[dpdk-dev] [PATCH 1/3] eal: add channel for multi-process communication

[Ananyev, Konstantin]

Hi Jianfeng,

> -----Original Message-----
> From: Tan, Jianfeng
> Sent: Thursday, November 30, 2017 6:44 PM
> To: dev at dpdk.org
> Cc: Burakov, Anatoly <anatoly.burakov at intel.com>; Richardson, Bruce <bruce.richardson at intel.com>; Ananyev, Konstantin
> <konstantin.ananyev at intel.com>; thomas at monjalon.net; Tan, Jianfeng <jianfeng.tan at intel.com>
> Subject: [PATCH 1/3] eal: add channel for multi-process communication
> 
> Previouly, there are three channels for multi-process
> (i.e., primary/secondary) communication.
>   1. Config-file based channel, in which, the primary process writes
>      info into a pre-defined config file, and the secondary process
>      reads info out.
>   2. vfio submodule has its own channel based on unix socket for the
>      secondary process to get container fd and group fd from the
>      primary process.
>   3. pdump submodule also has its own channel based on unix socket for
>      packet dump.
> 
> It'll be good to have a generic communication channel for multi-process
> communication to accomodate the requirements including:
>   a. Secondary wants to send info to primary, for example, secondary
>      would like to send request (about some specific vdev to primary).
>   b. Sending info at any time, instead of just initialization time.
>   c. Share FDs with the other side, for vdev like vhost, related FDs
>      (memory region, kick) should be shared.
>   d. A send message request needs the other side to response immediately.
> 
> This patch proposes to create a communication channel, as an unix
> socket connection, for above requirements. Primary will listen on
> the unix socket; secondary will connect this socket to talk.

Kind of generic question - why do you need a connection-oriented socket here?
Why just connection-less socket wouldn't be enough?
In that case you don't need to do listen/accept, again you don't need epoll() loop.
Instead with connection-less socket you can just use blocking recvmsg() to
inside mp_handler().

> 
> Three new APIs are added:
> 
>   1. rte_eal_mp_action_register is used to register an action,
>      indexed by a string; if the calling component wants to
>      response the messages from the corresponding component in
>      its primary process or secondary processes.
>   2. rte_eal_mp_action_unregister is used to unregister the action
>      if the calling component does not want to response the messages.

I think you need some sort of synchronization between action_register/unregister()
and action_process() - mutex_lock or so.
Another thing - as I understand you do use string as message*action identification?
I think you need to limit max length of it.
Konstantin

>   3. rte_eal_mp_sendmsg is used to send a message.
> 
> Signed-off-by: Jianfeng Tan <jianfeng.tan at intel.com>
> ---
>  lib/librte_eal/common/eal_common_proc.c | 497 ++++++++++++++++++++++++++++++++
