resolv.c

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/*
 * Copyright (C) 2007 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 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 <stdlib.h>
#include <string.h>
#include <errno.h>
#include <ipxe/xfer.h>
#include <ipxe/open.h>
#include <ipxe/process.h>
#include <ipxe/socket.h>
#include <ipxe/resolv.h>

/** @file
 *
 * Name resolution
 *
 */

/***************************************************************************
 *
 * Name resolution interfaces
 *
 ***************************************************************************
 */

/**
 * Name resolved
 *
 * @v intf              Object interface
 * @v sa                Completed socket address (if successful)
 */
void resolv_done ( struct interface *intf, struct sockaddr *sa ) {
        struct interface *dest;
        resolv_done_TYPE ( void * ) *op =
                intf_get_dest_op ( intf, resolv_done, &dest );
        void *object = intf_object ( dest );

        DBGC ( INTF_COL ( intf ), "INTF " INTF_INTF_FMT " resolv_done\n",
               INTF_INTF_DBG ( intf, dest ) );

        if ( op ) {
                op ( object, sa );
        } else {
                /* Default is to ignore resolutions */
        }

        intf_put ( dest );
}

/***************************************************************************
 *
 * Numeric name resolver
 *
 ***************************************************************************
 */

/** A numeric name resolver */
struct numeric_resolv {
        /** Reference counter */
        struct refcnt refcnt;
        /** Name resolution interface */
        struct interface resolv;
        /** Process */
        struct process process;
        /** Completed socket address */
        struct sockaddr sa;
        /** Overall status code */
        int rc;
};

static void numeric_step ( struct numeric_resolv *numeric ) {

        if ( numeric->rc == 0 )
                resolv_done ( &numeric->resolv, &numeric->sa );
        intf_shutdown ( &numeric->resolv, numeric->rc );
}

static struct process_descriptor numeric_process_desc =
        PROC_DESC_ONCE ( struct numeric_resolv, process, numeric_step );

static int numeric_resolv ( struct interface *resolv,
                            const char *name, struct sockaddr *sa ) {
        struct numeric_resolv *numeric;

        /* Allocate and initialise structure */
        numeric = zalloc ( sizeof ( *numeric ) );
        if ( ! numeric )
                return -ENOMEM;
        ref_init ( &numeric->refcnt, NULL );
        intf_init ( &numeric->resolv, &null_intf_desc, &numeric->refcnt );
        process_init ( &numeric->process, &numeric_process_desc,
                       &numeric->refcnt );
        memcpy ( &numeric->sa, sa, sizeof ( numeric->sa ) );

        /* Attempt to resolve name */
        numeric->rc = sock_aton ( name, &numeric->sa );

        /* Attach to parent interface, mortalise self, and return */
        intf_plug_plug ( &numeric->resolv, resolv );
        ref_put ( &numeric->refcnt );
        return 0;
}

struct resolver numeric_resolver __resolver ( RESOLV_NUMERIC ) = {
        .name = "NUMERIC",
        .resolv = numeric_resolv,
};

/***************************************************************************
 *
 * Name resolution multiplexer
 *
 ***************************************************************************
 */

/** A name resolution multiplexer */
struct resolv_mux {
        /** Reference counter */
        struct refcnt refcnt;
        /** Parent name resolution interface */
        struct interface parent;

        /** Child name resolution interface */
        struct interface child;
        /** Current child resolver */
        struct resolver *resolver;

        /** Socket address to complete */
        struct sockaddr sa;
        /** Name to be resolved
         *
         * Must be at end of structure
         */
        char name[0];
};

/**
 * Try current child name resolver
 *
 * @v mux               Name resolution multiplexer
 * @ret rc              Return status code
 */
static int resmux_try ( struct resolv_mux *mux ) {
        struct resolver *resolver = mux->resolver;
        int rc;

