root/usr.bin/dig/lib/isc/unix/socket.c 
/*
 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/*! \file */

#include <sys/socket.h>
#include <sys/time.h>
#include <sys/uio.h>

#include <netinet/tcp.h>

#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <isc/buffer.h>
#include <isc/bufferlist.h>

#include <isc/list.h>
#include <isc/log.h>
#include <isc/region.h>
#include <isc/socket.h>
#include <isc/task.h>
#include <isc/util.h>

#include "errno2result.h"

#include "socket_p.h"
#include "../task_p.h"

struct isc_socketwait {
        fd_set *readset;
        fd_set *writeset;
        int nfds;
        int maxfd;
};

/*
 * Set by the -T dscp option on the command line. If set to a value
 * other than -1, we check to make sure DSCP values match it, and
 * assert if not.
 */
int isc_dscp_check_value = -1;

/*%
 * Some systems define the socket length argument as an int, some as size_t,
 * some as socklen_t.  This is here so it can be easily changed if needed.
 */

/*%
 * Define what the possible "soft" errors can be.  These are non-fatal returns
 * of various network related functions, like recv() and so on.
 *
 * For some reason, BSDI (and perhaps others) will sometimes return <0
 * from recv() but will have errno==0.  This is broken, but we have to
 * work around it here.
 */
#define SOFT_ERROR(e)   ((e) == EAGAIN || \
                         (e) == EWOULDBLOCK || \
                         (e) == EINTR || \
                         (e) == 0)

#define DLVL(x) ISC_LOGCATEGORY_GENERAL, ISC_LOGMODULE_SOCKET, ISC_LOG_DEBUG(x)

/*!<
 * DLVL(90)  --  Function entry/exit and other tracing.
 * DLVL(60)  --  Socket data send/receive
 * DLVL(50)  --  Event tracing, including receiving/sending completion events.
 * DLVL(20)  --  Socket creation/destruction.
 */
#define TRACE_LEVEL             90
#define IOEVENT_LEVEL           60
#define EVENT_LEVEL             50
#define CREATION_LEVEL          20

#define TRACE           DLVL(TRACE_LEVEL)
#define IOEVENT         DLVL(IOEVENT_LEVEL)
#define EVENT           DLVL(EVENT_LEVEL)
#define CREATION        DLVL(CREATION_LEVEL)

typedef isc_event_t intev_t;

/*!
 * IPv6 control information.  If the socket is an IPv6 socket we want
 * to collect the destination address and interface so the client can
 * set them on outgoing packets.
 */

/*%
 * NetBSD and FreeBSD can timestamp packets.  XXXMLG Should we have
 * a setsockopt() like interface to request timestamps, and if the OS
 * doesn't do it for us, call gettimeofday() on every UDP receive?
 */

/*%
 * Instead of calculating the cmsgbuf lengths every time we take
 * a rule of thumb approach - sizes are taken from x86_64 linux,
 * multiplied by 2, everything should fit. Those sizes are not
 * large enough to cause any concern.
 */
#define CMSG_SP_IN6PKT 40

#define CMSG_SP_TIMESTAMP 32

#define CMSG_SP_TCTOS 24

#define CMSG_SP_INT 24

#define RECVCMSGBUFLEN (2*(CMSG_SP_IN6PKT + CMSG_SP_TIMESTAMP + CMSG_SP_TCTOS)+1)
#define SENDCMSGBUFLEN (2*(CMSG_SP_IN6PKT + CMSG_SP_INT + CMSG_SP_TCTOS)+1)

/*%
 * The number of times a send operation is repeated if the result is EINTR.
 */
#define NRETRIES 10

struct isc_socket {
        /* Not locked. */
        isc_socketmgr_t *manager;
        isc_sockettype_t        type;

        /* Locked by socket lock. */
        ISC_LINK(isc_socket_t)  link;
        unsigned int            references;
        int                     fd;
        int                     pf;

        ISC_LIST(isc_socketevent_t)             send_list;
        ISC_LIST(isc_socketevent_t)             recv_list;
        isc_socket_connev_t                    *connect_ev;

        /*
         * Internal events.  Posted when a descriptor is readable or
         * writable.  These are statically allocated and never freed.
         * They will be set to non-purgable before use.
         */
        intev_t                 readable_ev;
        intev_t                 writable_ev;

        struct sockaddr_storage         peer_address;       /* remote address */

        unsigned int            pending_recv : 1,
                                pending_send : 1,
                                connected : 1,
                                connecting : 1,     /* connect pending */
                                bound : 1,          /* bound to local addr */
                                active : 1,         /* currently active */
                                pktdscp : 1;        /* per packet dscp */
        unsigned int            dscp;
};

struct isc_socketmgr {
        /* Not locked. */
        int                     fd_bufsize;
        unsigned int            maxsocks;

        isc_socket_t           **fds;
        int                     *fdstate;

        /* Locked by manager lock. */
        ISC_LIST(isc_socket_t)  socklist;
        fd_set                  *read_fds;
        fd_set                  *read_fds_copy;
        fd_set                  *write_fds;
        fd_set                  *write_fds_copy;
        int                     maxfd;
        unsigned int            refs;
};

static isc_socketmgr_t *socketmgr = NULL;

#define CLOSED                  0       /* this one must be zero */
#define MANAGED                 1
#define CLOSE_PENDING           2

/*
 * send() and recv() iovec counts
 */
#define MAXSCATTERGATHER_SEND   (ISC_SOCKET_MAXSCATTERGATHER)
#define MAXSCATTERGATHER_RECV   (ISC_SOCKET_MAXSCATTERGATHER)

static isc_result_t socket_create(isc_socketmgr_t *manager0, int pf,
                                  isc_sockettype_t type,
                                  isc_socket_t **socketp);
static void send_recvdone_event(isc_socket_t *, isc_socketevent_t **);
static void send_senddone_event(isc_socket_t *, isc_socketevent_t **);
static void free_socket(isc_socket_t **);
static isc_result_t allocate_socket(isc_socketmgr_t *, isc_sockettype_t,
                                    isc_socket_t **);
static void destroy(isc_socket_t **);
static void internal_connect(isc_task_t *, isc_event_t *);
static void internal_recv(isc_task_t *, isc_event_t *);
static void internal_send(isc_task_t *, isc_event_t *);
static void process_cmsg(isc_socket_t *, struct msghdr *, isc_socketevent_t *);
static void build_msghdr_send(isc_socket_t *, char *, isc_socketevent_t *,
                              struct msghdr *, struct iovec *, size_t *);
static void build_msghdr_recv(isc_socket_t *, char *, isc_socketevent_t *,
                              struct msghdr *, struct iovec *, size_t *);

#define SELECT_POKE_SHUTDOWN            (-1)
#define SELECT_POKE_READ                (-3)
#define SELECT_POKE_WRITE               (-4)
#define SELECT_POKE_CONNECT             (-4) /*%< Same as _WRITE */
#define SELECT_POKE_CLOSE               (-5)

#define SOCK_DEAD(s)                    ((s)->references == 0)

/*%
 * Shortcut index arrays to get access to statistics counters.
 */
enum {
        STATID_OPEN = 0,
        STATID_OPENFAIL = 1,
        STATID_CLOSE = 2,
        STATID_BINDFAIL = 3,
        STATID_CONNECTFAIL = 4,
        STATID_CONNECT = 5,
        STATID_ACCEPTFAIL = 6,
        STATID_ACCEPT = 7,
        STATID_SENDFAIL = 8,
        STATID_RECVFAIL = 9,
        STATID_ACTIVE = 10
};

static void
socket_log(isc_socket_t *sock, struct sockaddr_storage *address,
           isc_logcategory_t *category, isc_logmodule_t *module, int level,
           const char *fmt, ...) __attribute__((__format__(__printf__, 6, 7)));
static void
socket_log(isc_socket_t *sock, struct sockaddr_storage *address,
           isc_logcategory_t *category, isc_logmodule_t *module, int level,
           const char *fmt, ...)
{
        char msgbuf[2048];
        char peerbuf[ISC_SOCKADDR_FORMATSIZE];
        va_list ap;

        if (! isc_log_wouldlog(isc_lctx, level))
                return;

        va_start(ap, fmt);
        vsnprintf(msgbuf, sizeof(msgbuf), fmt, ap);
        va_end(ap);

        if (address == NULL) {
                isc_log_write(isc_lctx, category, module, level,
                               "socket %p: %s", sock, msgbuf);
        } else {
                isc_sockaddr_format(address, peerbuf, sizeof(peerbuf));
                isc_log_write(isc_lctx, category, module, level,
                               "socket %p %s: %s", sock, peerbuf, msgbuf);
        }
}

static inline isc_result_t
watch_fd(isc_socketmgr_t *manager, int fd, int msg) {
        isc_result_t result = ISC_R_SUCCESS;

        if (msg == SELECT_POKE_READ)
                FD_SET(fd, manager->read_fds);
        if (msg == SELECT_POKE_WRITE)
                FD_SET(fd, manager->write_fds);

        return (result);
}

static inline isc_result_t
unwatch_fd(isc_socketmgr_t *manager, int fd, int msg) {
        isc_result_t result = ISC_R_SUCCESS;

        if (msg == SELECT_POKE_READ)
                FD_CLR(fd, manager->read_fds);
        else if (msg == SELECT_POKE_WRITE)
                FD_CLR(fd, manager->write_fds);

        return (result);
}

static void
wakeup_socket(isc_socketmgr_t *manager, int fd, int msg) {
        isc_result_t result;

        /*
         * This is a wakeup on a socket.  If the socket is not in the
         * process of being closed, start watching it for either reads
         * or writes.
         */

        INSIST(fd >= 0 && fd < (int)manager->maxsocks);

        if (msg == SELECT_POKE_CLOSE) {
                /* No one should be updating fdstate, so no need to lock it */
                INSIST(manager->fdstate[fd] == CLOSE_PENDING);
                manager->fdstate[fd] = CLOSED;
                (void)unwatch_fd(manager, fd, SELECT_POKE_READ);
                (void)unwatch_fd(manager, fd, SELECT_POKE_WRITE);
                (void)close(fd);
                return;
        }

        if (manager->fdstate[fd] == CLOSE_PENDING) {

                /*
                 * We accept (and ignore) any error from unwatch_fd() as we are
                 * closing the socket, hoping it doesn't leave dangling state in
                 * the kernel.
                 */
                (void)unwatch_fd(manager, fd, SELECT_POKE_READ);
                (void)unwatch_fd(manager, fd, SELECT_POKE_WRITE);
                return;
        }
        if (manager->fdstate[fd] != MANAGED) {
                return;
        }

