 908 RDT: 927 rxrearm_nb: 991 rxrearm_start: 928 rx_tail: 895
RDH: 940 RDT: 959 rxrearm_nb: 991 rxrearm_start: 960 rx_tail: 927
RDH: 980 RDT: 991 rxrearm_nb: 991 rxrearm_start: 992 rx_tail: 959
RDH: 991 RDT: 991 rxrearm_nb: 1026 rxrearm_start: 992 rx_tail: 994
when `rx_tail` catches up with `rxrearm_start`,
2(994 - 992) mbufs be reused by application !
Bugzilla ID: 882
Fixes: 5a3cca342417 ("net/ixgbe: fix vector Rx")
Cc: stable@dpdk.org
Signed-off-by: Bin Zheng <zhengbin.89740@bytedance.com>
Acked-by: Leyi Rong <leyi.rong@intel.com>
Reviewed-by: Haiyue Wang <haiyue.wang@intel.com>
Reviewed-by: Liang Ma <liangma@liangbit.com>
c59f93d9a1