8322 nl: misleading-indentation

[unleashed/tickless.git] / usr / src / lib / libdhcpagent / common / dhcpagent_ipc.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */
/*
 * Copyright (c) 2016 by Delphix. All rights reserved.
 */

#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/uio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <fcntl.h>
#include <errno.h>
#include <limits.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <net/if.h>
#include <sys/sockio.h>
#include <sys/fcntl.h>
#include <sys/time.h>
#include <stdio.h>              /* snprintf */
#include <arpa/inet.h>          /* ntohl, ntohs, etc */

#include "dhcpagent_ipc.h"
#include "dhcpagent_util.h"

/*
 * the protocol used here is a simple request/reply scheme: a client
 * sends a dhcp_ipc_request_t message to the agent, and the agent
 * sends a dhcp_ipc_reply_t back to the client.  since the requests
 * and replies can be variable-length, they are prefixed on "the wire"
 * by a 32-bit number that tells the other end how many bytes to
 * expect.
 *
 * the format of a request consists of a single dhcp_ipc_request_t;
 * note that the length of this dhcp_ipc_request_t is variable (using
 * the standard c array-of-size-1 trick).  the type of the payload is
 * given by `data_type', which is guaranteed to be `data_length' bytes
 * long starting at `buffer'.  note that `buffer' is guaranteed to be
 * 32-bit aligned but it is poor taste to rely on this.
 *
 * the format of a reply is much the same: a single dhcp_ipc_reply_t;
 * note again that the length of the dhcp_ipc_reply_t is variable.
 * the type of the payload is given by `data_type', which is
 * guaranteed to be `data_length' bytes long starting at `buffer'.
 * once again, note that `buffer' is guaranteed to be 32-bit aligned
 * but it is poor taste to rely on this.
 *
 * requests and replies can be paired up by comparing `ipc_id' fields.
 */

#define BUFMAX  256

static int      dhcp_ipc_timed_read(int, void *, unsigned int, int *);
static int      getinfo_ifnames(const char *, dhcp_optnum_t *, DHCP_OPT **);
static char     *get_ifnames(int, int);

/* must be kept in sync with enum in dhcpagent_ipc.h */
static const char *ipc_typestr[] = {
        "drop", "extend", "ping", "release", "start", "status",
        "inform", "get_tag"
};

/*
 * dhcp_ipc_alloc_request(): allocates a dhcp_ipc_request_t of the given type
 *                           and interface, with a timeout of 0.
 *
 *   input: dhcp_ipc_type_t: the type of ipc request to allocate
 *          const char *: the interface to associate the request with
 *          const void *: the payload to send with the message (NULL if none)
 *          uint32_t: the payload size (0 if none)
 *          dhcp_data_type_t: the description of the type of payload
 *  output: dhcp_ipc_request_t *: the request on success, NULL on failure
 */

dhcp_ipc_request_t *
dhcp_ipc_alloc_request(dhcp_ipc_type_t type, const char *ifname,
    const void *buffer, uint32_t buffer_size, dhcp_data_type_t data_type)
{
        dhcp_ipc_request_t *request = calloc(1, DHCP_IPC_REQUEST_SIZE +
            buffer_size);

        if (request == NULL)
                return (NULL);

        request->message_type   = type;
        request->data_length    = buffer_size;
        request->data_type      = data_type;

        if (ifname != NULL)
                (void) strlcpy(request->ifname, ifname, LIFNAMSIZ);

        if (buffer != NULL)
                (void) memcpy(request->buffer, buffer, buffer_size);

        return (request);
}

/*
 * dhcp_ipc_alloc_reply(): allocates a dhcp_ipc_reply_t
 *
 *   input: dhcp_ipc_request_t *: the request the reply is for
 *          int: the return code (0 for success, DHCP_IPC_E_* otherwise)
 *          const void *: the payload to send with the message (NULL if none)
 *          uint32_t: the payload size (0 if none)
 *          dhcp_data_type_t: the description of the type of payload
 *  output: dhcp_ipc_reply_t *: the reply on success, NULL on failure
 */

dhcp_ipc_reply_t *
dhcp_ipc_alloc_reply(dhcp_ipc_request_t *request, int return_code,
    const void *buffer, uint32_t buffer_size, dhcp_data_type_t data_type)
{
        dhcp_ipc_reply_t *reply = calloc(1, DHCP_IPC_REPLY_SIZE + buffer_size);

