source: bootcd/isolinux/syslinux-6.03/gpxe/src/core/resolv.c

/*
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <gpxe/in.h>
#include <gpxe/xfer.h>
#include <gpxe/open.h>
#include <gpxe/process.h>
#include <gpxe/resolv.h>

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

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

/**
 * Name resolution completed
 *
 * @v resolv            Name resolution interface
 * @v sa                Completed socket address (if successful)
 * @v rc                Final status code
 */
void resolv_done ( struct resolv_interface *resolv, struct sockaddr *sa,
                   int rc ) {
        struct resolv_interface *dest = resolv_get_dest ( resolv );

        resolv_unplug ( resolv );
        dest->op->done ( dest, sa, rc );
        resolv_put ( dest );
}

/**
 * Ignore name resolution done() event
 *
 * @v resolv            Name resolution interface
 * @v sa                Completed socket address (if successful)
 * @v rc                Final status code
 */
void ignore_resolv_done ( struct resolv_interface *resolv __unused,
                          struct sockaddr *sa __unused, int rc __unused ) {
        /* Do nothing */
}

/** Null name resolution interface operations */
struct resolv_interface_operations null_resolv_ops = {
        .done           = ignore_resolv_done,
};

/** Null name resolution interface */
struct resolv_interface null_resolv = {
        .intf = {
                .dest = &null_resolv.intf,
                .refcnt = NULL,
        },
        .op = &null_resolv_ops,
};

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

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

static void numeric_step ( struct process *process ) {
        struct numeric_resolv *numeric =
                container_of ( process, struct numeric_resolv, process );
        
        resolv_done ( &numeric->resolv, &numeric->sa, numeric->rc );
        process_del ( process );
}

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

        /* Allocate and initialise structure */
        numeric = zalloc ( sizeof ( *numeric ) );
        if ( ! numeric )
                return -ENOMEM;
        resolv_init ( &numeric->resolv, &null_resolv_ops, &numeric->refcnt );
        process_init ( &numeric->process, numeric_step, &numeric->refcnt );
        memcpy ( &numeric->sa, sa, sizeof ( numeric->sa ) );

        DBGC ( numeric, "NUMERIC %p attempting to resolve \"%s\"\n",
               numeric, name );

        /* Attempt to resolve name */
        sin = ( ( struct sockaddr_in * ) &numeric->sa );
        sin->sin_family = AF_INET;
        if ( inet_aton ( name, &sin->sin_addr ) == 0 )
                numeric->rc = -EINVAL;

        /* Attach to parent interface, mortalise self, and return */
        resolv_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 resolv_interface parent;

        /** Child name resolution interface */
        struct resolv_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 resolv_mux_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;
}

/**
 * Handle done() event from child name resolver
 *
 * @v resolv            Child name resolution interface
 * @v sa                Completed socket address (if successful)
 * @v rc                Final status code
 */
static void resolv_mux_done ( struct resolv_interface *resolv,
                              struct sockaddr *sa, int rc ) {
        struct resolv_mux *mux =
                container_of ( resolv, struct resolv_mux, child );

        /* Unplug child */
        resolv_unplug ( &mux->child );

        /* 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 = resolv_mux_try ( mux ) ) != 0 )
                goto finished;

        /* Next resolver is now running */
        return;
        
 finished:
        resolv_done ( &mux->parent, sa, rc );
}

/** Name resolution multiplexer operations */
static struct resolv_interface_operations resolv_mux_child_ops = {
        .done           = resolv_mux_done,
};

/**
 * 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 resolv_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;
        resolv_init ( &mux->parent, &null_resolv_ops, &mux->refcnt );
        resolv_init ( &mux->child, &resolv_mux_child_ops, &mux->refcnt );
        mux->resolver = table_start ( RESOLVERS );
        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 = resolv_mux_try ( mux ) ) != 0 )
                goto err;

        /* Attach parent interface, mortalise self, and return */
        resolv_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 xfer_interface xfer;
        /** Name resolution interface */
        struct resolv_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;
};

/**
 * Finish using named socket
 *
 * @v named             Named socket
 * @v rc                Reason for finish
 */
static void named_done ( struct named_socket *named, int rc ) {

        /* Close all interfaces */
        resolv_nullify ( &named->resolv );
        xfer_nullify ( &named->xfer );
        xfer_close ( &named->xfer, rc );
}

/**
 * Handle close() event
 *
 * @v xfer              Data transfer interface
 * @v rc                Reason for close
 */
static void named_xfer_close ( struct xfer_interface *xfer, int rc ) {
        struct named_socket *named =
                container_of ( xfer, struct named_socket, xfer );

        named_done ( named, rc );
}

/** Named socket opener data transfer interface operations */
static struct xfer_interface_operations named_xfer_ops = {
        .close          = named_xfer_close,
        .vredirect      = ignore_xfer_vredirect,
        .window         = no_xfer_window,
        .alloc_iob      = default_xfer_alloc_iob,
        .deliver_iob    = xfer_deliver_as_raw,
        .deliver_raw    = ignore_xfer_deliver_raw,
};

/**
 * Handle done() event
 *
 * @v resolv            Name resolution interface
 * @v sa                Completed socket address (if successful)
 * @v rc                Final status code
 */
static void named_resolv_done ( struct resolv_interface *resolv,
                                struct sockaddr *sa, int rc ) {
        struct named_socket *named =
                container_of ( resolv, struct named_socket, resolv );

        /* Redirect if name resolution was successful */
        if ( rc == 0 ) {
                rc = xfer_redirect ( &named->xfer, LOCATION_SOCKET,
                                     named->semantics, sa,
                                     ( named->have_local ?
                                       &named->local : NULL ) );
        }

        /* Terminate resolution */
        named_done ( named, rc );
}

/** Named socket opener name resolution interface operations */
static struct resolv_interface_operations named_resolv_ops = {
        .done           = named_resolv_done,
};

/**
 * 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 xfer_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;
        xfer_init ( &named->xfer, &named_xfer_ops, &named->refcnt );
        resolv_init ( &named->resolv, &named_resolv_ops, &named->refcnt );
        named->semantics = semantics;
        if ( local ) {
                memcpy ( &named->local, local, sizeof ( named->local ) );
                named->have_local = 1;
        }

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

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

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

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