[dpdk-dev,v6] net/virtio-user: add support for server mode

Message ID 20180406001855.54062-1-zhiyong.yang@intel.com (mailing list archive)
State Superseded, archived
Delegated to: Maxime Coquelin
Headers

Checks

Context Check Description
ci/checkpatch success coding style OK
ci/Intel-compilation fail apply issues

Commit Message

Yang, Zhiyong April 6, 2018, 12:18 a.m. UTC
  In a container environment if the vhost-user backend restarts, there's
no way for it to reconnect to virtio-user. To address this, support for
server mode is added. In this mode the socket file is created by virtio-
user, which the backend then connects to. This means that if the backend
restarts, it can reconnect to virtio-user and continue communications.

With current implementation, LSC is enabled at virtio-user side to
support to accept the coming connection.

Release note is updated in this patch.

Signed-off-by: Zhiyong Yang <zhiyong.yang@intel.com>
---

Changes in V6:
1. fix report wrong link stauts in server mode.
2. fix some code style issues.

Changes in V5:
1. Support server mode virtio-user startup in non-blocking mode.
2. rebase on top of dpdk-next-virtio.

Changes in V4:
1. Don't create new pthread any more and use librte_eal interrupt thread.
2. virtio-user doesn't work in blocking mode any more for the first connection.
Client mode vhost-user startups firstly, then server mode virtio-user creates
socket file and startups. Keep consistency with usage of client mode
virtio-user. 

Changes in V3:
1. use EAL epoll mechanism instead of vhost events. Cancel to export vhost
event APIs.
2. rebase the code on top of dpdk-next-virtio

Changes in V2:
1. split two patches 1/5 and 2/5 from v1 patchset to fix some existing issues
which is not strongly related to support for server mode
2. move fdset related functions to librte_eal from librte_vhost exposed as
new APIs.
3. release note is added in the patch 5/5.
4. squash data structure change patch into 4/5 according to Maxime's suggestion.

 doc/guides/rel_notes/release_18_05.rst           |   6 ++
 drivers/net/virtio/virtio_user/vhost_user.c      |  45 ++++++++--
 drivers/net/virtio/virtio_user/virtio_user_dev.c |  40 +++++++--
 drivers/net/virtio/virtio_user/virtio_user_dev.h |   3 +
 drivers/net/virtio/virtio_user_ethdev.c          | 101 ++++++++++++++++++++---
 5 files changed, 171 insertions(+), 24 deletions(-)
  

Comments

Jianfeng Tan April 5, 2018, 6:13 p.m. UTC | #1
On 4/6/2018 8:18 AM, zhiyong.yang@intel.com wrote:
> In a container environment if the vhost-user backend restarts, there's
> no way for it to reconnect to virtio-user. To address this, support for
> server mode is added. In this mode the socket file is created by virtio-
> user, which the backend then connects to. This means that if the backend
> restarts, it can reconnect to virtio-user and continue communications.
>
> With current implementation, LSC is enabled at virtio-user side to
> support to accept the coming connection.
>
> Release note is updated in this patch.
>
> Signed-off-by: Zhiyong Yang <zhiyong.yang@intel.com>
> ---
>
> Changes in V6:
> 1. fix report wrong link stauts in server mode.
> 2. fix some code style issues.
>
> Changes in V5:
> 1. Support server mode virtio-user startup in non-blocking mode.
> 2. rebase on top of dpdk-next-virtio.
>
> Changes in V4:
> 1. Don't create new pthread any more and use librte_eal interrupt thread.
> 2. virtio-user doesn't work in blocking mode any more for the first connection.
> Client mode vhost-user startups firstly, then server mode virtio-user creates
> socket file and startups. Keep consistency with usage of client mode
> virtio-user.
>
> Changes in V3:
> 1. use EAL epoll mechanism instead of vhost events. Cancel to export vhost
> event APIs.
> 2. rebase the code on top of dpdk-next-virtio
>
> Changes in V2:
> 1. split two patches 1/5 and 2/5 from v1 patchset to fix some existing issues
> which is not strongly related to support for server mode
> 2. move fdset related functions to librte_eal from librte_vhost exposed as
> new APIs.
> 3. release note is added in the patch 5/5.
> 4. squash data structure change patch into 4/5 according to Maxime's suggestion.
>
>   doc/guides/rel_notes/release_18_05.rst           |   6 ++
>   drivers/net/virtio/virtio_user/vhost_user.c      |  45 ++++++++--
>   drivers/net/virtio/virtio_user/virtio_user_dev.c |  40 +++++++--
>   drivers/net/virtio/virtio_user/virtio_user_dev.h |   3 +
>   drivers/net/virtio/virtio_user_ethdev.c          | 101 ++++++++++++++++++++---
>   5 files changed, 171 insertions(+), 24 deletions(-)
>
> diff --git a/doc/guides/rel_notes/release_18_05.rst b/doc/guides/rel_notes/release_18_05.rst
> index 9cc77f893..f8897b2e9 100644
> --- a/doc/guides/rel_notes/release_18_05.rst
> +++ b/doc/guides/rel_notes/release_18_05.rst
> @@ -58,6 +58,12 @@ New Features
>     * Added support for NVGRE, VXLAN and GENEVE filters in flow API.
>     * Added support for DROP action in flow API.
>   
> +* **Added support for virtio-user server mode.**
> +  In a container environment if the vhost-user backend restarts, there's no way
> +  for it to reconnect to virtio-user. To address this, support for server mode
> +  is added. In this mode the socket file is created by virtio-user, which the
> +  backend connects to. This means that if the backend restarts, it can reconnect
> +  to virtio-user and continue communications.
>   
>   API Changes
>   -----------
> diff --git a/drivers/net/virtio/virtio_user/vhost_user.c b/drivers/net/virtio/virtio_user/vhost_user.c
> index 91c6449bb..a6df97a00 100644
> --- a/drivers/net/virtio/virtio_user/vhost_user.c
> +++ b/drivers/net/virtio/virtio_user/vhost_user.c
> @@ -378,6 +378,30 @@ vhost_user_sock(struct virtio_user_dev *dev,
>   	return 0;
>   }
>   
> +#define MAX_VIRTIO_USER_BACKLOG 1
> +static int
> +virtio_user_start_server(struct virtio_user_dev *dev, struct sockaddr_un *un)
> +{
> +	int ret;
> +	int flag;
> +	int fd = dev->listenfd;
> +
> +	ret = bind(fd, (struct sockaddr *)un, sizeof(*un));
> +	if (ret < 0) {
> +		PMD_DRV_LOG(ERR, "failed to bind to %s: %s; remove it and try again\n",
> +			    dev->path, strerror(errno));
> +		return -1;
> +	}
> +	ret = listen(fd, MAX_VIRTIO_USER_BACKLOG);
> +	if (ret < 0)
> +		return -1;
> +
> +	flag = fcntl(fd, F_GETFL);
> +	fcntl(fd, F_SETFL, flag | O_NONBLOCK);
> +
> +	return 0;
> +}
> +
>   /**
>    * Set up environment to talk with a vhost user backend.
>    *
> @@ -405,13 +429,24 @@ vhost_user_setup(struct virtio_user_dev *dev)
>   	memset(&un, 0, sizeof(un));
>   	un.sun_family = AF_UNIX;
>   	snprintf(un.sun_path, sizeof(un.sun_path), "%s", dev->path);
> -	if (connect(fd, (struct sockaddr *)&un, sizeof(un)) < 0) {
> -		PMD_DRV_LOG(ERR, "connect error, %s", strerror(errno));
> -		close(fd);
> -		return -1;
> +
> +	if (dev->is_server) {
> +		dev->listenfd = fd;
> +		if (virtio_user_start_server(dev, &un) < 0) {
> +			PMD_DRV_LOG(ERR, "virtio-user startup fails in server mode");
> +			close(fd);
> +			return -1;
> +		}
> +		dev->vhostfd = -1;
> +	} else {
> +		if (connect(fd, (struct sockaddr *)&un, sizeof(un)) < 0) {
> +			PMD_DRV_LOG(ERR, "connect error, %s", strerror(errno));
> +			close(fd);
> +			return -1;
> +		}
> +		dev->vhostfd = fd;
>   	}
>   
> -	dev->vhostfd = fd;
>   	return 0;
>   }
>   
> diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.c b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> index f90fee9e5..3b776282c 100644
> --- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
> +++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> @@ -99,6 +99,9 @@ virtio_user_start_device(struct virtio_user_dev *dev)
>   	uint64_t features;
>   	int ret;
>   
> +	if (dev->vhostfd < 0)
> +		return -1;