>  lib/librte_eal/common/eal_filesystem.h  |  18 ++
>  lib/librte_eal/common/eal_private.h     |  10 +
>  lib/librte_eal/common/include/rte_eal.h |  68 +++++
>  lib/librte_eal/linuxapp/eal/eal.c       |   9 +
>  lib/librte_eal/rte_eal_version.map      |  22 ++
>  6 files changed, 624 insertions(+)
> 
> diff --git a/lib/librte_eal/common/eal_common_proc.c b/lib/librte_eal/common/eal_common_proc.c
> index 60526ca..5d0a095 100644
> --- a/lib/librte_eal/common/eal_common_proc.c
> +++ b/lib/librte_eal/common/eal_common_proc.c
> @@ -33,8 +33,21 @@
>  #include <stdio.h>
>  #include <fcntl.h>
>  #include <stdlib.h>
> +#include <sys/types.h>
> +#include <sys/socket.h>
> +#include <sys/epoll.h>
> +#include <limits.h>
> +#include <unistd.h>
> +#include <sys/un.h>
> +#include <errno.h>
> +#include <pthread.h>
> +
> +#include <rte_log.h>
>  #include <rte_eal.h>
> +#include <rte_lcore.h>
> +#include <rte_common.h>
> 
> +#include "eal_private.h"
>  #include "eal_filesystem.h"
>  #include "eal_internal_cfg.h"
> 
> @@ -59,3 +72,487 @@ rte_eal_primary_proc_alive(const char *config_file_path)
> 
>  	return !!ret;
>  }
> +
> +struct action_entry {
> +	TAILQ_ENTRY(action_entry) next;      /**< Next attached action entry */
> +
> +#define MAX_ACTION_NAME_LEN	64
> +	char action_name[MAX_ACTION_NAME_LEN];
> +	rte_eal_mp_t action;
> +};
> +
> +/** Double linked list of actions. */
> +TAILQ_HEAD(action_entry_list, action_entry);
> +
> +static struct action_entry_list action_entry_list =
> +	TAILQ_HEAD_INITIALIZER(action_entry_list);
> +
> +static struct action_entry *
> +find_action_entry_by_name(const char *name)
> +{
> +	int len = strlen(name);
> +	struct action_entry *entry;
> +
> +	TAILQ_FOREACH(entry, &action_entry_list, next) {
> +		if (strncmp(entry->action_name, name, len) == 0)
> +			break;
> +	}
> +
> +	return entry;
> +}
> +
> +int
> +rte_eal_mp_action_register(const char *action_name, rte_eal_mp_t action)
> +{
> +	struct action_entry *entry = malloc(sizeof(struct action_entry));
> +
> +	if (entry == NULL)
> +		return -ENOMEM;
> +
> +	if (find_action_entry_by_name(action_name) != NULL)
> +		return -EEXIST;
> +
> +	strncpy(entry->action_name, action_name, MAX_ACTION_NAME_LEN);
> +	entry->action = action;
> +	TAILQ_INSERT_TAIL(&action_entry_list, entry, next);
> +	return 0;
> +}
> +
> +void
> +rte_eal_mp_action_unregister(const char *name)
> +{
> +	struct action_entry *entry = find_action_entry_by_name(name);
> +
> +	TAILQ_REMOVE(&action_entry_list, entry, next);
> +	free(entry);
> +}
> +
> +/* The maximum amount of fd for one recvmsg/sendmsg */
> +#define SCM_MAX_FD		253
> +#define MAX_SECONDARY_PROCS	8
> +#define MAX_MESSAGE_LENGTH	1024
> +
> +struct mp_fds {
> +	int efd;
> +
> +	union {
> +		/* fds for primary process */
> +		struct {
> +			int listen;
> +			/* fds used to send msg to secondary process(es) */
> +			int secondaries[MAX_SECONDARY_PROCS];
> +		};
> +
> +		/* fds for secondary process */
> +		struct {
> +			/* fds used to send msg to the primary process */
