call clientWriteComplete so the client socket gets closed

[thirdparty/squid.git] / src / comm.cc

/*
 * $Id: comm.cc,v 1.238 1998/03/27 19:42:22 wessels Exp $
 *
 * DEBUG: section 5     Socket Functions
 * AUTHOR: Harvest Derived
 *
 * SQUID Internet Object Cache  http://squid.nlanr.net/Squid/
 * --------------------------------------------------------
 *
 *  Squid is the result of efforts by numerous individuals from the
 *  Internet community.  Development is led by Duane Wessels of the
 *  National Laboratory for Applied Network Research and funded by
 *  the National Science Foundation.
 *
 *  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 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, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *  
 */

/*
 * Copyright (c) 1994, 1995.  All rights reserved.
 *  
 *   The Harvest software was developed by the Internet Research Task
 *   Force Research Group on Resource Discovery (IRTF-RD):
 *  
 *         Mic Bowman of Transarc Corporation.
 *         Peter Danzig of the University of Southern California.
 *         Darren R. Hardy of the University of Colorado at Boulder.
 *         Udi Manber of the University of Arizona.
 *         Michael F. Schwartz of the University of Colorado at Boulder.
 *         Duane Wessels of the University of Colorado at Boulder.
 *  
 *   This copyright notice applies to software in the Harvest
 *   ``src/'' directory only.  Users should consult the individual
 *   copyright notices in the ``components/'' subdirectories for
 *   copyright information about other software bundled with the
 *   Harvest source code distribution.
 *  
 * TERMS OF USE
 *   
 *   The Harvest software may be used and re-distributed without
 *   charge, provided that the software origin and research team are
 *   cited in any use of the system.  Most commonly this is
 *   accomplished by including a link to the Harvest Home Page
 *   (http://harvest.cs.colorado.edu/) from the query page of any
 *   Broker you deploy, as well as in the query result pages.  These
 *   links are generated automatically by the standard Broker
 *   software distribution.
 *   
 *   The Harvest software is provided ``as is'', without express or
 *   implied warranty, and with no support nor obligation to assist
 *   in its use, correction, modification or enhancement.  We assume
 *   no liability with respect to the infringement of copyrights,
 *   trade secrets, or any patents, and are not responsible for
 *   consequential damages.  Proper use of the Harvest software is
 *   entirely the responsibility of the user.
 *  
 * DERIVATIVE WORKS
 *  
 *   Users may make derivative works from the Harvest software, subject 
 *   to the following constraints:
 *  
 *     - You must include the above copyright notice and these 
 *       accompanying paragraphs in all forms of derivative works, 
 *       and any documentation and other materials related to such 
 *       distribution and use acknowledge that the software was 
 *       developed at the above institutions.
 *  
 *     - You must notify IRTF-RD regarding your distribution of 
 *       the derivative work.
 *  
 *     - You must clearly notify users that your are distributing 
 *       a modified version and not the original Harvest software.
 *  
 *     - Any derivative product is also subject to these copyright 
 *       and use restrictions.
 *  
 *   Note that the Harvest software is NOT in the public domain.  We
 *   retain copyright, as specified above.
 *  
 * HISTORY OF FREE SOFTWARE STATUS
 *  
 *   Originally we required sites to license the software in cases
 *   where they were going to build commercial products/services
 *   around Harvest.  In June 1995 we changed this policy.  We now
 *   allow people to use the core Harvest software (the code found in
 *   the Harvest ``src/'' directory) for free.  We made this change
 *   in the interest of encouraging the widest possible deployment of
 *   the technology.  The Harvest software is really a reference
 *   implementation of a set of protocols and formats, some of which
 *   we intend to standardize.  We encourage commercial
 *   re-implementations of code complying to this set of standards.  
 */

#include "squid.h"
#include <errno.h>

#ifdef HAVE_NETINET_TCP_H
#include <netinet/tcp.h>
#endif

typedef struct {
    char *host;
    u_short port;
    struct sockaddr_in S;
    CNCB *callback;
    void *data;
    struct in_addr in_addr;
    int locks;
    int fd;
    int tries;
    int addrcount;
    int connstart;
} ConnectStateData;

/* STATIC */
static int polledinc = 0;
static int commBind(int s, struct in_addr, u_short port);
#if !HAVE_POLL
static int examine_select(fd_set *, fd_set *);
#endif
static void checkTimeouts(void);
static void commSetReuseAddr(int);
static void commSetNoLinger(int);
#if HAVE_POLL
static void comm_poll_incoming(void);
#else
static void comm_select_incoming(void);
#endif
static void CommWriteStateCallbackAndFree(int fd, int code);
#ifdef TCP_NODELAY
static void commSetTcpNoDelay(int);
#endif
static void commSetTcpRcvbuf(int, int);
static PF commConnectFree;
static PF commConnectHandle;
static PF commHandleWrite;
static int fdIsHttpOrIcp(int fd);
static IPH commConnectDnsHandle;
static void commConnectCallback(ConnectStateData * cs, int status);
static int commDeferRead(int fd);
static void commSetConnectTimeout(int fd, time_t timeout);
static int commResetFD(ConnectStateData * cs);
static int commRetryConnect(ConnectStateData * cs);
static time_t commBackoffTimeout(int);

static struct timeval zero_tv;

static void
CommWriteStateCallbackAndFree(int fd, int code)
{
    CommWriteStateData *CommWriteState = fd_table[fd].rwstate;
    CWCB *callback = NULL;
    void *data;
    fd_table[fd].rwstate = NULL;
    if (CommWriteState == NULL)
	return;
    if (CommWriteState->free_func) {
	CommWriteState->free_func(CommWriteState->buf);
	CommWriteState->buf = NULL;
    }
    callback = CommWriteState->handler;
    data = CommWriteState->handler_data;
    CommWriteState->handler = NULL;
    if (callback && cbdataValid(data))
	callback(fd, CommWriteState->buf, CommWriteState->offset, code, data);
    cbdataUnlock(data);
    safe_free(CommWriteState);
}

/* Return the local port associated with fd. */
u_short
comm_local_port(int fd)
{
    struct sockaddr_in addr;
    int addr_len = 0;
    fde *F = &fd_table[fd];

