peerdisc.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 <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#include <assert.h>
#include <ipxe/xfer.h>
#include <ipxe/iobuf.h>
#include <ipxe/open.h>
#include <ipxe/tcpip.h>
#include <ipxe/uuid.h>
#include <ipxe/base16.h>
#include <ipxe/netdevice.h>
#include <ipxe/timer.h>
#include <ipxe/fault.h>
#include <ipxe/settings.h>
#include <ipxe/pccrd.h>
#include <ipxe/peerdisc.h>

/** @file
 *
 * Peer Content Caching and Retrieval (PeerDist) protocol peer discovery
 *
 */

/** List of discovery segments */
static LIST_HEAD ( peerdisc_segments );

/** Number of repeated discovery attempts */
#define PEERDISC_REPEAT_COUNT 2

/** Time between repeated discovery attempts */
#define PEERDISC_REPEAT_TIMEOUT ( 1 * TICKS_PER_SEC )

/** Default discovery timeout (in seconds) */
#define PEERDISC_DEFAULT_TIMEOUT_SECS 2

/** Recommended discovery timeout (in seconds)
 *
 * We reduce the recommended discovery timeout whenever a segment
 * fails to discover any peers, and restore the default value whenever
 * a valid discovery reply is received.  We continue to send discovery
 * requests even if the recommended timeout is reduced to zero.
 *
 * This strategy is intended to minimise discovery delays when no
 * peers are available on the network, while allowing downloads to
 * quickly switch back to using PeerDist acceleration if new peers
 * become available.
 */
unsigned int peerdisc_timeout_secs = PEERDISC_DEFAULT_TIMEOUT_SECS;

/** Most recently discovered peer (for any block) */
static char *peerdisc_recent;

/** Hosted cache server */
static char *peerhost;

static struct peerdisc_segment * peerdisc_find ( const char *id );
static int peerdisc_discovered ( struct peerdisc_segment *segment,
                                 const char *location );

/******************************************************************************
 *
 * Statistics reporting
 *
 ******************************************************************************
 */

/**
 * Report peer discovery statistics
 *
 * @v intf              Interface
 * @v peer              Selected peer (or NULL)
 * @v peers             List of available peers
 */
void peerdisc_stat ( struct interface *intf, struct peerdisc_peer *peer,
                     struct list_head *peers ) {
        struct interface *dest;
        peerdisc_stat_TYPE ( void * ) *op =
                intf_get_dest_op ( intf, peerdisc_stat, &dest );
        void *object = intf_object ( dest );

        if ( op ) {
                op ( object, peer, peers );
        } else {
                /* Default is to do nothing */
        }

        intf_put ( dest );
}

/******************************************************************************
 *
 * Discovery sockets
 *
 ******************************************************************************
 */

/**
 * Open all PeerDist discovery sockets
 *
 * @ret rc              Return status code
 */
static int peerdisc_socket_open ( void ) {
        struct peerdisc_socket *socket;
        int rc;

        /* Open each socket */
        for_each_table_entry ( socket, PEERDISC_SOCKETS ) {
                if ( ( rc = xfer_open_socket ( &socket->xfer, SOCK_DGRAM,
                                               &socket->address.sa,
                                               NULL ) ) != 0 ) {
                        DBGC ( socket, "PEERDISC %s could not open socket: "
                               "%s\n", socket->name, strerror ( rc ) );
                        goto err;
                }
        }

        return 0;

 err:
        for_each_table_entry_continue_reverse ( socket, PEERDISC_SOCKETS )
                intf_restart ( &socket->xfer, rc );
        return rc;
}

/**
 * Attempt to transmit PeerDist discovery requests on all sockets
 *
 * @v uuid              Message UUID string
 * @v id                Segment identifier string
 */
static void peerdisc_socket_tx ( const char *uuid, const char *id ) {
        struct peerdisc_socket *socket;
        struct net_device *netdev;
        struct xfer_metadata meta;
        union {
                struct sockaddr sa;
                struct sockaddr_tcpip st;
        } address;
        char *request;
        size_t len;
        int rc;

