ctdb-common: Add sock_client abstraction

This sets up boilerplate required for a client code connecting to a
server over unix domain socket.  The communication between client
and server is "request" from client to server and "reply" from
server to client.

Signed-off-by: Amitay Isaacs <amitay@gmail.com>
Reviewed-by: Martin Schwenke <martin@meltin.net>

2 files changed, 461 insertions, 0 deletions

diff --git a/ctdb/common/sock_client.c b/ctdb/common/sock_client.c
new file mode 100644
index 00000000000..e5f993e085c
--- /dev/null
+++ b/ctdb/common/sock_client.c
@@ -0,0 +1,332 @@
+/*
+   A client based on unix domain socket
+
+   Copyright (C) Amitay Isaacs  2017
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "replace.h"
+#include "system/filesys.h"
+#include "system/network.h"
+
+#include <talloc.h>
+#include <tevent.h>
+
+#include "lib/util/debug.h"
+#include "lib/util/time.h"
+#include "lib/util/tevent_unix.h"
+
+#include "common/logging.h"
+#include "common/reqid.h"
+#include "common/comm.h"
+#include "common/sock_client.h"
+
+struct sock_client_context {
+	struct sock_client_proto_funcs *funcs;
+	void *private_data;
+
+	void (*disconnect_callback)(void *private_data);
+	void *disconnect_data;
+
+	int fd;
+	struct comm_context *comm;
+	struct reqid_context *idr;
+};
+
+/*
+ * connect to a unix domain socket
+ */
+
+static int socket_connect(const char *sockpath)
+{
+	struct sockaddr_un addr;
+	size_t len;
+	int fd, ret;
+
+	memset(&addr, 0, sizeof(addr));
+	addr.sun_family = AF_UNIX;
+
+	len = strlcpy(addr.sun_path, sockpath, sizeof(addr.sun_path));
+	if (len >= sizeof(addr.sun_path)) {
+		D_ERR("socket path too long: %s\n", sockpath);
+		return -1;
+	}
+
+	fd = socket(AF_UNIX, SOCK_STREAM, 0);
+	if (fd == -1) {
+		D_ERR("socket create failed - %s\n", sockpath);
+		return -1;
+	}
+
+	ret = connect(fd, (struct sockaddr *)&addr, sizeof(addr));
+	if (ret != 0) {
+		D_ERR("socket connect failed - %s\n", sockpath);
+		close(fd);
+		return -1;
+	}
+
+	return fd;
+}
+
+/*
+ * Socket client
+ */
+
+static int sock_client_context_destructor(struct sock_client_context *sockc);
+static void sock_client_read_handler(uint8_t *buf, size_t buflen,
+				     void *private_data);
+static void sock_client_dead_handler(void *private_data);
+
+static void sock_client_msg_reply(struct sock_client_context *sockc,
+				  uint8_t *buf, size_t buflen);
+
+int sock_client_setup(TALLOC_CTX *mem_ctx, struct tevent_context *ev,
+		      const char *sockpath,
+		      struct sock_client_proto_funcs *funcs,
+		      void *private_data,
+		      struct sock_client_context **result)
+{
+	struct sock_client_context *sockc;
+	int ret;
+
+	if (sockpath == NULL) {
+		return EINVAL;
+	}
+
+	if (funcs == NULL || funcs->request_push == NULL ||
+	    funcs->reply_pull == NULL || funcs->reply_reqid == NULL) {
+		return EINVAL;
+	}
+
+	sockc = talloc_zero(mem_ctx, struct sock_client_context);
+	if (sockc == NULL) {
+		return ENOMEM;
+	}
+
+	sockc->funcs = funcs;
+	sockc->private_data = private_data;
+
+	sockc->fd = socket_connect(sockpath);
+	if (sockc->fd == -1) {
+		talloc_free(sockc);
+		return EIO;
+	}
+
+	ret = comm_setup(sockc, ev, sockc->fd,
+			 sock_client_read_handler, sockc,
+			 sock_client_dead_handler, sockc,
+			 &sockc->comm);
+	if (ret != 0) {
+		D_ERR("comm_setup() failed, ret=%d\n", ret);
+		close(sockc->fd);
+		talloc_free(sockc);
+		return ret;
+	}
+
+	ret = reqid_init(sockc, INT_MAX-200, &sockc->idr);
+	if (ret != 0) {
+		D_ERR("reqid_init() failed, ret=%d\n", ret);
+		close(sockc->fd);
+		talloc_free(sockc);
+		return ret;
+	}
+
+	talloc_set_destructor(sockc, sock_client_context_destructor);
+
+	*result = sockc;
+	return 0;
+}
+
+static int sock_client_context_destructor(struct sock_client_context *sockc)
+{
+	TALLOC_FREE(sockc->comm);
+	if (sockc->fd != -1) {
+		close(sockc->fd);
+		sockc->fd = -1;
+	}
+	return 0;
+}
+
+
+static void sock_client_read_handler(uint8_t *buf, size_t buflen,
+				     void *private_data)
+{
+	struct sock_client_context *sockc = talloc_get_type_abort(
+		private_data, struct sock_client_context);
+
+	sock_client_msg_reply(sockc, buf, buflen);
+}
+
+static void sock_client_dead_handler(void *private_data)
+{