    /* If the fd is closed already, just return */
    if (!F->open) {
	debug(5, 0) ("comm_local_port: FD %d has been closed.\n", fd);
	return 0;
    }
    if (F->local_port)
	return F->local_port;
    addr_len = sizeof(addr);
    if (getsockname(fd, (struct sockaddr *) &addr, &addr_len)) {
	debug(50, 1) ("comm_local_port: Failed to retrieve TCP/UDP port number for socket: FD %d: %s\n", fd, xstrerror());
	return 0;
    }
    debug(5, 6) ("comm_local_port: FD %d: sockaddr %u.\n", fd, addr.sin_addr.s_addr);
    F->local_port = ntohs(addr.sin_port);
    return F->local_port;
}

static int
commBind(int s, struct in_addr in_addr, u_short port)
{
    struct sockaddr_in S;

    memset(&S, '\0', sizeof(S));
    S.sin_family = AF_INET;
    S.sin_port = htons(port);
    S.sin_addr = in_addr;
    if (bind(s, (struct sockaddr *) &S, sizeof(S)) == 0)
	return COMM_OK;
    debug(50, 0) ("commBind: Cannot bind socket FD %d to %s:%d: %s\n",
	s,
	S.sin_addr.s_addr == INADDR_ANY ? "*" : inet_ntoa(S.sin_addr),
	(int) port,
	xstrerror());
    return COMM_ERROR;
}

/* Create a socket. Default is blocking, stream (TCP) socket.  IO_TYPE
 * is OR of flags specified in comm.h. */
int
comm_open(int sock_type,
    int proto,
    struct in_addr addr,
    u_short port,
    int flags,
    const char *note)
{
    int new_socket;
    fde *F = NULL;
    int tcp_rcv_bufsz = Config.tcpRcvBufsz;

    /* Create socket for accepting new connections. */
    if ((new_socket = socket(AF_INET, sock_type, proto)) < 0) {
	/* Increase the number of reserved fd's if calls to socket()
	 * are failing because the open file table is full.  This
	 * limits the number of simultaneous clients */
	switch (errno) {
	case ENFILE:
	case EMFILE:
	    debug(50, 1) ("comm_open: socket failure: %s\n", xstrerror());
	    break;
	default:
	    debug(50, 0) ("comm_open: socket failure: %s\n", xstrerror());
	}
	fdAdjustReserved();
	return -1;
    }
    /* update fdstat */
    debug(5, 5) ("comm_open: FD %d is a new socket\n", new_socket);
    fd_open(new_socket, FD_SOCKET, note);
    F = &fd_table[new_socket];
    if (!(flags & COMM_NOCLOEXEC))
	commSetCloseOnExec(new_socket);
    if ((flags & COMM_REUSEADDR))
	commSetReuseAddr(new_socket);
    if (port > (u_short) 0) {
	commSetNoLinger(new_socket);
	if (opt_reuseaddr)
	    commSetReuseAddr(new_socket);
    }
    if (addr.s_addr != no_addr.s_addr) {
	if (commBind(new_socket, addr, port) != COMM_OK) {
	    comm_close(new_socket);
	    return -1;
	}
    }
    F->local_port = port;

    if (flags & COMM_NONBLOCKING)
	if (commSetNonBlocking(new_socket) == COMM_ERROR)
	    return -1;
#ifdef TCP_NODELAY
    if (sock_type == SOCK_STREAM)
	commSetTcpNoDelay(new_socket);
#endif
    if (tcp_rcv_bufsz > 0 && sock_type == SOCK_STREAM)
	commSetTcpRcvbuf(new_socket, tcp_rcv_bufsz);
    return new_socket;
}

/*
 * NOTE: set the listen queue to Squid_MaxFD/4 and rely on the kernel to      
 * impose an upper limit.  Solaris' listen(3n) page says it has   
 * no limit on this parameter, but sys/socket.h sets SOMAXCONN 
 * to 5.  HP-UX currently has a limit of 20.  SunOS is 5 and
 * OSF 3.0 is 8.
 */
int
comm_listen(int sock)
{
    int x;
    if ((x = listen(sock, Squid_MaxFD >> 2)) < 0) {
	debug(50, 0) ("comm_listen: listen(%d, %d): %s\n",
	    Squid_MaxFD >> 2,
	    sock, xstrerror());
	return x;
    }
    return sock;
}

void
commConnectStart(int fd, const char *host, u_short port, CNCB * callback, void *data)
{
    ConnectStateData *cs = xcalloc(1, sizeof(ConnectStateData));
    cbdataAdd(cs, MEM_NONE);
    cs->fd = fd;
    cs->host = xstrdup(host);
    cs->port = port;
    cs->callback = callback;
    cs->data = data;
    cbdataLock(cs->data);
    comm_add_close_handler(fd, commConnectFree, cs);
    cs->locks++;
    ipcache_nbgethostbyname(host, commConnectDnsHandle, cs);
}

static void
commConnectDnsHandle(const ipcache_addrs * ia, void *data)
{
    ConnectStateData *cs = data;
    assert(cs->locks == 1);
    cs->locks--;
    if (ia == NULL) {
	debug(5, 3) ("commConnectDnsHandle: Unknown host: %s\n", cs->host);
	if (!dns_error_message) {
	    dns_error_message = "Unknown DNS error";
	    debug(5, 1) ("commConnectDnsHandle: Bad dns_error_message\n");
	}
	assert(dns_error_message != NULL);
	commConnectCallback(cs, COMM_ERR_DNS);
	return;
    }
    assert(ia->cur < ia->count);
    cs->in_addr = ia->in_addrs[ia->cur];
    ipcacheCycleAddr(cs->host);
    cs->addrcount = ia->count;
    cs->connstart = squid_curtime;
    commSetConnectTimeout(cs->fd, commBackoffTimeout((int) ia->count));
    commConnectHandle(cs->fd, cs);
}

static void
commConnectCallback(ConnectStateData * cs, int status)
{
    CNCB *callback = cs->callback;
    void *data = cs->data;
    int fd = cs->fd;
    comm_remove_close_handler(fd, commConnectFree, cs);
    cs->callback = NULL;
    cs->data = NULL;
    commSetTimeout(fd, -1, NULL, NULL);
    commConnectFree(fd, cs);
    if (cbdataValid(data))
	callback(fd, status, data);
    cbdataUnlock(data);
}

static void
commConnectFree(int fd, void *data)
{
    ConnectStateData *cs = data;
    debug(5, 3) ("commConnectFree: FD %d\n", fd);
    if (cs->locks)
	ipcacheUnregister(cs->host, cs);
    if (cs->data)
	cbdataUnlock(cs->data);
    safe_free(cs->host);
    cbdataFree(cs);
}