        /* Construct discovery request */
        request = peerdist_discovery_request ( uuid, id );
        if ( ! request )
                goto err_request;
        len = strlen ( request );

        /* Initialise data transfer metadata */
        memset ( &meta, 0, sizeof ( meta ) );
        meta.dest = &address.sa;

        /* Send message on each socket */
        for_each_table_entry ( socket, PEERDISC_SOCKETS ) {

                /* Initialise socket address */
                memcpy ( &address.sa, &socket->address.sa,
                         sizeof ( address.sa ) );

                /* Send message on each open network device */
                for_each_netdev ( netdev ) {

                        /* Skip unopened network devices */
                        if ( ! netdev_is_open ( netdev ) )
                                continue;
                        address.st.st_scope_id = netdev->scope_id;

                        /* Discard request (for test purposes) if applicable */
                        if ( inject_fault ( PEERDISC_DISCARD_RATE ) )
                                continue;

                        /* Transmit request */
                        if ( ( rc = xfer_deliver_raw_meta ( &socket->xfer,
                                                            request, len,
                                                            &meta ) ) != 0 ) {
                                DBGC ( socket, "PEERDISC %s could not transmit "
                                       "via %s: %s\n", socket->name,
                                       netdev->name, strerror ( rc ) );
                                /* Contine to try other net devices/sockets */
                                continue;
                        }
                }
        }

        free ( request );
 err_request:
        return;
}

/**
 * Handle received PeerDist discovery reply
 *
 * @v socket            PeerDist discovery socket
 * @v iobuf             I/O buffer
 * @v meta              Data transfer metadata
 * @ret rc              Return status code
 */
static int peerdisc_socket_rx ( struct peerdisc_socket *socket,
                                struct io_buffer *iobuf,
                                struct xfer_metadata *meta __unused ) {
        struct peerdist_discovery_reply reply;
        struct peerdisc_segment *segment;
        char *id;
        char *location;
        int rc;

        /* Discard reply (for test purposes) if applicable */
        if ( ( rc = inject_fault ( PEERDISC_DISCARD_RATE ) ) != 0 )
                goto err;

        /* Parse reply */
        if ( ( rc = peerdist_discovery_reply ( iobuf->data, iob_len ( iobuf ),
                                               &reply ) ) != 0 ) {
                DBGC ( socket, "PEERDISC %s could not parse reply: %s\n",
                       socket->name, strerror ( rc ) );
                DBGC_HDA ( socket, 0, iobuf->data, iob_len ( iobuf ) );
                goto err;
        }

        /* Any kind of discovery reply indicates that there are active
         * peers on a local network, so restore the recommended
         * discovery timeout to its default value for future requests.
         */
        if ( peerdisc_timeout_secs != PEERDISC_DEFAULT_TIMEOUT_SECS ) {
                DBGC ( socket, "PEERDISC %s restoring timeout to %d seconds\n",
                       socket->name, PEERDISC_DEFAULT_TIMEOUT_SECS );
        }
        peerdisc_timeout_secs = PEERDISC_DEFAULT_TIMEOUT_SECS;

        /* Iterate over segment IDs */
        for ( id = reply.ids ; *id ; id += ( strlen ( id ) + 1 /* NUL */ ) ) {

                /* Find corresponding segment */
                segment = peerdisc_find ( id );
                if ( ! segment ) {
                        DBGC ( socket, "PEERDISC %s ignoring reply for %s\n",
                               socket->name, id );
                        continue;
                }

                /* Report all discovered peer locations */
                for ( location = reply.locations ; *location ;
                      location += ( strlen ( location ) + 1 /* NUL */ ) ) {

                        /* Report discovered peer location */
                        if ( ( rc = peerdisc_discovered ( segment,
                                                          location ) ) != 0 )
                                goto err;
                }
        }

 err:
        free_iob ( iobuf );
        return rc;
}

/**
 * Close all PeerDist discovery sockets
 *
 * @v rc                Reason for close
 */
static void peerdisc_socket_close ( int rc ) {
        struct peerdisc_socket *socket;