        DBGC ( mux, "RESOLV %p trying method %s\n", mux, resolver->name );

        if ( ( rc = resolver->resolv ( &mux->child, mux->name,
                                       &mux->sa ) ) != 0 ) {
                DBGC ( mux, "RESOLV %p could not use method %s: %s\n",
                       mux, resolver->name, strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Close name resolution multiplexer
 *
 * @v mux               Name resolution multiplexer
 * @v rc                Reason for close
 */
static void resmux_close ( struct resolv_mux *mux, int rc ) {

        /* Shut down all interfaces */
        intf_shutdown ( &mux->child, rc );
        intf_shutdown ( &mux->parent, rc );
}

/**
 * Child finished resolution
 *
 * @v mux               Name resolution multiplexer
 * @v rc                Return status code
 */
static void resmux_child_close ( struct resolv_mux *mux, int rc ) {

        /* Restart child interface */
        intf_restart ( &mux->child, rc );

        /* If this resolution succeeded, stop now */
        if ( rc == 0 ) {
                DBGC ( mux, "RESOLV %p succeeded using method %s\n",
                       mux, mux->resolver->name );
                goto finished;
        }

        /* Attempt next child resolver, if possible */
        mux->resolver++;
        if ( mux->resolver >= table_end ( RESOLVERS ) ) {
                DBGC ( mux, "RESOLV %p failed to resolve name\n", mux );
                goto finished;
        }
        if ( ( rc = resmux_try ( mux ) ) != 0 )
                goto finished;

        /* Next resolver is now running */
        return;

 finished:
        resmux_close ( mux, rc );
}

/** Name resolution multiplexer child interface operations */
static struct interface_operation resmux_child_op[] = {
        INTF_OP ( intf_close, struct resolv_mux *, resmux_child_close ),
};

/** Name resolution multiplexer child interface descriptor */
static struct interface_descriptor resmux_child_desc =
        INTF_DESC_PASSTHRU ( struct resolv_mux, child, resmux_child_op,
                             parent );

/** Name resolution multiplexer parent interface operations */
static struct interface_operation resmux_parent_op[] = {
        INTF_OP ( intf_close, struct resolv_mux *, resmux_close ),
};

/** Name resolution multiplexer parent interface descriptor */
static struct interface_descriptor resmux_parent_desc =
        INTF_DESC_PASSTHRU ( struct resolv_mux, parent, resmux_parent_op,
                             child );

/**
 * Start name resolution
 *
 * @v resolv            Name resolution interface
 * @v name              Name to resolve
 * @v sa                Socket address to complete
 * @ret rc              Return status code
 */
int resolv ( struct interface *resolv, const char *name,
             struct sockaddr *sa ) {
        struct resolv_mux *mux;
        size_t name_len = ( strlen ( name ) + 1 );
        int rc;

        /* Allocate and initialise structure */
        mux = zalloc ( sizeof ( *mux ) + name_len );
        if ( ! mux )
                return -ENOMEM;
        ref_init ( &mux->refcnt, NULL );
        intf_init ( &mux->parent, &resmux_parent_desc, &mux->refcnt );
        intf_init ( &mux->child, &resmux_child_desc, &mux->refcnt );
        mux->resolver = table_start ( RESOLVERS );
        if ( sa )
                memcpy ( &mux->sa, sa, sizeof ( mux->sa ) );
        memcpy ( mux->name, name, name_len );

        DBGC ( mux, "RESOLV %p attempting to resolve \"%s\"\n", mux, name );

        /* Start first resolver in chain.  There will always be at
         * least one resolver (the numeric resolver), so no need to
         * check for the zero-resolvers-available case.
         */
        if ( ( rc = resmux_try ( mux ) ) != 0 )
                goto err;

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

 err:
        ref_put ( &mux->refcnt );
        return rc;      
}

/***************************************************************************
 *
 * Named socket opening
 *
 ***************************************************************************
 */

