src/sink.c

/*
 * Event sink management
 *
 * Copyright (C) 2000-2019 Willy Tarreau - w@1wt.eu
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation, version 2.1
 * exclusively.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include <sys/mman.h>
#include <errno.h>
#include <fcntl.h>

#include <import/ist.h>
#include <haproxy/api.h>
#include <haproxy/applet.h>
#include <haproxy/cfgparse.h>
#include <haproxy/cli.h>
#include <haproxy/errors.h>
#include <haproxy/list.h>
#include <haproxy/log.h>
#include <haproxy/proxy.h>
#include <haproxy/ring.h>
#include <haproxy/sc_strm.h>
#include <haproxy/signal.h>
#include <haproxy/sink.h>
#include <haproxy/stconn.h>
#include <haproxy/time.h>
#include <haproxy/tools.h>

struct list sink_list = LIST_HEAD_INIT(sink_list);

/* sink proxies list */
struct proxy *sink_proxies_list;

struct sink *cfg_sink;

struct sink *sink_find(const char *name)
{
	struct sink *sink;

	list_for_each_entry(sink, &sink_list, sink_list)
		if (strcmp(sink->name, name) == 0)
			return sink;
	return NULL;
}

/* creates a new sink and adds it to the list, it's still generic and not fully
 * initialized. Returns NULL on allocation failure. If another one already
 * exists with the same name, it will be returned. The caller can detect it as
 * a newly created one has type SINK_TYPE_NEW.
 */
static struct sink *__sink_new(const char *name, const char *desc, int fmt)
{
	struct sink *sink;

	sink = sink_find(name);
	if (sink)
		goto end;

	sink = calloc(1, sizeof(*sink));
	if (!sink)
		goto end;

	sink->name = strdup(name);
	if (!sink->name)
		goto err;

	sink->desc = strdup(desc);
	if (!sink->desc)
		goto err;

	sink->fmt  = fmt;
	sink->type = SINK_TYPE_NEW;
	sink->maxlen = BUFSIZE;
	/* address will be filled by the caller if needed */
	sink->ctx.fd = -1;
	sink->ctx.dropped = 0;
	HA_RWLOCK_INIT(&sink->ctx.lock);
	LIST_APPEND(&sink_list, &sink->sink_list);
 end:
	return sink;

 err:
	ha_free(&sink->name);
	ha_free(&sink->desc);
	ha_free(&sink);

	return NULL;
}

/* creates a sink called <name> of type FD associated to fd <fd>, format <fmt>,
 * and description <desc>. Returns NULL on allocation failure or conflict.
 * Perfect duplicates are merged (same type, fd, and name).
 */
struct sink *sink_new_fd(const char *name, const char *desc, enum log_fmt fmt, int fd)
{
	struct sink *sink;

	sink = __sink_new(name, desc, fmt);
	if (!sink || (sink->type == SINK_TYPE_FD && sink->ctx.fd == fd))
		goto end;

	if (sink->type != SINK_TYPE_NEW) {
		sink = NULL;
		goto end;
	}

	sink->type = SINK_TYPE_FD;
	sink->ctx.fd = fd;
 end:
	return sink;
}

/* creates a sink called <name> of type BUF of size <size>, format <fmt>,
 * and description <desc>. Returns NULL on allocation failure or conflict.
 * Perfect duplicates are merged (same type and name). If sizes differ, the
 * largest one is kept.
 */
struct sink *sink_new_buf(const char *name, const char *desc, enum log_fmt fmt, size_t size)
{
	struct sink *sink;

	sink = __sink_new(name, desc, fmt);
	if (!sink)
		goto fail;

	if (sink->type == SINK_TYPE_BUFFER) {
		/* such a buffer already exists, we may have to resize it */
		if (!ring_resize(sink->ctx.ring, size))
			goto fail;
		goto end;
	}

	if (sink->type != SINK_TYPE_NEW) {
		/* already exists of another type */
		goto fail;
	}

	sink->ctx.ring = ring_new(size);
	if (!sink->ctx.ring) {
		LIST_DELETE(&sink->sink_list);
		free(sink->name);
		free(sink->desc);
		free(sink);
		goto fail;
	}

	sink->type = SINK_TYPE_BUFFER;
 end:
	return sink;
 fail:
	return NULL;
}

/* tries to send <nmsg> message parts (up to 8, ignored above) from message
 * array <msg> to sink <sink>. Formatting according to the sink's preference is
 * done here. Lost messages are NOT accounted for. It is preferable to call
 * sink_write() instead which will also try to emit the number of dropped
 * messages when there are any. It returns >0 if it could write anything,
 * <=0 otherwise.
 */
 ssize_t __sink_write(struct sink *sink, const struct ist msg[], size_t nmsg,
	             int level, int facility, struct ist *metadata)
 {
	struct ist *pfx = NULL;
	size_t npfx = 0;

	if (sink->fmt == LOG_FORMAT_RAW)
		goto send;

	pfx = build_log_header(sink->fmt, level, facility, metadata, &npfx);

send:
	if (sink->type == SINK_TYPE_FD) {
		return fd_write_frag_line(sink->ctx.fd, sink->maxlen, pfx, npfx, msg, nmsg, 1);
	}
	else if (sink->type == SINK_TYPE_BUFFER) {
		return ring_write(sink->ctx.ring, sink->maxlen, pfx, npfx, msg, nmsg);
	}
	return 0;
}