        /*
         * Set requested bit.
         */
        result = watch_fd(manager, fd, msg);
        if (result != ISC_R_SUCCESS) {
                /*
                 * XXXJT: what should we do?  Ignoring the failure of watching
                 * a socket will make the application dysfunctional, but there
                 * seems to be no reasonable recovery process.
                 */
                isc_log_write(isc_lctx, ISC_LOGCATEGORY_GENERAL,
                              ISC_LOGMODULE_SOCKET, ISC_LOG_ERROR,
                              "failed to start watching FD (%d): %s",
                              fd, isc_result_totext(result));
        }
}

/*
 * Update the state of the socketmgr when something changes.
 */
static void
select_poke(isc_socketmgr_t *manager, int fd, int msg) {
        if (msg == SELECT_POKE_SHUTDOWN)
                return;
        else if (fd >= 0)
                wakeup_socket(manager, fd, msg);
        return;
}

/*
 * Make a fd non-blocking.
 */
static isc_result_t
make_nonblock(int fd) {
        int ret;
        int flags;

        flags = fcntl(fd, F_GETFL, 0);
        flags |= O_NONBLOCK;
        ret = fcntl(fd, F_SETFL, flags);

        if (ret == -1) {
                UNEXPECTED_ERROR(__FILE__, __LINE__,
                                 "fcntl(%d, F_SETFL, %d): %s", fd, flags,
                                 strerror(errno));
                return (ISC_R_UNEXPECTED);
        }

        return (ISC_R_SUCCESS);
}

/*
 * Not all OSes support advanced CMSG macros: CMSG_LEN and CMSG_SPACE.
 * In order to ensure as much portability as possible, we provide wrapper
 * functions of these macros.
 * Note that cmsg_space() could run slow on OSes that do not have
 * CMSG_SPACE.
 */
static inline socklen_t
cmsg_len(socklen_t len) {
        return (CMSG_LEN(len));
}

static inline socklen_t
cmsg_space(socklen_t len) {
        return (CMSG_SPACE(len));
}

/*
 * Process control messages received on a socket.
 */
static void
process_cmsg(isc_socket_t *sock, struct msghdr *msg, isc_socketevent_t *dev) {
        struct cmsghdr *cmsgp;
        struct in6_pktinfo *pktinfop;
        void *timevalp;

        /*
         * sock is used only when ISC_NET_BSD44MSGHDR and USE_CMSG are defined.
         * msg and dev are used only when ISC_NET_BSD44MSGHDR is defined.
         * They are all here, outside of the CPP tests, because it is
         * more consistent with the usual ISC coding style.
         */
        UNUSED(sock);
        UNUSED(msg);
        UNUSED(dev);

        if ((msg->msg_flags & MSG_TRUNC) == MSG_TRUNC)
                dev->attributes |= ISC_SOCKEVENTATTR_TRUNC;

        if ((msg->msg_flags & MSG_CTRUNC) == MSG_CTRUNC)
                dev->attributes |= ISC_SOCKEVENTATTR_CTRUNC;

        if (msg->msg_controllen == 0U || msg->msg_control == NULL)
                return;

        timevalp = NULL;
        pktinfop = NULL;

        cmsgp = CMSG_FIRSTHDR(msg);
        while (cmsgp != NULL) {
                socket_log(sock, NULL, TRACE,
                           "processing cmsg %p", cmsgp);

                if (cmsgp->cmsg_level == IPPROTO_IPV6
                    && cmsgp->cmsg_type == IPV6_PKTINFO) {

                        pktinfop = (struct in6_pktinfo *)CMSG_DATA(cmsgp);
                        memmove(&dev->pktinfo, pktinfop,
                                sizeof(struct in6_pktinfo));
                        dev->attributes |= ISC_SOCKEVENTATTR_PKTINFO;
                        socket_log(sock, NULL, TRACE,
                                   "interface received on ifindex %u",
                                   dev->pktinfo.ipi6_ifindex);
                        if (IN6_IS_ADDR_MULTICAST(&pktinfop->ipi6_addr))
                                dev->attributes |= ISC_SOCKEVENTATTR_MULTICAST;
                        goto next;
                }

                if (cmsgp->cmsg_level == SOL_SOCKET
                    && cmsgp->cmsg_type == SCM_TIMESTAMP) {
                        struct timeval tv;
                        timevalp = CMSG_DATA(cmsgp);
                        memmove(&tv, timevalp, sizeof(tv));
                        TIMEVAL_TO_TIMESPEC(&tv, &dev->timestamp);
                        dev->attributes |= ISC_SOCKEVENTATTR_TIMESTAMP;
                        goto next;
                }

                if (cmsgp->cmsg_level == IPPROTO_IPV6
                    && cmsgp->cmsg_type == IPV6_TCLASS) {
                        dev->dscp = *(int *)CMSG_DATA(cmsgp);
                        dev->dscp >>= 2;
                        dev->attributes |= ISC_SOCKEVENTATTR_DSCP;
                        goto next;
                }

                if (cmsgp->cmsg_level == IPPROTO_IP
                    && (cmsgp->cmsg_type == IP_TOS)) {
                        dev->dscp = (int) *(unsigned char *)CMSG_DATA(cmsgp);
                        dev->dscp >>= 2;
                        dev->attributes |= ISC_SOCKEVENTATTR_DSCP;
                        goto next;
                }
        next:
                cmsgp = CMSG_NXTHDR(msg, cmsgp);
        }

}

/*
 * Construct an iov array and attach it to the msghdr passed in.  This is
 * the SEND constructor, which will use the used region of the buffer
 * (if using a buffer list) or will use the internal region (if a single
 * buffer I/O is requested).
 *
 * Nothing can be NULL, and the done event must list at least one buffer
 * on the buffer linked list for this function to be meaningful.
 *
 * If write_countp != NULL, *write_countp will hold the number of bytes
 * this transaction can send.
 */
static void
build_msghdr_send(isc_socket_t *sock, char* cmsgbuf, isc_socketevent_t *dev,
                  struct msghdr *msg, struct iovec *iov, size_t *write_countp)
{
        unsigned int iovcount;
        isc_buffer_t *buffer;
        isc_region_t used;
        size_t write_count;
        size_t skip_count;
        struct cmsghdr *cmsgp;

        memset(msg, 0, sizeof(*msg));

        if (!sock->connected) {
                msg->msg_name = (void *)&dev->address;
                msg->msg_namelen = dev->address.ss_len;
        } else {
                msg->msg_name = NULL;
                msg->msg_namelen = 0;
        }

        buffer = ISC_LIST_HEAD(dev->bufferlist);
        write_count = 0;
        iovcount = 0;

        /*
         * Single buffer I/O?  Skip what we've done so far in this region.
         */
        if (buffer == NULL) {
                write_count = dev->region.length - dev->n;
                iov[0].iov_base = (void *)(dev->region.base + dev->n);
                iov[0].iov_len = write_count;
                iovcount = 1;

                goto config;
        }

        /*
         * Multibuffer I/O.
         * Skip the data in the buffer list that we have already written.
         */
        skip_count = dev->n;
        while (buffer != NULL) {
                if (skip_count < isc_buffer_usedlength(buffer))
                        break;
                skip_count -= isc_buffer_usedlength(buffer);
                buffer = ISC_LIST_NEXT(buffer, link);
        }

        while (buffer != NULL) {
                INSIST(iovcount < MAXSCATTERGATHER_SEND);

                isc_buffer_usedregion(buffer, &used);

                if (used.length > 0) {
                        iov[iovcount].iov_base = (void *)(used.base
                                                          + skip_count);
                        iov[iovcount].iov_len = used.length - skip_count;
                        write_count += (used.length - skip_count);
                        skip_count = 0;
                        iovcount++;
                }
                buffer = ISC_LIST_NEXT(buffer, link);
        }

        INSIST(skip_count == 0U);

 config:
        msg->msg_iov = iov;
        msg->msg_iovlen = iovcount;

        msg->msg_control = NULL;
        msg->msg_controllen = 0;
        msg->msg_flags = 0;

        if ((sock->type == isc_sockettype_udp) &&
            ((dev->attributes & ISC_SOCKEVENTATTR_PKTINFO) != 0))
        {
                struct in6_pktinfo *pktinfop;

                socket_log(sock, NULL, TRACE,
                           "sendto pktinfo data, ifindex %u",
                           dev->pktinfo.ipi6_ifindex);

                msg->msg_control = (void *)cmsgbuf;
                msg->msg_controllen = cmsg_space(sizeof(struct in6_pktinfo));
                INSIST(msg->msg_controllen <= SENDCMSGBUFLEN);

                cmsgp = (struct cmsghdr *)cmsgbuf;
                cmsgp->cmsg_level = IPPROTO_IPV6;
                cmsgp->cmsg_type = IPV6_PKTINFO;
                cmsgp->cmsg_len = cmsg_len(sizeof(struct in6_pktinfo));
                pktinfop = (struct in6_pktinfo *)CMSG_DATA(cmsgp);
                memmove(pktinfop, &dev->pktinfo, sizeof(struct in6_pktinfo));
        }

        if ((sock->type == isc_sockettype_udp) &&
            ((dev->attributes & ISC_SOCKEVENTATTR_USEMINMTU) != 0))
        {
                int use_min_mtu = 1;    /* -1, 0, 1 */

                cmsgp = (struct cmsghdr *)(cmsgbuf +
                                           msg->msg_controllen);

                msg->msg_control = (void *)cmsgbuf;
                msg->msg_controllen += cmsg_space(sizeof(use_min_mtu));
                INSIST(msg->msg_controllen <= SENDCMSGBUFLEN);

                cmsgp->cmsg_level = IPPROTO_IPV6;
                cmsgp->cmsg_type = IPV6_USE_MIN_MTU;
                cmsgp->cmsg_len = cmsg_len(sizeof(use_min_mtu));
                memmove(CMSG_DATA(cmsgp), &use_min_mtu, sizeof(use_min_mtu));
        }

        if (isc_dscp_check_value > -1) {
                if (sock->type == isc_sockettype_udp)
                        INSIST((int)dev->dscp == isc_dscp_check_value);
                else if (sock->type == isc_sockettype_tcp)
                        INSIST((int)sock->dscp == isc_dscp_check_value);
        }

        if ((sock->type == isc_sockettype_udp) &&
            ((dev->attributes & ISC_SOCKEVENTATTR_DSCP) != 0))
        {
                int dscp = (dev->dscp << 2) & 0xff;