/* Reset FD so that we can connect() again */
static int
commResetFD(ConnectStateData * cs)
{
    int fd2;
    if (!cbdataValid(cs->data))
	return 0;
    fd2 = socket(AF_INET, SOCK_STREAM, 0);
    if (fd2 < 0) {
	debug(5, 0) ("commResetFD: socket: %s\n", xstrerror());
	fdAdjustReserved();
	return 0;
    }
    if (dup2(fd2, cs->fd) < 0) {
	debug(5, 0) ("commResetFD: dup2: %s\n", xstrerror());
	fdAdjustReserved();
	return 0;
    }
    close(fd2);
    commSetConnectTimeout(cs->fd, commBackoffTimeout((int) cs->addrcount));
    commSetNonBlocking(cs->fd);
    return 1;
}

static int
commRetryConnect(ConnectStateData * cs)
{
    assert(cs->addrcount > 0);
    if (cs->addrcount == 1) {
	if (cs->tries >= Config.retry.maxtries)
	    return 0;
	if (squid_curtime - cs->connstart > Config.Timeout.connect)
	    return 0;
	commSetConnectTimeout(cs->fd, commBackoffTimeout(100));
    } else {
	if (cs->tries > cs->addrcount)
	    return 0;
    }
    return commResetFD(cs);
}

/* Back off the socket timeout if there are several addresses available */
static time_t
commBackoffTimeout(int numaddrs)
{
    time_t timeout;
    timeout = (time_t) Config.Timeout.connect;
    if (numaddrs > 2) {
	timeout = (time_t) (Config.Timeout.connect / numaddrs);
	if (timeout < Config.retry.timeout)
	    timeout = (time_t) Config.retry.timeout;
    }
    return timeout;
}

/* Connect SOCK to specified DEST_PORT at DEST_HOST. */
static void
commConnectHandle(int fd, void *data)
{
    ConnectStateData *cs = data;
    if (cs->S.sin_addr.s_addr == 0) {
	cs->S.sin_family = AF_INET;
	cs->S.sin_addr = cs->in_addr;
	cs->S.sin_port = htons(cs->port);
	if (Config.onoff.log_fqdn)
	    fqdncache_gethostbyaddr(cs->S.sin_addr, FQDN_LOOKUP_IF_MISS);
    }
    switch (comm_connect_addr(fd, &cs->S)) {
    case COMM_INPROGRESS:
	debug(5, 5) ("commConnectHandle: FD %d: COMM_INPROGRESS\n", fd);
	commSetSelect(fd, COMM_SELECT_WRITE, commConnectHandle, cs, 0);
	break;
    case COMM_OK:
	ipcacheMarkGoodAddr(cs->host, cs->S.sin_addr);
	commConnectCallback(cs, COMM_OK);
	break;
    default:
	cs->tries++;
	ipcacheMarkBadAddr(cs->host, cs->S.sin_addr);
	if (Config.onoff.test_reachability)
	    netdbDeleteAddrNetwork(cs->S.sin_addr);
	if (commRetryConnect(cs)) {
	    cs->locks++;
	    ipcache_nbgethostbyname(cs->host, commConnectDnsHandle, cs);
	} else {
	    commConnectCallback(cs, COMM_ERR_CONNECT);
	}
	break;
    }
}

int
commSetTimeout(int fd, int timeout, PF * handler, void *data)
{
    fde *F;
    debug(5, 3) ("commSetTimeout: FD %d timeout %d\n", fd, timeout);
    assert(fd >= 0);
    assert(fd < Squid_MaxFD);
    F = &fd_table[fd];
    assert(F->open);
    if (timeout < 0) {
	F->timeout_handler = NULL;
	F->timeout_data = NULL;
	return F->timeout = 0;
    }
    if (shutdown_pending || reconfigure_pending) {
	/* don't increase the timeout if something pending */
	if (F->timeout > 0 && (int) (F->timeout - squid_curtime) < timeout)
	    return F->timeout;
    }
    assert(handler || F->timeout_handler);
    if (handler || data) {
	F->timeout_handler = handler;
	F->timeout_data = data;
    }
    return F->timeout = squid_curtime + (time_t) timeout;
}

int
comm_connect_addr(int sock, const struct sockaddr_in *address)
{
    int status = COMM_OK;
    fde *F = &fd_table[sock];
    int len;
    int x;
    assert(ntohs(address->sin_port) != 0);
    /* Establish connection. */
    if (connect(sock, (struct sockaddr *) address, sizeof(struct sockaddr_in)) < 0) {
	debug(5, 9) ("connect FD %d: %s\n", sock, xstrerror());
	switch (errno) {
	case EALREADY:
#ifdef _SQUID_HPUX_
	    /*
	     * On my HP-UX box (HP-UX tirana B.10.10 A 9000/851), 
	     * we get into fast loops on EALREADY.  select(2) continually
	     * says the FD is ready for writing, but connect always
	     * returns EALREADY. I applied a patch (PHNE_12906) but
	     * it didn't help.  -DW Dec 1, 1997
	     */
	    debug(50, 1) ("connect: %s:%d: %s.\n",
		fqdnFromAddr(address->sin_addr),
		ntohs(address->sin_port),
		xstrerror());
	    return COMM_ERROR;
	    /* NOTREACHEd */
#endif
#if EAGAIN != EWOULDBLOCK
	case EAGAIN:
#endif
	case EINTR:
	case EWOULDBLOCK:
	case EINPROGRESS:
	    status = COMM_INPROGRESS;
	    break;
	case EISCONN:
	    status = COMM_OK;
	    break;
	case EINVAL:
	    len = sizeof(x);
	    if (getsockopt(sock, SOL_SOCKET, SO_ERROR, (char *) &x, &len) >= 0)
		errno = x;
	default:
	    debug(50, 2) ("connect: %s:%d: %s.\n",
		fqdnFromAddr(address->sin_addr),
		ntohs(address->sin_port),
		xstrerror());
	    return COMM_ERROR;
	}
    }
    xstrncpy(F->ipaddr, inet_ntoa(address->sin_addr), 16);
    F->remote_port = ntohs(address->sin_port);
    if (status == COMM_OK) {
	debug(5, 10) ("comm_connect_addr: FD %d connected to %s:%d\n",
	    sock, F->ipaddr, F->remote_port);
    } else if (status == COMM_INPROGRESS) {
	debug(5, 10) ("comm_connect_addr: FD %d connection pending\n", sock);
    }
    /* Add new socket to list of open sockets. */
    return status;
}