/* Tries to emit a message indicating the number of dropped events. In case of
 * success, the amount of drops is reduced by as much. It's supposed to be
 * called under an exclusive lock on the sink to avoid multiple produces doing
 * the same. On success, >0 is returned, otherwise <=0 on failure.
 */
int sink_announce_dropped(struct sink *sink, int facility)
{
	static THREAD_LOCAL struct ist metadata[LOG_META_FIELDS];
	static THREAD_LOCAL pid_t curr_pid;
	static THREAD_LOCAL char pidstr[16];
	unsigned int dropped;
	struct buffer msg;
	struct ist msgvec[1];
	char logbuf[64];

	while (unlikely((dropped = sink->ctx.dropped) > 0)) {
		chunk_init(&msg, logbuf, sizeof(logbuf));
		chunk_printf(&msg, "%u event%s dropped", dropped, dropped > 1 ? "s" : "");
		msgvec[0] = ist2(msg.area, msg.data);

		if (!metadata[LOG_META_HOST].len) {
			if (global.log_send_hostname)
				metadata[LOG_META_HOST] = ist(global.log_send_hostname);
		}

		if (!metadata[LOG_META_TAG].len)
			metadata[LOG_META_TAG] = ist2(global.log_tag.area, global.log_tag.data);

		if (unlikely(curr_pid != getpid()))
			 metadata[LOG_META_PID].len = 0;

		if (!metadata[LOG_META_PID].len) {
			curr_pid = getpid();
			ltoa_o(curr_pid, pidstr, sizeof(pidstr));
			metadata[LOG_META_PID] = ist2(pidstr, strlen(pidstr));
		}

		if (__sink_write(sink, msgvec, 1, LOG_NOTICE, facility, metadata) <= 0)
			return 0;
		/* success! */
		HA_ATOMIC_SUB(&sink->ctx.dropped, dropped);
	}
	return 1;
}

/* parse the "show events" command, returns 1 if a message is returned, otherwise zero */
static int cli_parse_show_events(char **args, char *payload, struct appctx *appctx, void *private)
{
	struct sink *sink;
	uint ring_flags;
	int arg;

	args++; // make args[1] the 1st arg

	if (!*args[1]) {
		/* no arg => report the list of supported sink */
		chunk_printf(&trash, "Supported events sinks are listed below. Add -w(wait), -n(new). Any key to stop\n");
		list_for_each_entry(sink, &sink_list, sink_list) {
			chunk_appendf(&trash, "    %-10s : type=%s, %u dropped, %s\n",
				      sink->name,
				      sink->type == SINK_TYPE_NEW ? "init" :
				      sink->type == SINK_TYPE_FD ? "fd" :
				      sink->type == SINK_TYPE_BUFFER ? "buffer" : "?",
				      sink->ctx.dropped, sink->desc);
		}

		trash.area[trash.data] = 0;
		return cli_msg(appctx, LOG_WARNING, trash.area);
	}

	if (!cli_has_level(appctx, ACCESS_LVL_OPER))
		return 1;

	sink = sink_find(args[1]);
	if (!sink)
		return cli_err(appctx, "No such event sink");

	if (sink->type != SINK_TYPE_BUFFER)
		return cli_msg(appctx, LOG_NOTICE, "Nothing to report for this sink");

	ring_flags = 0;
	for (arg = 2; *args[arg]; arg++) {
		if (strcmp(args[arg], "-w") == 0)
			ring_flags |= RING_WF_WAIT_MODE;
		else if (strcmp(args[arg], "-n") == 0)
			ring_flags |= RING_WF_SEEK_NEW;
		else if (strcmp(args[arg], "-nw") == 0 || strcmp(args[arg], "-wn") == 0)
			ring_flags |= RING_WF_WAIT_MODE | RING_WF_SEEK_NEW;
		else
			return cli_err(appctx, "unknown option");
	}
	return ring_attach_cli(sink->ctx.ring, appctx, ring_flags);
}

/* Pre-configures a ring proxy to emit connections */
void sink_setup_proxy(struct proxy *px)
{
	px->last_change = now.tv_sec;
	px->cap = PR_CAP_BE;
	px->maxconn = 0;
	px->conn_retries = 1;
	px->timeout.server = TICK_ETERNITY;
	px->timeout.client = TICK_ETERNITY;
	px->timeout.connect = TICK_ETERNITY;
	px->accept = NULL;
	px->options2 |= PR_O2_INDEPSTR | PR_O2_SMARTCON | PR_O2_SMARTACC;
	px->next = sink_proxies_list;
	sink_proxies_list = px;
}

/*
 * IO Handler to handle message push to syslog tcp server.
 * It takes its context from appctx->svcctx.
 */
static void sink_forward_io_handler(struct appctx *appctx)
{
	struct stconn *sc = appctx_sc(appctx);
	struct stream *s = __sc_strm(sc);
	struct sink *sink = strm_fe(s)->parent;
	struct sink_forward_target *sft = appctx->svcctx;
	struct ring *ring = sink->ctx.ring;
	struct buffer *buf = &ring->buf;
	uint64_t msg_len;
	size_t len, cnt, ofs, last_ofs;
	int ret = 0;

	/* if stopping was requested, close immediately */
	if (unlikely(stopping))
		goto close;

	if (unlikely(sc_ic(sc)->flags & CF_SHUTW))
		goto close;

	/* con closed by server side */
	if ((sc_oc(sc)->flags & CF_SHUTW))
		goto close;

	/* if the connection is not established, inform the stream that we want
	 * to be notified whenever the connection completes.
	 */
	if (sc_opposite(sc)->state < SC_ST_EST) {
		applet_need_more_data(appctx);
		se_need_remote_conn(appctx->sedesc);
		applet_have_more_data(appctx);
		return;
	}

	HA_SPIN_LOCK(SFT_LOCK, &sft->lock);
	if (appctx != sft->appctx) {
		HA_SPIN_UNLOCK(SFT_LOCK, &sft->lock);
		goto close;
	}

	HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &ring->lock);
	LIST_DEL_INIT(&appctx->wait_entry);
	HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &ring->lock);

	HA_RWLOCK_RDLOCK(LOGSRV_LOCK, &ring->lock);