                INSIST(dev->dscp < 0x40);

                if (sock->pf == AF_INET && sock->pktdscp) {
                        cmsgp = (struct cmsghdr *)(cmsgbuf +
                                                   msg->msg_controllen);
                        msg->msg_control = (void *)cmsgbuf;
                        msg->msg_controllen += cmsg_space(sizeof(dscp));
                        INSIST(msg->msg_controllen <= SENDCMSGBUFLEN);

                        cmsgp->cmsg_level = IPPROTO_IP;
                        cmsgp->cmsg_type = IP_TOS;
                        cmsgp->cmsg_len = cmsg_len(sizeof(char));
                        *(unsigned char*)CMSG_DATA(cmsgp) = dscp;
                } else if (sock->pf == AF_INET && sock->dscp != dev->dscp) {
                        if (setsockopt(sock->fd, IPPROTO_IP, IP_TOS,
                               (void *)&dscp, sizeof(int)) < 0)
                        {
                                UNEXPECTED_ERROR(__FILE__, __LINE__,
                                                 "setsockopt(%d, IP_TOS, %.02x)"
                                                 " %s: %s",
                                                 sock->fd, dscp >> 2,
                                                 "failed", strerror(errno));
                        } else
                                sock->dscp = dscp;
                }

                if (sock->pf == AF_INET6 && sock->pktdscp) {
                        cmsgp = (struct cmsghdr *)(cmsgbuf +
                                                   msg->msg_controllen);
                        msg->msg_control = (void *)cmsgbuf;
                        msg->msg_controllen += cmsg_space(sizeof(dscp));
                        INSIST(msg->msg_controllen <= SENDCMSGBUFLEN);

                        cmsgp->cmsg_level = IPPROTO_IPV6;
                        cmsgp->cmsg_type = IPV6_TCLASS;
                        cmsgp->cmsg_len = cmsg_len(sizeof(dscp));
                        memmove(CMSG_DATA(cmsgp), &dscp, sizeof(dscp));
                } else if (sock->pf == AF_INET6 && sock->dscp != dev->dscp) {
                        if (setsockopt(sock->fd, IPPROTO_IPV6, IPV6_TCLASS,
                                       (void *)&dscp, sizeof(int)) < 0) {
                                UNEXPECTED_ERROR(__FILE__, __LINE__,
                                                 "setsockopt(%d, IPV6_TCLASS, "
                                                 "%.02x) %s: %s",
                                                 sock->fd, dscp >> 2,
                                                 "failed", strerror(errno));
                        } else
                                sock->dscp = dscp;
                }

                if (msg->msg_controllen != 0 &&
                    msg->msg_controllen < SENDCMSGBUFLEN)
                {
                        memset(cmsgbuf + msg->msg_controllen, 0,
                               SENDCMSGBUFLEN - msg->msg_controllen);
                }
        }

        if (write_countp != NULL)
                *write_countp = write_count;
}

/*
 * Construct an iov array and attach it to the msghdr passed in.  This is
 * the RECV constructor, which will use the available region of the buffer
 * (if using a buffer list) or will use the internal region (if a single
 * buffer I/O is requested).
 *
 * Nothing can be NULL, and the done event must list at least one buffer
 * on the buffer linked list for this function to be meaningful.
 *
 * If read_countp != NULL, *read_countp will hold the number of bytes
 * this transaction can receive.
 */
static void
build_msghdr_recv(isc_socket_t *sock, char *cmsgbuf, isc_socketevent_t *dev,
                  struct msghdr *msg, struct iovec *iov, size_t *read_countp)
{
        unsigned int iovcount;
        isc_buffer_t *buffer;
        isc_region_t available;
        size_t read_count;

        memset(msg, 0, sizeof(struct msghdr));

        if (sock->type == isc_sockettype_udp) {
                memset(&dev->address, 0, sizeof(dev->address));
                msg->msg_name = (void *)&dev->address;
                msg->msg_namelen = sizeof(dev->address);
        } else { /* TCP */
                msg->msg_name = NULL;
                msg->msg_namelen = 0;
                dev->address = sock->peer_address;
        }

        buffer = ISC_LIST_HEAD(dev->bufferlist);
        read_count = 0;

        /*
         * Single buffer I/O?  Skip what we've done so far in this region.
         */
        if (buffer == NULL) {
                read_count = dev->region.length - dev->n;
                iov[0].iov_base = (void *)(dev->region.base + dev->n);
                iov[0].iov_len = read_count;
                iovcount = 1;

                goto config;
        }

        /*
         * Multibuffer I/O.
         * Skip empty buffers.
         */
        while (buffer != NULL) {
                if (isc_buffer_availablelength(buffer) != 0)
                        break;
                buffer = ISC_LIST_NEXT(buffer, link);
        }

        iovcount = 0;
        while (buffer != NULL) {
                INSIST(iovcount < MAXSCATTERGATHER_RECV);

                isc_buffer_availableregion(buffer, &available);

                if (available.length > 0) {
                        iov[iovcount].iov_base = (void *)(available.base);
                        iov[iovcount].iov_len = available.length;
                        read_count += available.length;
                        iovcount++;
                }
                buffer = ISC_LIST_NEXT(buffer, link);
        }

 config:

        /*
         * If needed, set up to receive that one extra byte.
         */
        msg->msg_iov = iov;
        msg->msg_iovlen = iovcount;

        msg->msg_control = cmsgbuf;
        msg->msg_controllen = RECVCMSGBUFLEN;
        msg->msg_flags = 0;

        if (read_countp != NULL)
                *read_countp = read_count;
}

static void
set_dev_address(struct sockaddr_storage *address, isc_socket_t *sock,
                isc_socketevent_t *dev)
{
        if (sock->type == isc_sockettype_udp) {
                if (address != NULL)
                        dev->address = *address;
                else
                        dev->address = sock->peer_address;
        } else if (sock->type == isc_sockettype_tcp) {
                INSIST(address == NULL);
                dev->address = sock->peer_address;
        }
}

static void
destroy_socketevent(isc_event_t *event) {
        isc_socketevent_t *ev = (isc_socketevent_t *)event;

        INSIST(ISC_LIST_EMPTY(ev->bufferlist));

        (ev->destroy)(event);
}

static isc_socketevent_t *
allocate_socketevent(void *sender,
                     isc_eventtype_t eventtype, isc_taskaction_t action,
                     void *arg)
{
        isc_socketevent_t *ev;

        ev = (isc_socketevent_t *)isc_event_allocate(sender,
                                                     eventtype, action, arg,
                                                     sizeof(*ev));

        if (ev == NULL)
                return (NULL);

        ev->result = ISC_R_UNSET;
        ISC_LINK_INIT(ev, ev_link);
        ISC_LIST_INIT(ev->bufferlist);
        ev->region.base = NULL;
        ev->n = 0;
        ev->offset = 0;
        ev->attributes = 0;
        ev->destroy = ev->ev_destroy;
        ev->ev_destroy = destroy_socketevent;
        ev->dscp = 0;

        return (ev);
}

#define DOIO_SUCCESS            0       /* i/o ok, event sent */
#define DOIO_SOFT               1       /* i/o ok, soft error, no event sent */
#define DOIO_HARD               2       /* i/o error, event sent */
#define DOIO_EOF                3       /* EOF, no event sent */

static int
doio_recv(isc_socket_t *sock, isc_socketevent_t *dev) {
        int cc;
        struct iovec iov[MAXSCATTERGATHER_RECV];
        size_t read_count;
        size_t actual_count;
        struct msghdr msghdr;
        isc_buffer_t *buffer;
        int recv_errno;
        union {
                struct msghdr msghdr;
                char m[RECVCMSGBUFLEN];
        } cmsgbuf;
        
        memset(&cmsgbuf, 0, sizeof(cmsgbuf));

        build_msghdr_recv(sock, cmsgbuf.m, dev, &msghdr, iov, &read_count);

        cc = recvmsg(sock->fd, &msghdr, 0);
        recv_errno = errno;

        if (cc < 0) {
                if (SOFT_ERROR(recv_errno))
                        return (DOIO_SOFT);

                if (isc_log_wouldlog(isc_lctx, IOEVENT_LEVEL)) {
                        socket_log(sock, NULL, IOEVENT,
                                  "doio_recv: recvmsg(%d) %d bytes, err %d/%s",
                                   sock->fd, cc, recv_errno,
                                   strerror(recv_errno));
                }

#define SOFT_OR_HARD(_system, _isc) \
        if (recv_errno == _system) { \
                if (sock->connected) { \
                        dev->result = _isc; \
                        return (DOIO_HARD); \
                } \
                return (DOIO_SOFT); \
        }
#define ALWAYS_HARD(_system, _isc) \
        if (recv_errno == _system) { \
                dev->result = _isc; \
                return (DOIO_HARD); \
        }

                SOFT_OR_HARD(ECONNREFUSED, ISC_R_CONNREFUSED);
                SOFT_OR_HARD(ENETUNREACH, ISC_R_NETUNREACH);
                SOFT_OR_HARD(EHOSTUNREACH, ISC_R_HOSTUNREACH);
                SOFT_OR_HARD(EHOSTDOWN, ISC_R_HOSTDOWN);
                /* HPUX 11.11 can return EADDRNOTAVAIL. */
                SOFT_OR_HARD(EADDRNOTAVAIL, ISC_R_ADDRNOTAVAIL);
                ALWAYS_HARD(ENOBUFS, ISC_R_NORESOURCES);
                /* Should never get this one but it was seen. */
                SOFT_OR_HARD(ENOPROTOOPT, ISC_R_HOSTUNREACH);
                /*
                 * HPUX returns EPROTO and EINVAL on receiving some ICMP/ICMPv6
                 * errors.
                 */
                SOFT_OR_HARD(EPROTO, ISC_R_HOSTUNREACH);
                SOFT_OR_HARD(EINVAL, ISC_R_HOSTUNREACH);

#undef SOFT_OR_HARD
#undef ALWAYS_HARD

                dev->result = isc__errno2result(recv_errno);
                return (DOIO_HARD);
        }

        /*
         * On TCP and UNIX sockets, zero length reads indicate EOF,
         * while on UDP sockets, zero length reads are perfectly valid,
         * although strange.
         */
        switch (sock->type) {
        case isc_sockettype_tcp:
                if (cc == 0)
                        return (DOIO_EOF);
                break;
        case isc_sockettype_udp:
                break;
        default:
                INSIST(0);
        }

        if (sock->type == isc_sockettype_udp) {
                dev->address.ss_len = msghdr.msg_namelen;
                if (isc_sockaddr_getport(&dev->address) == 0) {
                        if (isc_log_wouldlog(isc_lctx, IOEVENT_LEVEL)) {
                                socket_log(sock, &dev->address, IOEVENT,
                                           "dropping source port zero packet");
                        }
                        return (DOIO_SOFT);
                }
        }

        socket_log(sock, &dev->address, IOEVENT,
                   "packet received correctly");