/* Wait for an incoming connection on FD.  FD should be a socket returned
 * from comm_listen. */
int
comm_accept(int fd, struct sockaddr_in *peer, struct sockaddr_in *me)
{
    int sock;
    struct sockaddr_in P;
    struct sockaddr_in M;
    int Slen;
    fde *F = NULL;

    Slen = sizeof(P);
    while ((sock = accept(fd, (struct sockaddr *) &P, &Slen)) < 0) {
	switch (errno) {
#if EAGAIN != EWOULDBLOCK
	case EAGAIN:
#endif
	case EWOULDBLOCK:
	case EINTR:
	    return COMM_NOMESSAGE;
	case ENFILE:
	case EMFILE:
	    return COMM_ERROR;
	default:
	    debug(50, 1) ("comm_accept: FD %d: accept failure: %s\n",
		fd, xstrerror());
	    return COMM_ERROR;
	}
	/* NOTREACHED */
    }

    if (peer)
	*peer = P;
    Slen = sizeof(M);
    memset(&M, '\0', Slen);
    getsockname(sock, (struct sockaddr *) &M, &Slen);
    if (me)
	*me = M;
    commSetCloseOnExec(sock);
    /* fdstat update */
    fd_open(sock, FD_SOCKET, "HTTP Request");
    F = &fd_table[sock];
    xstrncpy(F->ipaddr, inet_ntoa(P.sin_addr), 16);
    F->remote_port = htons(P.sin_port);
    F->local_port = htons(M.sin_port);
    commSetNonBlocking(sock);
    return sock;
}

void
commCallCloseHandlers(int fd)
{
    fde *F = &fd_table[fd];
    close_handler *ch;
    debug(5, 5) ("commCallCloseHandlers: FD %d\n", fd);
    while ((ch = F->close_handler) != NULL) {
	F->close_handler = ch->next;
	debug(5, 5) ("commCallCloseHandlers: ch->handler=%p\n", ch->handler);
	if (cbdataValid(ch->data))
	    ch->handler(fd, ch->data);
	cbdataUnlock(ch->data);
	safe_free(ch);
    }
}

void
comm_close(int fd)
{
    fde *F = NULL;
    debug(5, 5) ("comm_close: FD %d\n", fd);
    assert(fd >= 0);
    assert(fd < Squid_MaxFD);
    F = &fd_table[fd];
    if (EBIT_TEST(F->flags, FD_CLOSING))
	return;
    if (shutdown_pending && (!F->open || F->type == FD_FILE))
	return;
    assert(F->open);
    assert(F->type != FD_FILE);
    EBIT_SET(F->flags, FD_CLOSING);
    CommWriteStateCallbackAndFree(fd, COMM_ERR_CLOSING);
    commCallCloseHandlers(fd);
    if (F->uses)		/* assume persistent connect count */
	pconnHistCount(1, F->uses);
    fd_close(fd);		/* update fdstat */
#if defined(_SQUID_LINUX_)
    /*
     * michael@metal.iinet.net.au sez close() on
     * network sockets never blocks.
     */
    close(fd);
#elsif USE_ASYNC_IO
    aioClose(fd);
#else
    close(fd);
#endif
}

/* Send a udp datagram to specified TO_ADDR. */
int
comm_udp_sendto(int fd,
    const struct sockaddr_in *to_addr,
    int addr_len,
    const char *buf,
    int len)
{
    int x;
    x = sendto(fd, buf, len, 0, (struct sockaddr *) to_addr, addr_len);
    if (x < 0) {
	debug(50, 1) ("comm_udp_sendto: FD %d, %s, port %d: %s\n",
	    fd,
	    inet_ntoa(to_addr->sin_addr),
	    (int) htons(to_addr->sin_port),
	    xstrerror());
	return COMM_ERROR;
    }
    return x;
}

void
commSetDefer(int fd, DEFER * func, void *data)
{
    fde *F = &fd_table[fd];
    F->defer_check = func;
    F->defer_data = data;
}

static int
commDeferRead(int fd)
{
    fde *F = &fd_table[fd];
    if (F->defer_check == NULL)
	return 0;
    return F->defer_check(fd, F->defer_data);
}

#if HAVE_POLL

/* poll() version by:
 * Stewart Forster <slf@connect.com.au>, and
 * Anthony Baxter <arb@connect.com.au> */

static void
comm_poll_incoming(void)
{
    int fd;
    int fds[4];
    struct pollfd pfds[3 + MAXHTTPPORTS];
    unsigned long N = 0;
    unsigned long i, nfds;
    int j;
    PF *hdl = NULL;
    polledinc = 0;
    if (theInIcpConnection >= 0)
	fds[N++] = theInIcpConnection;
    if (theInIcpConnection != theOutIcpConnection)
	if (theOutIcpConnection >= 0)
	    fds[N++] = theOutIcpConnection;
    for (j = 0; j < NHttpSockets; j++) {
	if (HttpSockets[j] < 0)
	    continue;
	if (commDeferRead(HttpSockets[j]))
	    continue;
	fds[N++] = HttpSockets[j];
    }
    for (i = nfds = 0; i < N; i++) {
	int events;
	fd = fds[i];
	events = 0;
	if (fd_table[fd].read_handler)
	    events |= POLLRDNORM;
	if (fd_table[fd].write_handler)
	    events |= POLLWRNORM;
	if (events) {
	    pfds[nfds].fd = fd;
	    pfds[nfds].events = events;
	    pfds[nfds].revents = 0;
	    nfds++;
	}
    }
    if (!nfds)
	return;
#if !ALARM_UPDATES_TIME
    getCurrentTime();
#endif
    polledinc = poll(pfds, nfds, 0);
    if (polledinc < 1) {
	polledinc = 0;
	return;
    }
    for (i = 0; i < nfds; i++) {
	int revents;
	if (((revents = pfds[i].revents) == 0) || ((fd = pfds[i].fd) == -1))
	    continue;
	if (revents & (POLLRDNORM | POLLIN | POLLHUP | POLLERR)) {
	    if (hdl = fd_table[fd].read_handler) {
		fd_table[fd].read_handler = NULL;
		hdl(fd, fd_table[fd].read_data);
	    } else
		debug(5, 1) ("comm_poll_incoming: NULL read handler\n");
	}
	if (revents & (POLLWRNORM | POLLOUT | POLLHUP | POLLERR)) {
	    if (hdl = fd_table[fd].write_handler) {
		fd_table[fd].write_handler = NULL;
		hdl(fd, fd_table[fd].write_data);
	    } else
		debug(5, 1) ("comm_poll_incoming: NULL write handler\n");
	}
    }
    /* TO FIX: repoll ICP connection here */
}