This breaks virtio-user with vhost-kernel which does not need vhostfd, 
and will be always -1.

> +
>   	/* Do not check return as already done in init, or reset in stop */
>   	dev->ops->send_request(dev, VHOST_USER_SET_OWNER, NULL);
>   
> @@ -254,6 +257,8 @@ virtio_user_fill_intr_handle(struct virtio_user_dev *dev)
>   	eth_dev->intr_handle->fd = -1;
>   	if (dev->vhostfd >= 0)
>   		eth_dev->intr_handle->fd = dev->vhostfd;
> +	else if (dev->is_server)
> +		eth_dev->intr_handle->fd = dev->listenfd;
>   
>   	return 0;
>   }
> @@ -267,7 +272,7 @@ virtio_user_dev_setup(struct virtio_user_dev *dev)
>   	dev->vhostfds = NULL;
>   	dev->tapfds = NULL;
>   
> -	if (is_vhost_user_by_type(dev->path)) {
> +	if (dev->is_server || is_vhost_user_by_type(dev->path)) {

I think we still fail to pick out an invalidated case: specify "server" 
parameter for a vhost-kernel path.

>   		dev->ops = &ops_user;
>   	} else {
>   		dev->ops = &ops_kernel;
> @@ -337,16 +342,25 @@ virtio_user_dev_init(struct virtio_user_dev *dev, char *path, int queues,
>   		return -1;
>   	}
>   
> -	if (dev->ops->send_request(dev, VHOST_USER_SET_OWNER, NULL) < 0) {
> -		PMD_INIT_LOG(ERR, "set_owner fails: %s", strerror(errno));
> -		return -1;
> -	}
> +	if (dev->vhostfd >= 0) {
> +		if (dev->ops->send_request(dev, VHOST_USER_SET_OWNER,
> +					   NULL) < 0) {
> +			PMD_INIT_LOG(ERR, "set_owner fails: %s",
> +				     strerror(errno));
> +			return -1;
> +		}
>   
> -	if (dev->ops->send_request(dev, VHOST_USER_GET_FEATURES,
> -			    &dev->device_features) < 0) {
> -		PMD_INIT_LOG(ERR, "get_features failed: %s", strerror(errno));
> -		return -1;
> +		if (dev->ops->send_request(dev, VHOST_USER_GET_FEATURES,
> +					   &dev->device_features) < 0) {
> +			PMD_INIT_LOG(ERR, "get_features failed: %s",
> +				     strerror(errno));
> +			return -1;
> +		}
> +	} else {
> +		/* Just pretend vhost-user can support all these features */

Although I don't think we need to fix this, please also note that this 
could be problematic that if some feature is negotiated but not 
supported by the vhost-user which comes later.

