Windows DPDK L2fwd- Receiving packets out of sequence - network-programming

Question

I am validating DPDK receive functionality & for this I'm shooting a pcap externally &
added code in l2fwd to dump received packets to pcap, the l2fwd dumped pcap have all the packets from shooter but some of them are not in sequence.
Shooter is already validated.
DPDK version in use-21.11
link of the pcap used : https://wiki.wireshark.org/uploads/__moin_import__/attachments/SampleCaptures/tcp-ecn-sample.pcap
Out of order packets are random. For the first run I saw no jumbled packets but was able to replicate the issue on second run with the 2nd,3rd,4th packets jumbled having order 3,4,2.
Below is snipped from l2fwd example & our modifications as //TESTCODE..
/* Read packet from RX queues. 8< */
for (i = 0; i < qconf->n_rx_port; i++) {
portid = qconf->rx_port_list[i];
nb_rx = rte_eth_rx_burst(portid, 0,
pkts_burst, MAX_PKT_BURST);
port_statistics[portid].rx += nb_rx;
for (j = 0; j < nb_rx; j++) {
m = pkts_burst[j];
// TESTCODE_STARTS
uint8_t* pkt = rte_pktmbuf_mtod(m, uint8_t*);
dump_to_pcap(pkt, rte_pktmbuf_pkt_len(m));
// TESTCODE_ENDS
rte_prefetch0(rte_pktmbuf_mtod(m, void *));
l2fwd_simple_forward(m, portid);
}
}
/* >8 End of read packet from RX queues. */
Below is code for dump_to_pcap
static int
dump_to_pcap(uint8_t* pkt, int pkt_len)
{
static FILE* fp = NULL;
static int init_file = 0;
if (0 == init_file) {
printf("Creating pcap\n");
char pcap_filename[256] = { 0 };
char Two_pcap_filename[256] = { 0 };
currentDateTime(pcap_filename);
sprintf(Two_pcap_filename,".\\Rx_%d_%s.pcap", 0, pcap_filename);
printf("FileSName to Create: %s\n", Two_pcap_filename);
fp = fopen(Two_pcap_filename, "wb");
if (NULL == fp) {
printf("Unable to open file\n");
fp = NULL;
}
else {
printf("File create success..\n");
init_file = 1;
typedef struct pcap_file_header1 {
unsigned int magic; // a 32-bit "magic number"
unsigned short version_major; //a 16-bit major version number
unsigned short version_minor; //a 16-bit minor version number
unsigned int thiszone; //a 32-bit "time zone offset" field that's actually not used, so ou can (and probably should) just make it 0
unsigned int sigfigs; //a 32-bit "time stamp accuracy" field that's not actually used,so you can (and probably should) just make it 0;
unsigned int snaplen; //a 32-bit "snapshot length" field
unsigned int linktype; //a 32-bit "link layer type" field
}dumpFileHdr;
dumpFileHdr file_hdr;
file_hdr.magic = 2712847316; //0xa1b2c3d4;
file_hdr.version_major = 2;
file_hdr.version_minor = 4;
file_hdr.thiszone = 0;
file_hdr.sigfigs = 0;
file_hdr.snaplen = 65535;
file_hdr.linktype = 1;
fwrite((void*)(&file_hdr), sizeof(dumpFileHdr), 1, fp);
//printf("Pcap Header written\n");
}
}
typedef struct pcap_pkthdr1 {
unsigned int ts_sec; /* time stamp */
unsigned int ts_usec;
unsigned int caplen; /* length of portion present */
unsigned int len; /* length this packet (off wire) */
}dumpPktHdr;
dumpPktHdr pkt_hdr;
static int ts_sec = 1;
pkt_hdr.ts_sec = ts_sec++;
pkt_hdr.ts_usec = 0;
pkt_hdr.caplen = pkt_hdr.len = pkt_len;
if (NULL != fp) {
fwrite((void*)(&pkt_hdr), sizeof(dumpPktHdr), 1, fp);
fwrite((void*)(pkt), pkt_len, 1, fp);
fflush(fp);
}
return 0;
}