Why does the NetFilter rule have no effect on the raw socket?

Open source DHCP client code in which you want to set the DSCP to 0xc0, but found that the discovery package can be set successfully, but the renew packet is not able to view the code found that the discovery packet is running raw socket. However, renew is sent through the UDP socket to view the kernel code found that the raw socket does not pass the NetFilter rule, as follows:

Kernel/linux/net/packet/af_packet.c

Packet_sendmsg->dev_queue_xmit directly into the TC, and then send.

Udp_sendmsg->udp_push_pending_frames->ip_push_pending_frames->ip_local_out into NetFilter, So it can be intercepted or modified by netfilter rules.

Make a record, beware of forgetting, if there is a mistake, please understand.