XMIT_CSUM_ENC_V6
#define XMIT_CSUM_ENC (XMIT_CSUM_ENC_V4 | XMIT_CSUM_ENC_V6)
rc |= XMIT_CSUM_ENC_V6;
if (xmit_type & (XMIT_CSUM_ENC_V6 | XMIT_CSUM_V6))