	/* explanation for the initialization below: it would be better to do
	 * this in the parsing function but this would occasionally result in
	 * dropped events because we'd take a reference on the oldest message
	 * and keep it while being scheduled. Thus instead let's take it the
	 * first time we enter here so that we have a chance to pass many
	 * existing messages before grabbing a reference to a location. This
	 * value cannot be produced after initialization.
	 */
	if (unlikely(sft->ofs == ~0)) {
		sft->ofs = b_peek_ofs(buf, 0);
		HA_ATOMIC_INC(b_orig(buf) + sft->ofs);
	}

	/* in this loop, ofs always points to the counter byte that precedes
	 * the message so that we can take our reference there if we have to
	 * stop before the end (ret=0).
	 */
	if (sc_opposite(sc)->state == SC_ST_EST) {
		/* we were already there, adjust the offset to be relative to
		 * the buffer's head and remove us from the counter.
		 */
		ofs = sft->ofs - b_head_ofs(buf);
		if (sft->ofs < b_head_ofs(buf))
			ofs += b_size(buf);
		BUG_ON(ofs >= buf->size);
		HA_ATOMIC_DEC(b_peek(buf, ofs));

		ret = 1;
		while (ofs + 1 < b_data(buf)) {
			cnt = 1;
			len = b_peek_varint(buf, ofs + cnt, &msg_len);
			if (!len)
				break;
			cnt += len;
			BUG_ON(msg_len + ofs + cnt + 1 > b_data(buf));

			if (unlikely(msg_len + 1 > b_size(&trash))) {
				/* too large a message to ever fit, let's skip it */
				ofs += cnt + msg_len;
				continue;
			}

			chunk_reset(&trash);
			len = b_getblk(buf, trash.area, msg_len, ofs + cnt);
			trash.data += len;
			trash.area[trash.data++] = '\n';

			if (applet_putchk(appctx, &trash) == -1) {
				ret = 0;
				break;
			}
			ofs += cnt + msg_len;
		}

		HA_ATOMIC_INC(b_peek(buf, ofs));
		last_ofs = b_tail_ofs(buf);
		sft->ofs = b_peek_ofs(buf, ofs);
	}
	HA_RWLOCK_RDUNLOCK(LOGSRV_LOCK, &ring->lock);

	if (ret) {
		/* let's be woken up once new data arrive */
		HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &ring->lock);
		LIST_APPEND(&ring->waiters, &appctx->wait_entry);
		ofs = b_tail_ofs(buf);
		HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &ring->lock);
		if (ofs != last_ofs) {
			/* more data was added into the ring between the
			 * unlock and the lock, and the writer might not
			 * have seen us. We need to reschedule a read.
			 */
			applet_have_more_data(appctx);
		} else
			applet_have_no_more_data(appctx);
	}
	HA_SPIN_UNLOCK(SFT_LOCK, &sft->lock);

	/* always drain data from server */
	co_skip(sc_oc(sc), sc_oc(sc)->output);
	return;

close:
	sc_shutw(sc);
	sc_shutr(sc);
}

/*
 * IO Handler to handle message push to syslog tcp server
 * using octet counting frames
 * It takes its context from appctx->svcctx.
 */
static void sink_forward_oc_io_handler(struct appctx *appctx)
{
	struct stconn *sc = appctx_sc(appctx);
	struct stream *s = __sc_strm(sc);
	struct sink *sink = strm_fe(s)->parent;
	struct sink_forward_target *sft = appctx->svcctx;
	struct ring *ring = sink->ctx.ring;
	struct buffer *buf = &ring->buf;
	uint64_t msg_len;
	size_t len, cnt, ofs;
	int ret = 0;
	char *p;

	/* if stopping was requested, close immediately */
	if (unlikely(stopping))
		goto close;

	/* an error was detected */
	if (unlikely(sc_ic(sc)->flags & CF_SHUTW))
		goto close;

	/* con closed by server side */
	if ((sc_oc(sc)->flags & CF_SHUTW))
		goto close;

	/* if the connection is not established, inform the stream that we want
	 * to be notified whenever the connection completes.
	 */
	if (sc_opposite(sc)->state < SC_ST_EST) {
		applet_need_more_data(appctx);
		se_need_remote_conn(appctx->sedesc);
		applet_have_more_data(appctx);
		return;
	}

	HA_SPIN_LOCK(SFT_LOCK, &sft->lock);
	if (appctx != sft->appctx) {
		HA_SPIN_UNLOCK(SFT_LOCK, &sft->lock);
		goto close;
	}

	HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &ring->lock);
	LIST_DEL_INIT(&appctx->wait_entry);
	HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &ring->lock);

	HA_RWLOCK_RDLOCK(LOGSRV_LOCK, &ring->lock);

	/* explanation for the initialization below: it would be better to do
	 * this in the parsing function but this would occasionally result in
	 * dropped events because we'd take a reference on the oldest message
	 * and keep it while being scheduled. Thus instead let's take it the
	 * first time we enter here so that we have a chance to pass many
	 * existing messages before grabbing a reference to a location. This
	 * value cannot be produced after initialization.
	 */
	if (unlikely(sft->ofs == ~0)) {
		sft->ofs = b_peek_ofs(buf, 0);
		HA_ATOMIC_INC(b_orig(buf) + sft->ofs);
	}

