samba-mirror/ctdb/common/ctdb_io.c

/* 
   ctdb database library
   Utility functions to read/write blobs of data from a file descriptor
   and handle the case where we might need multiple read/writes to get all the
   data.

   Copyright (C) Andrew Tridgell  2006

   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 "includes.h"
#include "lib/tdb/include/tdb.h"
#include "lib/events/events.h"
#include "lib/util/dlinklist.h"
#include "system/network.h"
#include "system/filesys.h"
#include "../include/ctdb_private.h"
#include "../include/ctdb.h"

/* structures for packet queueing - see common/ctdb_io.c */
struct ctdb_partial {
	uint8_t *data;
	uint32_t length;
};

struct ctdb_queue_pkt {
	struct ctdb_queue_pkt *next, *prev;
	uint8_t *data;
	uint32_t length;
	uint32_t full_length;
};

struct ctdb_queue {
	struct ctdb_context *ctdb;
	struct ctdb_partial partial; /* partial input packet */
	struct ctdb_queue_pkt *out_queue;
	/* This field is used to track the last added item so we
	   can append new items to the end cheaply.
	   This relies of that items are always appended to the tail
	   and that when reamoving items we only remove the head.
	*/
	struct ctdb_queue_pkt *out_queue_last_added;
	uint32_t out_queue_length;
	struct fd_event *fde;
	int fd;
	size_t alignment;
	void *private_data;
	ctdb_queue_cb_fn_t callback;
	bool *destroyed;
};



int ctdb_queue_length(struct ctdb_queue *queue)
{
	return queue->out_queue_length;
}

/*
  called when an incoming connection is readable
*/
static void queue_io_read(struct ctdb_queue *queue)
{
	int num_ready = 0;
	ssize_t nread;
	uint8_t *data, *data_base;

	if (ioctl(queue->fd, FIONREAD, &num_ready) != 0) {
		return;
	}
	if (num_ready == 0) {
		/* the descriptor has been closed */
		goto failed;
	}


	queue->partial.data = talloc_realloc_size(queue, queue->partial.data, 
						  num_ready + queue->partial.length);

	if (queue->partial.data == NULL) {
		DEBUG(DEBUG_ERR,("read error alloc failed for %u\n", 
			 num_ready + queue->partial.length));
		goto failed;
	}

	nread = read(queue->fd, queue->partial.data + queue->partial.length, num_ready);
	if (nread <= 0) {
		DEBUG(DEBUG_ERR,("read error nread=%d\n", (int)nread));
		goto failed;
	}


	data = queue->partial.data;
	nread += queue->partial.length;

	queue->partial.data = NULL;
	queue->partial.length = 0;

	if (nread >= 4 && *(uint32_t *)data == nread) {
		/* it is the responsibility of the incoming packet
		 function to free 'data' */
		queue->callback(data, nread, queue->private_data);
		return;
	}

	data_base = data;

	while (nread >= 4 && *(uint32_t *)data <= nread) {
		/* we have at least one packet */
		uint8_t *d2;
		uint32_t len;
		bool destroyed = false;

		len = *(uint32_t *)data;
		if (len == 0) {
			/* bad packet! treat as EOF */
			DEBUG(DEBUG_CRIT,("Invalid packet of length 0\n"));
			goto failed;
		}
		d2 = talloc_memdup(queue, data, len);
		if (d2 == NULL) {
			DEBUG(DEBUG_ERR,("read error memdup failed for %u\n", len));
			/* sigh */
			goto failed;
		}

		queue->destroyed = &destroyed;
		queue->callback(d2, len, queue->private_data);
		/* If callback freed us, don't do anything else. */
		if (destroyed) {
			return;
		}
		queue->destroyed = NULL;

