tevent: Add echo server sample code

This is under a deliberately permissive license. I would like people to start
using libtevent and tevent_req (LGPL) without any worries about where to start
from.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>

Autobuild-User(master): Amitay Isaacs <amitay@samba.org>
Autobuild-Date(master): Mon Aug  5 04:07:58 CEST 2013 on sn-devel-104

lib/tevent/echo_server.c

@@ -0,0 +1,664 @@
+/**
+ ** NOTE! The following liberal license applies to this sample file only.
+ ** This does NOT imply that all of Samba is released under this license.
+ **
+ ** This file is meant as a starting point for libtevent users to be used
+ ** in any program linking against the LGPL licensed libtevent.
+ **/
+
+/*
+ * This file is being made available by the Samba Team under the following
+ * license:
+ *
+ * Permission to use, copy, modify, and distribute this sample file for any
+ * purpose is hereby granted without fee.
+ *
+ * This work 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.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <netinet/in.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <errno.h>
+#include <unistd.h>
+#include "tevent.h"
+#include "talloc.h"
+
+/**
+ * @brief Helper function to get a useful unix error from tevent_req
+ */
+
+static bool tevent_req_is_unix_error(struct tevent_req *req, int *perrno)
+{
+	enum tevent_req_state state;
+	uint64_t err;
+
+	if (!tevent_req_is_error(req, &state, &err)) {
+		return false;
+	}
+	switch (state) {
+	case TEVENT_REQ_TIMED_OUT:
+		*perrno = ETIMEDOUT;
+		break;
+	case TEVENT_REQ_NO_MEMORY:
+		*perrno = ENOMEM;
+		break;
+	case TEVENT_REQ_USER_ERROR:
+		*perrno = err;
+		break;
+	default:
+		*perrno = EINVAL;
+		break;
+	}
+	return true;
+}
+
+/**
+ * @brief Wrapper around accept(2)
+ */
+
+struct accept_state {
+	struct tevent_fd *fde;
+	int listen_sock;
+	socklen_t addrlen;
+	struct sockaddr addr;
+	int sock;
+};
+
+static void accept_handler(struct tevent_context *ev, struct tevent_fd *fde,
+			   uint16_t flags, void *private_data);
+
+static struct tevent_req *accept_send(TALLOC_CTX *mem_ctx,
+				      struct tevent_context *ev,
+				      int listen_sock)
+{
+	struct tevent_req *req;
+	struct accept_state *state;
+
+	req = tevent_req_create(mem_ctx, &state, struct accept_state);
+	if (req == NULL) {
+		return NULL;
+	}
+
+	state->listen_sock = listen_sock;
+
+	state->fde = tevent_add_fd(ev, state, listen_sock, TEVENT_FD_READ,
+				   accept_handler, req);
+	if (tevent_req_nomem(state->fde, req)) {
+		return tevent_req_post(req, ev);
+	}
+	return req;
+}
+
+static void accept_handler(struct tevent_context *ev, struct tevent_fd *fde,
+			   uint16_t flags, void *private_data)
+{
+	struct tevent_req *req = talloc_get_type_abort(
+		private_data, struct tevent_req);
+	struct accept_state *state = tevent_req_data(req, struct accept_state);
+	int ret;
+
+	TALLOC_FREE(state->fde);
+
+	if ((flags & TEVENT_FD_READ) == 0) {
+		tevent_req_error(req, EIO);
+		return;
+	}
+	state->addrlen = sizeof(state->addr);
+
+	ret = accept(state->listen_sock, &state->addr, &state->addrlen);
+	if (ret == -1) {
+		tevent_req_error(req, errno);
+		return;
+	}
+	state->sock = ret;
+	tevent_req_done(req);
+}
+
+static int accept_recv(struct tevent_req *req, struct sockaddr *paddr,
+		       socklen_t *paddrlen, int *perr)
+{
+	struct accept_state *state = tevent_req_data(req, struct accept_state);
+	int err;
+
+	if (tevent_req_is_unix_error(req, &err)) {
+		if (perr != NULL) {
+			*perr = err;
+		}
+		return -1;
+	}
+	if (paddr != NULL) {
+		*paddr = state->addr;
+	}
+	if (paddrlen != NULL) {
+		*paddrlen = state->addrlen;
+	}
+	return state->sock;
+}
+
+/**
+ * @brief Wrapper around read(2)
+ */
+
+struct read_state {
+	struct tevent_fd *fde;
+	int fd;
+	void *buf;
+	size_t count;
+
+	ssize_t nread;