> +		dev->device_features = VIRTIO_USER_SUPPORTED_FEATURES;
>   	}
> +
>   	if (dev->mac_specified)
>   		dev->device_features |= (1ull << VIRTIO_NET_F_MAC);
>   
> @@ -388,6 +402,11 @@ virtio_user_dev_uninit(struct virtio_user_dev *dev)
>   
>   	close(dev->vhostfd);
>   
> +	if (dev->is_server && dev->listenfd >= 0) {
> +		close(dev->listenfd);
> +		dev->listenfd = -1;
> +	}
> +
>   	if (dev->vhostfds) {
>   		for (i = 0; i < dev->max_queue_pairs; ++i)
>   			close(dev->vhostfds[i]);
> @@ -396,6 +415,9 @@ virtio_user_dev_uninit(struct virtio_user_dev *dev)
>   	}
>   
>   	free(dev->ifname);
> +
> +	if (dev->is_server)
> +		unlink(dev->path);
>   }
>   
>   static uint8_t
> diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.h b/drivers/net/virtio/virtio_user/virtio_user_dev.h
> index 5f8755771..ade727e46 100644
> --- a/drivers/net/virtio/virtio_user/virtio_user_dev.h
> +++ b/drivers/net/virtio/virtio_user/virtio_user_dev.h
> @@ -6,6 +6,7 @@
>   #define _VIRTIO_USER_DEV_H
>   
>   #include <limits.h>
> +#include <stdbool.h>
>   #include "../virtio_pci.h"
>   #include "../virtio_ring.h"
>   #include "vhost.h"
> @@ -13,6 +14,8 @@
>   struct virtio_user_dev {
>   	/* for vhost_user backend */
>   	int		vhostfd;
> +	int		listenfd;   /* listening fd */
> +	bool		is_server;  /* server or client mode */
>   
>   	/* for vhost_kernel backend */
>   	char		*ifname;
> diff --git a/drivers/net/virtio/virtio_user_ethdev.c b/drivers/net/virtio/virtio_user_ethdev.c
> index 263649006..4e7b3c34f 100644
> --- a/drivers/net/virtio/virtio_user_ethdev.c
> +++ b/drivers/net/virtio/virtio_user_ethdev.c
> @@ -24,15 +24,73 @@
>   #define virtio_user_get_dev(hw) \
>   	((struct virtio_user_dev *)(hw)->virtio_user_dev)
>   
> +static int
> +virtio_user_server_reconnect(struct virtio_user_dev *dev)
> +{
> +	int ret;
> +	int flag;
> +	int connectfd;
> +	struct rte_eth_dev *eth_dev = &rte_eth_devices[dev->port_id];
> +
> +	connectfd = accept(dev->listenfd, NULL, NULL);
> +	if (connectfd < 0)
> +		return -1;
> +
> +	dev->vhostfd = connectfd;
> +	flag = fcntl(connectfd, F_GETFD);
> +	fcntl(connectfd, F_SETFL, flag | O_NONBLOCK);
> +
> +	ret = virtio_user_start_device(dev);
> +	if (ret < 0)
> +		return -1;
> +
> +	if (eth_dev->data->dev_flags & RTE_ETH_DEV_INTR_LSC) {
> +		if (rte_intr_disable(eth_dev->intr_handle) < 0) {
> +			PMD_DRV_LOG(ERR, "interrupt disable failed");
> +			return -1;
> +		}
> +		rte_intr_callback_unregister(eth_dev->intr_handle,
> +					     virtio_interrupt_handler,
> +					     eth_dev);
> +		eth_dev->intr_handle->fd = connectfd;
> +		rte_intr_callback_register(eth_dev->intr_handle,
> +					   virtio_interrupt_handler, eth_dev);
> +
> +		if (rte_intr_enable(eth_dev->intr_handle) < 0) {
> +			PMD_DRV_LOG(ERR, "interrupt enable failed");
> +			return -1;
> +		}
> +	}
> +	PMD_INIT_LOG(NOTICE, "server mode virtio-user reconnection succeeds!");
> +	return 0;
> +}
> +
>   static void
>   virtio_user_delayed_handler(void *param)
>   {
>   	struct virtio_hw *hw = (struct virtio_hw *)param;
> -	struct rte_eth_dev *dev = &rte_eth_devices[hw->port_id];
> +	struct rte_eth_dev *eth_dev = &rte_eth_devices[hw->port_id];
> +	struct virtio_user_dev *dev = virtio_user_get_dev(hw);
>   
> -	rte_intr_callback_unregister(dev->intr_handle,
> -				     virtio_interrupt_handler,
> -				     dev);
> +	if (rte_intr_disable(eth_dev->intr_handle) < 0) {
> +		PMD_DRV_LOG(ERR, "interrupt disable failed");
> +		return;
> +	}
> +	rte_intr_callback_unregister(eth_dev->intr_handle,
> +				     virtio_interrupt_handler, eth_dev);
> +	if (dev->is_server) {
> +		if (dev->vhostfd >= 0) {
> +			close(dev->vhostfd);
> +			dev->vhostfd = -1;