        if (reply == NULL)
                return (NULL);

        reply->message_type     = request->message_type;
        reply->ipc_id           = request->ipc_id;
        reply->return_code      = return_code;
        reply->data_length      = buffer_size;
        reply->data_type        = data_type;

        if (buffer != NULL)
                (void) memcpy(reply->buffer, buffer, buffer_size);

        return (reply);
}

/*
 * dhcp_ipc_get_data(): gets the data and data type from a dhcp_ipc_reply_t
 *
 *   input: dhcp_ipc_reply_t *: the reply to get data from
 *          size_t *: the size of the resulting data
 *          dhcp_data_type_t *: the type of the message (returned)
 *  output: void *: a pointer to the data, if there is any.
 */

void *
dhcp_ipc_get_data(dhcp_ipc_reply_t *reply, size_t *size, dhcp_data_type_t *type)
{
        if (reply == NULL || reply->data_length == 0) {
                *size = 0;
                return (NULL);
        }

        if (type != NULL)
                *type = reply->data_type;

        *size = reply->data_length;
        return (reply->buffer);
}

/*
 * dhcp_ipc_recv_msg(): gets a message using the agent's ipc protocol
 *
 *   input: int: the file descriptor to get the message from
 *          void **: the address of a pointer to store the message
 *                   (dynamically allocated)
 *          uint32_t: the minimum length of the packet
 *          int: the # of milliseconds to wait for the message (-1 is forever)
 *  output: int: DHCP_IPC_SUCCESS on success, DHCP_IPC_E_* otherwise
 */

static int
dhcp_ipc_recv_msg(int fd, void **msg, uint32_t base_length, int msec)
{
        int                     retval;
        dhcp_ipc_reply_t        *ipc_msg;
        uint32_t                length;

        retval = dhcp_ipc_timed_read(fd, &length, sizeof (uint32_t), &msec);
        if (retval != DHCP_IPC_SUCCESS)
                return (retval);

        if (length == 0)
                return (DHCP_IPC_E_PROTO);

        *msg = malloc(length);
        if (*msg == NULL)
                return (DHCP_IPC_E_MEMORY);

        retval = dhcp_ipc_timed_read(fd, *msg, length, &msec);
        if (retval != DHCP_IPC_SUCCESS) {
                free(*msg);
                return (retval);
        }

        if (length < base_length) {
                free(*msg);
                return (DHCP_IPC_E_PROTO);
        }

        /*
         * the data_length field is in the same place in either ipc message.
         */

        ipc_msg = (dhcp_ipc_reply_t *)(*msg);
        if (ipc_msg->data_length + base_length != length) {
                free(*msg);
                return (DHCP_IPC_E_PROTO);
        }

        return (DHCP_IPC_SUCCESS);
}

/*
 * dhcp_ipc_recv_request(): gets a request using the agent's ipc protocol
 *
 *   input: int: the file descriptor to get the message from
 *          dhcp_ipc_request_t **: address of a pointer to store the request
 *                               (dynamically allocated)
 *          int: the # of milliseconds to wait for the message (-1 is forever)
 *  output: int: 0 on success, DHCP_IPC_E_* otherwise
 */

int
dhcp_ipc_recv_request(int fd, dhcp_ipc_request_t **request, int msec)
{
        int     retval;

        retval = dhcp_ipc_recv_msg(fd, (void **)request, DHCP_IPC_REQUEST_SIZE,
            msec);

        /* guarantee that ifname will be NUL-terminated */
        if (retval == 0)
                (*request)->ifname[LIFNAMSIZ - 1] = '\0';

        return (retval);
}

/*
 * dhcp_ipc_recv_reply(): gets a reply using the agent's ipc protocol
 *
 *   input: int: the file descriptor to get the message from
 *          dhcp_ipc_reply_t **: address of a pointer to store the reply
 *                               (dynamically allocated)
 *          int32_t: timeout (in seconds), or DHCP_IPC_WAIT_FOREVER,
 *                   or DHCP_IPC_WAIT_DEFAULT
 *  output: int: 0 on success, DHCP_IPC_E_* otherwise
 */