        /*
         * Overflow bit detection.  If we received MORE bytes than we should,
         * this indicates an overflow situation.  Set the flag in the
         * dev entry and adjust how much we read by one.
         */
        /*
         * If there are control messages attached, run through them and pull
         * out the interesting bits.
         */
        process_cmsg(sock, &msghdr, dev);

        /*
         * update the buffers (if any) and the i/o count
         */
        dev->n += cc;
        actual_count = cc;
        buffer = ISC_LIST_HEAD(dev->bufferlist);
        while (buffer != NULL && actual_count > 0U) {
                if (isc_buffer_availablelength(buffer) <= actual_count) {
                        actual_count -= isc_buffer_availablelength(buffer);
                        isc_buffer_add(buffer,
                                       isc_buffer_availablelength(buffer));
                } else {
                        isc_buffer_add(buffer, actual_count);
                        actual_count = 0;
                        POST(actual_count);
                        break;
                }
                buffer = ISC_LIST_NEXT(buffer, link);
                if (buffer == NULL) {
                        INSIST(actual_count == 0U);
                }
        }

        /*
         * If we read less than we expected, update counters,
         * and let the upper layer poke the descriptor.
         */
        if (((size_t)cc != read_count) && (dev->n < dev->minimum))
                return (DOIO_SOFT);

        /*
         * Full reads are posted, or partials if partials are ok.
         */
        dev->result = ISC_R_SUCCESS;
        return (DOIO_SUCCESS);
}

/*
 * Returns:
 *      DOIO_SUCCESS    The operation succeeded.  dev->result contains
 *                      ISC_R_SUCCESS.
 *
 *      DOIO_HARD       A hard or unexpected I/O error was encountered.
 *                      dev->result contains the appropriate error.
 *
 *      DOIO_SOFT       A soft I/O error was encountered.  No senddone
 *                      event was sent.  The operation should be retried.
 *
 *      No other return values are possible.
 */
static int
doio_send(isc_socket_t *sock, isc_socketevent_t *dev) {
        int cc;
        struct iovec iov[MAXSCATTERGATHER_SEND];
        size_t write_count;
        struct msghdr msghdr;
        char addrbuf[ISC_SOCKADDR_FORMATSIZE];
        int attempts = 0;
        int send_errno;
        union {
                struct msghdr msghdr;
                char m[SENDCMSGBUFLEN];
        } cmsgbuf;
        
        memset(&cmsgbuf, 0, sizeof(cmsgbuf));

        build_msghdr_send(sock, cmsgbuf.m, dev, &msghdr, iov, &write_count);

 resend:
        cc = sendmsg(sock->fd, &msghdr, 0);
        send_errno = errno;

        /*
         * Check for error or block condition.
         */
        if (cc < 0) {
                if (send_errno == EINTR && ++attempts < NRETRIES)
                        goto resend;

                if (SOFT_ERROR(send_errno)) {
                        if (errno == EWOULDBLOCK || errno == EAGAIN)
                                dev->result = ISC_R_WOULDBLOCK;
                        return (DOIO_SOFT);
                }

#define SOFT_OR_HARD(_system, _isc) \
        if (send_errno == _system) { \
                if (sock->connected) { \
                        dev->result = _isc; \
                        return (DOIO_HARD); \
                } \
                return (DOIO_SOFT); \
        }
#define ALWAYS_HARD(_system, _isc) \
        if (send_errno == _system) { \
                dev->result = _isc; \
                return (DOIO_HARD); \
        }

                SOFT_OR_HARD(ECONNREFUSED, ISC_R_CONNREFUSED);
                ALWAYS_HARD(EACCES, ISC_R_NOPERM);
                ALWAYS_HARD(EAFNOSUPPORT, ISC_R_ADDRNOTAVAIL);
                ALWAYS_HARD(EADDRNOTAVAIL, ISC_R_ADDRNOTAVAIL);
                ALWAYS_HARD(EHOSTUNREACH, ISC_R_HOSTUNREACH);
                ALWAYS_HARD(EHOSTDOWN, ISC_R_HOSTUNREACH);
                ALWAYS_HARD(ENETUNREACH, ISC_R_NETUNREACH);
                ALWAYS_HARD(ENOBUFS, ISC_R_NORESOURCES);
                ALWAYS_HARD(EPERM, ISC_R_HOSTUNREACH);
                ALWAYS_HARD(EPIPE, ISC_R_NOTCONNECTED);
                ALWAYS_HARD(ECONNRESET, ISC_R_CONNECTIONRESET);

#undef SOFT_OR_HARD
#undef ALWAYS_HARD

                /*
                 * The other error types depend on whether or not the
                 * socket is UDP or TCP.  If it is UDP, some errors
                 * that we expect to be fatal under TCP are merely
                 * annoying, and are really soft errors.
                 *
                 * However, these soft errors are still returned as
                 * a status.
                 */
                isc_sockaddr_format(&dev->address, addrbuf, sizeof(addrbuf));
                UNEXPECTED_ERROR(__FILE__, __LINE__, "internal_send: %s: %s",
                                 addrbuf, strerror(send_errno));
                dev->result = isc__errno2result(send_errno);
                return (DOIO_HARD);
        }

        if (cc == 0) {
                UNEXPECTED_ERROR(__FILE__, __LINE__,
                                 "doio_send: send() %s 0", "returned");
        }

        /*
         * If we write less than we expected, update counters, poke.
         */
        dev->n += cc;
        if ((size_t)cc != write_count)
                return (DOIO_SOFT);

        /*
         * Exactly what we wanted to write.  We're done with this
         * entry.  Post its completion event.
         */
        dev->result = ISC_R_SUCCESS;
        return (DOIO_SUCCESS);
}

/*
 * Kill.
 *
 * Caller must ensure that the socket is not locked and no external
 * references exist.
 */
static void
socketclose(isc_socketmgr_t *manager, isc_socket_t *sock, int fd) {
        /*
         * No one has this socket open, so the watcher doesn't have to be
         * poked, and the socket doesn't have to be locked.
         */
        manager->fds[fd] = NULL;
        manager->fdstate[fd] = CLOSE_PENDING;
        select_poke(manager, fd, SELECT_POKE_CLOSE);

        if (sock->active == 1) {
                sock->active = 0;
        }

        /*
         * update manager->maxfd here (XXX: this should be implemented more
         * efficiently)
         */
        if (manager->maxfd == fd) {
                int i;

                manager->maxfd = 0;
                for (i = fd - 1; i >= 0; i--) {
                        if (manager->fdstate[i] == MANAGED) {
                                manager->maxfd = i;
                                break;
                        }
                }
        }

}

static void
destroy(isc_socket_t **sockp) {
        int fd;
        isc_socket_t *sock = *sockp;
        isc_socketmgr_t *manager = sock->manager;

        socket_log(sock, NULL, CREATION, "destroying");

        INSIST(ISC_LIST_EMPTY(sock->recv_list));
        INSIST(ISC_LIST_EMPTY(sock->send_list));
        INSIST(sock->connect_ev == NULL);
        INSIST(sock->fd >= -1 && sock->fd < (int)manager->maxsocks);

        if (sock->fd >= 0) {
                fd = sock->fd;
                sock->fd = -1;
                socketclose(manager, sock, fd);
        }

        ISC_LIST_UNLINK(manager->socklist, sock, link);

        /* can't unlock manager as its memory context is still used */
        free_socket(sockp);
}

static isc_result_t
allocate_socket(isc_socketmgr_t *manager, isc_sockettype_t type,
                isc_socket_t **socketp)
{
        isc_socket_t *sock;

        sock = malloc(sizeof(*sock));

        if (sock == NULL)
                return (ISC_R_NOMEMORY);

        sock->references = 0;

        sock->manager = manager;
        sock->type = type;
        sock->fd = -1;
        sock->dscp = 0;         /* TOS/TCLASS is zero until set. */
        sock->active = 0;

        ISC_LINK_INIT(sock, link);

        /*
         * Set up list of readers and writers to be initially empty.
         */
        ISC_LIST_INIT(sock->recv_list);
        ISC_LIST_INIT(sock->send_list);
        sock->connect_ev = NULL;
        sock->pending_recv = 0;
        sock->pending_send = 0;
        sock->connected = 0;
        sock->connecting = 0;
        sock->bound = 0;
        sock->pktdscp = 0;

        /*
         * Initialize readable and writable events.
         */
        ISC_EVENT_INIT(&sock->readable_ev, sizeof(intev_t),
                       ISC_EVENTATTR_NOPURGE, NULL, ISC_SOCKEVENT_INTR,
                       NULL, sock, sock, NULL);
        ISC_EVENT_INIT(&sock->writable_ev, sizeof(intev_t),
                       ISC_EVENTATTR_NOPURGE, NULL, ISC_SOCKEVENT_INTW,
                       NULL, sock, sock, NULL);

        *socketp = sock;

        return (ISC_R_SUCCESS);
}

/*
 * This event requires that the various lists be empty, that the reference
 * count be 1.  The other socket bits,
 * like the lock, must be initialized as well.  The fd associated must be
 * marked as closed, by setting it to -1 on close, or this routine will
 * also close the socket.
 */
static void
free_socket(isc_socket_t **socketp) {
        isc_socket_t *sock = *socketp;

        INSIST(sock->references == 0);
        INSIST(!sock->connecting);
        INSIST(!sock->pending_recv);
        INSIST(!sock->pending_send);
        INSIST(ISC_LIST_EMPTY(sock->recv_list));
        INSIST(ISC_LIST_EMPTY(sock->send_list));
        INSIST(!ISC_LINK_LINKED(sock, link));

        free(sock);

