> > > + /* When sw csum is needed, multi-segs needs a buf to contain
> > > + * the whole packet for later UDP/TCP csum calculation.
> > > + */
> > > + if (m->nb_segs > 1 && !(tx_ol_flags & PKT_TX_TCP_SEG) &&
> > > + !(tx_offloads & UDP_TCP_CSUM)) {
> > > + l3_buf = rte_zmalloc("csum l3_buf",
> > > + info.pkt_len - info.l2_len,
> > > + RTE_CACHE_LINE_SIZE);
> > > + rte_pktmbuf_read(m, info.l2_len,
> > > + info.pkt_len - info.l2_len, l3_buf);
> > > + l3_hdr = l3_buf;
> > > + } else
> > > + l3_hdr = (char *)eth_hdr + info.l2_len;
> > >
> >
> > Rather than copying whole packet, make the code handle checksum streaming.
>
> Copying is the easiest way to do this.
>
> The problem of handling checksum streaming is that in the first segment, l2
> and l3 hdr len is 14 bytes when checksum takes 4 bytes each
> time.
> If the datalen of the first segment is 4 bytes aligned (usual case), for the
> second segment and the following segments, they may need to add
> a special 2 bytes 0x0 at the start.
Didn't understand that one...
Why you suddenly need to pad non-first segments with zeroes?
Why simply rte_raw_cksum() can't be used for multi-seg case?
> Also, mbuf is not passed down to process_inner/outer_chksum so the change
> will be a lot.
I also think that copying whole packet just to calculate a checksum - way too
much overhead.