> +		}
> +		eth_dev->intr_handle->fd = dev->listenfd;
> +		rte_intr_callback_register(eth_dev->intr_handle,
> +					   virtio_interrupt_handler, eth_dev);
> +		if (rte_intr_enable(eth_dev->intr_handle) < 0) {
> +			PMD_DRV_LOG(ERR, "interrupt enable failed");
> +			return;
> +		}
> +	}
>   }
>   
>   static void
> @@ -67,12 +125,10 @@ virtio_user_read_dev_config(struct virtio_hw *hw, size_t offset,
>   				dev->status &= (~VIRTIO_NET_S_LINK_UP);
>   				PMD_DRV_LOG(ERR, "virtio-user port %u is down",
>   					    hw->port_id);
> -				/* Only client mode is available now. Once the
> -				 * connection is broken, it can never be up
> -				 * again. Besides, this function could be called
> -				 * in the process of interrupt handling,
> -				 * callback cannot be unregistered here, set an
> -				 * alarm to do it.
> +
> +				/* This function could be called in the process
> +				 * of interrupt handling, callback cannot be
> +				 * unregistered here, set an alarm to do it.
>   				 */
>   				rte_eal_alarm_set(1,
>   						  virtio_user_delayed_handler,
> @@ -85,7 +141,12 @@ virtio_user_read_dev_config(struct virtio_hw *hw, size_t offset,
>   				PMD_DRV_LOG(ERR, "error clearing O_NONBLOCK flag");
>   				return;
>   			}
> +		} else if (dev->is_server) {
> +			dev->status &= (~VIRTIO_NET_S_LINK_UP);
> +			if (virtio_user_server_reconnect(dev) >= 0)
> +				dev->status |= VIRTIO_NET_S_LINK_UP;
>   		}
> +
>   		*(uint16_t *)dst = dev->status;
>   	}
>   
> @@ -278,12 +339,15 @@ static const char *valid_args[] = {
>   	VIRTIO_USER_ARG_QUEUE_SIZE,
>   #define VIRTIO_USER_ARG_INTERFACE_NAME "iface"
>   	VIRTIO_USER_ARG_INTERFACE_NAME,
> +#define VIRTIO_USER_ARG_SERVER_MODE "server"
> +	VIRTIO_USER_ARG_SERVER_MODE,
>   	NULL
>   };
>   
>   #define VIRTIO_USER_DEF_CQ_EN	0
>   #define VIRTIO_USER_DEF_Q_NUM	1
>   #define VIRTIO_USER_DEF_Q_SZ	256
> +#define VIRTIO_USER_DEF_SERVER_MODE	0
>   
>   static int
>   get_string_arg(const char *key __rte_unused,
> @@ -378,6 +442,7 @@ virtio_user_pmd_probe(struct rte_vdev_device *dev)
>   	uint64_t queues = VIRTIO_USER_DEF_Q_NUM;
>   	uint64_t cq = VIRTIO_USER_DEF_CQ_EN;
>   	uint64_t queue_size = VIRTIO_USER_DEF_Q_SZ;
> +	uint64_t server_mode = VIRTIO_USER_DEF_SERVER_MODE;
>   	char *path = NULL;
>   	char *ifname = NULL;
>   	char *mac_addr = NULL;
> @@ -445,6 +510,15 @@ virtio_user_pmd_probe(struct rte_vdev_device *dev)
>   		}
>   	}
>   
> +	if (rte_kvargs_count(kvlist, VIRTIO_USER_ARG_SERVER_MODE) == 1) {
> +		if (rte_kvargs_process(kvlist, VIRTIO_USER_ARG_SERVER_MODE,
> +				       &get_integer_arg, &server_mode) < 0) {
> +			PMD_INIT_LOG(ERR, "error to parse %s",
> +				     VIRTIO_USER_ARG_SERVER_MODE);
> +			goto end;
> +		}
> +	}
> +
>   	if (rte_kvargs_count(kvlist, VIRTIO_USER_ARG_CQ_NUM) == 1) {
>   		if (rte_kvargs_process(kvlist, VIRTIO_USER_ARG_CQ_NUM,
>   				       &get_integer_arg, &cq) < 0) {
> @@ -469,6 +543,8 @@ virtio_user_pmd_probe(struct rte_vdev_device *dev)
>   	}
>   
>   	if (rte_eal_process_type() == RTE_PROC_PRIMARY) {
> +		struct virtio_user_dev *vu_dev;
> +
>   		eth_dev = virtio_user_eth_dev_alloc(dev);
>   		if (!eth_dev) {
>   			PMD_INIT_LOG(ERR, "virtio_user fails to alloc device");
> @@ -476,6 +552,11 @@ virtio_user_pmd_probe(struct rte_vdev_device *dev)
>   		}
>   
>   		hw = eth_dev->data->dev_private;
> +		vu_dev = virtio_user_get_dev(hw);
> +		if (server_mode == 1)
> +			vu_dev->is_server = true;
> +		else
> +			vu_dev->is_server = false;
>   		if (virtio_user_dev_init(hw->virtio_user_dev, path, queues, cq,
>   				 queue_size, mac_addr, &ifname) < 0) {
>   			PMD_INIT_LOG(ERR, "virtio_user_dev_init fails");
  
