ntp.c

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/*
 * Copyright (C) 2016 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <time.h>
#include <ipxe/malloc.h>
#include <ipxe/refcnt.h>
#include <ipxe/iobuf.h>
#include <ipxe/xfer.h>
#include <ipxe/open.h>
#include <ipxe/retry.h>
#include <ipxe/timer.h>
#include <ipxe/time.h>
#include <ipxe/tcpip.h>
#include <ipxe/dhcp.h>
#include <ipxe/settings.h>
#include <ipxe/ntp.h>

/** @file
 *
 * Network Time Protocol
 *
 */

/** An NTP client */
struct ntp_client {
        /** Reference count */
        struct refcnt refcnt;
        /** Job control interface */
        struct interface job;
        /** Data transfer interface */
        struct interface xfer;
        /** Retransmission timer */
        struct retry_timer timer;
};

/**
 * Close NTP client
 *
 * @v ntp               NTP client
 * @v rc                Reason for close
 */
static void ntp_close ( struct ntp_client *ntp, int rc ) {

        /* Stop timer */
        stop_timer ( &ntp->timer );

        /* Shut down interfaces */
        intf_shutdown ( &ntp->xfer, rc );
        intf_shutdown ( &ntp->job, rc );
}

/**
 * Send NTP request
 *
 * @v ntp               NTP client
 * @ret rc              Return status code
 */
static int ntp_request ( struct ntp_client *ntp ) {
        struct ntp_header hdr;
        int rc;

        DBGC ( ntp, "NTP %p sending request\n", ntp );

        /* Construct header */
        memset ( &hdr, 0, sizeof ( hdr ) );
        hdr.flags = ( NTP_FL_LI_UNKNOWN | NTP_FL_VN_1 | NTP_FL_MODE_CLIENT );
        hdr.transmit.seconds = htonl ( time ( NULL ) + NTP_EPOCH );
        hdr.transmit.fraction = htonl ( NTP_FRACTION_MAGIC );

        /* Send request */
        if ( ( rc = xfer_deliver_raw ( &ntp->xfer, &hdr,
                                       sizeof ( hdr ) ) ) != 0 ) {
                DBGC ( ntp, "NTP %p could not send request: %s\n",
                       ntp, strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Handle NTP response
 *
 * @v ntp               NTP client
 * @v iobuf             I/O buffer
 * @v meta              Data transfer metadata
 * @ret rc              Return status code
 */
static int ntp_deliver ( struct ntp_client *ntp, struct io_buffer *iobuf,
                         struct xfer_metadata *meta ) {
        struct ntp_header *hdr;
        struct sockaddr_tcpip *st_src;
        int32_t delta;
        int rc;

        /* Check source port */
        st_src = ( ( struct sockaddr_tcpip * ) meta->src );
        if ( st_src->st_port != htons ( NTP_PORT ) ) {
                DBGC ( ntp, "NTP %p received non-NTP packet:\n", ntp );
                DBGC_HDA ( ntp, 0, iobuf->data, iob_len ( iobuf ) );
                goto ignore;
        }

        /* Check packet length */
        if ( iob_len ( iobuf ) < sizeof ( *hdr ) ) {
                DBGC ( ntp, "NTP %p received malformed packet:\n", ntp );
                DBGC_HDA ( ntp, 0, iobuf->data, iob_len ( iobuf ) );
                goto ignore;
        }
        hdr = iobuf->data;

        /* Check mode */
        if ( ( hdr->flags & NTP_FL_MODE_MASK ) != NTP_FL_MODE_SERVER ) {
                DBGC ( ntp, "NTP %p received non-server packet:\n", ntp );
                DBGC_HDA ( ntp, 0, iobuf->data, iob_len ( iobuf ) );
                goto ignore;
        }

        /* Check magic value */
        if ( hdr->originate.fraction != htonl ( NTP_FRACTION_MAGIC ) ) {
                DBGC ( ntp, "NTP %p received unrecognised packet:\n", ntp );
                DBGC_HDA ( ntp, 0, iobuf->data, iob_len ( iobuf ) );
                goto ignore;
        }

        /* Check for Kiss-o'-Death packets */
        if ( ! hdr->stratum ) {
                DBGC ( ntp, "NTP %p received kiss-o'-death:\n", ntp );
                DBGC_HDA ( ntp, 0, iobuf->data, iob_len ( iobuf ) );
                rc = -EPROTO;
                goto close;
        }