        /* Close all sockets */
        for_each_table_entry ( socket, PEERDISC_SOCKETS )
                intf_restart ( &socket->xfer, rc );
}

/** PeerDist discovery socket interface operations */
static struct interface_operation peerdisc_socket_operations[] = {
        INTF_OP ( xfer_deliver, struct peerdisc_socket *, peerdisc_socket_rx ),
};

/** PeerDist discovery socket interface descriptor */
static struct interface_descriptor peerdisc_socket_desc =
        INTF_DESC ( struct peerdisc_socket, xfer, peerdisc_socket_operations );

/** PeerDist discovery IPv4 socket */
struct peerdisc_socket peerdisc_socket_ipv4 __peerdisc_socket = {
        .name = "IPv4",
        .address = {
                .sin = {
                        .sin_family = AF_INET,
                        .sin_port = htons ( PEERDIST_DISCOVERY_PORT ),
                        .sin_addr.s_addr = htonl ( PEERDIST_DISCOVERY_IPV4 ),
                },
        },
        .xfer = INTF_INIT ( peerdisc_socket_desc ),
};

/** PeerDist discovery IPv6 socket */
struct peerdisc_socket peerdisc_socket_ipv6 __peerdisc_socket = {
        .name = "IPv6",
        .address = {
                .sin6 = {
                        .sin6_family = AF_INET6,
                        .sin6_port = htons ( PEERDIST_DISCOVERY_PORT ),
                        .sin6_addr.s6_addr = PEERDIST_DISCOVERY_IPV6,
                },
        },
        .xfer = INTF_INIT ( peerdisc_socket_desc ),
};

/******************************************************************************
 *
 * Discovery segments
 *
 ******************************************************************************
 */

/**
 * Free PeerDist discovery segment
 *
 * @v refcnt            Reference count
 */
static void peerdisc_free ( struct refcnt *refcnt ) {
        struct peerdisc_segment *segment =
                container_of ( refcnt, struct peerdisc_segment, refcnt );
        struct peerdisc_peer *peer;
        struct peerdisc_peer *tmp;

        /* Free all discovered peers */
        list_for_each_entry_safe ( peer, tmp, &segment->peers, list ) {
                list_del ( &peer->list );
                free ( peer );
        }

        /* Free segment */
        free ( segment );
}

/**
 * Find PeerDist discovery segment
 *
 * @v id                Segment ID
 * @ret segment         PeerDist discovery segment, or NULL if not found
 */
static struct peerdisc_segment * peerdisc_find ( const char *id ) {
        struct peerdisc_segment *segment;

        /* Look for a matching segment */
        list_for_each_entry ( segment, &peerdisc_segments, list ) {
                if ( strcmp ( id, segment->id ) == 0 )
                        return segment;
        }

        return NULL;
}

/**
 * Add discovered PeerDist peer
 *
 * @v segment           PeerDist discovery segment
 * @v location          Peer location
 * @ret rc              Return status code
 */
static int peerdisc_discovered ( struct peerdisc_segment *segment,
                                 const char *location ) {
        struct peerdisc_peer *peer;
        struct peerdisc_client *peerdisc;
        struct peerdisc_client *tmp;
        char *recent;

        /* Ignore duplicate peers */
        list_for_each_entry ( peer, &segment->peers, list ) {
                if ( strcmp ( peer->location, location ) == 0 ) {
                        DBGC2 ( segment, "PEERDISC %p duplicate %s\n",
                                segment, location );
                        return 0;
                }
        }
        DBGC2 ( segment, "PEERDISC %p discovered %s\n", segment, location );

        /* Allocate and initialise structure */
        peer = zalloc ( sizeof ( *peer ) + strlen ( location ) + 1 /* NUL */ );
        if ( ! peer )
                return -ENOMEM;
        strcpy ( peer->location, location );

        /* Add to end of list of peers */
        list_add_tail ( &peer->list, &segment->peers );

