2015-11-04 18:54, Jijiang Liu:
> + /* if vhost TX checksum offload is required */
> + if (m->ol_flags & PKT_TX_IP_CKSUM) {
> + hdr->csum_start = m->l2_len;
> + hdr->csum_offset = offsetof(struct ipv4_hdr, hdr_checksum);
> + } else if (m->ol_flags & PKT_TX_L4_MASK) {
> + hdr->csum_start = m->l2_len + m->l3_len;
> + switch (m->ol_flags & PKT_TX_L4_MASK) {
> + case PKT_TX_TCP_CKSUM:
> + hdr->csum_offset = offsetof(struct tcp_hdr, cksum);
> + break;
> + case PKT_TX_UDP_CKSUM:
> + hdr->csum_offset = offsetof(struct udp_hdr,
> + dgram_cksum);
> + break;
> + case PKT_TX_SCTP_CKSUM:
> + hdr->csum_offset = offsetof(struct sctp_hdr, cksum);
> + break;
> + default:
> + break;
> + }
The header checksum to offload is deduced from csum_offset.
Your vhost implementation do some parsing to deduce it:
> + parse_ethernet(m, &l4_proto, &l4_hdr);
> + if (hdr->flags == VIRTIO_NET_HDR_F_NEEDS_CSUM) {
> + if ((hdr->csum_start == m->l2_len) &&
> + (hdr->csum_offset == offsetof(struct ipv4_hdr,
> + hdr_checksum)))
> + m->ol_flags |= PKT_TX_IP_CKSUM;
> + else if (hdr->csum_start == (m->l2_len + m->l3_len)) {
> + switch (hdr->csum_offset) {
> + case (offsetof(struct tcp_hdr, cksum)):
> + if (l4_proto == IPPROTO_TCP)
> + m->ol_flags |= PKT_TX_TCP_CKSUM;
> + break;
> + case (offsetof(struct udp_hdr, dgram_cksum)):
> + if (l4_proto == IPPROTO_UDP)
> + m->ol_flags |= PKT_TX_UDP_CKSUM;
> + break;
> + case (offsetof(struct sctp_hdr, cksum)):
> + if (l4_proto == IPPROTO_SCTP)
> + m->ol_flags |= PKT_TX_SCTP_CKSUM;
> + break;
> + default:
> + break;
> + }
> + }
The kernel doesn't work this way.
Please could you check that your virtio implementation works with a
vanilla Linux with or without vhost?
Thanks