static int
dhcp_ipc_recv_reply(int fd, dhcp_ipc_reply_t **reply, int32_t timeout)
{
        /*
         * If the caller doesn't want to wait forever, and the amount of time
         * it wants to wait is expressible as an integer number of milliseconds
         * (as needed by the msg function), then we wait that amount of time
         * plus an extra two seconds for the daemon to do its work.  The extra
         * two seconds is arbitrary; it should allow plenty of time for the
         * daemon to respond within the existing timeout, as specified in the
         * original request, so the only time we give up is when the daemon is
         * stopped or otherwise malfunctioning.
         *
         * Note that the wait limit (milliseconds in an 'int') is over 24 days,
         * so it's unlikely that any request will actually be that long, and
         * it's unlikely that anyone will care if we wait forever on a request
         * for a 30 day timer.  The point is to protect against daemon
         * malfunction in the usual cases, not to provide an absolute command
         * timer.
         */
        if (timeout == DHCP_IPC_WAIT_DEFAULT)
                timeout = DHCP_IPC_DEFAULT_WAIT;
        if (timeout != DHCP_IPC_WAIT_FOREVER && timeout < INT_MAX / 1000 - 2)
                timeout = (timeout + 2) * 1000;
        else
                timeout = -1;
        return (dhcp_ipc_recv_msg(fd, (void **)reply, DHCP_IPC_REPLY_SIZE,
            timeout));
}

/*
 * dhcp_ipc_send_msg(): transmits a message using the agent's ipc protocol
 *
 *   input: int: the file descriptor to transmit on
 *          void *: the message to send
 *          uint32_t: the message length
 *  output: int: 0 on success, DHCP_IPC_E_* otherwise
 */

static int
dhcp_ipc_send_msg(int fd, void *msg, uint32_t message_length)
{
        struct iovec    iovec[2];

        iovec[0].iov_base = (caddr_t)&message_length;
        iovec[0].iov_len  = sizeof (uint32_t);
        iovec[1].iov_base = msg;
        iovec[1].iov_len  = message_length;

        if (writev(fd, iovec, sizeof (iovec) / sizeof (*iovec)) == -1)
                return (DHCP_IPC_E_WRITEV);

        return (0);
}

/*
 * dhcp_ipc_send_reply(): transmits a reply using the agent's ipc protocol
 *
 *   input: int: the file descriptor to transmit on
 *          dhcp_ipc_reply_t *: the reply to send
 *  output: int: 0 on success, DHCP_IPC_E_* otherwise
 */

int
dhcp_ipc_send_reply(int fd, dhcp_ipc_reply_t *reply)
{
        return (dhcp_ipc_send_msg(fd, reply, DHCP_IPC_REPLY_SIZE +
            reply->data_length));
}

/*
 * dhcp_ipc_send_request(): transmits a request using the agent's ipc protocol
 *
 *   input: int: the file descriptor to transmit on
 *          dhcp_ipc_request_t *: the request to send
 *  output: int: 0 on success, DHCP_IPC_E_* otherwise
 */

static int
dhcp_ipc_send_request(int fd, dhcp_ipc_request_t *request)
{
        /*
         * for now, ipc_ids aren't really used, but they're intended
         * to make it easy to send several requests and then collect
         * all of the replies (and pair them with the requests).
         */

        request->ipc_id = gethrtime();

        return (dhcp_ipc_send_msg(fd, request, DHCP_IPC_REQUEST_SIZE +
            request->data_length));
}

/*
 * dhcp_ipc_make_request(): sends the provided request to the agent and reaps
 *                          the reply
 *
 *   input: dhcp_ipc_request_t *: the request to make
 *          dhcp_ipc_reply_t **: the reply (dynamically allocated)
 *          int32_t: timeout (in seconds), or DHCP_IPC_WAIT_FOREVER,
 *                   or DHCP_IPC_WAIT_DEFAULT
 *  output: int: 0 on success, DHCP_IPC_E_* otherwise
 */

int
dhcp_ipc_make_request(dhcp_ipc_request_t *request, dhcp_ipc_reply_t **reply,
    int32_t timeout)
{
        int                     fd, on, retval;
        struct sockaddr_in      sinv;

        fd = socket(AF_INET, SOCK_STREAM, 0);
        if (fd == -1)
                return (DHCP_IPC_E_SOCKET);