        /* Record as most recently discovered peer */
        if ( location != peerdisc_recent ) {
                recent = strdup ( location );
                if ( recent ) {
                        free ( peerdisc_recent );
                        peerdisc_recent = recent;
                }
        }

        /* Notify all clients */
        list_for_each_entry_safe ( peerdisc, tmp, &segment->clients, list )
                peerdisc->op->discovered ( peerdisc );

        return 0;
}

/**
 * Handle discovery timer expiry
 *
 * @v timer             Discovery timer
 * @v over              Failure indicator
 */
static void peerdisc_expired ( struct retry_timer *timer, int over __unused ) {
        struct peerdisc_segment *segment =
                container_of ( timer, struct peerdisc_segment, timer );

        /* Attempt to transmit discovery requests */
        peerdisc_socket_tx ( segment->uuid, segment->id );

        /* Schedule next transmission, if applicable */
        if ( timer->count < PEERDISC_REPEAT_COUNT )
                start_timer_fixed ( &segment->timer, PEERDISC_REPEAT_TIMEOUT );
}

/**
 * Create PeerDist discovery segment
 *
 * @v id                Segment ID
 * @ret segment         PeerDist discovery segment, or NULL on error
 */
static struct peerdisc_segment * peerdisc_create ( const char *id ) {
        struct peerdisc_segment *segment;
        union {
                union uuid uuid;
                uint32_t dword[ sizeof ( union uuid ) / sizeof ( uint32_t ) ];
        } random_uuid;
        size_t uuid_len;
        size_t id_len;
        const char *uuid;
        char *uuid_copy;
        char *id_copy;
        unsigned int i;
        int rc;

        /* Generate a random message UUID.  This does not require high
         * quality randomness.
         */
        for ( i = 0 ; i < ( sizeof ( random_uuid.dword ) /
                            sizeof ( random_uuid.dword[0] ) ) ; i++ )
                random_uuid.dword[i] = random();
        uuid = uuid_ntoa ( &random_uuid.uuid );

        /* Calculate string lengths */
        id_len = ( strlen ( id ) + 1 /* NUL */ );
        uuid_len = ( strlen ( uuid ) + 1 /* NUL */ );

        /* Allocate and initialise structure */
        segment = zalloc ( sizeof ( *segment ) + id_len + uuid_len );
        if ( ! segment )
                goto err_alloc;
        id_copy = ( ( ( void * ) segment ) + sizeof ( *segment ) );
        memcpy ( id_copy, id, id_len );
        uuid_copy = ( ( ( void * ) id_copy ) + id_len );
        memcpy ( uuid_copy, uuid, uuid_len );
        ref_init ( &segment->refcnt, peerdisc_free );
        segment->id = id_copy;
        segment->uuid = uuid_copy;
        INIT_LIST_HEAD ( &segment->peers );
        INIT_LIST_HEAD ( &segment->clients );
        timer_init ( &segment->timer, peerdisc_expired, &segment->refcnt );

        /* Add hosted cache server or initiate discovery */
        if ( peerhost ) {

                /* Add hosted cache server to list of peers */
                if ( ( rc = peerdisc_discovered ( segment, peerhost ) ) != 0 )
                        goto err_peerhost;

        } else {

                /* Add most recently discovered peer to list of peers
                 *
                 * This is a performance optimisation: we assume that
                 * the most recently discovered peer for any block has
                 * a high probability of also having a copy of the
                 * next block that we attempt to discover.
                 */
                if ( peerdisc_recent )
                        peerdisc_discovered ( segment, peerdisc_recent );

                /* Start discovery timer */
                start_timer_nodelay ( &segment->timer );
                DBGC2 ( segment, "PEERDISC %p discovering %s\n",
                        segment, segment->id );
        }

        /* Add to list of segments, transfer reference to list, and return */
        list_add_tail ( &segment->list, &peerdisc_segments );
        return segment;

 err_peerhost:
        ref_put ( &segment->refcnt );
 err_alloc:
        return NULL;
}