+	struct sock_client_context *sockc = talloc_get_type_abort(
+		private_data, struct sock_client_context);
+
+	if (sockc->disconnect_callback != NULL) {
+		sockc->disconnect_callback(sockc->disconnect_data);
+		talloc_free(sockc);
+		return;
+	}
+
+	D_NOTICE("connection to daemon closed, exiting\n");
+	exit(1);
+}
+
+void sock_client_set_disconnect_callback(struct sock_client_context *sockc,
+					 sock_client_callback_func_t callback,
+					 void *private_data)
+{
+	sockc->disconnect_callback = callback;
+	sockc->disconnect_data = private_data;
+}
+
+
+struct sock_client_msg_state {
+	struct sock_client_context *sockc;
+	uint32_t reqid;
+	struct tevent_req *req;
+	void *reply;
+};
+
+static int sock_client_msg_state_destructor(
+				struct sock_client_msg_state *state);
+static void sock_client_msg_done(struct tevent_req *subreq);
+
+struct tevent_req *sock_client_msg_send(TALLOC_CTX *mem_ctx,
+				        struct tevent_context *ev,
+					struct sock_client_context *sockc,
+					struct timeval timeout,
+					void *request)
+{
+	struct tevent_req *req, *subreq;
+	struct sock_client_msg_state *state;
+	uint8_t *buf;
+	size_t buflen;
+	int ret;
+
+	req = tevent_req_create(mem_ctx, &state, struct sock_client_msg_state);
+	if (req == NULL) {
+		return NULL;
+	}
+
+	state->sockc = sockc;
+
+	state->reqid = reqid_new(sockc->idr, state);
+	if (state->reqid == REQID_INVALID) {
+		talloc_free(req);
+		return NULL;
+	}
+
+	state->req = req;
+
+	talloc_set_destructor(state, sock_client_msg_state_destructor);
+
+	ret = sockc->funcs->request_push(request, state->reqid, state,
+					 &buf, &buflen, sockc->private_data);
+	if (ret != 0) {
+		tevent_req_error(req, ret);
+		return tevent_req_post(req, ev);
+	}
+
+	subreq = comm_write_send(state, ev, sockc->comm, buf, buflen);
+	if (tevent_req_nomem(subreq, req)) {
+		return tevent_req_post(req, ev);
+	}
+	tevent_req_set_callback(subreq, sock_client_msg_done, req);
+
+	if (! timeval_is_zero(&timeout)) {
+		tevent_req_set_endtime(req, ev, timeout);
+	}
+
+	return req;
+}
+
+static int sock_client_msg_state_destructor(
+				struct sock_client_msg_state *state)
+{
+	reqid_remove(state->sockc->idr, state->reqid);
+	return 0;
+}
+
+static void sock_client_msg_done(struct tevent_req *subreq)
+{
+	struct tevent_req *req = tevent_req_callback_data(
+		subreq, struct tevent_req);
+	int ret;
+	bool status;
+
+	status = comm_write_recv(subreq, &ret);
+	TALLOC_FREE(subreq);
+	if (! status) {
+		tevent_req_error(req, ret);
+		return;
+	}
+
+	/* wait for the reply or timeout */
+}
+
+static void sock_client_msg_reply(struct sock_client_context *sockc,
+				  uint8_t *buf, size_t buflen)
+{
+	struct sock_client_msg_state *state;
+	uint32_t reqid;
+	int ret;
+
+	ret = sockc->funcs->reply_reqid(buf, buflen, &reqid,
+					sockc->private_data);
+	if (ret != 0) {
+		D_WARNING("Invalid packet received, ret=%d\n", ret);
+		return;
+	}
+
+	state = reqid_find(sockc->idr, reqid, struct sock_client_msg_state);
+	if (state == NULL) {
+		return;
+	}
+
+	if (reqid != state->reqid) {
+		return;
+	}
+
+	ret = sockc->funcs->reply_pull(buf, buflen, state, &state->reply,
+				       sockc->private_data);
+	if (ret != 0) {
+		tevent_req_error(state->req, ret);
+		return;
+	}
+
+	tevent_req_done(state->req);
+}
+
+bool sock_client_msg_recv(struct tevent_req *req, int *perr,
+			  TALLOC_CTX *mem_ctx, void **reply)
+{
+	struct sock_client_msg_state *state = tevent_req_data(
+		req, struct sock_client_msg_state);
+	int ret;
+
+	if (tevent_req_is_unix_error(req, &ret)) {
+		if (perr != NULL) {
+			*perr = ret;
+		}
+		return false;
+	}
+
+	if (reply != NULL) {
+		*reply = talloc_steal(mem_ctx, state->reply);
+	}
+
+	return true;
+}
diff --git a/ctdb/common/sock_client.h b/ctdb/common/sock_client.h
new file mode 100644
index 00000000000..c640767c3a7
--- /dev/null
+++ b/ctdb/common/sock_client.h
@@ -0,0 +1,129 @@
+/*
+   A client based on unix domain socket
+
+   Copyright (C) Amitay Isaacs  2017
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __CTDB_SOCK_CLIENT_H__
+#define __CTDB_SOCK_CLIENT_H__
+
+#include <talloc.h>
+#include <tevent.h>
+
+/**
+ * @file sock_client.h
+ *
+ * @brief A framework for a client based on unix-domain sockets.