        /*
         * Bind a privileged port if we have sufficient privilege to do so.
         * Continue as non-privileged otherwise.
         */
        on = 1;
        (void) setsockopt(fd, IPPROTO_TCP, TCP_ANONPRIVBIND, &on, sizeof (on));

        (void) memset(&sinv, 0, sizeof (sinv));
        sinv.sin_family  = AF_INET;
        if (bind(fd, (struct sockaddr *)&sinv, sizeof (sinv)) == -1) {
                (void) dhcp_ipc_close(fd);
                return (DHCP_IPC_E_BIND);
        }

        sinv.sin_port = htons(IPPORT_DHCPAGENT);
        sinv.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
        retval = connect(fd, (struct sockaddr *)&sinv, sizeof (sinv));
        if (retval == -1) {
                (void) dhcp_ipc_close(fd);
                return (DHCP_IPC_E_CONNECT);
        }

        request->timeout = timeout;

        retval = dhcp_ipc_send_request(fd, request);
        if (retval == 0)
                retval = dhcp_ipc_recv_reply(fd, reply, timeout);

        (void) dhcp_ipc_close(fd);

        return (retval);
}

/*
 * dhcp_ipc_init(): initializes the ipc channel for use by the agent
 *
 *   input: int *: the file descriptor to accept on (returned)
 *  output: int: 0 on success, DHCP_IPC_E_* otherwise
 */

int
dhcp_ipc_init(int *listen_fd)
{
        struct sockaddr_in      sin;
        int                     on = 1;

        (void) memset(&sin, 0, sizeof (struct sockaddr_in));

        sin.sin_family          = AF_INET;
        sin.sin_port            = htons(IPPORT_DHCPAGENT);
        sin.sin_addr.s_addr     = htonl(INADDR_LOOPBACK);

        *listen_fd = socket(AF_INET, SOCK_STREAM, 0);
        if (*listen_fd == -1)
                return (DHCP_IPC_E_SOCKET);

        /*
         * we use SO_REUSEADDR here since in the case where there
         * really is another daemon running that is using the agent's
         * port, bind(3N) will fail.  so we can't lose.
         */

        (void) setsockopt(*listen_fd, SOL_SOCKET, SO_REUSEADDR, &on,
            sizeof (on));

        if (bind(*listen_fd, (struct sockaddr *)&sin, sizeof (sin)) == -1) {
                (void) close(*listen_fd);
                return (DHCP_IPC_E_BIND);
        }

        if (listen(*listen_fd, DHCP_IPC_LISTEN_BACKLOG) == -1) {
                (void) close(*listen_fd);
                return (DHCP_IPC_E_LISTEN);
        }

        return (0);
}

/*
 * dhcp_ipc_accept(): accepts an incoming connection for the agent
 *
 *   input: int: the file descriptor to accept on
 *          int *: the accepted file descriptor (returned)
 *          int *: nonzero if the client is privileged (returned)
 *  output: int: 0 on success, DHCP_IPC_E_* otherwise
 *    note: sets the socket into nonblocking mode
 */

int
dhcp_ipc_accept(int listen_fd, int *fd, int *is_priv)
{
        struct sockaddr_in      sin_peer;
        int                     sin_len = sizeof (sin_peer);
        int                     sockflags;

        /*
         * if we were extremely concerned with portability, we would
         * set the socket into nonblocking mode before doing the
         * accept(3N), since on BSD-based networking stacks, there is
         * a potential race that can occur if the socket which
         * connected to us performs a TCP RST before we accept, since
         * BSD handles this case entirely in the kernel and as a
         * result even though select said we will not block, we can
         * end up blocking since there is no longer a connection to
         * accept.  on SVR4-based systems, this should be okay,
         * and we will get EPROTO back, even though POSIX.1g says
         * we should get ECONNABORTED.
         */

        *fd = accept(listen_fd, (struct sockaddr *)&sin_peer, &sin_len);
        if (*fd == -1)
                return (DHCP_IPC_E_ACCEPT);

        /* get credentials */
        *is_priv = ntohs(sin_peer.sin_port) < IPPORT_RESERVED;