        *socketp = NULL;
}

static void
use_min_mtu(isc_socket_t *sock) {
        /* use minimum MTU */
        if (sock->pf == AF_INET6) {
                int on = 1;
                (void)setsockopt(sock->fd, IPPROTO_IPV6, IPV6_USE_MIN_MTU,
                                (void *)&on, sizeof(on));
        }
}

static void
set_tcp_maxseg(isc_socket_t *sock, int size) {
        if (sock->type == isc_sockettype_tcp)
                (void)setsockopt(sock->fd, IPPROTO_TCP, TCP_MAXSEG,
                                (void *)&size, sizeof(size));
}

static isc_result_t
opensocket(isc_socket_t *sock)
{
        isc_result_t result;
        const char *err = "socket";
        int on = 1;

        switch (sock->type) {
        case isc_sockettype_udp:
                sock->fd = socket(sock->pf, SOCK_DGRAM, IPPROTO_UDP);
                break;
        case isc_sockettype_tcp:
                sock->fd = socket(sock->pf, SOCK_STREAM, IPPROTO_TCP);
                break;
        }

        if (sock->fd < 0) {
                switch (errno) {
                case EMFILE:
                case ENFILE:
                        isc_log_write(isc_lctx, ISC_LOGCATEGORY_GENERAL,
                                       ISC_LOGMODULE_SOCKET, ISC_LOG_ERROR,
                                       "%s: %s", err, strerror(errno));
                        /* fallthrough */
                case ENOBUFS:
                        return (ISC_R_NORESOURCES);

                case EPROTONOSUPPORT:
                case EPFNOSUPPORT:
                case EAFNOSUPPORT:
                /*
                 * Linux 2.2 (and maybe others) return EINVAL instead of
                 * EAFNOSUPPORT.
                 */
                case EINVAL:
                        return (ISC_R_FAMILYNOSUPPORT);

                default:
                        UNEXPECTED_ERROR(__FILE__, __LINE__,
                                         "%s() %s: %s", err, "failed",
                                         strerror(errno));
                        return (ISC_R_UNEXPECTED);
                }
        }

        result = make_nonblock(sock->fd);
        if (result != ISC_R_SUCCESS) {
                (void)close(sock->fd);
                return (result);
        }

        /*
         * Use minimum mtu if possible.
         */
        if (sock->type == isc_sockettype_tcp && sock->pf == AF_INET6) {
                use_min_mtu(sock);
                set_tcp_maxseg(sock, 1280 - 20 - 40); /* 1280 - TCP - IPV6 */
        }

        if (sock->type == isc_sockettype_udp) {

                if (setsockopt(sock->fd, SOL_SOCKET, SO_TIMESTAMP,
                               (void *)&on, sizeof(on)) < 0
                    && errno != ENOPROTOOPT) {
                        UNEXPECTED_ERROR(__FILE__, __LINE__,
                                         "setsockopt(%d, SO_TIMESTAMP) %s: %s",
                                         sock->fd, "failed", strerror(errno));
                        /* Press on... */
                }

                /* RFC 3542 */
                if ((sock->pf == AF_INET6)
                    && (setsockopt(sock->fd, IPPROTO_IPV6, IPV6_RECVPKTINFO,
                                   (void *)&on, sizeof(on)) < 0)) {
                        UNEXPECTED_ERROR(__FILE__, __LINE__,
                                         "setsockopt(%d, IPV6_RECVPKTINFO) "
                                         "%s: %s", sock->fd, "failed",
                                         strerror(errno));
                }
        }

        if (sock->active == 0) {
                sock->active = 1;
        }

        return (ISC_R_SUCCESS);
}

/*
 * Create a 'type' socket managed
 * by 'manager'.  Events will be posted to 'task' and when dispatched
 * 'action' will be called with 'arg' as the arg value.  The new
 * socket is returned in 'socketp'.
 */
static isc_result_t
socket_create(isc_socketmgr_t *manager0, int pf, isc_sockettype_t type,
              isc_socket_t **socketp)
{
        isc_socket_t *sock = NULL;
        isc_socketmgr_t *manager = (isc_socketmgr_t *)manager0;
        isc_result_t result;

        REQUIRE(socketp != NULL && *socketp == NULL);

        result = allocate_socket(manager, type, &sock);
        if (result != ISC_R_SUCCESS)
                return (result);

        switch (sock->type) {
        case isc_sockettype_udp:
                sock->pktdscp = 1;
                break;
        case isc_sockettype_tcp:
                break;
        default:
                INSIST(0);
        }

        sock->pf = pf;

        result = opensocket(sock);
        if (result != ISC_R_SUCCESS) {
                free_socket(&sock);
                return (result);
        }

        sock->references = 1;
        *socketp = (isc_socket_t *)sock;

        /*
         * Note we don't have to lock the socket like we normally would because
         * there are no external references to it yet.
         */

        manager->fds[sock->fd] = sock;
        manager->fdstate[sock->fd] = MANAGED;

        ISC_LIST_APPEND(manager->socklist, sock, link);
        if (manager->maxfd < sock->fd)
                manager->maxfd = sock->fd;

        socket_log(sock, NULL, CREATION, "created");

        return (ISC_R_SUCCESS);
}

/*%
 * Create a new 'type' socket managed by 'manager'.  Events
 * will be posted to 'task' and when dispatched 'action' will be
 * called with 'arg' as the arg value.  The new socket is returned
 * in 'socketp'.
 */
isc_result_t
isc_socket_create(isc_socketmgr_t *manager0, int pf, isc_sockettype_t type,
                   isc_socket_t **socketp)
{
        return (socket_create(manager0, pf, type, socketp));
}

/*
 * Attach to a socket.  Caller must explicitly detach when it is done.
 */
void
isc_socket_attach(isc_socket_t *sock0, isc_socket_t **socketp) {
        isc_socket_t *sock = (isc_socket_t *)sock0;

        REQUIRE(socketp != NULL && *socketp == NULL);

        sock->references++;

        *socketp = (isc_socket_t *)sock;
}

/*
 * Dereference a socket.  If this is the last reference to it, clean things
 * up by destroying the socket.
 */
void
isc_socket_detach(isc_socket_t **socketp) {
        isc_socket_t *sock;
        int kill_socket = 0;

        REQUIRE(socketp != NULL);
        sock = (isc_socket_t *)*socketp;

        REQUIRE(sock->references > 0);
        sock->references--;
        if (sock->references == 0)
                kill_socket = 1;

        if (kill_socket)
                destroy(&sock);

        *socketp = NULL;
}

/*
 * I/O is possible on a given socket.  Schedule an event to this task that
 * will call an internal function to do the I/O.  This will charge the
 * task with the I/O operation and let our select loop handler get back
 * to doing something real as fast as possible.
 *
 * The socket and manager must be locked before calling this function.
 */
static void
dispatch_recv(isc_socket_t *sock) {
        intev_t *iev;
        isc_socketevent_t *ev;
        isc_task_t *sender;

        INSIST(!sock->pending_recv);

        ev = ISC_LIST_HEAD(sock->recv_list);
        if (ev == NULL)
                return;
        socket_log(sock, NULL, EVENT,
                   "dispatch_recv:  event %p -> task %p",
                   ev, ev->ev_sender);
        sender = ev->ev_sender;

        sock->pending_recv = 1;
        iev = &sock->readable_ev;

        sock->references++;
        iev->ev_sender = sock;
        iev->ev_action = internal_recv;
        iev->ev_arg = sock;

        isc_task_send(sender, (isc_event_t **)&iev);
}

static void
dispatch_send(isc_socket_t *sock) {
        intev_t *iev;
        isc_socketevent_t *ev;
        isc_task_t *sender;

        INSIST(!sock->pending_send);

        ev = ISC_LIST_HEAD(sock->send_list);
        if (ev == NULL)
                return;
        socket_log(sock, NULL, EVENT,
                   "dispatch_send:  event %p -> task %p",
                   ev, ev->ev_sender);
        sender = ev->ev_sender;

        sock->pending_send = 1;
        iev = &sock->writable_ev;

        sock->references++;
        iev->ev_sender = sock;
        iev->ev_action = internal_send;
        iev->ev_arg = sock;

        isc_task_send(sender, (isc_event_t **)&iev);
}

static void
dispatch_connect(isc_socket_t *sock) {
        intev_t *iev;
        isc_socket_connev_t *ev;

        iev = &sock->writable_ev;

        ev = sock->connect_ev;
        INSIST(ev != NULL); /* XXX */

        INSIST(sock->connecting);

        sock->references++;  /* keep socket around for this internal event */
        iev->ev_sender = sock;
        iev->ev_action = internal_connect;
        iev->ev_arg = sock;

        isc_task_send(ev->ev_sender, (isc_event_t **)&iev);
}

/*
 * Dequeue an item off the given socket's read queue, set the result code
 * in the done event to the one provided, and send it to the task it was
 * destined for.
 *
 * If the event to be sent is on a list, remove it before sending.  If
 * asked to, send and detach from the socket as well.
 *
 * Caller must have the socket locked if the event is attached to the socket.
 */
static void
send_recvdone_event(isc_socket_t *sock, isc_socketevent_t **dev) {
        isc_task_t *task;

        task = (*dev)->ev_sender;

        (*dev)->ev_sender = sock;

        if (ISC_LINK_LINKED(*dev, ev_link))
                ISC_LIST_DEQUEUE(sock->recv_list, *dev, ev_link);

        if (((*dev)->attributes & ISC_SOCKEVENTATTR_ATTACHED)
            == ISC_SOCKEVENTATTR_ATTACHED)
                isc_task_sendanddetach(&task, (isc_event_t **)dev);
        else
                isc_task_send(task, (isc_event_t **)dev);
}

/*
 * See comments for send_recvdone_event() above.
 *
 * Caller must have the socket locked if the event is attached to the socket.
 */
static void
send_senddone_event(isc_socket_t *sock, isc_socketevent_t **dev) {
        isc_task_t *task;

        INSIST(dev != NULL && *dev != NULL);

        task = (*dev)->ev_sender;
        (*dev)->ev_sender = sock;

        if (ISC_LINK_LINKED(*dev, ev_link))
                ISC_LIST_DEQUEUE(sock->send_list, *dev, ev_link);

        if (((*dev)->attributes & ISC_SOCKEVENTATTR_ATTACHED)
            == ISC_SOCKEVENTATTR_ATTACHED)
                isc_task_sendanddetach(&task, (isc_event_t **)dev);
        else
                isc_task_send(task, (isc_event_t **)dev);
}

static void
internal_recv(isc_task_t *me, isc_event_t *ev) {
        isc_socketevent_t *dev;
        isc_socket_t *sock;

        INSIST(ev->ev_type == ISC_SOCKEVENT_INTR);

        sock = ev->ev_sender;

        socket_log(sock, NULL, IOEVENT,
                   "internal_recv: task %p got event %p", me, ev);

        INSIST(sock->pending_recv == 1);
        sock->pending_recv = 0;

