bnxt: HW_LRO Rx Pkt with > 32 fragments caused Crash (iflib)

[bhargava.marreddy_broadcom.com]

Summary

Broadcom NIC with HW_LRO setting max_agg_segs = 6 can generate Rx pkt with 64 (2^6) fragments,
Modify IFLIB_MAX_RX_SEGS to 64 to avoid memory corruption / Crash.

Test Plan

Verified iperf TCP, no issue seen.

[shurd]

How many are required when max_agg_segs == 7? With that value change in future hardware designs?

[bhargava.marreddy_broadcom.com]

How many are required when max_agg_segs == 7? With that value change in future hardware designs?

Though I'm seeing max of 45 in my setup, Theoretical max num_frags is 66 (64 frags + 1 TPA_Start + 1 TPA_End).

[bhargava.marreddy_broadcom.com]

Modify IFLIB_MAX_RX_SEGS to 66 which is theoretical maximum for BRCM NIC (64 + 1 TPA_START + 1 TPA_END)

[shurd]

It doesn't look like the driver currently supports more than (RX_TPA_END_CMPL_AGG_BUFS_MASK >> RX_TPA_END_CMPL_AGG_BUFS_SFT) + 1 (64), so 64 seems like the best number if we change it here.

The other options are to put the max frags value in struct if_softc_ctx and have it dynamically allocated, or to have the driver limit the value to 32. I think this one is fine if changed back to 64 (or the driver is updated to support > 64).

[shurd]

sys/net/iflib.c

289 ↗

(On Diff #34316)

Change back to 64.

Add comment: /* bnxt supports 64 with hardware LRO enabled */ before the define.

[bhargava.marreddy_broadcom.com]

Taken care of review comments.

[bhargava.marreddy_broadcom.com]

sys/net/iflib.c

289 ↗

(On Diff #34316)

Taken care.

[shurd]