        /*
         * kick the socket into non-blocking mode so that later
         * operations on the socket don't block and hold up the whole
         * application.  with the event demuxing approach, this may
         * seem unnecessary, but in order to get partial reads/writes
         * and to handle our internal protocol for passing data
         * between the agent and its consumers, this is needed.
         */

        if ((sockflags = fcntl(*fd, F_GETFL, 0)) == -1) {
                (void) close(*fd);
                return (DHCP_IPC_E_FCNTL);
        }

        if (fcntl(*fd, F_SETFL, sockflags | O_NONBLOCK) == -1) {
                (void) close(*fd);
                return (DHCP_IPC_E_FCNTL);
        }

        return (0);
}

/*
 * dhcp_ipc_close(): closes an ipc descriptor
 *
 *   input: int: the file descriptor to close
 *  output: int: 0 on success, DHCP_IPC_E_* otherwise
 */

int
dhcp_ipc_close(int fd)
{
        return ((close(fd) == -1) ? DHCP_IPC_E_CLOSE : 0);
}

/*
 * dhcp_ipc_strerror(): maps an ipc error code into a human-readable string
 *
 *   input: int: the ipc error code to map
 *  output: const char *: the corresponding human-readable string
 */

const char *
dhcp_ipc_strerror(int error)
{
        /* note: this must be kept in sync with DHCP_IPC_E_* definitions */
        const char *syscalls[] = {
                "<unknown>", "socket", "fcntl", "read", "accept", "close",
                "bind", "listen", "malloc", "connect", "writev", "poll"
        };

        const char      *error_string;
        static char     buffer[BUFMAX];

        switch (error) {

        /*
         * none of these errors actually go over the wire.
         * hence, we assume that errno is still fresh.
         */

        case DHCP_IPC_E_SOCKET:                 /* FALLTHRU */
        case DHCP_IPC_E_FCNTL:                  /* FALLTHRU */
        case DHCP_IPC_E_READ:                   /* FALLTHRU */
        case DHCP_IPC_E_ACCEPT:                 /* FALLTHRU */
        case DHCP_IPC_E_CLOSE:                  /* FALLTHRU */
        case DHCP_IPC_E_BIND:                   /* FALLTHRU */
        case DHCP_IPC_E_LISTEN:                 /* FALLTHRU */
        case DHCP_IPC_E_CONNECT:                /* FALLTHRU */
        case DHCP_IPC_E_WRITEV:                 /* FALLTHRU */
        case DHCP_IPC_E_POLL:

                error_string = strerror(errno);
                if (error_string == NULL)
                        error_string = "unknown error";

                (void) snprintf(buffer, sizeof (buffer), "%s: %s",
                    syscalls[error], error_string);

                error_string = buffer;
                break;

        case DHCP_IPC_E_MEMORY:
                error_string = "out of memory";
                break;

        case DHCP_IPC_E_TIMEOUT:
                error_string = "wait timed out, operation still pending...";
                break;

        case DHCP_IPC_E_INVIF:
                error_string = "interface does not exist or cannot be managed "
                    "using DHCP";
                break;

        case DHCP_IPC_E_INT:
                error_string = "internal error (might work later)";
                break;

        case DHCP_IPC_E_PERM:
                error_string = "permission denied";
                break;

        case DHCP_IPC_E_OUTSTATE:
                error_string = "interface not in appropriate state for command";
                break;

        case DHCP_IPC_E_PEND:
                error_string = "interface currently has a pending command "
                    "(try later)";
                break;

        case DHCP_IPC_E_BOOTP:
                error_string = "interface is administered with BOOTP, not DHCP";
                break;

        case DHCP_IPC_E_CMD_UNKNOWN:
                error_string = "unknown command";
                break;

        case DHCP_IPC_E_UNKIF:
                error_string = "interface is not under DHCP control";
                break;

        case DHCP_IPC_E_PROTO:
                error_string = "ipc protocol violation";
                break;

        case DHCP_IPC_E_FAILEDIF:
                error_string = "interface is in a FAILED state and must be "
                    "manually restarted";
                break;

        case DHCP_IPC_E_NOPRIMARY:
                error_string = "primary interface requested but no primary "
                    "interface is set";
                break;

        case DHCP_IPC_E_NOIPIF:
                error_string = "interface currently has no IP address";
                break;

        case DHCP_IPC_E_DOWNIF:
                error_string = "interface is currently down";
                break;

        case DHCP_IPC_E_NOVALUE:
                error_string = "no value was found for this option";
                break;

        case DHCP_IPC_E_RUNNING:
                error_string = "DHCP is already running";
                break;

        case DHCP_IPC_E_SRVFAILED:
                error_string = "DHCP server refused request";
                break;

        case DHCP_IPC_E_EOF:
                error_string = "ipc connection closed";
                break;

        default:
                error_string = "unknown error";
                break;
        }