> +			int primary;
> +		};
> +	};
> +};
> +
> +static struct mp_fds mp_fds;
> +
> +struct msg_hdr {
> +	char action_name[MAX_ACTION_NAME_LEN];
> +	int fds_num;
> +	int len_params;
> +	char params[0];
> +} __rte_packed;
> +
> +static int
> +add_sec_proc(int fd)
> +{
> +	int i;
> +
> +	for (i = 0; i < MAX_SECONDARY_PROCS; ++i)
> +		if (mp_fds.secondaries[i] == -1)
> +			break;
> +
> +	if (i >= MAX_SECONDARY_PROCS)
> +		return -1;
> +
> +	mp_fds.secondaries[i] = fd;
> +
> +	return i;
> +}
> +
> +static void
> +del_sec_proc(int fd)
> +{
> +	int i;
> +
> +	for (i = 0; i < MAX_SECONDARY_PROCS; ++i) {
> +		if (mp_fds.secondaries[i] == fd) {
> +			mp_fds.secondaries[i] = -1;
> +			break;
> +		}
> +	}
> +}
> +
> +static int
> +read_msg(int sockfd, char *buf, int buflen, int *fds, int fds_num)
> +{
> +	struct iovec iov;
> +	struct msghdr msgh;
> +	size_t fdsize = fds_num * sizeof(int);
> +	char control[CMSG_SPACE(fdsize)];
> +	struct cmsghdr *cmsg;
> +	struct msg_hdr *hdr = (struct msg_hdr *)buf;
> +	int ret, total;
> +
> +	/* read msg_hdr */
> +	memset(&msgh, 0, sizeof(msgh));
> +	iov.iov_base = hdr;
> +	iov.iov_len  = sizeof(*hdr);
> +
> +	msgh.msg_iov = &iov;
> +	msgh.msg_iovlen = 1;
> +	msgh.msg_control = control;
> +	msgh.msg_controllen = sizeof(control);
> +
> +	ret = recvmsg(sockfd, &msgh, 0);
> +	if (ret != sizeof(struct msg_hdr)) {
> +		RTE_LOG(ERR, EAL, "recvmsg failed\n");
> +		return ret;
> +	}
> +
> +	if (msgh.msg_flags & (MSG_TRUNC | MSG_CTRUNC)) {
> +		RTE_LOG(ERR, EAL, "truncted msg\n");
> +		return -1;
> +	}
> +	total = ret;
> +
> +	/* read auxiliary FDs if any */
> +	for (cmsg = CMSG_FIRSTHDR(&msgh); cmsg != NULL;
> +		cmsg = CMSG_NXTHDR(&msgh, cmsg)) {
> +		if ((cmsg->cmsg_level == SOL_SOCKET) &&
> +			(cmsg->cmsg_type == SCM_RIGHTS)) {
> +			memcpy(fds, CMSG_DATA(cmsg), fdsize);
> +			break;
> +		}
> +	}
> +
> +	/* read params */
> +	if (hdr->len_params) {
> +		if (hdr->len_params > buflen - (int)sizeof(*hdr))
> +			rte_exit(EXIT_FAILURE, "params too long\n");
> +
> +		ret = read(sockfd, &hdr->params, hdr->len_params);
> +		if (ret != hdr->len_params)
> +			rte_exit(EXIT_FAILURE, "failed to recv params\n");
> +
> +		total += ret;
> +	}
> +
> +	RTE_LOG(INFO, EAL, "read msg: %s, %d\n", hdr->action_name,
> +		(int)sizeof(*hdr) + hdr->len_params);
> +	return total;
> +}
> +
> +static int
> +process_msg(int fd)
> +{
> +	int len;
> +	int params_len;
> +	char buf[MAX_MESSAGE_LENGTH];
> +	int fds[SCM_MAX_FD];
> +	struct msg_hdr *hdr;
> +	struct action_entry *entry;
> +
> +	len = read_msg(fd, buf, MAX_MESSAGE_LENGTH, fds, SCM_MAX_FD);
> +	if (len <= 0) {
> +		RTE_LOG(ERR, EAL, "failed to read message: %s\n",
> +			strerror(errno));
> +		return -1;
> +	}
> +
> +	hdr = (struct msg_hdr *) buf;
> +
> +	entry = find_action_entry_by_name(hdr->action_name);
> +	if (entry == NULL) {
> +		RTE_LOG(ERR, EAL, "cannot find action by: %s\n",
> +			hdr->action_name);
> +		return -1;
> +	}
> +
> +	params_len = len - sizeof(struct msg_hdr);
> +