Yang, Zhiyong April 6, 2018, 7:14 a.m. UTC | #2
Hi Jianfeng,

> -----Original Message-----
> From: Tan, Jianfeng
> Sent: Friday, April 6, 2018 2:13 AM
> To: Yang, Zhiyong <zhiyong.yang@intel.com>; dev@dpdk.org
> Cc: maxime.coquelin@redhat.com; Bie, Tiwei <tiwei.bie@intel.com>; Wang,
> Dong1 <dong1.wang@intel.com>; Wang, Zhihong <zhihong.wang@intel.com>
> Subject: Re: [PATCH v6] net/virtio-user: add support for server mode
> 
> 
> 
> On 4/6/2018 8:18 AM, zhiyong.yang@intel.com wrote:
> > In a container environment if the vhost-user backend restarts, there's
> > no way for it to reconnect to virtio-user. To address this, support
> > for server mode is added. In this mode the socket file is created by
> > virtio- user, which the backend then connects to. This means that if
> > the backend restarts, it can reconnect to virtio-user and continue
> communications.
> >
> > With current implementation, LSC is enabled at virtio-user side to
> > support to accept the coming connection.
> >
> > Release note is updated in this patch.
> >
> > Signed-off-by: Zhiyong Yang <zhiyong.yang@intel.com>
> > ---
> >
> > Changes in V6:
> > 1. fix report wrong link stauts in server mode.
> > 2. fix some code style issues.
> >
> > Changes in V5:
> > 1. Support server mode virtio-user startup in non-blocking mode.
> > 2. rebase on top of dpdk-next-virtio.
> >
> > Changes in V4:
> > 1. Don't create new pthread any more and use librte_eal interrupt thread.
> > 2. virtio-user doesn't work in blocking mode any more for the first
> connection.
> > Client mode vhost-user startups firstly, then server mode virtio-user
> > creates socket file and startups. Keep consistency with usage of
> > client mode virtio-user.
> >
> > Changes in V3:
> > 1. use EAL epoll mechanism instead of vhost events. Cancel to export
> > vhost event APIs.
> > 2. rebase the code on top of dpdk-next-virtio
> >
> > Changes in V2:
> > 1. split two patches 1/5 and 2/5 from v1 patchset to fix some existing
> > issues which is not strongly related to support for server mode 2.
> > move fdset related functions to librte_eal from librte_vhost exposed
> > as new APIs.
> > 3. release note is added in the patch 5/5.
> > 4. squash data structure change patch into 4/5 according to Maxime's
> suggestion.
> >
> >   doc/guides/rel_notes/release_18_05.rst           |   6 ++
> >   drivers/net/virtio/virtio_user/vhost_user.c      |  45 ++++++++--
> >   drivers/net/virtio/virtio_user/virtio_user_dev.c |  40 +++++++--
> >   drivers/net/virtio/virtio_user/virtio_user_dev.h |   3 +
> >   drivers/net/virtio/virtio_user_ethdev.c          | 101
> ++++++++++++++++++++---
> >   5 files changed, 171 insertions(+), 24 deletions(-)
> >
> > diff --git a/doc/guides/rel_notes/release_18_05.rst
> > b/doc/guides/rel_notes/release_18_05.rst
> > index 9cc77f893..f8897b2e9 100644
> > --- a/doc/guides/rel_notes/release_18_05.rst
> > +++ b/doc/guides/rel_notes/release_18_05.rst
> > @@ -58,6 +58,12 @@ New Features
> >     * Added support for NVGRE, VXLAN and GENEVE filters in flow API.
> >     * Added support for DROP action in flow API.
> >
> > +* **Added support for virtio-user server mode.**
> > +  In a container environment if the vhost-user backend restarts,
> > +there's no way
> > +  for it to reconnect to virtio-user. To address this, support for
> > +server mode
> > +  is added. In this mode the socket file is created by virtio-user,
> > +which the
> > +  backend connects to. This means that if the backend restarts, it
> > +can reconnect
> > +  to virtio-user and continue communications.
> >
> >   API Changes
> >   -----------
> > diff --git a/drivers/net/virtio/virtio_user/vhost_user.c
> > b/drivers/net/virtio/virtio_user/vhost_user.c
> > index 91c6449bb..a6df97a00 100644
> > --- a/drivers/net/virtio/virtio_user/vhost_user.c
> > +++ b/drivers/net/virtio/virtio_user/vhost_user.c
> > @@ -378,6 +378,30 @@ vhost_user_sock(struct virtio_user_dev *dev,
> >   	return 0;
> >   }
> >
> > +#define MAX_VIRTIO_USER_BACKLOG 1
> > +static int
> > +virtio_user_start_server(struct virtio_user_dev *dev, struct
> > +sockaddr_un *un) {
> > +	int ret;
> > +	int flag;
> > +	int fd = dev->listenfd;
> > +
> > +	ret = bind(fd, (struct sockaddr *)un, sizeof(*un));
> > +	if (ret < 0) {
> > +		PMD_DRV_LOG(ERR, "failed to bind to %s: %s; remove it and
> try again\n",
> > +			    dev->path, strerror(errno));
> > +		return -1;
> > +	}
> > +	ret = listen(fd, MAX_VIRTIO_USER_BACKLOG);
> > +	if (ret < 0)
> > +		return -1;
> > +
> > +	flag = fcntl(fd, F_GETFL);
> > +	fcntl(fd, F_SETFL, flag | O_NONBLOCK);
> > +
> > +	return 0;
> > +}
> > +
> >   /**
> >    * Set up environment to talk with a vhost user backend.
> >    *
> > @@ -405,13 +429,24 @@ vhost_user_setup(struct virtio_user_dev *dev)
> >   	memset(&un, 0, sizeof(un));
> >   	un.sun_family = AF_UNIX;
> >   	snprintf(un.sun_path, sizeof(un.sun_path), "%s", dev->path);
> > -	if (connect(fd, (struct sockaddr *)&un, sizeof(un)) < 0) {
> > -		PMD_DRV_LOG(ERR, "connect error, %s", strerror(errno));
> > -		close(fd);
> > -		return -1;
> > +
> > +	if (dev->is_server) {
> > +		dev->listenfd = fd;
> > +		if (virtio_user_start_server(dev, &un) < 0) {
> > +			PMD_DRV_LOG(ERR, "virtio-user startup fails in
> server mode");
> > +			close(fd);
> > +			return -1;
> > +		}
> > +		dev->vhostfd = -1;
> > +	} else {
> > +		if (connect(fd, (struct sockaddr *)&un, sizeof(un)) < 0) {
> > +			PMD_DRV_LOG(ERR, "connect error, %s",
> strerror(errno));
> > +			close(fd);
> > +			return -1;
> > +		}
> > +		dev->vhostfd = fd;
> >   	}
> >
> > -	dev->vhostfd = fd;
> >   	return 0;
> >   }
> >
> > diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.c
> > b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> > index f90fee9e5..3b776282c 100644
> > --- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
> > +++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> > @@ -99,6 +99,9 @@ virtio_user_start_device(struct virtio_user_dev *dev)
> >   	uint64_t features;
> >   	int ret;
> >
> > +	if (dev->vhostfd < 0)
> > +		return -1;
> 
> This breaks virtio-user with vhost-kernel which does not need vhostfd, and
> will be always -1.
> 

Ok, I will modify the code as followings
	if (is_vhost_user_by_type(dev->path) && dev->vhostfd < 0)
		return -1; 

(is_vhost_user_by_type(dev->path))
> > +
> >   	/* Do not check return as already done in init, or reset in stop */
> >   	dev->ops->send_request(dev, VHOST_USER_SET_OWNER, NULL);
> >
> > @@ -254,6 +257,8 @@ virtio_user_fill_intr_handle(struct virtio_user_dev
> *dev)
> >   	eth_dev->intr_handle->fd = -1;
> >   	if (dev->vhostfd >= 0)
> >   		eth_dev->intr_handle->fd = dev->vhostfd;
> > +	else if (dev->is_server)
> > +		eth_dev->intr_handle->fd = dev->listenfd;
> >
> >   	return 0;
> >   }
> > @@ -267,7 +272,7 @@ virtio_user_dev_setup(struct virtio_user_dev *dev)
> >   	dev->vhostfds = NULL;
> >   	dev->tapfds = NULL;
> >
> > -	if (is_vhost_user_by_type(dev->path)) {
> > +	if (dev->is_server || is_vhost_user_by_type(dev->path)) {
> 
> I think we still fail to pick out an invalidated case: specify "server"
> parameter for a vhost-kernel path.