/** A named socket */
struct named_socket {
        /** Reference counter */
        struct refcnt refcnt;
        /** Data transfer interface */
        struct interface xfer;
        /** Name resolution interface */
        struct interface resolv;
        /** Communication semantics (e.g. SOCK_STREAM) */
        int semantics;
        /** Stored local socket address, if applicable */
        struct sockaddr local;
        /** Stored local socket address exists */
        int have_local;
};

/**
 * Terminate named socket opener
 *
 * @v named             Named socket
 * @v rc                Reason for termination
 */
static void named_close ( struct named_socket *named, int rc ) {
        /* Shut down interfaces */
        intf_shutdown ( &named->resolv, rc );
        intf_shutdown ( &named->xfer, rc );
}

/**
 * Check flow control window
 *
 * @v named             Named socket
 * @ret len             Length of window
 */
static size_t named_window ( struct named_socket *named __unused ) {
        /* Not ready for data until we have redirected away */
        return 0;
}

/** Named socket opener data transfer interface operations */
static struct interface_operation named_xfer_ops[] = {
        INTF_OP ( xfer_window, struct named_socket *, named_window ),
        INTF_OP ( intf_close, struct named_socket *, named_close ),
};

/** Named socket opener data transfer interface descriptor */
static struct interface_descriptor named_xfer_desc =
        INTF_DESC_PASSTHRU ( struct named_socket, xfer, named_xfer_ops,
                             resolv );

/**
 * Name resolved
 *
 * @v named             Named socket
 * @v sa                Completed socket address
 */
static void named_resolv_done ( struct named_socket *named,
                                struct sockaddr *sa ) {
        int rc;

        /* Nullify data transfer interface */
        intf_nullify ( &named->xfer );

        /* Redirect data-xfer interface */
        if ( ( rc = xfer_redirect ( &named->xfer, LOCATION_SOCKET,
                                    named->semantics, sa,
                                    ( named->have_local ?
                                      &named->local : NULL ) ) ) != 0 ) {
                /* Redirection failed - do not unplug data-xfer interface */
                DBGC ( named, "NAMED %p could not redirect: %s\n",
                       named, strerror ( rc ) );
        } else {
                /* Redirection succeeded - unplug data-xfer interface */
                DBGC ( named, "NAMED %p redirected successfully\n", named );
                intf_unplug ( &named->xfer );
        }

        /* Terminate named socket opener */
        named_close ( named, rc );
}

/** Named socket opener resolver interface operations */
static struct interface_operation named_resolv_op[] = {
        INTF_OP ( intf_close, struct named_socket *, named_close ),
        INTF_OP ( resolv_done, struct named_socket *, named_resolv_done ),
};

/** Named socket opener resolver interface descriptor */
static struct interface_descriptor named_resolv_desc =
        INTF_DESC_PASSTHRU ( struct named_socket, resolv, named_resolv_op,
                             xfer );

/**
 * Open named socket
 *
 * @v semantics         Communication semantics (e.g. SOCK_STREAM)
 * @v peer              Peer socket address to complete
 * @v name              Name to resolve
 * @v local             Local socket address, or NULL
 * @ret rc              Return status code
 */
int xfer_open_named_socket ( struct interface *xfer, int semantics,
                             struct sockaddr *peer, const char *name,
                             struct sockaddr *local ) {
        struct named_socket *named;
        int rc;

        /* Allocate and initialise structure */
        named = zalloc ( sizeof ( *named ) );
        if ( ! named )
                return -ENOMEM;
        ref_init ( &named->refcnt, NULL );
        intf_init ( &named->xfer, &named_xfer_desc, &named->refcnt );
        intf_init ( &named->resolv, &named_resolv_desc, &named->refcnt );
        named->semantics = semantics;
        if ( local ) {
                memcpy ( &named->local, local, sizeof ( named->local ) );
                named->have_local = 1;
        }

        DBGC ( named, "NAMED %p opening \"%s\"\n",
               named, name );

        /* Start name resolution */
        if ( ( rc = resolv ( &named->resolv, name, peer ) ) != 0 )
                goto err;

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

 err:
        ref_put ( &named->refcnt );
        return rc;
}