> +	return entry->action(hdr->params, params_len, fds, hdr->fds_num);
> +}
> +
> +static int
> +add_secondary(void)
> +{
> +	int fd;
> +	struct epoll_event ev;
> +
> +	while (1) {
> +		fd = accept(mp_fds.listen, NULL, NULL);
> +		if (fd < 0 && errno == EAGAIN)
> +			break;
> +		else if (fd < 0) {
> +			RTE_LOG(ERR, EAL, "primary failed to accept: %s\n",
> +				strerror(errno));
> +			return -1;
> +		}
> +
> +		ev.events = EPOLLIN | EPOLLRDHUP;
> +		ev.data.fd = fd;
> +		if (epoll_ctl(mp_fds.efd, EPOLL_CTL_ADD, fd, &ev) < 0) {
> +			RTE_LOG(ERR, EAL, "failed to add secondary: %s\n",
> +				strerror(errno));
> +			break;
> +		}
> +		if (add_sec_proc(fd) < 0) {
> +			RTE_LOG(ERR, EAL, "too many secondary processes\n");
> +			close(fd);
> +			break;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static void *
> +mp_handler(void *arg __rte_unused)
> +{
> +	int fd;
> +	int i, n;
> +	struct epoll_event ev;
> +	struct epoll_event *events;
> +	int is_primary = rte_eal_process_type() == RTE_PROC_PRIMARY;
> +
> +	ev.events = EPOLLIN | EPOLLRDHUP;
> +	ev.data.fd = (is_primary) ? mp_fds.listen : mp_fds.primary;
> +	if (epoll_ctl(mp_fds.efd, EPOLL_CTL_ADD, ev.data.fd, &ev) < 0) {
> +		RTE_LOG(ERR, EAL, "failed to epoll_ctl: %s\n",
> +			strerror(errno));
> +		exit(EXIT_FAILURE);
> +	}
> +
> +	events = calloc(20, sizeof ev);
> +
> +	while (1) {
> +		n = epoll_wait(mp_fds.efd, events, 20, -1);
> +		for (i = 0; i < n; i++) {
> +			if (is_primary && events[i].data.fd == mp_fds.listen) {
> +				if (events[i].events != EPOLLIN) {
> +					RTE_LOG(ERR, EAL, "what happens?\n");
> +					exit(EXIT_FAILURE);
> +				}
> +
> +				if (add_secondary() < 0)
> +					break;
> +
> +				continue;
> +			}
> +
> +			fd = events[i].data.fd;
> +
> +			if ((events[i].events & EPOLLIN)) {
> +				if (process_msg(fd) < 0) {
> +					RTE_LOG(ERR, EAL,
> +						"failed to process msg\n");
> +					if (!is_primary)
> +						exit(EXIT_FAILURE);
> +				}
> +				continue;
> +			}
> +
> +			/* EPOLLERR, EPOLLHUP, etc */
> +			if (is_primary) {
> +				RTE_LOG(ERR, EAL, "secondary exit: %d\n", fd);
> +				epoll_ctl(mp_fds.efd, EPOLL_CTL_DEL, fd, NULL);
> +				del_sec_proc(fd);
> +				close(fd);
> +			} else {
> +				RTE_LOG(ERR, EAL, "primary exits, so do I\n");
> +				/* Exit secondary when primary exits? */
> +				exit(EXIT_FAILURE);
> +			}
> +		}
> +	}
> +
> +	return NULL;
> +}
> +
> +int
> +rte_eal_mp_channel_init(void)
> +{
> +	int i, fd, ret;
> +	const char *path;
> +	struct sockaddr_un un;
> +	pthread_t tid;
> +	char thread_name[RTE_MAX_THREAD_NAME_LEN];
> +
> +	mp_fds.efd = epoll_create1(0);
> +	if (mp_fds.efd < 0) {
> +		RTE_LOG(ERR, EAL, "epoll_create1 failed\n");
> +		return -1;
> +	}
> +
> +	fd = socket(AF_UNIX, SOCK_STREAM, 0);
> +	if (fd < 0) {
> +		RTE_LOG(ERR, EAL, "Failed to create unix socket\n");
> +		return -1;
> +	}
> +
> +	memset(&un, 0, sizeof(un));
> +	un.sun_family = AF_UNIX;
> +	path = eal_mp_unix_path();
> +	strncpy(un.sun_path, path, sizeof(un.sun_path));
> +	un.sun_path[sizeof(un.sun_path) - 1] = '\0';