#else

static void
comm_select_incoming(void)
{
    fd_set read_mask;
    fd_set write_mask;
    int maxfd = 0;
    int fd = 0;
    int fds[3 + MAXHTTPPORTS];
    int N = 0;
    int i = 0;
    PF *hdl = NULL;
    polledinc = 0;
    FD_ZERO(&read_mask);
    FD_ZERO(&write_mask);
    for (i = 0; i < NHttpSockets; i++) {
	if (HttpSockets[i] < 0)
	    continue;
	if (commDeferRead(HttpSockets[i]))
	    continue;
	fds[N++] = HttpSockets[i];
    }
    if (theInIcpConnection >= 0)
	fds[N++] = theInIcpConnection;
    if (theInIcpConnection != theOutIcpConnection)
	if (theOutIcpConnection >= 0)
	    fds[N++] = theOutIcpConnection;
    fds[N++] = 0;
    for (i = 0; i < N; i++) {
	fd = fds[i];
	if (fd_table[fd].read_handler) {
	    FD_SET(fd, &read_mask);
	    if (fd > maxfd)
		maxfd = fd;
	}
	if (fd_table[fd].write_handler) {
	    FD_SET(fd, &write_mask);
	    if (fd > maxfd)
		maxfd = fd;
	}
    }
    if (maxfd++ == 0)
	return;
#if !ALARM_UPDATES_TIME
    getCurrentTime();
#endif
    polledinc = select(maxfd, &read_mask, &write_mask, NULL, &zero_tv);
    if (polledinc < 1) {
	polledinc = 0;
	return;
    }
    for (i = 0; i < N; i++) {
	fd = fds[i];
	if (FD_ISSET(fd, &read_mask)) {
	    if ((hdl = fd_table[fd].read_handler) != NULL) {
		fd_table[fd].read_handler = NULL;
		hdl(fd, fd_table[fd].read_data);
	    } else {
		debug(5, 1) ("comm_select_incoming: NULL read handler\n");
	    }
	}
	if (FD_ISSET(fd, &write_mask)) {
	    if ((hdl = fd_table[fd].write_handler) != NULL) {
		fd_table[fd].write_handler = NULL;
		hdl(fd, fd_table[fd].write_data);
	    } else {
		debug(5, 1) ("comm_select_incoming: NULL write handler\n");
	    }
	}
    }
}
#endif

static int
fdIsHttpOrIcp(int fd)
{
    int j;
    if (fd == theInIcpConnection)
	return 1;
    if (fd == theOutIcpConnection)
	return 1;
    for (j = 0; j < NHttpSockets; j++) {
	if (fd == HttpSockets[j])
	    return 1;
    }
    return 0;
}

