[dpdk-users] Replicating PCAP packets read by pktgen for multiple source addresses

[Wiles, Keith]

You can edit the packet in the function below, but you have to do that action everytime. Freeing the mbuf I sok, you can look into the refcnt value in the mbuf if you want tx_burst to not free the packet completely.

From: users <users-bounces at dpdk.org>
Date: Sunday, September 13, 2020 at 5:00 PM
To: users at dpdk.org <users at dpdk.org>
Subject: [dpdk-users] Replicating PCAP packets read by pktgen for multiple source addresses
Hi,

I want to use pktgen to read a pcap file and play that pcap file say 10
times by editing the source IP address for each run, please let me know
what's the best way of doing this.

I first thought of editing the source IP in the rte_mbuf pointed by pkts
before calling the rte_eth_tx_burst(info->pid, qid, pkts, cnt) function but
it seems that rte_eth_tx_burst function frees up the rte_mbuf pointed by
pkts after sending the packet once so I cannot edit the pkts buffer again.


static __inline__ void
trafficgen_send_burst(port_info_t *info, uint16_t qid)
{
struct mbuf_table   *mtab = &info->q[qid].tx_mbufs;
struct rte_mbuf **pkts;
struct qstats_s *qstats;
uint32_t ret, cnt, tap, rnd, tstamp, i;
int32_t seq_idx;

if ((cnt = mtab->len) == 0)
return;

mtab->len = 0;
pkts = mtab->m_table;

if (trafficgen_tst_port_flags(info, SEND_RANGE_PKTS))
seq_idx = RANGE_PKT;
else if (trafficgen_tst_port_flags(info, SEND_RATE_PACKETS))
seq_idx = RATE_PKT;
else
seq_idx = SINGLE_PKT;

tap = trafficgen_tst_port_flags(info, PROCESS_TX_TAP_PKTS);
rnd = trafficgen_tst_port_flags(info, SEND_RANDOM_PKTS);
tstamp = trafficgen_tst_port_flags(info, (SEND_LATENCY_PKTS |
SEND_RATE_PACKETS));

qstats = &info->qstats[qid];
qstats->txpkts += cnt;
for (i = 0; i < cnt; i++)
qstats->txbytes += rte_pktmbuf_data_len(pkts[i]);

*/*Inserting a for loop here doesn't help as rte_mbuf is freed by
rte_eth_tx_burst*/*
/* Send all of the packets before we can exit this function */
while (cnt) {

if (rnd)
trafficgen_rnd_bits_apply(info, pkts, cnt, NULL);

if (tstamp)
trafficgen_tstamp_apply(info, pkts, cnt, seq_idx);

ret = rte_eth_tx_burst(info->pid, qid, pkts, cnt);

if (tap)
trafficgen_do_tx_tap(info, pkts, ret);

pkts += ret;
cnt -= ret;
}
}

Basically, I want to resend buffers stored in rte_mbuf again and again,
after modifying source IP in each run.

Thanks
Ravi