> +
> +	if (rte_eal_process_type() == RTE_PROC_PRIMARY) {
> +		for (i = 0; i < MAX_SECONDARY_PROCS; ++i)
> +			mp_fds.secondaries[i] = -1;
> +
> +		if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0) {
> +			RTE_LOG(ERR, EAL, "cannot set nonblocking mode\n");
> +			close(fd);
> +			return -1;
> +		}
> +
> +		/* The file still exists since last run */
> +		unlink(path);
> +
> +		ret = bind(fd, (struct sockaddr *)&un, sizeof(un));
> +		if (ret < 0) {
> +			RTE_LOG(ERR, EAL, "failed to bind to %s: %s\n",
> +				path, strerror(errno));
> +			close(fd);
> +			return -1;
> +		}
> +		RTE_LOG(INFO, EAL, "primary bind to %s\n", path);
> +
> +		ret = listen(fd, 1024);
> +		if (ret < 0) {
> +			RTE_LOG(ERR, EAL, "failed to listen: %s\n",
> +				strerror(errno));
> +			close(fd);
> +			return -1;
> +		}
> +		mp_fds.listen = fd;
> +	} else {
> +		ret = connect(fd, (struct sockaddr *)&un, sizeof(un));
> +		if (ret < 0) {
> +			RTE_LOG(ERR, EAL, "failed to connect primary\n");
> +			return -1;
> +		}
> +		mp_fds.primary = fd;
> +	}
> +
> +	ret = pthread_create(&tid, NULL, mp_handler, NULL);
> +	if (ret < 0) {
> +		RTE_LOG(ERR, EAL, "failed to create thead: %s\n",
> +			strerror(errno));
> +		close(fd);
> +		close(mp_fds.efd);
> +		return -1;
> +	}
> +
> +	snprintf(thread_name, RTE_MAX_THREAD_NAME_LEN,
> +		 "rte_mp_handle");
> +	ret = rte_thread_setname(tid, thread_name);
> +	if (ret < 0) {
> +		RTE_LOG(ERR, EAL, "failed to set thead name\n");
> +		close(fd);
> +		close(mp_fds.efd);
> +		return -1;
> +	}
> +
> +	return 0;
> +}
> +
> +static int
> +send_msg(int fd, struct msghdr *p_msgh)
> +{
> +	int ret;
> +
> +	do {
> +		ret = sendmsg(fd, p_msgh, 0);
> +	} while (ret < 0 && errno == EINTR);
> +
> +	if (ret < 0)
> +		RTE_LOG(ERR, EAL, "failed to send msg: %s\n", strerror(errno));
> +
> +	return ret;
> +}
> +
> +int
> +rte_eal_mp_sendmsg(const char *action_name,
> +		   const void *params,
> +		   int len_params,
> +		   int fds[],
> +		   int fds_num)
> +{
> +	int i;
> +	int ret = 0;
> +	struct msghdr msgh;
> +	struct iovec iov;
> +	size_t fd_size = fds_num * sizeof(int);
> +	char control[CMSG_SPACE(fd_size)];
> +	struct cmsghdr *cmsg;
> +	struct msg_hdr *msg;
> +	int len_msg;
> +
> +	if (fds_num > SCM_MAX_FD) {
> +		RTE_LOG(ERR, EAL,
> +			"Cannot send more than %d FDs\n", SCM_MAX_FD);
> +		return -E2BIG;
> +	}
> +
> +	len_msg = sizeof(struct msg_hdr) + len_params;
> +	if (len_msg > MAX_MESSAGE_LENGTH) {
> +		RTE_LOG(ERR, EAL, "Message is too long\n");
> +		return -ENOMEM;
> +	}
> +
> +	RTE_LOG(INFO, EAL, "send msg: %s, %d\n", action_name, len_msg);
> +
> +	msg = malloc(len_msg);
> +	if (!msg) {
> +		RTE_LOG(ERR, EAL, "Cannot alloc memory for msg\n");
> +		return -ENOMEM;
> +	}
> +	memset(msg, 0, len_msg);
> +	strcpy(msg->action_name, action_name);
> +	msg->fds_num = fds_num;
> +	msg->len_params = len_params;
> +	memcpy(msg->params, params, len_params);
> +
> +	memset(&msgh, 0, sizeof(msgh));
> +	memset(control, 0, sizeof(control));
> +