        /*
         * TODO: internationalize this error string
         */

        return (error_string);
}

/*
 * dhcp_string_to_request(): maps a string into a request code
 *
 *    input: const char *: the string to map
 *   output: dhcp_ipc_type_t: the request code, or -1 if unknown
 */

dhcp_ipc_type_t
dhcp_string_to_request(const char *request)
{
        unsigned int    i;

        for (i = 0; i < DHCP_NIPC; i++)
                if (strcmp(ipc_typestr[i], request) == 0)
                        return ((dhcp_ipc_type_t)i);

        return ((dhcp_ipc_type_t)-1);
}

/*
 * dhcp_ipc_type_to_string(): maps an ipc command code into a human-readable
 *                            string
 *
 *   input: int: the ipc command code to map
 *  output: const char *: the corresponding human-readable string
 */

const char *
dhcp_ipc_type_to_string(dhcp_ipc_type_t type)
{
        if (type < 0 || type >= DHCP_NIPC)
                return ("unknown");
        else
                return (ipc_typestr[(int)type]);
}

/*
 * getinfo_ifnames(): checks the value of a specified option on a list of
 *                    interface names.
 *   input: const char *: a list of interface names to query (in order) for
 *                        the option; "" queries the primary interface
 *          dhcp_optnum_t *: a description of the desired option
 *          DHCP_OPT **:  filled in with the (dynamically allocated) value of
 *                        the option upon success.
 *  output: int: DHCP_IPC_E_* on error, 0 on success or if no value was
 *               found but no error occurred either (*result will be NULL)
 */

static int
getinfo_ifnames(const char *ifn, dhcp_optnum_t *optnum, DHCP_OPT **result)
{
        dhcp_ipc_request_t      *request;
        dhcp_ipc_reply_t        *reply;
        char                    *ifnames, *ifnames_head;
        DHCP_OPT                *opt;
        size_t                  opt_size;
        int                     retval = 0;

        *result = NULL;
        ifnames_head = ifnames = strdup(ifn);
        if (ifnames == NULL)
                return (DHCP_IPC_E_MEMORY);

        request = dhcp_ipc_alloc_request(DHCP_GET_TAG, "", optnum,
            sizeof (dhcp_optnum_t), DHCP_TYPE_OPTNUM);

        if (request == NULL) {
                free(ifnames_head);
                return (DHCP_IPC_E_MEMORY);
        }

        ifnames = strtok(ifnames, " ");
        if (ifnames == NULL)
                ifnames = "";

        for (; ifnames != NULL; ifnames = strtok(NULL, " ")) {

                (void) strlcpy(request->ifname, ifnames, LIFNAMSIZ);
                retval = dhcp_ipc_make_request(request, &reply, 0);
                if (retval != 0)
                        break;

                if (reply->return_code == 0) {
                        opt = dhcp_ipc_get_data(reply, &opt_size, NULL);
                        if (opt_size > 2 && (opt->len == opt_size - 2)) {
                                *result = malloc(opt_size);
                                if (*result == NULL)
                                        retval = DHCP_IPC_E_MEMORY;
                                else
                                        (void) memcpy(*result, opt, opt_size);