+ *
+ * This abstraction allows to build clients that communicate using
+ * unix-domain sockets.  It takes care of the common boilerplate.
+ */
+
+/**
+ * @brief The abstract socket daemon context
+ */
+struct sock_client_context;
+
+/**
+ * @brief callback function
+ *
+ * This function can be registered to be called in case daemon goes away.
+ */
+typedef void (*sock_client_callback_func_t)(void *private_data);
+
+/**
+ * @brief Protocol marshalling functions
+ *
+ * The typical protocol packet will have a header and a payload.
+ * Header will contain at least 2 fields: length and reqid
+ *
+ * request_push() is called when the request packet needs to be marshalled
+ *
+ * reply_pull() is called to unmarshall data into a reply packet
+ *
+ * reply_reqid() is called to extract request id from a reply packet
+ */
+struct sock_client_proto_funcs {
+	int (*request_push)(void *request, uint32_t reqid,
+			    TALLOC_CTX *mem_ctx,
+			    uint8_t **buf, size_t *buflen,
+			    void *private_data);
+
+	int (*reply_pull)(uint8_t *buf, size_t buflen,
+			  TALLOC_CTX *mem_ctx, void **reply,
+			  void *private_data);
+
+	int (*reply_reqid)(uint8_t *buf, size_t buflen,
+			   uint32_t *reqid, void *private_data);
+};
+
+/**
+ * @brief Create a new socket client
+ *
+ * @param[in] mem_ctx Talloc memory context
+ * @param[in] ev Tevent context
+ * @param[in] sockpath Unix domain socket path
+ * @param[in] funcs Protocol marshalling functions
+ * @param[in] private_data Private data for protocol functions
+ * @param[out] result New socket client context
+ * @return 0 on success, errno on failure
+ */
+int sock_client_setup(TALLOC_CTX *mem_ctx, struct tevent_context *ev,
+		      const char *sockpath,
+		      struct sock_client_proto_funcs *funcs,
+		      void *private_data,
+		      struct sock_client_context **result);
+
+/**
+ * @brief Register a callback in case of client disconnection
+ *
+ * @param[in] sockc Socket client context
+ * @param[in] callback Callback function
+ * @param[in] private_data Private data for callback function
+ */
+void sock_client_set_disconnect_callback(struct sock_client_context *sockc,
+					 sock_client_callback_func_t callback,
+					 void *private_data);
+
+/**
+ * @brief Async computation to send data to the daemon
+ *
+ * @param[in] mem_ctx Talloc memory context
+ * @param[in] ev Tevent context
+ * @param[in] sockc The socket client context
+ * @param[in] timeout How long to wait for
+ * @param[in] request Requeset packet to be sent
+ * @return new tevent request, or NULL on failure
+ */
+struct tevent_req *sock_client_msg_send(TALLOC_CTX *mem_ctx,
+					struct tevent_context *ev,
+					struct sock_client_context *sockc,
+					struct timeval timeout,
+					void *request);
+
+/**
+ * @brief Async computation end to send data to the daemon
+ *
+ * @param[in] req Tevent request
+ * @param[out] perr errno in case of failure
+ * @param[in] mem_ctx Talloc memory context
+ * @param[out] reply Reply received from server
+ * @return true on success, false on failure
+ */
+bool sock_client_msg_recv(struct tevent_req *req, int *perr,
+			  TALLOC_CTX *mem_ctx, void **reply);
+
+#endif /* __CTDB_SOCK_CLIENT_H__ */