+};
+
+static void read_handler(struct tevent_context *ev, struct tevent_fd *fde,
+			 uint16_t flags, void *private_data);
+
+static struct tevent_req *read_send(TALLOC_CTX *mem_ctx,
+				    struct tevent_context *ev,
+				    int fd, void *buf, size_t count)
+{
+	struct tevent_req *req;
+	struct read_state *state;
+
+	req = tevent_req_create(mem_ctx, &state, struct read_state);
+	if (req == NULL) {
+		return NULL;
+	}
+
+	state->fd = fd;
+	state->buf = buf;
+	state->count = count;
+
+	state->fde = tevent_add_fd(ev, state, fd, TEVENT_FD_READ,
+				   read_handler, req);
+	if (tevent_req_nomem(state->fde, req)) {
+		return tevent_req_post(req, ev);
+	}
+	return req;
+}
+
+static void read_handler(struct tevent_context *ev, struct tevent_fd *fde,
+			 uint16_t flags, void *private_data)
+{
+	struct tevent_req *req = talloc_get_type_abort(
+		private_data, struct tevent_req);
+	struct read_state *state = tevent_req_data(req, struct read_state);
+	ssize_t ret;
+
+	TALLOC_FREE(state->fde);
+
+	if ((flags & TEVENT_FD_READ) == 0) {
+		tevent_req_error(req, EIO);
+		return;
+	}
+
+	ret = read(state->fd, state->buf, state->count);
+	if (ret == -1) {
+		tevent_req_error(req, errno);
+		return;
+	}
+	state->nread = ret;
+	tevent_req_done(req);
+}
+
+static ssize_t read_recv(struct tevent_req *req, int *perr)
+{
+	struct read_state *state = tevent_req_data(req, struct read_state);
+	int err;
+
+	if (tevent_req_is_unix_error(req, &err)) {
+		if (perr != NULL) {
+			*perr = err;
+		}
+		return -1;
+	}
+	return state->nread;
+}
+
+/**
+ * @brief Wrapper around write(2)
+ */
+
+struct write_state {
+	struct tevent_fd *fde;
+	int fd;
+	const void *buf;
+	size_t count;
+
+	ssize_t nwritten;
+};
+
+static void write_handler(struct tevent_context *ev, struct tevent_fd *fde,
+			 uint16_t flags, void *private_data);
+
+static struct tevent_req *write_send(TALLOC_CTX *mem_ctx,
+				    struct tevent_context *ev,
+				    int fd, const void *buf, size_t count)
+{
+	struct tevent_req *req;
+	struct write_state *state;
+
+	req = tevent_req_create(mem_ctx, &state, struct write_state);
+	if (req == NULL) {
+		return NULL;
+	}
+
+	state->fd = fd;
+	state->buf = buf;
+	state->count = count;
+
+	state->fde = tevent_add_fd(ev, state, fd, TEVENT_FD_WRITE,
+				   write_handler, req);
+	if (tevent_req_nomem(state->fde, req)) {
+		return tevent_req_post(req, ev);
+	}
+	return req;
+}
+
+static void write_handler(struct tevent_context *ev, struct tevent_fd *fde,
+			 uint16_t flags, void *private_data)
+{
+	struct tevent_req *req = talloc_get_type_abort(
+		private_data, struct tevent_req);
+	struct write_state *state = tevent_req_data(req, struct write_state);
+	ssize_t ret;
+
+	TALLOC_FREE(state->fde);
+
+	if ((flags & TEVENT_FD_WRITE) == 0) {
+		tevent_req_error(req, EIO);
+		return;
+	}
+
+	ret = write(state->fd, state->buf, state->count);
+	if (ret == -1) {
+		tevent_req_error(req, errno);
+		return;
+	}
+	state->nwritten = ret;
+	tevent_req_done(req);
+}
+
+static ssize_t write_recv(struct tevent_req *req, int *perr)
+{
+	struct write_state *state = tevent_req_data(req, struct write_state);
+	int err;
+
+	if (tevent_req_is_unix_error(req, &err)) {
+		if (perr != NULL) {
+			*perr = err;
+		}
+		return -1;
+	}
+	return state->nwritten;
+}
+
+/**
+ * @brief Wrapper function that deals with short writes
+ */
+
+struct writeall_state {
+	struct tevent_context *ev;
+	int fd;
+	const void *buf;
+	size_t count;
+	size_t nwritten;
+};
+
+static void writeall_done(struct tevent_req *subreq);
+
+static struct tevent_req *writeall_send(TALLOC_CTX *mem_ctx,
+					struct tevent_context *ev,
+					int fd, const void *buf, size_t count)
+{
+	struct tevent_req *req, *subreq;
+	struct writeall_state *state;
+
+	req = tevent_req_create(mem_ctx, &state, struct writeall_state);
+	if (req == NULL) {
