stp.c

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/*
 * Copyright (C) 2015 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 <errno.h>
#include <byteswap.h>
#include <ipxe/netdevice.h>
#include <ipxe/ethernet.h>
#include <ipxe/iobuf.h>
#include <ipxe/timer.h>
#include <ipxe/stp.h>

/** @file
 *
 * Spanning Tree Protocol (STP)
 *
 */

/* Disambiguate the various error causes */
#define ENOTSUP_PROTOCOL __einfo_error ( EINFO_ENOTSUP_PROTOCOL )
#define EINFO_ENOTSUP_PROTOCOL                                  \
        __einfo_uniqify ( EINFO_ENOTSUP, 0x02,                  \
                          "Non-STP packet received" )
#define ENOTSUP_VERSION __einfo_error ( EINFO_ENOTSUP_VERSION )
#define EINFO_ENOTSUP_VERSION                                   \
        __einfo_uniqify ( EINFO_ENOTSUP, 0x03,                  \
                          "Legacy STP packet received" )
#define ENOTSUP_TYPE __einfo_error ( EINFO_ENOTSUP_TYPE )
#define EINFO_ENOTSUP_TYPE                                      \
        __einfo_uniqify ( EINFO_ENOTSUP, 0x04,                  \
                          "Non-RSTP packet received" )

/**
 * Process incoming STP packets
 *
 * @v iobuf             I/O buffer
 * @v netdev            Network device
 * @v ll_source         Link-layer source address
 * @v flags             Packet flags
 * @ret rc              Return status code
 */
static int stp_rx ( struct io_buffer *iobuf, struct net_device *netdev,
                    const void *ll_dest __unused,
                    const void *ll_source __unused,
                    unsigned int flags __unused ) {
        struct stp_bpdu *stp;
        unsigned int hello;
        int rc;

        /* Sanity check */
        if ( iob_len ( iobuf ) < sizeof ( *stp ) ) {
                DBGC ( netdev, "STP %s received underlength packet (%zd "
                       "bytes):\n", netdev->name, iob_len ( iobuf ) );
                DBGC_HDA ( netdev, 0, iobuf->data, iob_len ( iobuf ) );
                rc = -EINVAL;
                goto done;
        }
        stp = iobuf->data;

        /* Ignore non-RSTP packets */
        if ( stp->protocol != htons ( STP_PROTOCOL ) ) {
                DBGC ( netdev, "STP %s ignoring non-STP packet (protocol "
                       "%#04x)\n", netdev->name, ntohs ( stp->protocol ) );
                rc = -ENOTSUP_PROTOCOL;
                goto done;
        }
        if ( stp->version < STP_VERSION_RSTP ) {
                DBGC ( netdev, "STP %s received legacy STP packet (version "
                       "%#02x)\n", netdev->name, stp->version );
                rc = -ENOTSUP_VERSION;
                goto done;
        }
        if ( stp->type != STP_TYPE_RSTP ) {
                DBGC ( netdev, "STP %s received non-RSTP packet (type %#02x)\n",
                       netdev->name, stp->type );
                rc = -ENOTSUP_TYPE;
                goto done;
        }

        /* Dump information */
        DBGC2 ( netdev, "STP %s %s port %#04x flags %#02x hello %d delay %d\n",
                netdev->name, eth_ntoa ( stp->sender.mac ), ntohs ( stp->port ),
                stp->flags, ntohs ( stp->hello ), ntohs ( stp->delay ) );

        /* Check if port is forwarding */
        if ( ! ( stp->flags & STP_FL_FORWARDING ) ) {
                /* Port is not forwarding: block link for two hello times */
                DBGC ( netdev, "STP %s %s port %#04x flags %#02x is not "
                       "forwarding\n",
                       netdev->name, eth_ntoa ( stp->sender.mac ),
                       ntohs ( stp->port ), stp->flags );
                hello = ( ntohs ( stp->hello ) * ( TICKS_PER_SEC / 256 ) );
                netdev_link_block ( netdev, ( hello * 2 ) );
                rc = -ENETUNREACH;
                goto done;
        }

        /* Success */
        if ( netdev_link_blocked ( netdev ) ) {
                DBGC ( netdev, "STP %s %s port %#04x flags %#02x is "
                       "forwarding\n",
                       netdev->name, eth_ntoa ( stp->sender.mac ),
                       ntohs ( stp->port ), stp->flags );
        }
        netdev_link_unblock ( netdev );
        rc = 0;

 done:
        free_iob ( iobuf );
        return rc;
}

/**
 * Transcribe STP address
 *
 * @v net_addr          STP address
 * @ret string          "<STP>"
 *
 * This operation is meaningless for the STP protocol.
 */
static const char * stp_ntoa ( const void *net_addr __unused ) {
        return "<STP>";
}

/** STP network protocol */
struct net_protocol stp_protocol __net_protocol = {
        .name = "STP",
        .net_proto = htons ( ETH_P_STP ),
        .rx = stp_rx,
        .ntoa = stp_ntoa,
};