> +	iov.iov_base = (uint8_t *)msg;
> +	iov.iov_len = len_msg;
> +
> +	msgh.msg_iov = &iov;
> +	msgh.msg_iovlen = 1;
> +	msgh.msg_control = control;
> +	msgh.msg_controllen = sizeof(control);
> +
> +	cmsg = CMSG_FIRSTHDR(&msgh);
> +	cmsg->cmsg_len = CMSG_LEN(fd_size);
> +	cmsg->cmsg_level = SOL_SOCKET;
> +	cmsg->cmsg_type = SCM_RIGHTS;
> +	memcpy(CMSG_DATA(cmsg), fds, fd_size);
> +
> +	if (rte_eal_process_type() == RTE_PROC_PRIMARY) {
> +		for (i = 0; i < MAX_SECONDARY_PROCS; ++i) {
> +			if (mp_fds.secondaries[i] == -1)
> +				continue;
> +
> +			ret = send_msg(mp_fds.secondaries[i], &msgh);
> +			if (ret < 0)
> +				break;
> +		}
> +	} else {
> +		ret = send_msg(mp_fds.primary, &msgh);
> +	}
> +
> +	free(msg);
> +
> +	return ret;
> +}
> diff --git a/lib/librte_eal/common/eal_filesystem.h b/lib/librte_eal/common/eal_filesystem.h
> index 8acbd99..3d9514f 100644
> --- a/lib/librte_eal/common/eal_filesystem.h
> +++ b/lib/librte_eal/common/eal_filesystem.h
> @@ -67,6 +67,24 @@ eal_runtime_config_path(void)
>  	return buffer;
>  }
> 
> +/** Path of primary/secondary communication unix socket file. */
> +#define MP_UNIX_PATH_FMT "%s/.%s_unix"
> +static inline const char *
> +eal_mp_unix_path(void)
> +{
> +	static char buffer[PATH_MAX]; /* static so auto-zeroed */
> +	const char *directory = default_config_dir;
> +	const char *home_dir = getenv("HOME");
> +
> +	if (getuid() != 0 && home_dir != NULL)
> +		directory = home_dir;
> +	snprintf(buffer, sizeof(buffer) - 1, MP_UNIX_PATH_FMT,
> +		 directory, internal_config.hugefile_prefix);
> +
> +	return buffer;
> +
> +}
> +
>  /** Path of hugepage info file. */
>  #define HUGEPAGE_INFO_FMT "%s/.%s_hugepage_info"
> 
> diff --git a/lib/librte_eal/common/eal_private.h b/lib/librte_eal/common/eal_private.h
> index 462226f..60944f2 100644
> --- a/lib/librte_eal/common/eal_private.h
> +++ b/lib/librte_eal/common/eal_private.h
> @@ -224,4 +224,14 @@ int rte_eal_hugepage_attach(void);
>   */
>  struct rte_bus *rte_bus_find_by_device_name(const char *str);
> 
> +/**
> + * Create the unix channel for primary/secondary communication.
> + *
> + * @return
> + *   0 on success;
> + *   (<0) on failure.
> + */
> +
> +int rte_eal_mp_channel_init(void);
> +
>  #endif /* _EAL_PRIVATE_H_ */
> diff --git a/lib/librte_eal/common/include/rte_eal.h b/lib/librte_eal/common/include/rte_eal.h
> index 8e4e71c..8776bcf 100644
> --- a/lib/librte_eal/common/include/rte_eal.h
> +++ b/lib/librte_eal/common/include/rte_eal.h
> @@ -215,6 +215,74 @@ int rte_eal_init(int argc, char **argv);
>  int rte_eal_primary_proc_alive(const char *config_file_path);
> 
>  /**
> + * Action function typedef used by other components.
> + *
> + * As we create unix socket channel for primary/secondary communication, use
> + * this function typedef to register action for coming messages.
> + */
> +typedef int (*rte_eal_mp_t)(const void *params, int len,
> +			    int fds[], int fds_num);
> +/**
> + * Register an action function for primary/secondary communication.