#if HAVE_POLL
/* poll all sockets; call handlers for those that are ready. */
int
comm_poll(time_t sec)
{
    struct pollfd pfds[SQUID_MAXFD];
    PF *hdl = NULL;
    int fd;
    int i;
    int maxfd;
    unsigned long nfds;
    int num;
    static time_t last_timeout = 0;
    static int lastinc = 0;
    int poll_time;
    static int incoming_counter = 0;
    time_t timeout;
    timeout = squid_curtime + sec;
    do {
#if !ALARM_UPDATES_TIME
	getCurrentTime();
#endif
	if (shutdown_pending) {
	    serverConnectionsClose();
	    dnsShutdownServers();
	    redirectShutdownServers();
	    /* shutdown_pending will be set to
	     * +1 for SIGTERM
	     * -1 for SIGINT */
	    /* reconfigure_pending always == 1 when SIGHUP received */
	    if (shutdown_pending > 0 || reconfigure_pending > 0)
		setSocketShutdownLifetimes(Config.shutdownLifetime);
	    else
		setSocketShutdownLifetimes(1);
	}
#if USE_ASYNC_IO
	aioCheckCallbacks();
#endif
	comm_poll_incoming();
	nfds = 0;
	maxfd = Biggest_FD + 1;
	for (i = 0; i < maxfd; i++) {
	    int events;
	    events = 0;
	    /* Check each open socket for a handler. */
	    if (fd_table[i].read_handler && !commDeferRead(i))
		events |= POLLRDNORM;
	    if (fd_table[i].write_handler)
		events |= POLLWRNORM;
	    if (events) {
		pfds[nfds].fd = i;
		pfds[nfds].events = events;
		pfds[nfds].revents = 0;
		nfds++;
	    }
	}
	if (shutdown_pending || reconfigure_pending)
	    debug(5, 2) ("comm_poll: Still waiting on %d FDs\n", nfds);
	if (nfds == 0)
	    return COMM_SHUTDOWN;
#if USE_ASYNC_IO
	poll_time = sec > 0 ? 50 : 0;
#else
	poll_time = sec > 0 ? 1000 : 0;
#endif
	for (;;) {
	    num = poll(pfds, nfds, poll_time);
	    Counter.select_loops++;
	    if (num >= 0)
		break;
	    if (errno == EINTR)
		continue;
	    debug(5, 0) ("comm_poll: poll failure: %s\n", xstrerror());
	    assert(errno != EINVAL);
	    return COMM_ERROR;
	    /* NOTREACHED */
	}
	debug(5, num ? 5 : 8) ("comm_poll: %d sockets ready\n", num);
	/* Check timeout handlers ONCE each second. */
	if (squid_curtime > last_timeout) {
	    last_timeout = squid_curtime;
	    checkTimeouts();
	}
	if (num == 0)
	    continue;
	/* scan each socket but the accept socket. Poll this 
	 * more frequently to minimize losses due to the 5 connect 
	 * limit in SunOS */
	for (i = 0; i < nfds; i++) {
	    int revents;
	    if (((revents = pfds[i].revents) == 0) || ((fd = pfds[i].fd) == -1))
		continue;
	    if (fdIsHttpOrIcp(fd))
		continue;
	    if (revents & (POLLRDNORM | POLLIN | POLLHUP | POLLERR)) {
		debug(5, 6) ("comm_poll: FD %d ready for reading\n", fd);
		if ((hdl = fd_table[fd].read_handler)) {
		    fd_table[fd].read_handler = NULL;
		    hdl(fd, fd_table[fd].read_data);
		}
		if ((++incoming_counter & 15) == 0)
		    comm_poll_incoming();
	    }
	    if (revents & (POLLWRNORM | POLLOUT | POLLHUP | POLLERR)) {
		debug(5, 5) ("comm_poll: FD %d ready for writing\n", fd);
		if ((hdl = fd_table[fd].write_handler)) {
		    fd_table[fd].write_handler = NULL;
		    hdl(fd, fd_table[fd].write_data);
		}
		if ((++incoming_counter & 15) == 0)
		    comm_poll_incoming();
	    }
	    if (revents & POLLNVAL) {
		close_handler *ch;
		fde *F = &fd_table[fd];
		debug(5, 0) ("WARNING: FD %d has handlers, but it's invalid.\n", fd);
		debug(5, 0) ("FD %d is a %s\n", fd, fdTypeStr[fd_table[fd].type]);
		debug(5, 0) ("--> %s\n", fd_table[fd].desc);
		debug(5, 0) ("tmout:%p read:%p write:%p\n",
		    F->timeout_handler,
		    F->read_handler,
		    F->write_handler);
		for (ch = F->close_handler; ch; ch = ch->next)
		    debug(5, 0) (" close handler: %p\n", ch->handler);
		if (F->close_handler) {
		    commCallCloseHandlers(fd);
		} else if (F->timeout_handler) {
		    debug(5, 0) ("comm_poll: Calling Timeout Handler\n");
		    F->timeout_handler(fd, F->timeout_data);
		}
		F->close_handler = NULL;
		F->timeout_handler = NULL;
		F->read_handler = NULL;
		F->write_handler = NULL;
		if (F->open != 0)
		    fd_close(fd);
	    }
	    lastinc = polledinc;
	}
	return COMM_OK;
    } while (timeout > squid_curtime);
    debug(5, 8) ("comm_poll: time out: %d.\n", squid_curtime);
    return COMM_TIMEOUT;
}

#else

/* Select on all sockets; call handlers for those that are ready. */
int
comm_select(time_t sec)
{
    fd_set readfds;
    fd_set writefds;
    PF *hdl = NULL;
    int fd;
    int i;
    int maxfd;
    int nfds;
    int num;
    static int incoming_counter = 0;
    static time_t last_timeout = 0;
    struct timeval poll_time;
    static int lastinc;
    time_t timeout;

    /* assume all process are very fast (less than 1 second). Call
     * time() only once */
    /* use only 1 second granularity */
    timeout = squid_curtime + sec;

    do {
#if !ALARM_UPDATES_TIME
	getCurrentTime();
#endif

#if USE_ASYNC_IO
	aioCheckCallbacks();
#endif

	FD_ZERO(&readfds);
	FD_ZERO(&writefds);
	if (shutdown_pending || reconfigure_pending) {
	    serverConnectionsClose();
	    dnsShutdownServers();
	    redirectShutdownServers();
	    /* shutdown_pending will be set to
	     * +1 for SIGTERM
	     * -1 for SIGINT */
	    /* reconfigure_pending always == 1 when SIGHUP received */
	    if (shutdown_pending > 0 || reconfigure_pending > 0)
		setSocketShutdownLifetimes(Config.shutdownLifetime);
	    else
		setSocketShutdownLifetimes(1);
	}
	comm_select_incoming();
	nfds = 0;
	maxfd = Biggest_FD + 1;
	for (i = 0; i < maxfd; i++) {
	    /* Check each open socket for a handler. */
	    if (fd_table[i].read_handler && !commDeferRead(i)) {
		nfds++;
		FD_SET(i, &readfds);
	    }
	    if (fd_table[i].write_handler) {
		nfds++;
		FD_SET(i, &writefds);
	    }
	}
	if (shutdown_pending || reconfigure_pending)
	    debug(5, 2) ("comm_select: Still waiting on %d FDs\n", nfds);
	if (nfds == 0)
	    return COMM_SHUTDOWN;
	for (;;) {
	    poll_time.tv_sec = sec > 0 ? 1 : 0;
	    poll_time.tv_usec = 0;
	    num = select(maxfd, &readfds, &writefds, NULL, &poll_time);
	    Counter.select_loops++;
	    if (num >= 0)
		break;
	    if (errno == EINTR)
		break;
	    debug(50, 0) ("comm_select: select failure: %s\n",
		xstrerror());
	    examine_select(&readfds, &writefds);
	    return COMM_ERROR;
	    /* NOTREACHED */
	}
	if (num < 0)
	    continue;
	debug(5, num ? 5 : 8) ("comm_select: %d sockets ready at %d\n",
	    num, (int) squid_curtime);

	/* Check lifetime and timeout handlers ONCE each second.
	 * Replaces brain-dead check every time through the loop! */
	if (squid_curtime > last_timeout) {
	    last_timeout = squid_curtime;
	    checkTimeouts();
	}
	if (num == 0)
	    continue;