        INSIST(sock->references > 0);
        sock->references--;  /* the internal event is done with this socket */
        if (sock->references == 0) {
                destroy(&sock);
                return;
        }

        /*
         * Try to do as much I/O as possible on this socket.  There are no
         * limits here, currently.
         */
        dev = ISC_LIST_HEAD(sock->recv_list);
        while (dev != NULL) {
                switch (doio_recv(sock, dev)) {
                case DOIO_SOFT:
                        goto poke;

                case DOIO_EOF:
                        /*
                         * read of 0 means the remote end was closed.
                         * Run through the event queue and dispatch all
                         * the events with an EOF result code.
                         */
                        do {
                                dev->result = ISC_R_EOF;
                                send_recvdone_event(sock, &dev);
                                dev = ISC_LIST_HEAD(sock->recv_list);
                        } while (dev != NULL);
                        goto poke;

                case DOIO_SUCCESS:
                case DOIO_HARD:
                        send_recvdone_event(sock, &dev);
                        break;
                }

                dev = ISC_LIST_HEAD(sock->recv_list);
        }

 poke:
        if (!ISC_LIST_EMPTY(sock->recv_list))
                select_poke(sock->manager, sock->fd, SELECT_POKE_READ);
}

static void
internal_send(isc_task_t *me, isc_event_t *ev) {
        isc_socketevent_t *dev;
        isc_socket_t *sock;

        INSIST(ev->ev_type == ISC_SOCKEVENT_INTW);

        /*
         * Find out what socket this is and lock it.
         */
        sock = (isc_socket_t *)ev->ev_sender;
        socket_log(sock, NULL, IOEVENT,
                   "internal_send: task %p got event %p", me, ev);

        INSIST(sock->pending_send == 1);
        sock->pending_send = 0;

        INSIST(sock->references > 0);
        sock->references--;  /* the internal event is done with this socket */
        if (sock->references == 0) {
                destroy(&sock);
                return;
        }

        /*
         * Try to do as much I/O as possible on this socket.  There are no
         * limits here, currently.
         */
        dev = ISC_LIST_HEAD(sock->send_list);
        while (dev != NULL) {
                switch (doio_send(sock, dev)) {
                case DOIO_SOFT:
                        goto poke;

                case DOIO_HARD:
                case DOIO_SUCCESS:
                        send_senddone_event(sock, &dev);
                        break;
                }

                dev = ISC_LIST_HEAD(sock->send_list);
        }

 poke:
        if (!ISC_LIST_EMPTY(sock->send_list))
                select_poke(sock->manager, sock->fd, SELECT_POKE_WRITE);
}

/*
 * Process read/writes on each fd here.  Avoid locking
 * and unlocking twice if both reads and writes are possible.
 */
static void
process_fd(isc_socketmgr_t *manager, int fd, int readable,
           int writeable)
{
        isc_socket_t *sock;
        int unwatch_read = 0, unwatch_write = 0;

        /*
         * If the socket is going to be closed, don't do more I/O.
         */
        if (manager->fdstate[fd] == CLOSE_PENDING) {
                (void)unwatch_fd(manager, fd, SELECT_POKE_READ);
                (void)unwatch_fd(manager, fd, SELECT_POKE_WRITE);
                return;
        }

        sock = manager->fds[fd];
        if (readable) {
                if (sock == NULL) {
                        unwatch_read = 1;
                        goto check_write;
                }
                if (!SOCK_DEAD(sock)) {
                        dispatch_recv(sock);
                }
                unwatch_read = 1;
        }
check_write:
        if (writeable) {
                if (sock == NULL) {
                        unwatch_write = 1;
                        goto unlock_fd;
                }
                if (!SOCK_DEAD(sock)) {
                        if (sock->connecting)
                                dispatch_connect(sock);
                        else
                                dispatch_send(sock);
                }
                unwatch_write = 1;
        }

 unlock_fd:
        if (unwatch_read)
                (void)unwatch_fd(manager, fd, SELECT_POKE_READ);
        if (unwatch_write)
                (void)unwatch_fd(manager, fd, SELECT_POKE_WRITE);

}

static void
process_fds(isc_socketmgr_t *manager, int maxfd, fd_set *readfds,
            fd_set *writefds)
{
        int i;

        REQUIRE(maxfd <= (int)manager->maxsocks);

        for (i = 0; i < maxfd; i++) {
                process_fd(manager, i, FD_ISSET(i, readfds),
                           FD_ISSET(i, writefds));
        }
}

/*
 * Create a new socket manager.
 */

static isc_result_t
setup_watcher(isc_socketmgr_t *manager) {
        isc_result_t result;

        UNUSED(result);

        manager->fd_bufsize = sizeof(fd_set);

        manager->read_fds = NULL;
        manager->read_fds_copy = NULL;
        manager->write_fds = NULL;
        manager->write_fds_copy = NULL;

        manager->read_fds = malloc(manager->fd_bufsize);
        if (manager->read_fds != NULL)
                manager->read_fds_copy = malloc(manager->fd_bufsize);
        if (manager->read_fds_copy != NULL)
                manager->write_fds = malloc(manager->fd_bufsize);
        if (manager->write_fds != NULL) {
                manager->write_fds_copy = malloc(manager->fd_bufsize);
        }
        if (manager->write_fds_copy == NULL) {
                if (manager->write_fds != NULL) {
                        free(manager->write_fds);
                }
                if (manager->read_fds_copy != NULL) {
                        free(manager->read_fds_copy);
                }
                if (manager->read_fds != NULL) {
                        free(manager->read_fds);
                }
                return (ISC_R_NOMEMORY);
        }
        memset(manager->read_fds, 0, manager->fd_bufsize);
        memset(manager->write_fds, 0, manager->fd_bufsize);

        manager->maxfd = 0;

        return (ISC_R_SUCCESS);
}

static void
cleanup_watcher(isc_socketmgr_t *manager) {

        if (manager->read_fds != NULL)
                free(manager->read_fds);
        if (manager->read_fds_copy != NULL)
                free(manager->read_fds_copy);
        if (manager->write_fds != NULL)
                free(manager->write_fds);
        if (manager->write_fds_copy != NULL)
                free(manager->write_fds_copy);
}

static isc_result_t
isc_socketmgr_create2(isc_socketmgr_t **managerp,
                       unsigned int maxsocks)
{
        isc_socketmgr_t *manager;
        isc_result_t result;

        REQUIRE(managerp != NULL && *managerp == NULL);

        if (socketmgr != NULL) {
                /* Don't allow maxsocks to be updated */
                if (maxsocks > 0 && socketmgr->maxsocks != maxsocks)
                        return (ISC_R_EXISTS);

                socketmgr->refs++;
                *managerp = (isc_socketmgr_t *)socketmgr;
                return (ISC_R_SUCCESS);
        }

        if (maxsocks == 0)
                maxsocks = FD_SETSIZE;

        manager = malloc(sizeof(*manager));
        if (manager == NULL)
                return (ISC_R_NOMEMORY);

        /* zero-clear so that necessary cleanup on failure will be easy */
        memset(manager, 0, sizeof(*manager));
        manager->maxsocks = maxsocks;
        manager->fds = reallocarray(NULL, manager->maxsocks, sizeof(isc_socket_t *));
        if (manager->fds == NULL) {
                result = ISC_R_NOMEMORY;
                goto free_manager;
        }
        manager->fdstate = reallocarray(NULL, manager->maxsocks, sizeof(int));
        if (manager->fdstate == NULL) {
                result = ISC_R_NOMEMORY;
                goto free_manager;
        }

        memset(manager->fds, 0, manager->maxsocks * sizeof(isc_socket_t *));
        ISC_LIST_INIT(manager->socklist);

        manager->refs = 1;

        /*
         * Set up initial state for the select loop
         */
        result = setup_watcher(manager);
        if (result != ISC_R_SUCCESS)
                goto cleanup;

        memset(manager->fdstate, 0, manager->maxsocks * sizeof(int));

        socketmgr = manager;
        *managerp = (isc_socketmgr_t *)manager;

        return (ISC_R_SUCCESS);

cleanup:

free_manager:
        if (manager->fdstate != NULL) {
                free(manager->fdstate);
        }
        if (manager->fds != NULL) {
                free(manager->fds);
        }
        free(manager);

        return (result);
}

isc_result_t
isc_socketmgr_create(isc_socketmgr_t **managerp) {
        return (isc_socketmgr_create2(managerp, 0));
}

void
isc_socketmgr_destroy(isc_socketmgr_t **managerp) {
        isc_socketmgr_t *manager;
        int i;

        /*
         * Destroy a socket manager.
         */

        REQUIRE(managerp != NULL);
        manager = (isc_socketmgr_t *)*managerp;

        manager->refs--;
        if (manager->refs > 0) {
                *managerp = NULL;
                return;
        }
        socketmgr = NULL;

        /*
         * Wait for all sockets to be destroyed.
         */
        while (!ISC_LIST_EMPTY(manager->socklist)) {
                isc_taskmgr_dispatch(NULL);
        }

        /*
         * Here, poke our select/poll thread.  Do this by closing the write
         * half of the pipe, which will send EOF to the read half.
         * This is currently a no-op in the non-threaded case.
         */
        select_poke(manager, 0, SELECT_POKE_SHUTDOWN);

        /*
         * Clean up.
         */
        cleanup_watcher(manager);

        for (i = 0; i < (int)manager->maxsocks; i++)
                if (manager->fdstate[i] == CLOSE_PENDING) /* no need to lock */
                        (void)close(i);

        free(manager->fds);
        free(manager->fdstate);

        free(manager);

        *managerp = NULL;

        socketmgr = NULL;
}

static isc_result_t
socket_recv(isc_socket_t *sock, isc_socketevent_t *dev, isc_task_t *task,
            unsigned int flags)
{
        int io_state;
        isc_task_t *ntask = NULL;
        isc_result_t result = ISC_R_SUCCESS;

        dev->ev_sender = task;

        if (sock->type == isc_sockettype_udp) {
                io_state = doio_recv(sock, dev);
        } else {
                if (ISC_LIST_EMPTY(sock->recv_list))
                        io_state = doio_recv(sock, dev);
                else
                        io_state = DOIO_SOFT;
        }

        switch (io_state) {
        case DOIO_SOFT:
                /*
                 * We couldn't read all or part of the request right now, so
                 * queue it.
                 *
                 * Attach to socket and to task
                 */
                isc_task_attach(task, &ntask);
                dev->attributes |= ISC_SOCKEVENTATTR_ATTACHED;