                                free(reply);
                                break;
                        }
                }

                free(reply);
                if (ifnames[0] == '\0')
                        break;
        }

        free(request);
        free(ifnames_head);

        return (retval);
}

/*
 * get_ifnames(): returns a space-separated list of interface names that
 *                match the specified flags
 *
 *   input: int: flags which must be on in each interface returned
 *          int: flags which must be off in each interface returned
 *  output: char *: a dynamically-allocated list of interface names, or
 *                  NULL upon failure.
 */

static char *
get_ifnames(int flags_on, int flags_off)
{
        struct ifconf   ifc;
        int             n_ifs, i, sock_fd;
        char            *ifnames;


        sock_fd = socket(AF_INET, SOCK_DGRAM, 0);
        if (sock_fd == -1)
                return (NULL);

        if ((ioctl(sock_fd, SIOCGIFNUM, &n_ifs) == -1) || (n_ifs <= 0)) {
                (void) close(sock_fd);
                return (NULL);
        }

        ifnames = calloc(1, n_ifs * (LIFNAMSIZ + 1));
        ifc.ifc_len = n_ifs * sizeof (struct ifreq);
        ifc.ifc_req = calloc(n_ifs, sizeof (struct ifreq));
        if (ifc.ifc_req != NULL && ifnames != NULL) {

                if (ioctl(sock_fd, SIOCGIFCONF, &ifc) == -1) {
                        (void) close(sock_fd);
                        free(ifnames);
                        free(ifc.ifc_req);
                        return (NULL);
                }

                for (i = 0; i < n_ifs; i++) {

                        if (ioctl(sock_fd, SIOCGIFFLAGS, &ifc.ifc_req[i]) == 0)
                                if ((ifc.ifc_req[i].ifr_flags &
                                    (flags_on | flags_off)) != flags_on)
                                        continue;

                        (void) strcat(ifnames, ifc.ifc_req[i].ifr_name);
                        (void) strcat(ifnames, " ");
                }

                if (strlen(ifnames) > 1)
                        ifnames[strlen(ifnames) - 1] = '\0';
        }

        (void) close(sock_fd);
        free(ifc.ifc_req);
        return (ifnames);
}

/*
 * dhcp_ipc_getinfo(): attempts to retrieve a value for the specified DHCP
 *                     option; tries primary interface, then all DHCP-owned
 *                     interfaces, then INFORMs on the remaining interfaces
 *                     (these interfaces are dropped prior to returning).
 *   input: dhcp_optnum_t *: a description of the desired option
 *          DHCP_OPT **:  filled in with the (dynamically allocated) value of
 *                        the option upon success.
 *          int32_t: timeout (in seconds), or DHCP_IPC_WAIT_FOREVER,
 *                   or DHCP_IPC_WAIT_DEFAULT.
 *  output: int: DHCP_IPC_E_* on error, 0 upon success.
 */

int
dhcp_ipc_getinfo(dhcp_optnum_t *optnum, DHCP_OPT **result, int32_t timeout)
{
        dhcp_ipc_request_t      *request;
        dhcp_ipc_reply_t        *reply;
        char                    *ifnames, *ifnames_copy, *ifnames_head;
        int                     retval;
        time_t                  start_time = time(NULL);

        if (timeout == DHCP_IPC_WAIT_DEFAULT)
                timeout = DHCP_IPC_DEFAULT_WAIT;

        /*
         * wait at most 5 seconds for the agent to start.
         */

        if (dhcp_start_agent((timeout > 5 || timeout < 0) ? 5 : timeout) == -1)
                return (DHCP_IPC_E_INT);

        /*
         * check the primary interface for the option value first.
         */

        retval = getinfo_ifnames("", optnum, result);
        if ((retval != 0) || (retval == 0 && *result != NULL))
                return (retval);

        /*
         * no luck.  get a list of the interfaces under DHCP control
         * and perform a GET_TAG on each one.
         */

        ifnames = get_ifnames(IFF_DHCPRUNNING, 0);
        if (ifnames != NULL && strlen(ifnames) != 0) {
                retval = getinfo_ifnames(ifnames, optnum, result);
                if ((retval != 0) || (retval == 0 && *result != NULL)) {
                        free(ifnames);
                        return (retval);
                }
        }
        free(ifnames);