		data += len;
		nread -= len;		
	}

	if (nread > 0) {
		/* we have only part of a packet */
		if (data_base == data) {
			queue->partial.data = data;
			queue->partial.length = nread;
		} else {
			queue->partial.data = talloc_memdup(queue, data, nread);
			if (queue->partial.data == NULL) {
				DEBUG(DEBUG_ERR,("read error memdup partial failed for %u\n", 
					 (unsigned)nread));
				goto failed;
			}
			queue->partial.length = nread;
			talloc_free(data_base);
		}
		return;
	}

	talloc_free(data_base);
	return;

failed:
	queue->callback(NULL, 0, queue->private_data);
}


/* used when an event triggers a dead queue */
static void queue_dead(struct event_context *ev, struct timed_event *te, 
		       struct timeval t, void *private_data)
{
	struct ctdb_queue *queue = talloc_get_type(private_data, struct ctdb_queue);
	queue->callback(NULL, 0, queue->private_data);
}


/*
  called when an incoming connection is writeable
*/
static void queue_io_write(struct ctdb_queue *queue)
{
	while (queue->out_queue) {
		struct ctdb_queue_pkt *pkt = queue->out_queue;
		ssize_t n;
		if (queue->ctdb->flags & CTDB_FLAG_TORTURE) {
			n = write(queue->fd, pkt->data, 1);
		} else {
			n = write(queue->fd, pkt->data, pkt->length);
		}

		if (n == -1 && errno != EAGAIN && errno != EWOULDBLOCK) {
			if (pkt->length != pkt->full_length) {
				/* partial packet sent - we have to drop it */
				DLIST_REMOVE(queue->out_queue, pkt);
				queue->out_queue_length--;
				talloc_free(pkt);
			}
			talloc_free(queue->fde);
			queue->fde = NULL;
			queue->fd = -1;
			event_add_timed(queue->ctdb->ev, queue, timeval_zero(), 
					queue_dead, queue);
			return;
		}
		if (n <= 0) return;
		
		if (n != pkt->length) {
			pkt->length -= n;
			pkt->data += n;
			return;
		}

		DLIST_REMOVE(queue->out_queue, pkt);
		queue->out_queue_length--;
		talloc_free(pkt);
	}

	EVENT_FD_NOT_WRITEABLE(queue->fde);
}

/*
  called when an incoming connection is readable or writeable
*/
static void queue_io_handler(struct event_context *ev, struct fd_event *fde, 
			     uint16_t flags, void *private_data)
{
	struct ctdb_queue *queue = talloc_get_type(private_data, struct ctdb_queue);

	if (flags & EVENT_FD_READ) {
		queue_io_read(queue);
	} else {
		queue_io_write(queue);
	}
}


/*
  queue a packet for sending
*/
int ctdb_queue_send(struct ctdb_queue *queue, uint8_t *data, uint32_t length)
{
	struct ctdb_queue_pkt *pkt;
	uint32_t length2, full_length;

	if (queue->alignment) {
		/* enforce the length and alignment rules from the tcp packet allocator */
		length2 = (length+(queue->alignment-1)) & ~(queue->alignment-1);
		*(uint32_t *)data = length2;
	} else {
		length2 = length;
	}

	if (length2 != length) {
		memset(data+length, 0, length2-length);
	}

	full_length = length2;
	
	/* if the queue is empty then try an immediate write, avoiding
	   queue overhead. This relies on non-blocking sockets */
	if (queue->out_queue == NULL && queue->fd != -1 &&
	    !(queue->ctdb->flags & CTDB_FLAG_TORTURE)) {
		ssize_t n = write(queue->fd, data, length2);
		if (n == -1 && errno != EAGAIN && errno != EWOULDBLOCK) {
			talloc_free(queue->fde);
			queue->fde = NULL;
			queue->fd = -1;
			event_add_timed(queue->ctdb->ev, queue, timeval_zero(), 
					queue_dead, queue);
			/* yes, we report success, as the dead node is 
			   handled via a separate event */
			return 0;
		}
		if (n > 0) {
			data += n;
			length2 -= n;
		}
		if (length2 == 0) return 0;
	}

	pkt = talloc(queue, struct ctdb_queue_pkt);
	CTDB_NO_MEMORY(queue->ctdb, pkt);

	pkt->data = talloc_memdup(pkt, data, length2);
	CTDB_NO_MEMORY(queue->ctdb, pkt->data);

	pkt->length = length2;
	pkt->full_length = full_length;

	if (queue->out_queue == NULL && queue->fd != -1) {
		EVENT_FD_WRITEABLE(queue->fde);
	}