	/* in this loop, ofs always points to the counter byte that precedes
	 * the message so that we can take our reference there if we have to
	 * stop before the end (ret=0).
	 */
	if (sc_opposite(sc)->state == SC_ST_EST) {
		/* we were already there, adjust the offset to be relative to
		 * the buffer's head and remove us from the counter.
		 */
		ofs = sft->ofs - b_head_ofs(buf);
		if (sft->ofs < b_head_ofs(buf))
			ofs += b_size(buf);
		BUG_ON(ofs >= buf->size);
		HA_ATOMIC_DEC(b_peek(buf, ofs));

		ret = 1;
		while (ofs + 1 < b_data(buf)) {
			cnt = 1;
			len = b_peek_varint(buf, ofs + cnt, &msg_len);
			if (!len)
				break;
			cnt += len;
			BUG_ON(msg_len + ofs + cnt + 1 > b_data(buf));

			chunk_reset(&trash);
			p = ulltoa(msg_len, trash.area, b_size(&trash));
			if (p) {
				trash.data = (p - trash.area) + 1;
				*p = ' ';
			}

			if (!p || (trash.data + msg_len > b_size(&trash))) {
				/* too large a message to ever fit, let's skip it */
				ofs += cnt + msg_len;
				continue;
			}

			trash.data += b_getblk(buf, p + 1, msg_len, ofs + cnt);

			if (applet_putchk(appctx, &trash) == -1) {
				ret = 0;
				break;
			}
			ofs += cnt + msg_len;
		}

		HA_ATOMIC_INC(b_peek(buf, ofs));
		sft->ofs = b_peek_ofs(buf, ofs);
	}
	HA_RWLOCK_RDUNLOCK(LOGSRV_LOCK, &ring->lock);

	if (ret) {
		/* let's be woken up once new data arrive */
		HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &ring->lock);
		LIST_APPEND(&ring->waiters, &appctx->wait_entry);
		HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &ring->lock);
		applet_have_no_more_data(appctx);
	}
	HA_SPIN_UNLOCK(SFT_LOCK, &sft->lock);

	/* always drain data from server */
	co_skip(sc_oc(sc), sc_oc(sc)->output);
	return;

close:
	sc_shutw(sc);
	sc_shutr(sc);
}

void __sink_forward_session_deinit(struct sink_forward_target *sft)
{
	struct stream *s = appctx_strm(sft->appctx);
	struct sink *sink;

	sink = strm_fe(s)->parent;
	if (!sink)
		return;

	HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &sink->ctx.ring->lock);
	LIST_DEL_INIT(&sft->appctx->wait_entry);
	HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &sink->ctx.ring->lock);

	sft->appctx = NULL;
	task_wakeup(sink->forward_task, TASK_WOKEN_MSG);
}

static int sink_forward_session_init(struct appctx *appctx)
{
	struct sink_forward_target *sft = appctx->svcctx;
	struct stream *s;
	struct sockaddr_storage *addr = NULL;

	if (!sockaddr_alloc(&addr, &sft->srv->addr, sizeof(sft->srv->addr)))
		goto out_error;

	if (appctx_finalize_startup(appctx, sft->sink->forward_px, &BUF_NULL) == -1)
		goto out_free_addr;

	s = appctx_strm(appctx);
	s->scb->dst = addr;
	s->scb->flags |= (SC_FL_RCV_ONCE|SC_FL_NOLINGER);

	s->target = &sft->srv->obj_type;
	s->flags = SF_ASSIGNED;

	s->do_log = NULL;
	s->uniq_id = 0;

	applet_expect_no_data(appctx);
	sft->appctx = appctx;

	return 0;

 out_free_addr:
	sockaddr_free(&addr);
 out_error:
	return -1;
}

static void sink_forward_session_release(struct appctx *appctx)
{
	struct sink_forward_target *sft = appctx->svcctx;

	if (!sft)
		return;

	HA_SPIN_LOCK(SFT_LOCK, &sft->lock);
	if (sft->appctx == appctx)
		__sink_forward_session_deinit(sft);
	HA_SPIN_UNLOCK(SFT_LOCK, &sft->lock);
}

static struct applet sink_forward_applet = {
	.obj_type = OBJ_TYPE_APPLET,
	.name = "<SINKFWD>", /* used for logging */
	.fct = sink_forward_io_handler,
	.init = sink_forward_session_init,
	.release = sink_forward_session_release,
};

static struct applet sink_forward_oc_applet = {
	.obj_type = OBJ_TYPE_APPLET,
	.name = "<SINKFWDOC>", /* used for logging */
	.fct = sink_forward_oc_io_handler,
	.init = sink_forward_session_init,
	.release = sink_forward_session_release,
};

/*
 * Create a new peer session in assigned state (connect will start automatically)
 * It sets its context into appctx->svcctx.
 */
static struct appctx *sink_forward_session_create(struct sink *sink, struct sink_forward_target *sft)
{
	struct appctx *appctx;
	struct applet *applet = &sink_forward_applet;

	if (sft->srv->log_proto == SRV_LOG_PROTO_OCTET_COUNTING)
		applet = &sink_forward_oc_applet;

	appctx = appctx_new_here(applet, NULL);
	if (!appctx)
		goto out_close;
	appctx->svcctx = (void *)sft;

	if (appctx_init(appctx) == -1)
		goto out_free_appctx;

	return appctx;

	/* Error unrolling */
 out_free_appctx:
	appctx_free_on_early_error(appctx);
 out_close:
	return NULL;
}

/*
 * Task to handle connctions to forward servers
 */
static struct task *process_sink_forward(struct task * task, void *context, unsigned int state)
{
	struct sink *sink = (struct sink *)context;
	struct sink_forward_target *sft = sink->sft;

	task->expire = TICK_ETERNITY;

	if (!stopping) {
		while (sft) {
			HA_SPIN_LOCK(SFT_LOCK, &sft->lock);
			/* if appctx is NULL, start a new session */
			if (!sft->appctx)
				sft->appctx = sink_forward_session_create(sink, sft);
			HA_SPIN_UNLOCK(SFT_LOCK, &sft->lock);
			sft = sft->next;
		}
	}
	else {
		while (sft) {
			HA_SPIN_LOCK(SFT_LOCK, &sft->lock);
			/* awake applet to perform a clean close */
			if (sft->appctx)
				appctx_wakeup(sft->appctx);
			HA_SPIN_UNLOCK(SFT_LOCK, &sft->lock);
			sft = sft->next;
		}
	}

	return task;
}
/*
 * Init task to manage connctions to forward servers
 *
 * returns 0 in case of error.
 */
int sink_init_forward(struct sink *sink)
{
	sink->forward_task = task_new_anywhere();
	if (!sink->forward_task)
		return 0;

	sink->forward_task->process = process_sink_forward;
	sink->forward_task->context = (void *)sink;
	sink->forward_sighandler = signal_register_task(0, sink->forward_task, 0);
	task_wakeup(sink->forward_task, TASK_WOKEN_INIT);
	return 1;
}