        /*
         * still no luck.  retrieve a list of all interfaces on the
         * system that could use DHCP but aren't.  send INFORMs out on
         * each one. after that, sit in a loop for the next `timeout'
         * seconds, trying every second to see if a response for the
         * option we want has come in on one of the interfaces.
         */

        ifnames = get_ifnames(IFF_UP|IFF_RUNNING, IFF_LOOPBACK|IFF_DHCPRUNNING);
        if (ifnames == NULL || strlen(ifnames) == 0) {
                free(ifnames);
                return (DHCP_IPC_E_NOVALUE);
        }

        ifnames_head = ifnames_copy = strdup(ifnames);
        if (ifnames_copy == NULL) {
                free(ifnames);
                return (DHCP_IPC_E_MEMORY);
        }

        request = dhcp_ipc_alloc_request(DHCP_INFORM, "", NULL, 0,
            DHCP_TYPE_NONE);
        if (request == NULL) {
                free(ifnames);
                free(ifnames_head);
                return (DHCP_IPC_E_MEMORY);
        }

        ifnames_copy = strtok(ifnames_copy, " ");
        for (; ifnames_copy != NULL; ifnames_copy = strtok(NULL, " ")) {
                (void) strlcpy(request->ifname, ifnames_copy, LIFNAMSIZ);
                if (dhcp_ipc_make_request(request, &reply, 0) == 0)
                        free(reply);
        }

        for (;;) {
                if ((timeout != DHCP_IPC_WAIT_FOREVER) &&
                    (time(NULL) - start_time > timeout)) {
                        retval = DHCP_IPC_E_TIMEOUT;
                        break;
                }

                retval = getinfo_ifnames(ifnames, optnum, result);
                if (retval != 0 || (retval == 0 && *result != NULL))
                        break;

                (void) sleep(1);
        }

        /*
         * drop any interfaces that weren't under DHCP control before
         * we got here; this keeps this function more of a black box
         * and the behavior more consistent from call to call.
         */

        request->message_type = DHCP_DROP;

        ifnames_copy = strcpy(ifnames_head, ifnames);
        ifnames_copy = strtok(ifnames_copy, " ");
        for (; ifnames_copy != NULL; ifnames_copy = strtok(NULL, " ")) {
                (void) strlcpy(request->ifname, ifnames_copy, LIFNAMSIZ);
                if (dhcp_ipc_make_request(request, &reply, 0) == 0)
                        free(reply);
        }

        free(request);
        free(ifnames_head);
        free(ifnames);
        return (retval);
}

/*
 * dhcp_ipc_timed_read(): reads from a descriptor using a maximum timeout
 *
 *   input: int: the file descriptor to read from
 *          void *: the buffer to read into
 *          unsigned int: the total length of data to read
 *          int *: the number of milliseconds to wait; the number of
 *                 milliseconds left are returned (-1 is "forever")
 *  output: int: DHCP_IPC_SUCCESS on success, DHCP_IPC_E_* otherwise
 */

static int
dhcp_ipc_timed_read(int fd, void *buffer, unsigned int length, int *msec)
{
        unsigned int    n_total = 0;
        ssize_t         n_read;
        struct pollfd   pollfd;
        hrtime_t        start, end;
        int             retv;

        pollfd.fd       = fd;
        pollfd.events   = POLLIN;

        while (n_total < length) {

                start = gethrtime();

                retv = poll(&pollfd, 1, *msec);
                if (retv == 0) {
                        /* This can happen only if *msec is not -1 */
                        *msec = 0;
                        return (DHCP_IPC_E_TIMEOUT);
                }

                if (*msec != -1) {
                        end = gethrtime();
                        *msec -= NSEC2MSEC(end - start);
                        if (*msec < 0)
                                *msec = 0;
                }

                if (retv == -1) {
                        if (errno != EINTR)
                                return (DHCP_IPC_E_POLL);
                        else if (*msec == 0)
                                return (DHCP_IPC_E_TIMEOUT);
                        continue;
                }

                if (!(pollfd.revents & POLLIN)) {
                        errno = EINVAL;
                        return (DHCP_IPC_E_POLL);
                }

                n_read = read(fd, (caddr_t)buffer + n_total, length - n_total);

                if (n_read == -1) {
                        if (errno != EINTR)
                                return (DHCP_IPC_E_READ);
                        else if (*msec == 0)
                                return (DHCP_IPC_E_TIMEOUT);
                        continue;
                }

                if (n_read == 0) {
                        return (n_total == 0 ? DHCP_IPC_E_EOF :
                            DHCP_IPC_E_PROTO);
                }

                n_total += n_read;

                if (*msec == 0 && n_total < length)
                        return (DHCP_IPC_E_TIMEOUT);
        }

        return (DHCP_IPC_SUCCESS);
}