/**
 * Destroy PeerDist discovery segment
 *
 * @v segment           PeerDist discovery segment
 */
static void peerdisc_destroy ( struct peerdisc_segment *segment ) {

        /* Sanity check */
        assert ( list_empty ( &segment->clients ) );

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

        /* Remove from list of segments and drop list's reference */
        list_del ( &segment->list );
        ref_put ( &segment->refcnt );
}

/******************************************************************************
 *
 * Discovery clients
 *
 ******************************************************************************
 */

/**
 * Open PeerDist discovery client
 *
 * @v peerdisc          PeerDist discovery client
 * @v id                Segment ID
 * @v len               Length of segment ID
 * @ret rc              Return status code
 */
int peerdisc_open ( struct peerdisc_client *peerdisc, const void *id,
                    size_t len ) {
        struct peerdisc_segment *segment;
        char id_string[ base16_encoded_len ( len ) + 1 /* NUL */ ];
        char *id_chr;
        int rc;

        /* Construct ID string */
        base16_encode ( id, len, id_string, sizeof ( id_string ) );
        for ( id_chr = id_string ; *id_chr ; id_chr++ )
                *id_chr = toupper ( *id_chr );

        /* Sanity check */
        assert ( peerdisc->segment == NULL );

        /* Open socket if this is the first segment */
        if ( list_empty ( &peerdisc_segments ) &&
             ( ( rc = peerdisc_socket_open() ) != 0 ) )
                return rc;

        /* Find or create segment */
        if ( ! ( ( segment = peerdisc_find ( id_string ) ) ||
                 ( segment = peerdisc_create ( id_string ) ) ) )
                return -ENOMEM;

        /* Add to list of clients */
        ref_get ( &segment->refcnt );
        peerdisc->segment = segment;
        list_add_tail ( &peerdisc->list, &segment->clients );

        return 0;
}

/**
 * Close PeerDist discovery client
 *
 * @v peerdisc          PeerDist discovery client
 */
void peerdisc_close ( struct peerdisc_client *peerdisc ) {
        struct peerdisc_segment *segment = peerdisc->segment;

        /* Ignore if discovery is already closed */
        if ( ! segment )
                return;

        /* If no peers were discovered, reduce the recommended
         * discovery timeout to minimise delays on future requests.
         */
        if ( list_empty ( &segment->peers ) && peerdisc_timeout_secs ) {
                peerdisc_timeout_secs--;
                DBGC ( segment, "PEERDISC %p reducing timeout to %d "
                       "seconds\n", peerdisc, peerdisc_timeout_secs );
        }

        /* Remove from list of clients */
        peerdisc->segment = NULL;
        list_del ( &peerdisc->list );
        ref_put ( &segment->refcnt );

        /* If this was the last clients, destroy the segment */
        if ( list_empty ( &segment->clients ) )
                peerdisc_destroy ( segment );

        /* If there are no more segments, close the socket */
        if ( list_empty ( &peerdisc_segments ) )
                peerdisc_socket_close ( 0 );
}

/******************************************************************************
 *
 * Settings
 *
 ******************************************************************************
 */

/** PeerDist hosted cache server setting */
const struct setting peerhost_setting __setting ( SETTING_MISC, peerhost ) = {
        .name = "peerhost",
        .description = "PeerDist hosted cache",
        .type = &setting_type_string,
};

/**
 * Apply PeerDist discovery settings
 *
 * @ret rc              Return status code
 */
static int apply_peerdisc_settings ( void ) {

        /* Free any existing hosted cache server */
        free ( peerhost );
        peerhost = NULL;

        /* Fetch hosted cache server */
        fetch_string_setting_copy ( NULL, &peerhost_setting, &peerhost );
        if ( peerhost ) {
                DBGC ( &peerhost, "PEERDISC using hosted cache %s\n",
                       peerhost );
        }

        return 0;
}

/** PeerDist discovery settings applicator */
struct settings_applicator peerdisc_applicator __settings_applicator = {
        .apply = apply_peerdisc_settings,
};