/* This tries to rotate a file-backed ring, but only if it contains contents.
 * This way empty rings will not cause backups to be overwritten and it's safe
 * to reload multiple times. That's only best effort, failures are silently
 * ignored.
 */
void sink_rotate_file_backed_ring(const char *name)
{
	struct ring ring;
	char *oldback;
	int ret;
	int fd;

	fd = open(name, O_RDONLY);
	if (fd < 0)
		return;

	/* check for contents validity */
	ret = read(fd, &ring, sizeof(ring));
	close(fd);

	if (ret != sizeof(ring))
		goto rotate;

	/* contents are present, we want to keep them => rotate. Note that
	 * an empty ring buffer has one byte (the marker).
	 */
	if (ring.buf.data > 1)
		goto rotate;

	/* nothing to keep, let's scratch the file and preserve the backup */
	return;

 rotate:
	oldback = NULL;
	memprintf(&oldback, "%s.bak", name);
	if (oldback) {
		/* try to rename any possibly existing ring file to
		 * ".bak" and delete remains of older ones. This will
		 * ensure we don't wipe useful debug info upon restart.
		 */
		unlink(oldback);
		if (rename(name, oldback) < 0)
			unlink(oldback);
		ha_free(&oldback);
	}
}

/*
 * Parse "ring" section and create corresponding sink buffer.
 *
 * The function returns 0 in success case, otherwise, it returns error
 * flags.
 */
int cfg_parse_ring(const char *file, int linenum, char **args, int kwm)
{
	int err_code = 0;
	const char *inv;
	size_t size = BUFSIZE;
	struct proxy *p;

	if (strcmp(args[0], "ring") == 0) { /* new ring section */
		if (!*args[1]) {
			ha_alert("parsing [%s:%d] : missing ring name.\n", file, linenum);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		inv = invalid_char(args[1]);
		if (inv) {
			ha_alert("parsing [%s:%d] : invalid ring name '%s' (character '%c' is not permitted).\n", file, linenum, args[1], *inv);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		if (sink_find(args[1])) {
			ha_alert("parsing [%s:%d] : sink named '%s' already exists.\n", file, linenum, args[1]);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		cfg_sink = sink_new_buf(args[1], args[1], LOG_FORMAT_RAW, size);
		if (!cfg_sink || cfg_sink->type != SINK_TYPE_BUFFER) {
			ha_alert("parsing [%s:%d] : unable to create a new sink buffer for ring '%s'.\n", file, linenum, args[1]);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		/* allocate new proxy to handle forwards */
		p = calloc(1, sizeof *p);
		if (!p) {
			ha_alert("parsing [%s:%d] : out of memory.\n", file, linenum);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		init_new_proxy(p);
		sink_setup_proxy(p);
		p->parent = cfg_sink;
		p->id = strdup(args[1]);
		p->conf.args.file = p->conf.file = strdup(file);
		p->conf.args.line = p->conf.line = linenum;
		cfg_sink->forward_px = p;
	}
	else if (strcmp(args[0], "size") == 0) {
		if (!cfg_sink || (cfg_sink->type != SINK_TYPE_BUFFER)) {
			ha_alert("parsing [%s:%d] : 'size' directive not usable with this type of sink.\n", file, linenum);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		size = atol(args[1]);
		if (!size) {
			ha_alert("parsing [%s:%d] : invalid size '%s' for new sink buffer.\n", file, linenum, args[1]);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		if (cfg_sink->store) {
			ha_alert("parsing [%s:%d] : cannot resize an already mapped file, please specify 'size' before 'backing-file'.\n", file, linenum);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		if (size < cfg_sink->ctx.ring->buf.size) {
			ha_warning("parsing [%s:%d] : ignoring new size '%llu' that is smaller than current size '%llu' for ring '%s'.\n",
				   file, linenum, (ullong)size, (ullong)cfg_sink->ctx.ring->buf.size, cfg_sink->name);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		if (!ring_resize(cfg_sink->ctx.ring, size)) {
			ha_alert("parsing [%s:%d] : fail to set sink buffer size '%llu' for ring '%s'.\n", file, linenum,
				 (ullong)cfg_sink->ctx.ring->buf.size, cfg_sink->name);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}
	}
	else if (strcmp(args[0], "backing-file") == 0) {
		/* This tries to mmap file <file> for size <size> and to use it as a backing store
		 * for ring <ring>. Existing data are delete. NULL is returned on error.
		 */
		const char *backing = args[1];
		size_t size;
		void *area;
		int fd;

		if (!cfg_sink || (cfg_sink->type != SINK_TYPE_BUFFER)) {
			ha_alert("parsing [%s:%d] : 'backing-file' only usable with existing rings.\n", file, linenum);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		if (cfg_sink->store) {
			ha_alert("parsing [%s:%d] : 'backing-file' already specified for ring '%s' (was '%s').\n", file, linenum, cfg_sink->name, cfg_sink->store);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		/* let's check if the file exists and is not empty. That's the
		 * only condition under which we'll trigger a rotate, so that
		 * config checks, reloads, or restarts that don't emit anything
		 * do not rotate it again.
		 */
		sink_rotate_file_backed_ring(backing);

		fd = open(backing, O_RDWR | O_CREAT, 0600);
		if (fd < 0) {
			ha_alert("parsing [%s:%d] : cannot open backing-file '%s' for ring '%s': %s.\n", file, linenum, backing, cfg_sink->name, strerror(errno));
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		size = (cfg_sink->ctx.ring->buf.size + 4095UL) & -4096UL;
		if (ftruncate(fd, size) != 0) {
			close(fd);
			ha_alert("parsing [%s:%d] : could not adjust size of backing-file for ring '%s': %s.\n", file, linenum, cfg_sink->name, strerror(errno));
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		area = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
		if (area == MAP_FAILED) {
			close(fd);
			ha_alert("parsing [%s:%d] : failed to use '%s' as a backing file for ring '%s': %s.\n", file, linenum, backing, cfg_sink->name, strerror(errno));
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		/* we don't need the file anymore */
		close(fd);
		cfg_sink->store = strdup(backing);

