IP GRO verifies csum again?

[Jacob Wen]

Hi,

inet_gro_receive verifies IP csum but a NIC already did so and set 
CHECKSUM_UNNECESSARY.


https://github.com/torvalds/linux/blob/v5.2/net/ipv4/af_inet.c#L1432-L1433

if (unlikely(ip_fast_csum((u8 *)iph, 5)))

        goto out_unlock;


Is this a bug?