[dpdk-dev] [PATCH v7 3/3] net/virtio: support GUEST ANNOUNCE

[Maxime Coquelin]

On 01/09/2018 03:26 PM, Xiao Wang wrote:
> When live migration is done, for the backup VM, either the virtio
> frontend or the vhost backend needs to send out gratuitous RARP packet
> to announce its new network location.
> 
> This patch enables VIRTIO_NET_F_GUEST_ANNOUNCE feature to support live
> migration scenario where the vhost backend doesn't have the ability to
> generate RARP packet.
> 
> Brief introduction of the work flow:
> 1. QEMU finishes live migration, pokes the backup VM with an interrupt.
> 2. Virtio interrupt handler reads out the interrupt status value, and
>     realizes it needs to send out RARP packet to announce its location.
> 3. Pause device to stop worker thread touching the queues.
> 4. Inject a RARP packet into a Tx Queue.
> 5. Ack the interrupt via control queue.
> 6. Resume device to continue packet processing.
> 
> Signed-off-by: Xiao Wang <xiao.w.wang at intel.com>
> ---
>   drivers/net/virtio/virtio_ethdev.c | 95 +++++++++++++++++++++++++++++++++++++-
>   drivers/net/virtio/virtio_ethdev.h |  1 +
>   drivers/net/virtio/virtqueue.h     | 11 +++++
>   3 files changed, 105 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
> index e8ff1e449..9606df514 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -19,6 +19,8 @@
>   #include <rte_pci.h>
>   #include <rte_bus_pci.h>
>   #include <rte_ether.h>
> +#include <rte_ip.h>
> +#include <rte_arp.h>
>   #include <rte_common.h>
>   #include <rte_errno.h>
>   #include <rte_cpuflags.h>
> @@ -78,6 +80,11 @@ static int virtio_dev_queue_stats_mapping_set(
>   	uint8_t stat_idx,
>   	uint8_t is_rx);
>   
> +static int make_rarp_packet(struct rte_mbuf *rarp_mbuf,
> +		const struct ether_addr *mac);
> +static void virtio_notify_peers(struct rte_eth_dev *dev);
> +static void virtio_ack_link_announce(struct rte_eth_dev *dev);
> +
>   /*
>    * The set of PCI devices this driver supports
>    */
> @@ -1272,9 +1279,89 @@ virtio_inject_pkts(struct rte_eth_dev *dev, struct rte_mbuf **tx_pkts,
>   	return ret;
>   }
>   
> +#define RARP_PKT_SIZE	64
> +static int
> +make_rarp_packet(struct rte_mbuf *rarp_mbuf, const struct ether_addr *mac)
> +{
> +	struct ether_hdr *eth_hdr;
> +	struct arp_hdr *rarp;
> +
> +	if (rarp_mbuf->buf_len < RARP_PKT_SIZE) {
> +		PMD_DRV_LOG(ERR, "mbuf size too small %u (< %d)",
> +				rarp_mbuf->buf_len, RARP_PKT_SIZE);
> +		return -1;
> +	}
> +
> +	/* Ethernet header. */
> +	eth_hdr = rte_pktmbuf_mtod(rarp_mbuf, struct ether_hdr *);
> +	memset(eth_hdr->d_addr.addr_bytes, 0xff, ETHER_ADDR_LEN);
> +	ether_addr_copy(mac, &eth_hdr->s_addr);
> +	eth_hdr->ether_type = htons(ETHER_TYPE_RARP);
> +
> +	/* RARP header. */
> +	rarp = (struct arp_hdr *)(eth_hdr + 1);
> +	rarp->arp_hrd = htons(ARP_HRD_ETHER);
> +	rarp->arp_pro = htons(ETHER_TYPE_IPv4);
> +	rarp->arp_hln = ETHER_ADDR_LEN;
> +	rarp->arp_pln = 4;
> +	rarp->arp_op  = htons(ARP_OP_REVREQUEST);
> +
> +	ether_addr_copy(mac, &rarp->arp_data.arp_sha);
> +	ether_addr_copy(mac, &rarp->arp_data.arp_tha);
> +	memset(&rarp->arp_data.arp_sip, 0x00, 4);
> +	memset(&rarp->arp_data.arp_tip, 0x00, 4);
> +
> +	rarp_mbuf->data_len = RARP_PKT_SIZE;
> +	rarp_mbuf->pkt_len = RARP_PKT_SIZE;
> +
> +	return 0;
> +}

Do you think it could make sense to have this function in a lib, as
vhost user lib does exactly the same?

I don't know if it could be useful to others than vhost/virtio though.

Thanks,
Maxime