		/* never fails */
		ring_free(cfg_sink->ctx.ring);
		cfg_sink->ctx.ring = ring_make_from_area(area, size);
	}
	else if (strcmp(args[0],"server") == 0) {
		if (!cfg_sink || (cfg_sink->type != SINK_TYPE_BUFFER)) {
			ha_alert("parsing [%s:%d] : unable to create server '%s'.\n", file, linenum, args[1]);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		err_code |= parse_server(file, linenum, args, cfg_sink->forward_px, NULL,
		                         SRV_PARSE_PARSE_ADDR|SRV_PARSE_INITIAL_RESOLVE);
	}
	else if (strcmp(args[0],"timeout") == 0) {
		if (!cfg_sink || !cfg_sink->forward_px) {
			ha_alert("parsing [%s:%d] : unable to set timeout '%s'.\n", file, linenum, args[1]);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

                if (strcmp(args[1], "connect") == 0 ||
		    strcmp(args[1], "server") == 0) {
			const char *res;
			unsigned int tout;

			if (!*args[2]) {
				ha_alert("parsing [%s:%d] : '%s %s' expects <time> as argument.\n",
					 file, linenum, args[0], args[1]);
				err_code |= ERR_ALERT | ERR_FATAL;
				goto err;
			}
			res = parse_time_err(args[2], &tout, TIME_UNIT_MS);
			if (res == PARSE_TIME_OVER) {
				ha_alert("parsing [%s:%d]: timer overflow in argument <%s> to <%s %s>, maximum value is 2147483647 ms (~24.8 days).\n",
					 file, linenum, args[2], args[0], args[1]);
				err_code |= ERR_ALERT | ERR_FATAL;
				goto err;
			}
			else if (res == PARSE_TIME_UNDER) {
				ha_alert("parsing [%s:%d]: timer underflow in argument <%s> to <%s %s>, minimum non-null value is 1 ms.\n",
					 file, linenum, args[2], args[0], args[1]);
				err_code |= ERR_ALERT | ERR_FATAL;
				goto err;
			}
			else if (res) {
				ha_alert("parsing [%s:%d]: unexpected character '%c' in argument to <%s %s>.\n",
					 file, linenum, *res, args[0], args[1]);
				err_code |= ERR_ALERT | ERR_FATAL;
				goto err;
			}
                        if (args[1][0] == 'c')
                                cfg_sink->forward_px->timeout.connect = tout;
                        else
                                cfg_sink->forward_px->timeout.server = tout;
		}
	}
	else if (strcmp(args[0],"format") == 0) {
		if (!cfg_sink) {
			ha_alert("parsing [%s:%d] : unable to set format '%s'.\n", file, linenum, args[1]);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		cfg_sink->fmt = get_log_format(args[1]);
		if (cfg_sink->fmt == LOG_FORMAT_UNSPEC) {
			ha_alert("parsing [%s:%d] : unknown format '%s'.\n", file, linenum, args[1]);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}
	}
	else if (strcmp(args[0],"maxlen") == 0) {
		if (!cfg_sink) {
			ha_alert("parsing [%s:%d] : unable to set event max length '%s'.\n", file, linenum, args[1]);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		cfg_sink->maxlen = atol(args[1]);
		if (!cfg_sink->maxlen) {
			ha_alert("parsing [%s:%d] : invalid size '%s' for new sink buffer.\n", file, linenum, args[1]);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}
	}
	else if (strcmp(args[0],"description") == 0) {
		if (!cfg_sink) {
			ha_alert("parsing [%s:%d] : unable to set description '%s'.\n", file, linenum, args[1]);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		if (!*args[1]) {
			ha_alert("parsing [%s:%d] : missing ring description text.\n", file, linenum);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}

		free(cfg_sink->desc);

		cfg_sink->desc = strdup(args[1]);
		if (!cfg_sink->desc) {
			ha_alert("parsing [%s:%d] : fail to set description '%s'.\n", file, linenum, args[1]);
			err_code |= ERR_ALERT | ERR_FATAL;
			goto err;
		}
	}
	else {
		ha_alert("parsing [%s:%d] : unknown statement '%s'.\n", file, linenum, args[0]);
		err_code |= ERR_ALERT | ERR_FATAL;
		goto err;
	}

err:
	return err_code;
}

/* Creates an new sink buffer from a log server.
 *
 * It uses the logsrvaddress to declare a forward
 * server for this buffer. And it initializes the
 * forwarding.
 *
 * The function returns a pointer on the
 * allocated struct sink if allocate
 * and initialize succeed, else if it fails
 * it returns NULL.
 *
 * Note: the sink is created using the name
 *       specified into logsrv->ring_name
 */
struct sink *sink_new_from_logsrv(struct logsrv *logsrv)
{
	struct proxy *p = NULL;
	struct sink *sink = NULL;
	struct server *srv = NULL;
	struct sink_forward_target *sft = NULL;

	/* allocate new proxy to handle
	 * forward to a stream server
	 */
	p = calloc(1, sizeof *p);
	if (!p) {
		goto error;
        }

	init_new_proxy(p);
	sink_setup_proxy(p);
	p->id = strdup(logsrv->ring_name);
	p->conf.args.file = p->conf.file = strdup(logsrv->conf.file);
	p->conf.args.line = p->conf.line = logsrv->conf.line;