> + *
> + * Call this function to register an action, if the calling component wants
> + * to response the messages from the corresponding component in its primary
> + * process or secondary processes.
> + *
> + * @param action_name
> + *   The action_name argument plays as the nonredundant key to find the action.
> + *
> + * @param action
> + *   The action argument is the function pointer to the action function.
> + *
> + * @return
> + *  - 0 on success.
> + *  - (<0) on failure.
> + */
> +int rte_eal_mp_action_register(const char *action_name, rte_eal_mp_t action);
> +/**
> + * Unregister an action function for primary/secondary communication.
> + *
> + * Call this function to unregister an action  if the calling component does
> + * not want to response the messages from the corresponding component in its
> + * primary process or secondary processes.
> + *
> + * @param action_name
> + *   The action_name argument plays as the nonredundant key to find the action.
> + *
> + */
> +void rte_eal_mp_action_unregister(const char *name);
> +
> +/**
> + * Send a message to the primary process or the secondary processes.
> + *
> + * This function will send a message which will be responsed by the action
> + * identified by action_name of the process on the other side.
> + *
> + * @param action_name
> + *   The action_name argument is used to identify which action will be used.
> + *
> + * @param params
> + *   The params argument contains the customized message.
> + *
> + * @param len_params
> + *   The len_params argument is the length of the customized message.
> + *
> + * @param fds
> + *   The fds argument is an array of fds sent with sendmsg.
> + *
> + * @param fds_num
> + *   The fds_num argument is number of fds to be sent with sendmsg.
> + *
> + * @return
> + *  - (>=0) on success.
> + *  - (<0) on failure.
> + */
> +int
> +rte_eal_mp_sendmsg(const char *action_name, const void *params,
> +		   int len_params, int fds[], int fds_num);
> +
> +/**
>   * Usage function typedef used by the application usage function.
>   *
>   * Use this function typedef to define and call rte_set_application_usage_hook()
> diff --git a/lib/librte_eal/linuxapp/eal/eal.c b/lib/librte_eal/linuxapp/eal/eal.c
> index 229eec9..a84eab4 100644
> --- a/lib/librte_eal/linuxapp/eal/eal.c
> +++ b/lib/librte_eal/linuxapp/eal/eal.c
> @@ -896,6 +896,15 @@ rte_eal_init(int argc, char **argv)
> 
>  	eal_check_mem_on_local_socket();
> 
> +	if (rte_eal_mp_channel_init() < 0) {
> +		rte_eal_init_alert("failed to init mp channel\n");
> +		rte_errno = EFAULT;
> +		return -1;
> +	}
> +
> +	if (eal_plugins_init() < 0)
> +		rte_eal_init_alert("Cannot init plugins\n");
> +
>  	eal_thread_init_master(rte_config.master_lcore);
> 
>  	ret = eal_thread_dump_affinity(cpuset, RTE_CPU_AFFINITY_STR_LEN);
> diff --git a/lib/librte_eal/rte_eal_version.map b/lib/librte_eal/rte_eal_version.map
> index f4f46c1..6762397 100644
> --- a/lib/librte_eal/rte_eal_version.map
> +++ b/lib/librte_eal/rte_eal_version.map
> @@ -235,4 +235,26 @@ EXPERIMENTAL {
>  	rte_service_set_stats_enable;
>  	rte_service_start_with_defaults;
> 
> +} DPDK_17.08;
> +
> +DPDK_17.11 {
> +	global:
> +
> +	rte_bus_get_iommu_class;
> +	rte_eal_iova_mode;
> +	rte_eal_mbuf_default_mempool_ops;
> +	rte_lcore_has_role;
> +	rte_memcpy_ptr;
> +	rte_pci_get_iommu_class;
> +	rte_pci_match;
> +
> +} DPDK_17.08;
> +
> +DPDK_18.02 {
> +	global:
> +
> +	rte_eal_mp_action_register;
> +	rte_eal_mp_action_unregister;
> +	rte_eal_mp_sendmsg;
> +
>  } DPDK_17.11;
> --
> 2.7.4