                /*
                 * Enqueue the request.  If the socket was previously not being
                 * watched, poke the watcher to start paying attention to it.
                 */
                if (ISC_LIST_EMPTY(sock->recv_list) && !sock->pending_recv)
                        select_poke(sock->manager, sock->fd, SELECT_POKE_READ);
                ISC_LIST_ENQUEUE(sock->recv_list, dev, ev_link);

                socket_log(sock, NULL, EVENT,
                           "socket_recv: event %p -> task %p",
                           dev, ntask);

                if ((flags & ISC_SOCKFLAG_IMMEDIATE) != 0)
                        result = ISC_R_INPROGRESS;
                break;

        case DOIO_EOF:
                dev->result = ISC_R_EOF;
                /* fallthrough */

        case DOIO_HARD:
        case DOIO_SUCCESS:
                if ((flags & ISC_SOCKFLAG_IMMEDIATE) == 0)
                        send_recvdone_event(sock, &dev);
                break;
        }

        return (result);
}

isc_result_t
isc_socket_recvv(isc_socket_t *sock0, isc_bufferlist_t *buflist,
                  unsigned int minimum, isc_task_t *task,
                  isc_taskaction_t action, void *arg)
{
        isc_socket_t *sock = (isc_socket_t *)sock0;
        isc_socketevent_t *dev;
        unsigned int iocount;
        isc_buffer_t *buffer;

        REQUIRE(buflist != NULL);
        REQUIRE(!ISC_LIST_EMPTY(*buflist));
        REQUIRE(task != NULL);
        REQUIRE(action != NULL);

        iocount = isc_bufferlist_availablecount(buflist);
        REQUIRE(iocount > 0);

        INSIST(sock->bound);

        dev = allocate_socketevent(sock,
                                   ISC_SOCKEVENT_RECVDONE, action, arg);
        if (dev == NULL)
                return (ISC_R_NOMEMORY);

        /*
         * UDP sockets are always partial read
         */
        if (sock->type == isc_sockettype_udp)
                dev->minimum = 1;
        else {
                if (minimum == 0)
                        dev->minimum = iocount;
                else
                        dev->minimum = minimum;
        }

        /*
         * Move each buffer from the passed in list to our internal one.
         */
        buffer = ISC_LIST_HEAD(*buflist);
        while (buffer != NULL) {
                ISC_LIST_DEQUEUE(*buflist, buffer, link);
                ISC_LIST_ENQUEUE(dev->bufferlist, buffer, link);
                buffer = ISC_LIST_HEAD(*buflist);
        }

        return (socket_recv(sock, dev, task, 0));
}

static isc_result_t
socket_send(isc_socket_t *sock, isc_socketevent_t *dev, isc_task_t *task,
            struct sockaddr_storage *address, struct in6_pktinfo *pktinfo,
            unsigned int flags)
{
        int io_state;
        isc_task_t *ntask = NULL;
        isc_result_t result = ISC_R_SUCCESS;

        dev->ev_sender = task;

        set_dev_address(address, sock, dev);
        if (pktinfo != NULL) {
                dev->attributes |= ISC_SOCKEVENTATTR_PKTINFO;
                dev->pktinfo = *pktinfo;

                if (!isc_sockaddr_issitelocal(&dev->address) &&
                    !isc_sockaddr_islinklocal(&dev->address)) {
                        socket_log(sock, NULL, TRACE,
                                   "pktinfo structure provided, ifindex %u "
                                   "(set to 0)", pktinfo->ipi6_ifindex);

                        /*
                         * Set the pktinfo index to 0 here, to let the
                         * kernel decide what interface it should send on.
                         */
                        dev->pktinfo.ipi6_ifindex = 0;
                }
        }

        if (sock->type == isc_sockettype_udp)
                io_state = doio_send(sock, dev);
        else {
                if (ISC_LIST_EMPTY(sock->send_list))
                        io_state = doio_send(sock, dev);
                else
                        io_state = DOIO_SOFT;
        }

        switch (io_state) {
        case DOIO_SOFT:
                /*
                 * We couldn't send all or part of the request right now, so
                 * queue it unless ISC_SOCKFLAG_NORETRY is set.
                 */
                if ((flags & ISC_SOCKFLAG_NORETRY) == 0) {
                        isc_task_attach(task, &ntask);
                        dev->attributes |= ISC_SOCKEVENTATTR_ATTACHED;

                        /*
                         * Enqueue the request.  If the socket was previously
                         * not being watched, poke the watcher to start
                         * paying attention to it.
                         */
                        if (ISC_LIST_EMPTY(sock->send_list) &&
                            !sock->pending_send)
                                select_poke(sock->manager, sock->fd,
                                            SELECT_POKE_WRITE);
                        ISC_LIST_ENQUEUE(sock->send_list, dev, ev_link);

                        socket_log(sock, NULL, EVENT,
                                   "socket_send: event %p -> task %p",
                                   dev, ntask);

                        if ((flags & ISC_SOCKFLAG_IMMEDIATE) != 0)
                                result = ISC_R_INPROGRESS;
                        break;
                }

                /* FALLTHROUGH */

        case DOIO_HARD:
        case DOIO_SUCCESS:
                if ((flags & ISC_SOCKFLAG_IMMEDIATE) == 0)
                        send_senddone_event(sock, &dev);
                break;
        }

        return (result);
}

isc_result_t
isc_socket_sendv(isc_socket_t *sock, isc_bufferlist_t *buflist,
                  isc_task_t *task, isc_taskaction_t action, void *arg)
{
        return (isc_socket_sendtov2(sock, buflist, task, action, arg, NULL,
                                     NULL, 0));
}

isc_result_t
isc_socket_sendtov2(isc_socket_t *sock0, isc_bufferlist_t *buflist,
                     isc_task_t *task, isc_taskaction_t action, void *arg,
                     struct sockaddr_storage *address, struct in6_pktinfo *pktinfo,
                     unsigned int flags)
{
        isc_socket_t *sock = (isc_socket_t *)sock0;
        isc_socketevent_t *dev;
        unsigned int iocount;
        isc_buffer_t *buffer;

        REQUIRE(buflist != NULL);
        REQUIRE(!ISC_LIST_EMPTY(*buflist));
        REQUIRE(task != NULL);
        REQUIRE(action != NULL);

        iocount = isc_bufferlist_usedcount(buflist);
        REQUIRE(iocount > 0);

        dev = allocate_socketevent(sock,
                                   ISC_SOCKEVENT_SENDDONE, action, arg);
        if (dev == NULL)
                return (ISC_R_NOMEMORY);

        /*
         * Move each buffer from the passed in list to our internal one.
         */
        buffer = ISC_LIST_HEAD(*buflist);
        while (buffer != NULL) {
                ISC_LIST_DEQUEUE(*buflist, buffer, link);
                ISC_LIST_ENQUEUE(dev->bufferlist, buffer, link);
                buffer = ISC_LIST_HEAD(*buflist);
        }

        return (socket_send(sock, dev, task, address, pktinfo, flags));
}

isc_result_t
isc_socket_bind(isc_socket_t *sock0, struct sockaddr_storage *sockaddr,
                 unsigned int options) {
        isc_socket_t *sock = (isc_socket_t *)sock0;
        int on = 1;

        INSIST(!sock->bound);

        if (sock->pf != sockaddr->ss_family) {
                return (ISC_R_FAMILYMISMATCH);
        }

        /*
         * Only set SO_REUSEADDR when we want a specific port.
         */
        if ((options & ISC_SOCKET_REUSEADDRESS) != 0 &&
            isc_sockaddr_getport(sockaddr) != (in_port_t)0 &&
            setsockopt(sock->fd, SOL_SOCKET, SO_REUSEADDR, (void *)&on,
                       sizeof(on)) < 0) {
                UNEXPECTED_ERROR(__FILE__, __LINE__,
                                 "setsockopt(%d) %s", sock->fd, "failed");
                /* Press on... */
        }
        if (bind(sock->fd, (struct sockaddr *)sockaddr, sockaddr->ss_len) < 0) {
                switch (errno) {
                case EACCES:
                        return (ISC_R_NOPERM);
                case EADDRNOTAVAIL:
                        return (ISC_R_ADDRNOTAVAIL);
                case EADDRINUSE:
                        return (ISC_R_ADDRINUSE);
                case EINVAL:
                        return (ISC_R_BOUND);
                default:
                        UNEXPECTED_ERROR(__FILE__, __LINE__, "bind: %s",
                                         strerror(errno));
                        return (ISC_R_UNEXPECTED);
                }
        }

        socket_log(sock, sockaddr, TRACE, "bound");
        sock->bound = 1;

        return (ISC_R_SUCCESS);
}

isc_result_t
isc_socket_connect(isc_socket_t *sock0, struct sockaddr_storage *addr,
                   isc_task_t *task, isc_taskaction_t action, void *arg)
{
        isc_socket_t *sock = (isc_socket_t *)sock0;
        isc_socket_connev_t *dev;
        isc_task_t *ntask = NULL;
        isc_socketmgr_t *manager;
        int cc;
        char addrbuf[ISC_SOCKADDR_FORMATSIZE];

        REQUIRE(addr != NULL);
        REQUIRE(task != NULL);
        REQUIRE(action != NULL);

        manager = sock->manager;
        REQUIRE(addr != NULL);

        if (isc_sockaddr_ismulticast(addr))
                return (ISC_R_MULTICAST);

        REQUIRE(!sock->connecting);

        dev = (isc_socket_connev_t *)isc_event_allocate(sock,
                                                        ISC_SOCKEVENT_CONNECT,
                                                        action, arg,
                                                        sizeof(*dev));
        if (dev == NULL) {
                return (ISC_R_NOMEMORY);
        }
        ISC_LINK_INIT(dev, ev_link);