	/* Set default connect and server timeout */
	p->timeout.connect = MS_TO_TICKS(1000);
	p->timeout.server = MS_TO_TICKS(5000);

	/* allocate a new server to forward messages
	 * from ring buffer
	 */
	srv = new_server(p);
	if (!srv)
		goto error;

	/* init server */
	srv->id = strdup(logsrv->ring_name);
	srv->conf.file = strdup(logsrv->conf.file);
	srv->conf.line = logsrv->conf.line;
	srv->addr = logsrv->addr;
        srv->svc_port = get_host_port(&logsrv->addr);
	HA_SPIN_INIT(&srv->lock);

	/* process per thread init */
	if (srv_init_per_thr(srv) == -1)
		goto error;

	/* the servers are linked backwards
	 * first into proxy
	 */
	p->srv = srv;
	srv->next = p->srv;

	/* allocate sink_forward_target descriptor */
	sft = calloc(1, sizeof(*sft));
	if (!sft)
		goto error;

	/* init sink_forward_target offset */
	sft->srv = srv;
	sft->appctx = NULL;
	sft->ofs = ~0;
	HA_SPIN_INIT(&sft->lock);

	/* prepare description for the sink */
	chunk_reset(&trash);
	chunk_printf(&trash, "created from logserver declared into '%s' at line %d", logsrv->conf.file, logsrv->conf.line);

	/* allocate a new sink buffer */
	sink = sink_new_buf(logsrv->ring_name, trash.area, logsrv->format, BUFSIZE);
	if (!sink || sink->type != SINK_TYPE_BUFFER) {
		goto error;
	}

	/* link sink_forward_target to proxy */
	sink->forward_px = p;
	p->parent = sink;

	/* insert into sink_forward_targets
	 * list into sink
	 */
	sft->sink = sink;
	sft->next = sink->sft;
	sink->sft = sft;

	/* mark server as an attached reader to the ring */
	if (!ring_attach(sink->ctx.ring)) {
		/* should never fail since there is
		 * only one reader
		 */
		goto error;
	}

	/* initialize sink buffer forwarding */
	if (!sink_init_forward(sink))
		goto error;

	/* reset familyt of logsrv to consider the ring buffer target */
	logsrv->addr.ss_family = AF_UNSPEC;

	return sink;
error:
	if (p) {
		if (p->id)
			free(p->id);
		if (p->conf.file)
			free(p->conf.file);

		free(p);
	}

	if (srv) {
		if (srv->id)
			free(srv->id);
		if (srv->conf.file)
			free((void *)srv->conf.file);
		if (srv->per_thr)
		       free(srv->per_thr);
		free(srv);
	}

	if (sft)
		free(sft);

	if (sink) {
		if (sink->ctx.ring)
			ring_free(sink->ctx.ring);

		LIST_DELETE(&sink->sink_list);
		free(sink->name);
		free(sink->desc);
		free(sink);
	}

	return NULL;
}

/*
 * Post parsing "ring" section.
 *
 * The function returns 0 in success case, otherwise, it returns error
 * flags.
 */
int cfg_post_parse_ring()
{
	int err_code = 0;
	struct server *srv;

	if (cfg_sink && (cfg_sink->type == SINK_TYPE_BUFFER)) {
		if (cfg_sink->maxlen > b_size(&cfg_sink->ctx.ring->buf)) {
			ha_warning("ring '%s' event max length '%u' exceeds size, forced to size '%lu'.\n",
			           cfg_sink->name, cfg_sink->maxlen, (unsigned long)b_size(&cfg_sink->ctx.ring->buf));
			cfg_sink->maxlen = b_size(&cfg_sink->ctx.ring->buf);
			err_code |= ERR_ALERT;
		}

		/* prepare forward server descriptors */
		if (cfg_sink->forward_px) {
			srv = cfg_sink->forward_px->srv;
			while (srv) {
				struct sink_forward_target *sft;

				/* allocate sink_forward_target descriptor */
				sft = calloc(1, sizeof(*sft));
				if (!sft) {
					ha_alert("memory allocation error initializing server '%s' in ring '%s'.\n",srv->id, cfg_sink->name);
					err_code |= ERR_ALERT | ERR_FATAL;
					break;
				}
				sft->srv = srv;
				sft->appctx = NULL;
				sft->ofs = ~0; /* init ring offset */
				sft->sink = cfg_sink;
				sft->next = cfg_sink->sft;
				HA_SPIN_INIT(&sft->lock);

				/* mark server attached to the ring */
				if (!ring_attach(cfg_sink->ctx.ring)) {
					ha_alert("server '%s' sets too many watchers > 255 on ring '%s'.\n", srv->id, cfg_sink->name);
					err_code |= ERR_ALERT | ERR_FATAL;
				}
				cfg_sink->sft = sft;
				srv = srv->next;
			}
			sink_init_forward(cfg_sink);
		}
	}
	cfg_sink = NULL;

	return err_code;
}

/* resolve sink names at end of config. Returns 0 on success otherwise error
 * flags.
*/
int post_sink_resolve()
{
	int err_code = ERR_NONE;
	struct logsrv *logsrv, *logb;
	struct sink *sink;
	struct proxy *px;

