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/* Listen queue functions
Copyright (C) 1995 Free Software Foundation, Inc.
Written by Miles Bader <miles@gnu.ai.mit.edu>
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 2, 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, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
#include <socket.h>
#include "pflocal.h"
/* A queue for queueing incoming connections. */
struct listenq
{
/* True if all connection requests should be treated as non-blocking. */
int noqueue;
/* The connection request queue. */
unsigned length;
unsigned head, tail;
struct listenq_request *queue;
/* Threads that have done an accept on this queue wait on this condition. */
struct condition listeners;
unsigned num_listeners;
struct mutex lock;
}
/* ---------------------------------------------------------------- */
/* A data block allocated by a thread waiting on a listenq, which is used to
get information from and to the thread. */
struct listenq_request
{
/* The socket that's waiting to connect. */
struct sock *sock;
/* What the waiting thread blocks on. */
struct condition signal;
struct mutex lock;
/* Set to true when this request has been dealt with, to guard against
spurious conditions being signaled. */
int completed;
/* After the waiting thread is unblocked, this is the result, either 0 if
SOCK has been connected, or an error. */
error_t err;
};
static inline void
listenq_request_init (struct sock *sock, struct listenq_request *lqr)
{
lqr->err = 0;
lqr->sock = sock;
lqr->completed = 0;
condition_init (&lqr->signal);
mutex_init (&lqr->lock);
}
/* ---------------------------------------------------------------- */
/* Create a new listening queue, returning it in LQ. The resulting queue
will be of zero length, that is it won't allow connections unless someone
is already listening (change this with listenq_set_length). */
error_t
listenq_create (struct listenq **lq)
{
struct listenq *new = malloc (sizeof (struct listenq));
if (!new)
return ENOMEM;
new->noqueue = 1; /* By default, don't queue requests. */
new->length = 0;
new->head = new->tail = 0;
new->queue = NULL;
new->num_listeners = 0;
mutex_init (&new->lock);
condition_init (&new->listeners);
*lq = new;
return 0;
}
/* ---------------------------------------------------------------- */
/* Wait for a connection attempt to be made on LQ, and return the connecting
socket in SOCK, and a request tag in REQ. listenq_request_complete must be
call on REQ to allow the requesting thread to continue. If NOBLOCK is
true, then return EWOULDBLOCK immediately when there are no immediate
connections available. */
error_t
listenq_listen (struct listenq *lq, int noblock,
struct sock **sock, struct listenq_request **req)
{
error_t err = 0;
mutex_lock (&lq->lock);
if (noblock && lq->head == lq->tail)
return EWOULDBLOCK;
lq->num_listeners++;
while (lq->head == lq->tail)
condition_wait (&lq->listeners, &lq->lock);
/* Dequeue the next request. */
*req = lq->queue[lq->tail];
lq->tail = (lq->tail + 1 == lq->length ? 0 : lq->tail + 1);
mutex_lock (&(*req)->lock);
lq->num_listeners--;
mutex_unlock (&lq->lock);
*sock = (*req)->sock;
return 0;
}
/* Return the error code ERR to the thread that made the listen request REQ,
returned from a previous listenq_listen. */
void
listenq_request_complete (struct listenq_request *req, error_t err)
{
req->err = err;
req->complete = 1;
condition_signal (&req->signal, &req->lock);
}
/* Try to connect SOCK with the socket listening on LQ. If NOBLOCK is true,
then return EWOULDBLOCK immediately when there are no immediate
connections available. */
error_t
listenq_connect (struct listenq *lq, int noblock, struct sock *sock)
{
error_t err = 0;
struct listenq_request req;
unsigned next;
mutex_lock (&lq->lock);
if ((noblock || lq->noqueue) && lq->num_listeners == 0)
return EWOULDBLOCK;
next = (lq->head + 1 == lq->length ? 0 : lq->head + 1);
if (next == lq->tail)
err = ECONNREFUSED;
else
{
lq->queue[lq->head] = &req;
lq->head = next;
}
/* Hold REQ.LOCK before we signal the condition so that we're sure to be
woken up. */
mutex_lock (&req.lock);
condition_signal (&lq->listeners, &lq->lock);
while (!req.completed)
condition_wait (&req.signal, &req.lock);
return req.err;
}
/* Set LQ's queue length to LENGTH. Any sockets already waiting for a
connections that are past the new length will fail with ECONNREFUSED. */
error_t
listenq_set_length (struct listenq *lq, int length)
{
int excess;
mutex_lock (&lq->lock);
lq->noqueue = 0; /* Turn on queueing. */
/* Force any excess requests to fail. */
excess = lq->length - length;
while (excess-- > 0)
{
assert (lq->head != lq->tail);
lq->head = (lq->head == 0 ? lq->length - 1 : lq->head - 1);
listenq_request_complete (lq->queue[lq->head], ECONNREFUSED);
}
/* ... */
}
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