Hello,
I am doing packet replication and I need to change the ethernet and IP
header field for each replicated packet. I did it in two different ways:
1. Share payload from the original packet using rte_mbuf_refcnt_update
and allocate new mbuf for L2-L4 headers.
2. memcpy() payload from the original packet to newly created mbuf and
prepend L2-L4 headers to the mbuf.
I performed experiments with varying replication factor as well as
varying packet size and found that memcpy() is performing way better
than using rte_mbuf_refcnt_update(). But I am not sure why it is
happening and what is making rte_mbuf_refcnt_update() even worse than
memcpy().
Here is the sample code for both implementations:
*1. Using rte_mbuf_refcnt_update:*
**struct rte_mbuf *pkt = original packet;**
**
******rte_pktmbuf_adj(pkt, (uint16_t)sizeof(struct
ether_hdr)+sizeof(struct ipv4_hdr));
rte_pktmbuf_refcnt_update(pkt, replication_factor);
for(int i = 0; i < replication_factor; i++) {
struct rte_mbuf *hdr;
if (unlikely ((hdr = rte_pktmbuf_alloc(header_pool)) ==
NULL)) {
printf("Failed while cloning $$$\n");
return NULL;
}
hdr->next = pkt;
hdr->pkt_len = (uint16_t)(hdr->data_len + pkt->pkt_len);
hdr->nb_segs = (uint8_t)(pkt->nb_segs + 1);
//*Update more metadate fields*
*
*
**rte_pktmbuf_prepend(hdr, (uint16_t)sizeof(struct ether_hdr));
//*modify L2 fields*
rte_pktmbuf_prepend(hdr, (uint16_t)sizeof(struct ipv4_hdr));
//Modify L3 fields
.
.
.
}
*
*
*
*
*2. Using memcpy():*
**struct rte_mbuf *pkt = original packet
**struct rte_mbuf *hdr;**
if (unlikely ((hdr = rte_pktmbuf_alloc(header_pool)) == NULL)) {
printf("Failed while cloning $$$\n");
return NULL;
}
/* prepend new header */
char *eth_hdr = (char *)rte_pktmbuf_prepend(hdr, pkt->pkt_len);
if(eth_hdr == NULL) {
printf("panic\n");
}
char *b = rte_pktmbuf_mtod((struct rte_mbuf*)pkt, char *);
memcpy(eth_hdr, b, pkt->pkt_len);
Change L2-L4 header fields in new packet
The throughput becomes roughly half when the packet size is increased
from 64 bytes to 128 bytes and replication is done using
*rte_mbuf_refcnt_update(). *The throughput remains more or less same
when packet size increases and replication is done using *memcpy()*.
Any help would be appreciated.
**
--
Thanks,
Shailja