	list_for_each_entry_safe(logsrv, logb, &global.logsrvs, list) {
		if (logsrv->type == LOG_TARGET_BUFFER) {
			sink = sink_find(logsrv->ring_name);
			if (!sink) {
				/* LOG_TARGET_BUFFER but !AF_UNSPEC
				 * means we must allocate a sink
				 * buffer to send messages to this logsrv
				 */
				if (logsrv->addr.ss_family != AF_UNSPEC) {
					sink = sink_new_from_logsrv(logsrv);
					if (!sink) {
						ha_alert("global stream log server declared in file '%s' at line %d cannot be initialized'.\n",
						         logsrv->conf.file, logsrv->conf.line);
						err_code |= ERR_ALERT | ERR_FATAL;
					}
				}
				else {
					ha_alert("global log server declared in file '%s' at line %d uses unknown ring named '%s'.\n",
					         logsrv->conf.file, logsrv->conf.line, logsrv->ring_name);
					err_code |= ERR_ALERT | ERR_FATAL;
				}
			}
			else if (sink->type != SINK_TYPE_BUFFER) {
				ha_alert("global log server declared in file '%s' at line %d uses incompatible ring '%s'.\n",
				         logsrv->conf.file, logsrv->conf.line, logsrv->ring_name);
				err_code |= ERR_ALERT | ERR_FATAL;
			}
			logsrv->sink = sink;
		}

	}

	for (px = proxies_list; px; px = px->next) {
		list_for_each_entry_safe(logsrv, logb, &px->logsrvs, list) {
			if (logsrv->type == LOG_TARGET_BUFFER) {
				sink = sink_find(logsrv->ring_name);
				if (!sink) {
					/* LOG_TARGET_BUFFER but !AF_UNSPEC
					 * means we must allocate a sink
					 * buffer to send messages to this logsrv
					 */
					if (logsrv->addr.ss_family != AF_UNSPEC) {
						sink = sink_new_from_logsrv(logsrv);
						if (!sink) {
							ha_alert("log server declared in proxy section '%s' file '%s' at line %d cannot be initialized'.\n",
							         px->id, logsrv->conf.file, logsrv->conf.line);
							err_code |= ERR_ALERT | ERR_FATAL;
						}
					}
					else {
						ha_alert("log server declared in proxy section '%s' in file '%s' at line %d uses unknown ring named '%s'.\n",
						         px->id, logsrv->conf.file, logsrv->conf.line, logsrv->ring_name);
						err_code |= ERR_ALERT | ERR_FATAL;
					}
				}
				else if (sink->type != SINK_TYPE_BUFFER) {
					ha_alert("log server declared in proxy section '%s' in file '%s' at line %d uses incomatible ring named '%s'.\n",
					         px->id, logsrv->conf.file, logsrv->conf.line, logsrv->ring_name);
					err_code |= ERR_ALERT | ERR_FATAL;
				}
				logsrv->sink = sink;
			}
		}
	}

	for (px = cfg_log_forward; px; px = px->next) {
		list_for_each_entry_safe(logsrv, logb, &px->logsrvs, list) {
			if (logsrv->type == LOG_TARGET_BUFFER) {
				sink = sink_find(logsrv->ring_name);
				if (!sink) {
					/* LOG_TARGET_BUFFER but !AF_UNSPEC
					 * means we must allocate a sink
					 * buffer to send messages to this logsrv
					 */
					if (logsrv->addr.ss_family != AF_UNSPEC) {
						sink = sink_new_from_logsrv(logsrv);
						if (!sink) {
							ha_alert("log server declared in log-forward section '%s' file '%s' at line %d cannot be initialized'.\n",
							         px->id, logsrv->conf.file, logsrv->conf.line);
							err_code |= ERR_ALERT | ERR_FATAL;
						}
					}
					else {
						ha_alert("log server declared in log-forward section '%s' in file '%s' at line %d uses unknown ring named '%s'.\n",
							 px->id, logsrv->conf.file, logsrv->conf.line, logsrv->ring_name);
						err_code |= ERR_ALERT | ERR_FATAL;
					}
				}
				else if (sink->type != SINK_TYPE_BUFFER) {
					ha_alert("log server declared in log-forward section '%s' in file '%s' at line %d uses unknown ring named '%s'.\n",
						 px->id, logsrv->conf.file, logsrv->conf.line, logsrv->ring_name);
					err_code |= ERR_ALERT | ERR_FATAL;
				}
				logsrv->sink = sink;
			}
		}
	}
	return err_code;
}


static void sink_init()
{
	sink_new_fd("stdout", "standard output (fd#1)", LOG_FORMAT_RAW, 1);
	sink_new_fd("stderr", "standard output (fd#2)", LOG_FORMAT_RAW, 2);
	sink_new_buf("buf0",  "in-memory ring buffer", LOG_FORMAT_TIMED, 1048576);
}

static void sink_deinit()
{
	struct sink *sink, *sb;

	list_for_each_entry_safe(sink, sb, &sink_list, sink_list) {
		if (sink->type == SINK_TYPE_BUFFER) {
			if (sink->store) {
				size_t size = (sink->ctx.ring->buf.size + 4095UL) & -4096UL;
				void *area = (sink->ctx.ring->buf.area - sizeof(*sink->ctx.ring));

				msync(area, size, MS_SYNC);
				munmap(area, size);
				ha_free(&sink->store);
			}
			else
				ring_free(sink->ctx.ring);
		}
		LIST_DELETE(&sink->sink_list);
		task_destroy(sink->forward_task);
		free(sink->name);
		free(sink->desc);
		free(sink);
	}
}

INITCALL0(STG_REGISTER, sink_init);
REGISTER_POST_DEINIT(sink_deinit);

static struct cli_kw_list cli_kws = {{ },{
	{ { "show", "events", NULL }, "show events [<sink>] [-w] [-n]          : show event sink state", cli_parse_show_events, NULL, NULL },
	{{},}
}};

INITCALL1(STG_REGISTER, cli_register_kw, &cli_kws);

/* config parsers for this section */
REGISTER_CONFIG_SECTION("ring", cfg_parse_ring, cfg_post_parse_ring);
REGISTER_POST_CHECK(post_sink_resolve);

/*
 * Local variables:
 *  c-indent-level: 8
 *  c-basic-offset: 8
 * End:
 */