Re: [dpdk-dev] [PATCH v1] net/tap: fix keep-alive queue not detached

["Wiles, Keith" <keith.wiles@intel.com>]

> On May 24, 2018, at 6:10 PM, Ophir Munk <ophirmu@mellanox.com> wrote:
> 
> The TAP keep-alive queue was created in order to keep the TAP device
> in Linux even in case all of its Rx/Tx queues are released (in Linux
> terminology: even in case all of the TAP device file descriptors are
> closed), however, the keep-alive queue itself is attached to the TAP
> device like all other Rx/Tx queues and therefore the kernel will
> enqueue to it some Rx packets based on the kernel RSS distribution
> rules. Those packets are unknown to the application and will remain
> lost in the keep-alive queue.
> All queues are attached by default to the TAP device after they are
> created though TUNSETIFF ioctl call.
> The fix is to detach the keep-alive queue after its creation through
> TUNSETQUEUE ioctl call.
> 
> Fixes: 3101191c63ab ("net/tap: fix device removal when no queue exist")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Ophir Munk <ophirmu@mellanox.com>
> ---
> drivers/net/tap/rte_eth_tap.c | 33 +++++++++++++++++++++++++++------
> 1 file changed, 27 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
> index 310c7d8..c3af608 100644
> --- a/drivers/net/tap/rte_eth_tap.c
> +++ b/drivers/net/tap/rte_eth_tap.c
> @@ -95,13 +95,20 @@ enum ioctl_mode {
> 
> static int tap_intr_handle_set(struct rte_eth_dev *dev, int set);
> 
> -/* Tun/Tap allocation routine
> +/**
> + * Tun/Tap allocation routine
> + *
> + * @param[in] pmd
> + *   Pointer to private structure.
> + *
> + * @param[in] is_keepalive
> + *   Keepliave flag
>  *
> - * name is the number of the interface to use, unless NULL to take the host
> - * supplied name.
> + * @return
> + *   -1 on failure, fd on success
>  */
> static int
> -tun_alloc(struct pmd_internals *pmd)
> +tun_alloc(struct pmd_internals *pmd, int is_keepalive)

This poor tun_alloc() routine did have a flag, then it was taken out and now it is back again :-(

> {
> 	struct ifreq ifr;
> #ifdef IFF_MULTI_QUEUE
> @@ -154,6 +161,20 @@ tun_alloc(struct pmd_internals *pmd)
> 		goto error;
> 	}
> 
> +	if (is_keepalive) {
> +		/*
> +		 * Detach the TUN/TAP keep-alive queue
> +		 * to avoid traffic through it
> +		 */
> +		ifr.ifr_flags = IFF_DETACH_QUEUE;
> +		if (ioctl(fd, TUNSETQUEUE, (void *)&ifr) < 0) {
> +			TAP_LOG(WARNING,
> +				"Unable to detach keep-alive queue for %s: %s",
> +				ifr.ifr_name, strerror(errno));
> +			goto error;
> +		}
> +	}
> +
> 	/* Always set the file descriptor to non-blocking */
> 	if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0) {
> 		TAP_LOG(WARNING,
> @@ -1020,7 +1041,7 @@ tap_setup_queue(struct rte_eth_dev *dev,
> 			pmd->name, *other_fd, dir, qid, *fd);
> 	} else {
> 		/* Both RX and TX fds do not exist (equal -1). Create fd */
> -		*fd = tun_alloc(pmd);
> +		*fd = tun_alloc(pmd, 0);
> 		if (*fd < 0) {
> 			*fd = -1; /* restore original value */
> 			TAP_LOG(ERR, "%s: tun_alloc() failed.", pmd->name);
> @@ -1425,7 +1446,7 @@ eth_dev_tap_create(struct rte_vdev_device *vdev, char *tap_name,
> 	 * This keep-alive file descriptor will guarantee that the TUN device
> 	 * exists even when all of its queues are closed
> 	 */
> -	pmd->ka_fd = tun_alloc(pmd);
> +	pmd->ka_fd = tun_alloc(pmd, 1);
> 	if (pmd->ka_fd == -1) {
> 		TAP_LOG(ERR, "Unable to create %s interface", tuntap_name);
> 		goto error_exit;
> -- 
> 2.7.4
> 

Looks good to me.

Acked-by: Keith Wiles<keith.wiles@intel.com>

Regards,
Keith