+		return NULL;
+	}
+	state->ev = ev;
+	state->fd = fd;
+	state->buf = buf;
+	state->count = count;
+	state->nwritten = 0;
+
+	subreq = write_send(state, state->ev, state->fd,
+			    ((char *)state->buf)+state->nwritten,
+			    state->count - state->nwritten);
+	if (tevent_req_nomem(subreq, req)) {
+		return tevent_req_post(req, ev);
+	}
+	tevent_req_set_callback(subreq, writeall_done, req);
+	return req;
+}
+
+static void writeall_done(struct tevent_req *subreq)
+{
+	struct tevent_req *req = tevent_req_callback_data(
+		subreq, struct tevent_req);
+	struct writeall_state *state = tevent_req_data(
+		req, struct writeall_state);
+	ssize_t nwritten;
+	int err = 0;
+
+	nwritten = write_recv(subreq, &err);
+	TALLOC_FREE(subreq);
+	if (nwritten == -1) {
+		tevent_req_error(req, err);
+		return;
+	}
+
+	state->nwritten += nwritten;
+
+	if (state->nwritten < state->count) {
+		subreq = write_send(state, state->ev, state->fd,
+				    ((char *)state->buf)+state->nwritten,
+				    state->count - state->nwritten);
+		if (tevent_req_nomem(subreq, req)) {
+			return;
+		}
+		tevent_req_set_callback(subreq, writeall_done, req);
+		return;
+	}
+	tevent_req_done(req);
+}
+
+static ssize_t writeall_recv(struct tevent_req *req, int *perr)
+{
+	struct writeall_state *state = tevent_req_data(
+		req, struct writeall_state);
+	int err;
+
+	if (tevent_req_is_unix_error(req, &err)) {
+		if (perr != NULL) {
+			*perr = err;
+		}
+		return -1;
+	}
+	return state->nwritten;
+}
+
+/**
+ * @brief Async echo handler code dealing with one client
+ */
+
+struct echo_state {
+	struct tevent_context *ev;
+	int fd;
+	uint8_t *buf;
+};
+
+static int echo_state_destructor(struct echo_state *s);
+static void echo_read_done(struct tevent_req *subreq);
+static void echo_writeall_done(struct tevent_req *subreq);
+
+static struct tevent_req *echo_send(TALLOC_CTX *mem_ctx,
+				    struct tevent_context *ev,
+				    int fd, size_t bufsize)
+{
+	struct tevent_req *req, *subreq;
+	struct echo_state *state;
+
+	req = tevent_req_create(mem_ctx, &state, struct echo_state);
+	if (req == NULL) {
+		return NULL;
+	}
+	state->ev = ev;
+	state->fd = fd;
+
+	talloc_set_destructor(state, echo_state_destructor);
+
+	state->buf = talloc_array(state, uint8_t, bufsize);
+	if (tevent_req_nomem(state->buf, req)) {
+		return tevent_req_post(req, ev);
+	}
+
+	subreq = read_send(state, state->ev, state->fd,
+			   state->buf, talloc_get_size(state->buf));
+	if (tevent_req_nomem(subreq, req)) {
+		return tevent_req_post(req, ev);
+	}
+	tevent_req_set_callback(subreq, echo_read_done, req);
+	return req;
+}
+
+static int echo_state_destructor(struct echo_state *s)
+{
+	if (s->fd != -1) {
+		printf("Closing client fd %d\n", s->fd);
+		close(s->fd);
+		s->fd = -1;
+	}
+	return 0;
+}
+
+static void echo_read_done(struct tevent_req *subreq)
+{
+	struct tevent_req *req = tevent_req_callback_data(
+		subreq, struct tevent_req);
+	struct echo_state *state = tevent_req_data(
+		req, struct echo_state);
+	ssize_t nread;
+	int err;
+
+	nread = read_recv(subreq, &err);
+	TALLOC_FREE(subreq);
+	if (nread == -1) {
+		tevent_req_error(req, err);
+		return;
+	}
+	if (nread == 0) {
+		tevent_req_done(req);
+		return;
+	}
+
+	subreq = writeall_send(state, state->ev, state->fd, state->buf, nread);
+	if (tevent_req_nomem(subreq, req)) {
+		return;
+	}
+	tevent_req_set_callback(subreq, echo_writeall_done, req);
+}
+
+static void echo_writeall_done(struct tevent_req *subreq)
+{
+	struct tevent_req *req = tevent_req_callback_data(
+		subreq, struct tevent_req);
+	struct echo_state *state = tevent_req_data(
+		req, struct echo_state);
+	ssize_t nwritten;
+	int err;
+
+	nwritten = writeall_recv(subreq, &err);
+	TALLOC_FREE(subreq);
+	if (nwritten == -1) {
+		if (err == EPIPE) {
+			tevent_req_done(req);
+			return;
+		}
+		tevent_req_error(req, err);