I will add the checking at the starting of the function.

If (dev->is_server && access(dev->path) == 0)
	Return -1;
How about the change ?

> 
> >   		dev->ops = &ops_user;
> >   	} else {
> >   		dev->ops = &ops_kernel;
> > @@ -337,16 +342,25 @@ virtio_user_dev_init(struct virtio_user_dev *dev,
> char *path, int queues,
> >   		return -1;
> >   	}
> >
> > -	if (dev->ops->send_request(dev, VHOST_USER_SET_OWNER, NULL)
> < 0) {
> > -		PMD_INIT_LOG(ERR, "set_owner fails: %s", strerror(errno));
> > -		return -1;
> > -	}
> > +	if (dev->vhostfd >= 0) {
> > +		if (dev->ops->send_request(dev,
> VHOST_USER_SET_OWNER,
> > +					   NULL) < 0) {
> > +			PMD_INIT_LOG(ERR, "set_owner fails: %s",
> > +				     strerror(errno));
> > +			return -1;
> > +		}
> >
> > -	if (dev->ops->send_request(dev, VHOST_USER_GET_FEATURES,
> > -			    &dev->device_features) < 0) {
> > -		PMD_INIT_LOG(ERR, "get_features failed: %s",
> strerror(errno));
> > -		return -1;
> > +		if (dev->ops->send_request(dev,
> VHOST_USER_GET_FEATURES,
> > +					   &dev->device_features) < 0) {
> > +			PMD_INIT_LOG(ERR, "get_features failed: %s",
> > +				     strerror(errno));
> > +			return -1;
> > +		}
> > +	} else {
> > +		/* Just pretend vhost-user can support all these features */
> 
> Although I don't think we need to fix this, please also note that this could be
> problematic that if some feature is negotiated but not supported by the
> vhost-user which comes later.
>

Good description. I will add it in next version.
 
Thanks for your those comments

Zhiyong
  

Patch

diff --git a/doc/guides/rel_notes/release_18_05.rst b/doc/guides/rel_notes/release_18_05.rst
index 9cc77f893..f8897b2e9 100644
--- a/doc/guides/rel_notes/release_18_05.rst
+++ b/doc/guides/rel_notes/release_18_05.rst
@@ -58,6 +58,12 @@  New Features
   * Added support for NVGRE, VXLAN and GENEVE filters in flow API.
   * Added support for DROP action in flow API.
 
+* **Added support for virtio-user server mode.**
+  In a container environment if the vhost-user backend restarts, there's no way
+  for it to reconnect to virtio-user. To address this, support for server mode
+  is added. In this mode the socket file is created by virtio-user, which the
+  backend connects to. This means that if the backend restarts, it can reconnect
+  to virtio-user and continue communications.
 
 API Changes
 -----------
diff --git a/drivers/net/virtio/virtio_user/vhost_user.c b/drivers/net/virtio/virtio_user/vhost_user.c
index 91c6449bb..a6df97a00 100644
--- a/drivers/net/virtio/virtio_user/vhost_user.c
+++ b/drivers/net/virtio/virtio_user/vhost_user.c
@@ -378,6 +378,30 @@  vhost_user_sock(struct virtio_user_dev *dev,
 	return 0;
 }
 
+#define MAX_VIRTIO_USER_BACKLOG 1
+static int
+virtio_user_start_server(struct virtio_user_dev *dev, struct sockaddr_un *un)
+{
+	int ret;
+	int flag;
+	int fd = dev->listenfd;
+
+	ret = bind(fd, (struct sockaddr *)un, sizeof(*un));
+	if (ret < 0) {
+		PMD_DRV_LOG(ERR, "failed to bind to %s: %s; remove it and try again\n",
+			    dev->path, strerror(errno));
+		return -1;
+	}
+	ret = listen(fd, MAX_VIRTIO_USER_BACKLOG);
+	if (ret < 0)
+		return -1;
+
+	flag = fcntl(fd, F_GETFL);
+	fcntl(fd, F_SETFL, flag | O_NONBLOCK);
+
+	return 0;
+}
+
 /**
  * Set up environment to talk with a vhost user backend.
  *
@@ -405,13 +429,24 @@  vhost_user_setup(struct virtio_user_dev *dev)
 	memset(&un, 0, sizeof(un));
 	un.sun_family = AF_UNIX;
 	snprintf(un.sun_path, sizeof(un.sun_path), "%s", dev->path);
-	if (connect(fd, (struct sockaddr *)&un, sizeof(un)) < 0) {
-		PMD_DRV_LOG(ERR, "connect error, %s", strerror(errno));
-		close(fd);
-		return -1;
+
+	if (dev->is_server) {
+		dev->listenfd = fd;
+		if (virtio_user_start_server(dev, &un) < 0) {
+			PMD_DRV_LOG(ERR, "virtio-user startup fails in server mode");
+			close(fd);
+			return -1;
+		}
+		dev->vhostfd = -1;
+	} else {
+		if (connect(fd, (struct sockaddr *)&un, sizeof(un)) < 0) {
+			PMD_DRV_LOG(ERR, "connect error, %s", strerror(errno));
+			close(fd);
+			return -1;
+		}
+		dev->vhostfd = fd;
 	}
 
-	dev->vhostfd = fd;
 	return 0;
 }
 
diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.c b/drivers/net/virtio/virtio_user/virtio_user_dev.c
index f90fee9e5..3b776282c 100644
--- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
+++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c
@@ -99,6 +99,9 @@  virtio_user_start_device(struct virtio_user_dev *dev)
 	uint64_t features;
 	int ret;
 