        /* Calculate clock delta */
        delta = ( ntohl ( hdr->receive.seconds ) -
                  ntohl ( hdr->originate.seconds ) );
        DBGC ( ntp, "NTP %p delta %d seconds\n", ntp, delta );

        /* Adjust system clock */
        time_adjust ( delta );

        /* Success */
        rc = 0;

 close:
        ntp_close ( ntp, rc );
 ignore:
        free_iob ( iobuf );
        return 0;
}

/**
 * Handle data transfer window change
 *
 * @v ntp               NTP client
 */
static void ntp_window_changed ( struct ntp_client *ntp ) {

        /* Start timer to send initial request */
        start_timer_nodelay ( &ntp->timer );
}

/** Data transfer interface operations */
static struct interface_operation ntp_xfer_op[] = {
        INTF_OP ( xfer_deliver, struct ntp_client *, ntp_deliver ),
        INTF_OP ( xfer_window_changed, struct ntp_client *,
                  ntp_window_changed ),
        INTF_OP ( intf_close, struct ntp_client *, ntp_close ),
};

/** Data transfer interface descriptor */
static struct interface_descriptor ntp_xfer_desc =
        INTF_DESC_PASSTHRU ( struct ntp_client, xfer, ntp_xfer_op, job );

/** Job control interface operations */
static struct interface_operation ntp_job_op[] = {
        INTF_OP ( intf_close, struct ntp_client *, ntp_close ),
};

/** Job control interface descriptor */
static struct interface_descriptor ntp_job_desc =
        INTF_DESC_PASSTHRU ( struct ntp_client, job, ntp_job_op, xfer );

/**
 * Handle NTP timer expiry
 *
 * @v timer             Retransmission timer
 * @v fail              Failure indicator
 */
static void ntp_expired ( struct retry_timer *timer, int fail ) {
        struct ntp_client *ntp =
                container_of ( timer, struct ntp_client, timer );

        /* Shut down client if we have failed */
        if ( fail ) {
                ntp_close ( ntp, -ETIMEDOUT );
                return;
        }

        /* Otherwise, restart timer and (re)transmit request */
        start_timer ( &ntp->timer );
        ntp_request ( ntp );
}

/**
 * Start NTP client
 *
 * @v job               Job control interface
 * @v hostname          NTP server
 * @ret rc              Return status code
 */
int start_ntp ( struct interface *job, const char *hostname ) {
        struct ntp_client *ntp;
        union {
                struct sockaddr_tcpip st;
                struct sockaddr sa;
        } server;
        int rc;

        /* Allocate and initialise structure*/
        ntp = zalloc ( sizeof ( *ntp ) );
        if ( ! ntp ) {
                rc = -ENOMEM;
                goto err_alloc;
        }
        ref_init ( &ntp->refcnt, NULL );
        intf_init ( &ntp->job, &ntp_job_desc, &ntp->refcnt );
        intf_init ( &ntp->xfer, &ntp_xfer_desc, &ntp->refcnt );
        timer_init ( &ntp->timer, ntp_expired, &ntp->refcnt );
        set_timer_limits ( &ntp->timer, NTP_MIN_TIMEOUT, NTP_MAX_TIMEOUT );

        /* Open socket */
        memset ( &server, 0, sizeof ( server ) );
        server.st.st_port = htons ( NTP_PORT );
        if ( ( rc = xfer_open_named_socket ( &ntp->xfer, SOCK_DGRAM, &server.sa,
                                             hostname, NULL ) ) != 0 ) {
                DBGC ( ntp, "NTP %p could not open socket: %s\n",
                       ntp, strerror ( rc ) );
                goto err_open;
        }

        /* Attach parent interface, mortalise self, and return */
        intf_plug_plug ( &ntp->job, job );
        ref_put ( &ntp->refcnt );
        return 0;

 err_open:
        ntp_close ( ntp, rc );
        ref_put ( &ntp->refcnt );
 err_alloc:
        return rc;
}

/** IPv4 NTP server setting */
const struct setting ntp_setting __setting ( SETTING_IP4_EXTRA, ntp ) = {
        .name = "ntp",
        .description = "NTP server",
        .tag = DHCP_NTP_SERVERS,
        .type = &setting_type_ipv4,
};