+		return;
+	}
+
+	subreq = read_send(state, state->ev, state->fd,
+			   state->buf, talloc_get_size(state->buf));
+	if (tevent_req_nomem(subreq, req)) {
+		return;
+	}
+	tevent_req_set_callback(subreq, echo_read_done, req);
+}
+
+static bool echo_recv(struct tevent_req *req, int *perr)
+{
+	int err;
+
+	if (tevent_req_is_unix_error(req, &err)) {
+		*perr = err;
+		return false;
+	}
+	return true;
+}
+
+/**
+ * @brief Full echo handler code accepting and handling clients
+ */
+
+struct echo_server_state {
+	struct tevent_context *ev;
+	int listen_sock;
+};
+
+static void echo_server_accepted(struct tevent_req *subreq);
+static void echo_server_client_done(struct tevent_req *subreq);
+
+static struct tevent_req *echo_server_send(TALLOC_CTX *mem_ctx,
+					   struct tevent_context *ev,
+					   int listen_sock)
+{
+	struct tevent_req *req, *subreq;
+	struct echo_server_state *state;
+
+	req = tevent_req_create(mem_ctx, &state,
+				struct echo_server_state);
+	if (req == NULL) {
+		return NULL;
+	}
+	state->ev = ev;
+	state->listen_sock = listen_sock;
+
+	subreq = accept_send(state, state->ev, state->listen_sock);
+	if (tevent_req_nomem(subreq, req)) {
+		return tevent_req_post(req, ev);
+	}
+	tevent_req_set_callback(subreq, echo_server_accepted, req);
+	return req;
+}
+
+static void echo_server_accepted(struct tevent_req *subreq)
+{
+	struct tevent_req *req = tevent_req_callback_data(
+		subreq, struct tevent_req);
+	struct echo_server_state *state = tevent_req_data(
+		req, struct echo_server_state);
+	int sock, err;
+
+	sock = accept_recv(subreq, NULL, NULL, &err);
+	TALLOC_FREE(subreq);
+	if (sock == -1) {
+		tevent_req_error(req, err);
+		return;
+	}
+
+	printf("new client fd %d\n", sock);
+
+	subreq = echo_send(state, state->ev, sock, 100);
+	if (tevent_req_nomem(subreq, req)) {
+		return;
+	}
+	tevent_req_set_callback(subreq, echo_server_client_done, req);
+
+	subreq = accept_send(state, state->ev, state->listen_sock);
+	if (tevent_req_nomem(subreq, req)) {
+		return;
+	}
+	tevent_req_set_callback(subreq, echo_server_accepted, req);
+}
+
+static void echo_server_client_done(struct tevent_req *subreq)
+{
+	bool ret;
+	int err;
+
+	ret = echo_recv(subreq, &err);
+	TALLOC_FREE(subreq);
+
+	if (ret) {
+		printf("Client done\n");
+	} else {
+		printf("Client failed: %s\n", strerror(err));
+	}
+}
+
+static bool echo_server_recv(struct tevent_req *req, int *perr)
+{
+	int err;
+
+	if (tevent_req_is_unix_error(req, &err)) {
+		*perr = err;
+		return false;
+	}
+	return true;
+}
+
+int main(int argc, const char **argv)
+{
+	int ret, port, listen_sock, err;
+	struct tevent_context *ev;
+	struct sockaddr_in addr;
+	struct tevent_req *req;
+	bool result;
+
+	if (argc != 2) {
+		fprintf(stderr, "Usage: %s <port>\n", argv[0]);
+		exit(1);
+	}
+
+	port = atoi(argv[1]);
+
+	printf("listening on port %d\n", port);
+
+	listen_sock = socket(AF_INET, SOCK_STREAM, 0);
+
+	if (listen_sock == -1) {
+		perror("socket() failed");
+		exit(1);
+	}
+
+	memset(&addr, 0, sizeof(addr));
+
+	addr.sin_family = AF_INET;
+	addr.sin_port = htons(port);
+
+	ret = bind(listen_sock, (struct sockaddr *)&addr, sizeof(addr));
+	if (ret == -1) {
+		perror("bind() failed");
+		exit(1);
+	}
+
+	ret = listen(listen_sock, 5);
+	if (ret == -1) {
+		perror("listen() failed");
+		exit(1);
+	}
+
+	ev = tevent_context_init(NULL);
+	if (ev == NULL) {
+		fprintf(stderr, "tevent_context_init failed\n");
+		exit(1);
+	}
+
+	req = echo_server_send(ev, ev, listen_sock);
+	if (req == NULL) {
+		fprintf(stderr, "echo_server_send failed\n");
+		exit(1);
+	}
+
+	if (!tevent_req_poll(req, ev)) {
+		perror("tevent_req_poll() failed");
+		exit(1);
+	}
+
+	result = echo_server_recv(req, &err);
+	TALLOC_FREE(req);
+	if (!result) {
+		fprintf(stderr, "echo_server failed: %s\n", strerror(err));
+		exit(1);
+	}
+
+	return 0;
+}