+	if (dev->vhostfd < 0)
+		return -1;
+
 	/* Do not check return as already done in init, or reset in stop */
 	dev->ops->send_request(dev, VHOST_USER_SET_OWNER, NULL);
 
@@ -254,6 +257,8 @@  virtio_user_fill_intr_handle(struct virtio_user_dev *dev)
 	eth_dev->intr_handle->fd = -1;
 	if (dev->vhostfd >= 0)
 		eth_dev->intr_handle->fd = dev->vhostfd;
+	else if (dev->is_server)
+		eth_dev->intr_handle->fd = dev->listenfd;
 
 	return 0;
 }
@@ -267,7 +272,7 @@  virtio_user_dev_setup(struct virtio_user_dev *dev)
 	dev->vhostfds = NULL;
 	dev->tapfds = NULL;
 
-	if (is_vhost_user_by_type(dev->path)) {
+	if (dev->is_server || is_vhost_user_by_type(dev->path)) {
 		dev->ops = &ops_user;
 	} else {
 		dev->ops = &ops_kernel;
@@ -337,16 +342,25 @@  virtio_user_dev_init(struct virtio_user_dev *dev, char *path, int queues,
 		return -1;
 	}
 
-	if (dev->ops->send_request(dev, VHOST_USER_SET_OWNER, NULL) < 0) {
-		PMD_INIT_LOG(ERR, "set_owner fails: %s", strerror(errno));
-		return -1;
-	}
+	if (dev->vhostfd >= 0) {
+		if (dev->ops->send_request(dev, VHOST_USER_SET_OWNER,
+					   NULL) < 0) {
+			PMD_INIT_LOG(ERR, "set_owner fails: %s",
+				     strerror(errno));
+			return -1;
+		}
 
-	if (dev->ops->send_request(dev, VHOST_USER_GET_FEATURES,
-			    &dev->device_features) < 0) {
-		PMD_INIT_LOG(ERR, "get_features failed: %s", strerror(errno));
-		return -1;
+		if (dev->ops->send_request(dev, VHOST_USER_GET_FEATURES,
+					   &dev->device_features) < 0) {
+			PMD_INIT_LOG(ERR, "get_features failed: %s",
+				     strerror(errno));
+			return -1;
+		}
+	} else {
+		/* Just pretend vhost-user can support all these features */
+		dev->device_features = VIRTIO_USER_SUPPORTED_FEATURES;
 	}
+
 	if (dev->mac_specified)
 		dev->device_features |= (1ull << VIRTIO_NET_F_MAC);
 
@@ -388,6 +402,11 @@  virtio_user_dev_uninit(struct virtio_user_dev *dev)
 
 	close(dev->vhostfd);
 
+	if (dev->is_server && dev->listenfd >= 0) {
+		close(dev->listenfd);
+		dev->listenfd = -1;
+	}
+
 	if (dev->vhostfds) {
 		for (i = 0; i < dev->max_queue_pairs; ++i)
 			close(dev->vhostfds[i]);
@@ -396,6 +415,9 @@  virtio_user_dev_uninit(struct virtio_user_dev *dev)
 	}
 
 	free(dev->ifname);
+
+	if (dev->is_server)
+		unlink(dev->path);
 }
 
 static uint8_t
diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.h b/drivers/net/virtio/virtio_user/virtio_user_dev.h
index 5f8755771..ade727e46 100644
--- a/drivers/net/virtio/virtio_user/virtio_user_dev.h
+++ b/drivers/net/virtio/virtio_user/virtio_user_dev.h
@@ -6,6 +6,7 @@ 
 #define _VIRTIO_USER_DEV_H
 
 #include <limits.h>
+#include <stdbool.h>
 #include "../virtio_pci.h"
 #include "../virtio_ring.h"
 #include "vhost.h"
@@ -13,6 +14,8 @@ 
 struct virtio_user_dev {
 	/* for vhost_user backend */
 	int		vhostfd;
+	int		listenfd;   /* listening fd */
+	bool		is_server;  /* server or client mode */
 
 	/* for vhost_kernel backend */
 	char		*ifname;
diff --git a/drivers/net/virtio/virtio_user_ethdev.c b/drivers/net/virtio/virtio_user_ethdev.c
index 263649006..4e7b3c34f 100644
--- a/drivers/net/virtio/virtio_user_ethdev.c
+++ b/drivers/net/virtio/virtio_user_ethdev.c
@@ -24,15 +24,73 @@ 
 #define virtio_user_get_dev(hw) \
 	((struct virtio_user_dev *)(hw)->virtio_user_dev)
 
+static int
+virtio_user_server_reconnect(struct virtio_user_dev *dev)
+{
+	int ret;
+	int flag;
+	int connectfd;
+	struct rte_eth_dev *eth_dev = &rte_eth_devices[dev->port_id];
+
+	connectfd = accept(dev->listenfd, NULL, NULL);
+	if (connectfd < 0)
+		return -1;
+
+	dev->vhostfd = connectfd;
+	flag = fcntl(connectfd, F_GETFD);
+	fcntl(connectfd, F_SETFL, flag | O_NONBLOCK);
+
+	ret = virtio_user_start_device(dev);
+	if (ret < 0)
+		return -1;
+
+	if (eth_dev->data->dev_flags & RTE_ETH_DEV_INTR_LSC) {
+		if (rte_intr_disable(eth_dev->intr_handle) < 0) {
+			PMD_DRV_LOG(ERR, "interrupt disable failed");
+			return -1;
+		}
+		rte_intr_callback_unregister(eth_dev->intr_handle,
+					     virtio_interrupt_handler,
+					     eth_dev);
+		eth_dev->intr_handle->fd = connectfd;
+		rte_intr_callback_register(eth_dev->intr_handle,
+					   virtio_interrupt_handler, eth_dev);
+
+		if (rte_intr_enable(eth_dev->intr_handle) < 0) {
+			PMD_DRV_LOG(ERR, "interrupt enable failed");
+			return -1;
+		}
+	}
+	PMD_INIT_LOG(NOTICE, "server mode virtio-user reconnection succeeds!");
+	return 0;
+}
+
 static void
 virtio_user_delayed_handler(void *param)
 {
 	struct virtio_hw *hw = (struct virtio_hw *)param;
-	struct rte_eth_dev *dev = &rte_eth_devices[hw->port_id];
+	struct rte_eth_dev *eth_dev = &rte_eth_devices[hw->port_id];
+	struct virtio_user_dev *dev = virtio_user_get_dev(hw);
 