	/* scan each socket but the accept socket. Poll this 
	 * more frequently to minimize losses due to the 5 connect 
	 * limit in SunOS */

	for (fd = 0; fd < maxfd; fd++) {
	    if (!FD_ISSET(fd, &readfds) && !FD_ISSET(fd, &writefds))
		continue;
	    if (fdIsHttpOrIcp(fd))
		continue;
	    if (FD_ISSET(fd, &readfds)) {
		debug(5, 6) ("comm_select: FD %d ready for reading\n", fd);
		if (fd_table[fd].read_handler) {
		    hdl = fd_table[fd].read_handler;
		    fd_table[fd].read_handler = NULL;
		    hdl(fd, fd_table[fd].read_data);
		}
		if ((++incoming_counter & 15) == 0)
		    comm_select_incoming();
	    }
	    if (FD_ISSET(fd, &writefds)) {
		debug(5, 5) ("comm_select: FD %d ready for writing\n", fd);
		if (fd_table[fd].write_handler) {
		    hdl = fd_table[fd].write_handler;
		    fd_table[fd].write_handler = NULL;
		    hdl(fd, fd_table[fd].write_data);
		}
		if ((++incoming_counter & 15) == 0)
		    comm_select_incoming();
	    }
	    lastinc = polledinc;
	}
	return COMM_OK;
    } while (timeout > squid_curtime);
    debug(5, 8) ("comm_select: time out: %d.\n", squid_curtime);
    return COMM_TIMEOUT;
}
#endif

void
commSetSelect(int fd, unsigned int type, PF * handler, void *client_data, time_t timeout)
{
    fde *F = &fd_table[fd];
    assert(fd >= 0);
    assert(F->open == FD_OPEN);
    debug(5, 5) ("commSetSelect: FD %d type %d\n", fd, type);
    if (type & COMM_SELECT_READ) {
	F->read_handler = handler;
	F->read_data = client_data;
    }
    if (type & COMM_SELECT_WRITE) {
	F->write_handler = handler;
	F->write_data = client_data;
    }
    if (timeout)
	F->timeout = squid_curtime + timeout;
}

void
comm_add_close_handler(int fd, PF * handler, void *data)
{
    close_handler *new = xmalloc(sizeof(*new));
    debug(5, 5) ("comm_add_close_handler: FD %d, handler=%p, data=%p\n",
	fd, handler, data);
    new->handler = handler;
    new->data = data;
    new->next = fd_table[fd].close_handler;
    fd_table[fd].close_handler = new;
    cbdataLock(data);
}

void
comm_remove_close_handler(int fd, PF * handler, void *data)
{
    close_handler *p;
    close_handler *last = NULL;
    /* Find handler in list */
    debug(5, 5) ("comm_remove_close_handler: FD %d, handler=%p, data=%p\n",
	fd, handler, data);
    for (p = fd_table[fd].close_handler; p != NULL; last = p, p = p->next)
	if (p->handler == handler && p->data == data)
	    break;		/* This is our handler */
    assert(p != NULL);
    /* Remove list entry */
    if (last)
	last->next = p->next;
    else
	fd_table[fd].close_handler = p->next;
    cbdataUnlock(p->data);
    safe_free(p);
}

static void
commSetNoLinger(int fd)
{
    struct linger L;
    L.l_onoff = 0;		/* off */
    L.l_linger = 0;
    if (setsockopt(fd, SOL_SOCKET, SO_LINGER, (char *) &L, sizeof(L)) < 0)
	debug(50, 0) ("commSetNoLinger: FD %d: %s\n", fd, xstrerror());
}

static void
commSetReuseAddr(int fd)
{
    int on = 1;
    if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char *) &on, sizeof(on)) < 0)
	debug(50, 1) ("commSetReuseAddr: FD %d: %s\n", fd, xstrerror());
}

static void
commSetTcpRcvbuf(int fd, int size)
{
    if (setsockopt(fd, SOL_SOCKET, SO_RCVBUF, (char *) &size, sizeof(size)) < 0)
	debug(50, 1) ("commSetTcpRcvbuf: FD %d, SIZE %d: %s\n",
	    fd, size, xstrerror());
}

int
commSetNonBlocking(int fd)
{
    int flags;
    int dummy = 0;
    if ((flags = fcntl(fd, F_GETFL, dummy)) < 0) {
	debug(50, 0) ("FD %d: fcntl F_GETFL: %s\n", fd, xstrerror());
	return COMM_ERROR;
    }
    if (fcntl(fd, F_SETFL, flags | SQUID_NONBLOCK) < 0) {
	debug(50, 0) ("commSetNonBlocking: FD %d: %s\n", fd, xstrerror());
	return COMM_ERROR;
    }
    return 0;
}

void
commSetCloseOnExec(int fd)
{
#ifdef FD_CLOEXEC
    int flags;
    int dummy = 0;
    if ((flags = fcntl(fd, F_GETFL, dummy)) < 0) {
	debug(50, 0) ("FD %d: fcntl F_GETFL: %s\n", fd, xstrerror());
	return;
    }
    if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) < 0)
	debug(50, 0) ("FD %d: set close-on-exec failed: %s\n", fd, xstrerror());
#endif
}

#ifdef TCP_NODELAY
static void
commSetTcpNoDelay(int fd)
{
    int on = 1;
    if (setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, (char *) &on, sizeof(on)) < 0)
	debug(50, 1) ("commSetTcpNoDelay: FD %d: %s\n", fd, xstrerror());
}
#endif

int
comm_init(void)
{
    fd_table = xcalloc(Squid_MaxFD, sizeof(fde));
    /* XXX account fd_table */
    /* Keep a few file descriptors free so that we don't run out of FD's
     * after accepting a client but before it opens a socket or a file.
     * Since Squid_MaxFD can be as high as several thousand, don't waste them */
    RESERVED_FD = XMIN(100, Squid_MaxFD / 4);
    zero_tv.tv_sec = 0;
    zero_tv.tv_usec = 0;
    return 0;
}