	/* This relies on that when adding items to the queue, we always add
	   them to the tail and that when removing items we only remove
	   the head of queue item.
	   The last_added item thus allows non n^2 behaviour when appending to
	   very long queues.
	*/
	if (queue->out_queue == NULL) {
		DLIST_ADD(queue->out_queue, pkt);
	} else {
		DLIST_ADD_END(queue->out_queue_last_added, pkt, struct ctdb_queue_pkt *);
	}
	queue->out_queue_last_added = pkt;
	queue->out_queue_length++;

	if (queue->ctdb->tunable.verbose_memory_names != 0) {
		struct ctdb_req_header *hdr = (struct ctdb_req_header *)pkt->data;
		switch (hdr->operation) {
		case CTDB_REQ_CONTROL: {
			struct ctdb_req_control *c = (struct ctdb_req_control *)hdr;
			talloc_set_name(pkt, "ctdb_queue_pkt: control opcode=%u srvid=%llu datalen=%u",
					(unsigned)c->opcode, (unsigned long long)c->srvid, (unsigned)c->datalen);
			break;
		}
		case CTDB_REQ_MESSAGE: {
			struct ctdb_req_message *m = (struct ctdb_req_message *)hdr;
			talloc_set_name(pkt, "ctdb_queue_pkt: message srvid=%llu datalen=%u",
					(unsigned long long)m->srvid, (unsigned)m->datalen);
			break;
		}
		default:
			talloc_set_name(pkt, "ctdb_queue_pkt: operation=%u length=%u src=%u dest=%u",
					(unsigned)hdr->operation, (unsigned)hdr->length, 
					(unsigned)hdr->srcnode, (unsigned)hdr->destnode);
			break;
		}
	}

	return 0;
}


/*
  setup the fd used by the queue
 */
int ctdb_queue_set_fd(struct ctdb_queue *queue, int fd)
{
	queue->fd = fd;
	talloc_free(queue->fde);
	queue->fde = NULL;

	if (fd != -1) {
		queue->fde = event_add_fd(queue->ctdb->ev, queue, fd, EVENT_FD_READ|EVENT_FD_AUTOCLOSE, 
					  queue_io_handler, queue);
		if (queue->fde == NULL) {
			return -1;
		}

		if (queue->out_queue) {
			EVENT_FD_WRITEABLE(queue->fde);		
		}
	}

	return 0;
}

/* If someone sets up this pointer, they want to know if the queue is freed */
static int queue_destructor(struct ctdb_queue *queue)
{
	if (queue->destroyed != NULL)
		*queue->destroyed = true;
	return 0;
}

/*
  setup a packet queue on a socket
 */
struct ctdb_queue *ctdb_queue_setup(struct ctdb_context *ctdb,
				    TALLOC_CTX *mem_ctx, int fd, int alignment,
				    
				    ctdb_queue_cb_fn_t callback,
				    void *private_data)
{
	struct ctdb_queue *queue;

	queue = talloc_zero(mem_ctx, struct ctdb_queue);
	CTDB_NO_MEMORY_NULL(ctdb, queue);

	queue->ctdb = ctdb;
	queue->fd = fd;
	queue->alignment = alignment;
	queue->private_data = private_data;
	queue->callback = callback;
	if (fd != -1) {
		if (ctdb_queue_set_fd(queue, fd) != 0) {
			talloc_free(queue);
			return NULL;
		}
	}
	talloc_set_destructor(queue, queue_destructor);

	return queue;
}