[dpdk-dev] How to update the sequence number in TCP packets using DPDK-pktgen?
keith.wiles at intel.com
Mon Oct 9 19:12:45 CEST 2017
> On Oct 9, 2017, at 8:42 AM, Shailja Pandey <csz168117 at iitd.ac.in> wrote:
> In the DPDK application, I am maintaining some state and due to that I need to generate the packets with monotonically increasing sequence numbers. As shown in the code below,
> /tip->tcp.seq = htonl(DEFAULT_PKT_NUMBER);/
> DPDK is putting some default number as a sequence number in the TCP packet and not using as defined by TCP protocol. I tried various workarounds but due to multi-threaded nature of the pktgen application, I am facing some issues and unable to put sequence numbers in increasing order. I tried thread_local and pthread_mutex_lock etc to generate packets with increasing sequence number.
> I am not very sure what am I missing, Please help me in this matter.
The way pktgen was written was for performance, which means I setup the mbufs at start time and do not touch them again till another start command. This causes packets to be sent out of order as I do not know when mbufs are returned to the free pool.
The only way to send a given sequence is to modified each packet as it is sent, which will impact performance. The random mode does just this type of packet mods and it would be a good model to look at if you want to modify the code.
> pktgen_tcp_hdr_ctor(pkt_seq_t *pkt, tcpip_t *tip, int type __rte_unused)
> uint16_t tlen;
> /* Zero out the header space */
> memset((char *)tip, 0, sizeof(tcpip_t));
> /* Create the TCP header */
> tip->ip.src = htonl(pkt->ip_src_addr.addr.ipv4.s_addr);
> tip->ip.dst = htonl(pkt->ip_dst_addr.addr.ipv4.s_addr);
> tlen = pkt->pktSize -
> (pkt->ether_hdr_size + sizeof(ipHdr_t));
> tip->ip.len = htons(tlen);
> tip->ip.proto = pkt->ipProto;
> tip->tcp.sport = htons(pkt->sport);
> tip->tcp.dport = htons(pkt->dport);
> *tip->tcp.seq = htonl(DEFAULT_PKT_NUMBER);*
> tip->tcp.ack = htonl(DEFAULT_ACK_NUMBER);
> tip->tcp.offset = ((sizeof(tcpHdr_t) / sizeof(uint32_t)) << 4); /* Offset in words */
> tip->tcp.flags = ACK_FLAG; /* ACK */
> tip->tcp.window = htons(DEFAULT_WND_SIZE);
> tip->tcp.urgent = 0;
> tlen = pkt->pktSize - pkt->ether_hdr_size;
> tip->tcp.cksum = cksum(tip, tlen, 0);
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