#if !HAVE_POLL
/*
 * examine_select - debug routine.
 *
 * I spend the day chasing this core dump that occurs when both the client
 * and the server side of a cache fetch simultaneoulsy abort the
 * connection.  While I haven't really studied the code to figure out how
 * it happens, the snippet below may prevent the cache from exitting:
 * 
 * Call this from where the select loop fails.
 */
static int
examine_select(fd_set * readfds, fd_set * writefds)
{
    int fd = 0;
    fd_set read_x;
    fd_set write_x;
    int num;
    struct timeval tv;
    close_handler *ch = NULL;
    fde *F = NULL;

    debug(5, 0) ("examine_select: Examining open file descriptors...\n");
    for (fd = 0; fd < Squid_MaxFD; fd++) {
	FD_ZERO(&read_x);
	FD_ZERO(&write_x);
	tv.tv_sec = tv.tv_usec = 0;
	if (FD_ISSET(fd, readfds))
	    FD_SET(fd, &read_x);
	else if (FD_ISSET(fd, writefds))
	    FD_SET(fd, &write_x);
	else
	    continue;
	num = select(Squid_MaxFD, &read_x, &write_x, NULL, &tv);
	if (num > -1) {
	    debug(5, 5) ("FD %d is valid.\n", fd);
	    continue;
	}
	F = &fd_table[fd];
	debug(5, 0) ("FD %d: %s\n", fd, xstrerror());
	debug(5, 0) ("WARNING: FD %d has handlers, but it's invalid.\n", fd);
	debug(5, 0) ("FD %d is a %s called '%s'\n",
	    fd,
	    fdTypeStr[fd_table[fd].type],
	    F->desc);
	debug(5, 0) ("tmout:%p read:%p write:%p\n",
	    F->timeout_handler,
	    F->read_handler,
	    F->write_handler);
	for (ch = F->close_handler; ch; ch = ch->next)
	    debug(5, 0) (" close handler: %p\n", ch->handler);
	if (F->close_handler) {
	    commCallCloseHandlers(fd);
	} else if (F->timeout_handler) {
	    debug(5, 0) ("examine_select: Calling Timeout Handler\n");
	    F->timeout_handler(fd, F->timeout_data);
	}
	F->close_handler = NULL;
	F->timeout_handler = NULL;
	F->read_handler = NULL;
	F->write_handler = NULL;
	FD_CLR(fd, readfds);
	FD_CLR(fd, writefds);
    }
    return 0;
}
#endif

static void
checkTimeouts(void)
{
    int fd;
    fde *F = NULL;
    PF *callback;
    for (fd = 0; fd <= Biggest_FD; fd++) {
	F = &fd_table[fd];
	if (F->open != FD_OPEN)
	    continue;
	if (F->timeout == 0)
	    continue;
	if (F->timeout > squid_curtime)
	    continue;
	debug(5, 5) ("checkTimeouts: FD %d Expired\n", fd);
	if (F->timeout_handler) {
	    debug(5, 5) ("checkTimeouts: FD %d: Call timeout handler\n", fd);
	    callback = F->timeout_handler;
	    F->timeout_handler = NULL;
	    callback(fd, F->timeout_data);
	} else {
	    debug(5, 5) ("checkTimeouts: FD %d: Forcing comm_close()\n", fd);
	    comm_close(fd);
	}
    }
}

/* Write to FD. */
static void
commHandleWrite(int fd, void *data)
{
    CommWriteStateData *state = data;
    int len = 0;
    int nleft;

    debug(5, 5) ("commHandleWrite: FD %d: off %d, sz %d.\n",
	fd, state->offset, state->size);

    nleft = state->size - state->offset;
    len = write(fd, state->buf + state->offset, nleft);
    fd_bytes(fd, len, FD_WRITE);

    if (len == 0) {
	/* Note we even call write if nleft == 0 */
	/* We're done */
	if (nleft != 0)
	    debug(5, 1) ("commHandleWrite: FD %d: write failure: connection closed with %d bytes remaining.\n", fd, nleft);
	CommWriteStateCallbackAndFree(fd, nleft ? COMM_ERROR : COMM_OK);
    } else if (len < 0) {
	/* An error */
	if (ignoreErrno(errno)) {
	    debug(50, 10) ("commHandleWrite: FD %d: write failure: %s.\n",
		fd, xstrerror());
	    commSetSelect(fd,
		COMM_SELECT_WRITE,
		commHandleWrite,
		state,
		0);
	} else {
	    debug(50, 2) ("commHandleWrite: FD %d: write failure: %s.\n",
		fd, xstrerror());
	    CommWriteStateCallbackAndFree(fd, COMM_ERROR);
	}
    } else {
	/* A successful write, continue */
	state->offset += len;
	if (state->offset < state->size) {
	    /* Not done, reinstall the write handler and write some more */
	    commSetSelect(fd,
		COMM_SELECT_WRITE,
		commHandleWrite,
		state,
		0);
	} else {
	    CommWriteStateCallbackAndFree(fd, COMM_OK);
	}
    }
}



/* Select for Writing on FD, until SIZE bytes are sent.  Call
 * * HANDLER when complete. */
void
comm_write(int fd, char *buf, int size, CWCB * handler, void *handler_data, FREE * free_func)
{
    CommWriteStateData *state = fd_table[fd].rwstate;
    debug(5, 5) ("comm_write: FD %d: sz %d: hndl %p: data %p.\n",
	fd, size, handler, handler_data);
    if (NULL != state) {
	debug(5, 1) ("comm_write: fd_table[%d].rwstate != NULL", fd);
	safe_free(state);
	fd_table[fd].rwstate = NULL;
    }
    assert(state == NULL);
    fd_table[fd].rwstate = state = xcalloc(1, sizeof(CommWriteStateData));
    state->buf = buf;
    state->size = size;
    state->offset = 0;
    state->handler = handler;
    state->handler_data = handler_data;
    state->free_func = free_func;
    cbdataLock(handler_data);
    commSetSelect(fd, COMM_SELECT_WRITE, commHandleWrite, state, 0);
}

/* a wrapper around comm_write to allow for MemBuf to comm_written in a snap */
void
comm_write_mbuf(int fd, MemBuf mb, CWCB * handler, void *handler_data)
{
    comm_write(fd, mb.buf, mb.size, handler, handler_data, memBufFreeFunc(&mb));
}

int
ignoreErrno(int ierrno)
{
    if (ierrno == EWOULDBLOCK)
	return 1;
#if EAGAIN != EWOULDBLOCK
    if (ierrno == EAGAIN)
	return 1;
#endif
    if (ierrno == EALREADY)
	return 1;
    if (ierrno == EINTR)
	return 1;
    return 0;
}

static void
commSetConnectTimeout(int fd, time_t timeout)
{
    fde *F = &fd_table[fd];
    F->connect_timeout = timeout;
}