-	rte_intr_callback_unregister(dev->intr_handle,
-				     virtio_interrupt_handler,
-				     dev);
+	if (rte_intr_disable(eth_dev->intr_handle) < 0) {
+		PMD_DRV_LOG(ERR, "interrupt disable failed");
+		return;
+	}
+	rte_intr_callback_unregister(eth_dev->intr_handle,
+				     virtio_interrupt_handler, eth_dev);
+	if (dev->is_server) {
+		if (dev->vhostfd >= 0) {
+			close(dev->vhostfd);
+			dev->vhostfd = -1;
+		}
+		eth_dev->intr_handle->fd = dev->listenfd;
+		rte_intr_callback_register(eth_dev->intr_handle,
+					   virtio_interrupt_handler, eth_dev);
+		if (rte_intr_enable(eth_dev->intr_handle) < 0) {
+			PMD_DRV_LOG(ERR, "interrupt enable failed");
+			return;
+		}
+	}
 }
 
 static void
@@ -67,12 +125,10 @@  virtio_user_read_dev_config(struct virtio_hw *hw, size_t offset,
 				dev->status &= (~VIRTIO_NET_S_LINK_UP);
 				PMD_DRV_LOG(ERR, "virtio-user port %u is down",
 					    hw->port_id);
-				/* Only client mode is available now. Once the
-				 * connection is broken, it can never be up
-				 * again. Besides, this function could be called
-				 * in the process of interrupt handling,
-				 * callback cannot be unregistered here, set an
-				 * alarm to do it.
+
+				/* This function could be called in the process
+				 * of interrupt handling, callback cannot be
+				 * unregistered here, set an alarm to do it.
 				 */
 				rte_eal_alarm_set(1,
 						  virtio_user_delayed_handler,
@@ -85,7 +141,12 @@  virtio_user_read_dev_config(struct virtio_hw *hw, size_t offset,
 				PMD_DRV_LOG(ERR, "error clearing O_NONBLOCK flag");
 				return;
 			}
+		} else if (dev->is_server) {
+			dev->status &= (~VIRTIO_NET_S_LINK_UP);
+			if (virtio_user_server_reconnect(dev) >= 0)
+				dev->status |= VIRTIO_NET_S_LINK_UP;
 		}
+
 		*(uint16_t *)dst = dev->status;
 	}
 
@@ -278,12 +339,15 @@  static const char *valid_args[] = {
 	VIRTIO_USER_ARG_QUEUE_SIZE,
 #define VIRTIO_USER_ARG_INTERFACE_NAME "iface"
 	VIRTIO_USER_ARG_INTERFACE_NAME,
+#define VIRTIO_USER_ARG_SERVER_MODE "server"
+	VIRTIO_USER_ARG_SERVER_MODE,
 	NULL
 };
 
 #define VIRTIO_USER_DEF_CQ_EN	0
 #define VIRTIO_USER_DEF_Q_NUM	1
 #define VIRTIO_USER_DEF_Q_SZ	256
+#define VIRTIO_USER_DEF_SERVER_MODE	0
 
 static int
 get_string_arg(const char *key __rte_unused,
@@ -378,6 +442,7 @@  virtio_user_pmd_probe(struct rte_vdev_device *dev)
 	uint64_t queues = VIRTIO_USER_DEF_Q_NUM;
 	uint64_t cq = VIRTIO_USER_DEF_CQ_EN;
 	uint64_t queue_size = VIRTIO_USER_DEF_Q_SZ;
+	uint64_t server_mode = VIRTIO_USER_DEF_SERVER_MODE;
 	char *path = NULL;
 	char *ifname = NULL;
 	char *mac_addr = NULL;
@@ -445,6 +510,15 @@  virtio_user_pmd_probe(struct rte_vdev_device *dev)
 		}
 	}
 
+	if (rte_kvargs_count(kvlist, VIRTIO_USER_ARG_SERVER_MODE) == 1) {
+		if (rte_kvargs_process(kvlist, VIRTIO_USER_ARG_SERVER_MODE,
+				       &get_integer_arg, &server_mode) < 0) {
+			PMD_INIT_LOG(ERR, "error to parse %s",
+				     VIRTIO_USER_ARG_SERVER_MODE);
+			goto end;
+		}
+	}
+
 	if (rte_kvargs_count(kvlist, VIRTIO_USER_ARG_CQ_NUM) == 1) {
 		if (rte_kvargs_process(kvlist, VIRTIO_USER_ARG_CQ_NUM,
 				       &get_integer_arg, &cq) < 0) {
@@ -469,6 +543,8 @@  virtio_user_pmd_probe(struct rte_vdev_device *dev)
 	}
 
 	if (rte_eal_process_type() == RTE_PROC_PRIMARY) {
+		struct virtio_user_dev *vu_dev;
+
 		eth_dev = virtio_user_eth_dev_alloc(dev);
 		if (!eth_dev) {
 			PMD_INIT_LOG(ERR, "virtio_user fails to alloc device");
@@ -476,6 +552,11 @@  virtio_user_pmd_probe(struct rte_vdev_device *dev)
 		}
 
 		hw = eth_dev->data->dev_private;
+		vu_dev = virtio_user_get_dev(hw);
+		if (server_mode == 1)
+			vu_dev->is_server = true;
+		else
+			vu_dev->is_server = false;
 		if (virtio_user_dev_init(hw->virtio_user_dev, path, queues, cq,
 				 queue_size, mac_addr, &ifname) < 0) {
 			PMD_INIT_LOG(ERR, "virtio_user_dev_init fails");