        /*
         * Try to do the connect right away, as there can be only one
         * outstanding, and it might happen to complete.
         */
        sock->peer_address = *addr;
        cc = connect(sock->fd, (struct sockaddr *)addr, addr->ss_len);
        if (cc < 0) {
                /*
                 * HP-UX "fails" to connect a UDP socket and sets errno to
                 * EINPROGRESS if it's non-blocking.  We'd rather regard this as
                 * a success and let the user detect it if it's really an error
                 * at the time of sending a packet on the socket.
                 */
                if (sock->type == isc_sockettype_udp && errno == EINPROGRESS) {
                        cc = 0;
                        goto success;
                }
                if (SOFT_ERROR(errno) || errno == EINPROGRESS)
                        goto queue;

                switch (errno) {
#define ERROR_MATCH(a, b) case a: dev->result = b; goto err_exit;
                        ERROR_MATCH(EACCES, ISC_R_NOPERM);
                        ERROR_MATCH(EADDRNOTAVAIL, ISC_R_ADDRNOTAVAIL);
                        ERROR_MATCH(EAFNOSUPPORT, ISC_R_ADDRNOTAVAIL);
                        ERROR_MATCH(ECONNREFUSED, ISC_R_CONNREFUSED);
                        ERROR_MATCH(EHOSTUNREACH, ISC_R_HOSTUNREACH);
                        ERROR_MATCH(EHOSTDOWN, ISC_R_HOSTUNREACH);
                        ERROR_MATCH(ENETUNREACH, ISC_R_NETUNREACH);
                        ERROR_MATCH(ENOBUFS, ISC_R_NORESOURCES);
                        ERROR_MATCH(EPERM, ISC_R_HOSTUNREACH);
                        ERROR_MATCH(EPIPE, ISC_R_NOTCONNECTED);
                        ERROR_MATCH(ECONNRESET, ISC_R_CONNECTIONRESET);
#undef ERROR_MATCH
                }

                sock->connected = 0;

                isc_sockaddr_format(addr, addrbuf, sizeof(addrbuf));
                UNEXPECTED_ERROR(__FILE__, __LINE__, "connect(%s) %d/%s",
                                 addrbuf, errno, strerror(errno));

                isc_event_free(ISC_EVENT_PTR(&dev));
                return (ISC_R_UNEXPECTED);

        err_exit:
                sock->connected = 0;
                isc_task_send(task, ISC_EVENT_PTR(&dev));

                return (ISC_R_SUCCESS);
        }

        /*
         * If connect completed, fire off the done event.
         */
 success:
        if (cc == 0) {
                sock->connected = 1;
                sock->bound = 1;
                dev->result = ISC_R_SUCCESS;
                isc_task_send(task, ISC_EVENT_PTR(&dev));

                return (ISC_R_SUCCESS);
        }

 queue:

        /*
         * Attach to task.
         */
        isc_task_attach(task, &ntask);

        sock->connecting = 1;

        dev->ev_sender = ntask;

        /*
         * Poke watcher here.  We still have the socket locked, so there
         * is no race condition.  We will keep the lock for such a short
         * bit of time waking it up now or later won't matter all that much.
         */
        if (sock->connect_ev == NULL)
                select_poke(manager, sock->fd, SELECT_POKE_CONNECT);

        sock->connect_ev = dev;

        return (ISC_R_SUCCESS);
}

/*
 * Called when a socket with a pending connect() finishes.
 */
static void
internal_connect(isc_task_t *me, isc_event_t *ev) {
        isc_socket_t *sock;
        isc_socket_connev_t *dev;
        isc_task_t *task;
        int cc;
        socklen_t optlen;
        char peerbuf[ISC_SOCKADDR_FORMATSIZE];

        UNUSED(me);
        INSIST(ev->ev_type == ISC_SOCKEVENT_INTW);

        sock = ev->ev_sender;

        /*
         * When the internal event was sent the reference count was bumped
         * to keep the socket around for us.  Decrement the count here.
         */
        INSIST(sock->references > 0);
        sock->references--;
        if (sock->references == 0) {
                destroy(&sock);
                return;
        }

        /*
         * Has this event been canceled?
         */
        dev = sock->connect_ev;
        if (dev == NULL) {
                INSIST(!sock->connecting);
                return;
        }

        INSIST(sock->connecting);
        sock->connecting = 0;

        /*
         * Get any possible error status here.
         */
        optlen = sizeof(cc);
        if (getsockopt(sock->fd, SOL_SOCKET, SO_ERROR,
                       (void *)&cc, (void *)&optlen) < 0)
                cc = errno;
        else
                errno = cc;

        if (errno != 0) {
                /*
                 * If the error is EAGAIN, just re-select on this
                 * fd and pretend nothing strange happened.
                 */
                if (SOFT_ERROR(errno) || errno == EINPROGRESS) {
                        sock->connecting = 1;
                        select_poke(sock->manager, sock->fd,
                                    SELECT_POKE_CONNECT);
                        return;
                }

                /*
                 * Translate other errors into ISC_R_* flavors.
                 */
                switch (errno) {
#define ERROR_MATCH(a, b) case a: dev->result = b; break;
                        ERROR_MATCH(EACCES, ISC_R_NOPERM);
                        ERROR_MATCH(EADDRNOTAVAIL, ISC_R_ADDRNOTAVAIL);
                        ERROR_MATCH(EAFNOSUPPORT, ISC_R_ADDRNOTAVAIL);
                        ERROR_MATCH(ECONNREFUSED, ISC_R_CONNREFUSED);
                        ERROR_MATCH(EHOSTUNREACH, ISC_R_HOSTUNREACH);
                        ERROR_MATCH(EHOSTDOWN, ISC_R_HOSTUNREACH);
                        ERROR_MATCH(ENETUNREACH, ISC_R_NETUNREACH);
                        ERROR_MATCH(ENOBUFS, ISC_R_NORESOURCES);
                        ERROR_MATCH(EPERM, ISC_R_HOSTUNREACH);
                        ERROR_MATCH(EPIPE, ISC_R_NOTCONNECTED);
                        ERROR_MATCH(ETIMEDOUT, ISC_R_TIMEDOUT);
                        ERROR_MATCH(ECONNRESET, ISC_R_CONNECTIONRESET);
#undef ERROR_MATCH
                default:
                        dev->result = ISC_R_UNEXPECTED;
                        isc_sockaddr_format(&sock->peer_address, peerbuf,
                                            sizeof(peerbuf));
                        UNEXPECTED_ERROR(__FILE__, __LINE__,
                                         "internal_connect: connect(%s) %s",
                                         peerbuf, strerror(errno));
                }
        } else {
                dev->result = ISC_R_SUCCESS;
                sock->connected = 1;
                sock->bound = 1;
        }

        sock->connect_ev = NULL;

        task = dev->ev_sender;
        dev->ev_sender = sock;
        isc_task_sendanddetach(&task, ISC_EVENT_PTR(&dev));
}

/*
 * Run through the list of events on this socket, and cancel the ones
 * queued for task "task" of type "how".  "how" is a bitmask.
 */
void
isc_socket_cancel(isc_socket_t *sock0, isc_task_t *task, unsigned int how) {
        isc_socket_t *sock = (isc_socket_t *)sock0;

        /*
         * Quick exit if there is nothing to do.  Don't even bother locking
         * in this case.
         */
        if (how == 0)
                return;

        /*
         * All of these do the same thing, more or less.
         * Each will:
         *      o If the internal event is marked as "posted" try to
         *        remove it from the task's queue.  If this fails, mark it
         *        as canceled instead, and let the task clean it up later.
         *      o For each I/O request for that task of that type, post
         *        its done event with status of "ISC_R_CANCELED".
         *      o Reset any state needed.
         */
        if (((how & ISC_SOCKCANCEL_RECV) == ISC_SOCKCANCEL_RECV)
            && !ISC_LIST_EMPTY(sock->recv_list)) {
                isc_socketevent_t      *dev;
                isc_socketevent_t      *next;
                isc_task_t             *current_task;

                dev = ISC_LIST_HEAD(sock->recv_list);

                while (dev != NULL) {
                        current_task = dev->ev_sender;
                        next = ISC_LIST_NEXT(dev, ev_link);

                        if ((task == NULL) || (task == current_task)) {
                                dev->result = ISC_R_CANCELED;
                                send_recvdone_event(sock, &dev);
                        }
                        dev = next;
                }
        }

        if (((how & ISC_SOCKCANCEL_SEND) == ISC_SOCKCANCEL_SEND)
            && !ISC_LIST_EMPTY(sock->send_list)) {
                isc_socketevent_t      *dev;
                isc_socketevent_t      *next;
                isc_task_t             *current_task;

                dev = ISC_LIST_HEAD(sock->send_list);

                while (dev != NULL) {
                        current_task = dev->ev_sender;
                        next = ISC_LIST_NEXT(dev, ev_link);

                        if ((task == NULL) || (task == current_task)) {
                                dev->result = ISC_R_CANCELED;
                                send_senddone_event(sock, &dev);
                        }
                        dev = next;
                }
        }

        /*
         * Connecting is not a list.
         */
        if (((how & ISC_SOCKCANCEL_CONNECT) == ISC_SOCKCANCEL_CONNECT)
            && sock->connect_ev != NULL) {
                isc_socket_connev_t    *dev;
                isc_task_t             *current_task;

                INSIST(sock->connecting);
                sock->connecting = 0;

                dev = sock->connect_ev;
                current_task = dev->ev_sender;

                if ((task == NULL) || (task == current_task)) {
                        sock->connect_ev = NULL;

                        dev->result = ISC_R_CANCELED;
                        dev->ev_sender = sock;
                        isc_task_sendanddetach(&current_task,
                                               ISC_EVENT_PTR(&dev));
                }
        }

}

/*
 * In our assumed scenario, we can simply use a single static object.
 * XXX: this is not true if the application uses multiple threads with
 *      'multi-context' mode.  Fixing this is a future TODO item.
 */
static isc_socketwait_t swait_private;

int
isc_socketmgr_waitevents(isc_socketmgr_t *manager0, struct timeval *tvp,
                          isc_socketwait_t **swaitp)
{
        isc_socketmgr_t *manager = (isc_socketmgr_t *)manager0;
        int n;

        REQUIRE(swaitp != NULL && *swaitp == NULL);

        if (manager == NULL)
                manager = socketmgr;
        if (manager == NULL)
                return (0);

        memmove(manager->read_fds_copy, manager->read_fds, manager->fd_bufsize);
        memmove(manager->write_fds_copy, manager->write_fds,
                manager->fd_bufsize);

        swait_private.readset = manager->read_fds_copy;
        swait_private.writeset = manager->write_fds_copy;
        swait_private.maxfd = manager->maxfd + 1;

        n = select(swait_private.maxfd, swait_private.readset,
                   swait_private.writeset, NULL, tvp);

        *swaitp = &swait_private;
        return (n);
}

isc_result_t
isc_socketmgr_dispatch(isc_socketmgr_t *manager0, isc_socketwait_t *swait) {
        isc_socketmgr_t *manager = (isc_socketmgr_t *)manager0;

        REQUIRE(swait == &swait_private);

        if (manager == NULL)
                manager = socketmgr;
        if (manager == NULL)
                return (ISC_R_NOTFOUND);

        process_fds(manager, swait->maxfd, swait->readset, swait->writeset);
        return (ISC_R_SUCCESS);
}