CODEWITHSUNDEEP
dpdk
hybang
hybang

Reputation: 65

using DPDK-basicfwd example how to send custom packet to desired port

Requirement: I would like to make use of DPDK basicfwd, to send back custom reply to the incoming port.

Explanation:

DPDK ports: Port-0 and Port-1 Sample code: edited DPDK basicfwd. Custom Function: PacketHandler() Requirement: Sometimes I need to send custom packet(kind of RST packet) to incoming port.

example: Port-0 -> RX burst -> PacketHandler() -> normal packets fwd to Port-1, special packets send back to Port-0

Code Snippet:

while (isRun) {
    num_rx = rte_eth_rx_burst(port_id, queue_id, mbufs, BURST_SIZE);
    if (num_rx == 0) {
        continue;
    }

    num_tx = 0;
    for (int idx = 0; idx < num_rx; idx++) {
        struct pcap_pkthdr pktHdr;
        gettimeofday(&pktHdr.ts, NULL);
        pktHdr.caplen = rte_pktmbuf_pkt_len(mbufs[idx]);
        pktHdr.len = rte_pktmbuf_pkt_len(mbufs[idx]);

        if (PacketHandler(&pktHdr, rte_pktmbuf_mtod(mbufs[idx], unsigned char *)) > 1) {
            printf("Blocked Packets, do not fwd");
            //TODO: send custom packet to incoming way
            rte_pktmbuf_free(mbufs[idx]);
            continue;
        }

        txbufs[num_tx++] = mbufs[idx];            
    }

    if (num_tx > 0) {
        sent = rte_eth_tx_burst(port_id ^ 1, queue_id, txbufs, num_tx);
        for (int idx = sent; idx < num_tx; idx++) {
            rte_pktmbuf_free(txbufs[idx]);
        }
    }
}

My custom packet type is u_char. How can i send my packet to incoming way?

Thanks

Upvotes: 1

Views: 770

Answers (1)

Vipin Varghese
Vipin Varghese

Reputation: 4798

Option 1: Simple way (but can affect performance)

  1. get packets via rte_eth_rx_burst

  2. iterate packets, to update dest_port = PacketHandler() ? mbufs[idx]->port : (mbufs[idx]->port ^ 1)

  3. Send packet out with rte_eth_tx_burst with dest_port

  4. Comment out the tx_burst generic call below.

Option 2:

  1. Create 2 mbuf-array namely mbufs_inport, and mbufs_outport.

  2. Iterate packets, to invoke PacketHandler(). Matching Packets goes to mbufs_inport and non-matching goes to mbufs_outport

  3. to invoke rte_eth_tx_burst for mbufs_inport and mbufs_outprt.

Option 3:

  1. register rx-callback to filter packets with packethandler.

  2. Now you have the option to directly send back the selected back based on mbuf->portid. While non-matching packets continue in the main loop.

  3. If there is concern about packet order or previous packets needs to be processed, make use of mbuf-udata64 as a place holder for exit port. For cases not matching set is as -1. Then in the main loop, you have convert tx_burst for n packets to iterate for each as you have to check for udata64 value.

Upvotes: 2

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