udp.c

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#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <byteswap.h>
#include <errno.h>
#include <ipxe/tcpip.h>
#include <ipxe/iobuf.h>
#include <ipxe/xfer.h>
#include <ipxe/open.h>
#include <ipxe/uri.h>
#include <ipxe/netdevice.h>
#include <ipxe/udp.h>

/** @file
 *
 * UDP protocol
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

/**
 * A UDP connection
 *
 */
struct udp_connection {
        /** Reference counter */
        struct refcnt refcnt;
        /** List of UDP connections */
        struct list_head list;

        /** Data transfer interface */
        struct interface xfer;

        /** Local socket address */
        struct sockaddr_tcpip local;
        /** Remote socket address */
        struct sockaddr_tcpip peer;
};

/**
 * List of registered UDP connections
 */
static LIST_HEAD ( udp_conns );

/* Forward declatations */
static struct interface_descriptor udp_xfer_desc;
struct tcpip_protocol udp_protocol __tcpip_protocol;

/**
 * Check if local UDP port is available
 *
 * @v port              Local port number
 * @ret port            Local port number, or negative error
 */
static int udp_port_available ( int port ) {
        struct udp_connection *udp;

        list_for_each_entry ( udp, &udp_conns, list ) {
                if ( udp->local.st_port == htons ( port ) )
                        return -EADDRINUSE;
        }
        return port;
}

/**
 * Open a UDP connection
 *
 * @v xfer              Data transfer interface
 * @v peer              Peer socket address, or NULL
 * @v local             Local socket address, or NULL
 * @v promisc           Socket is promiscuous
 * @ret rc              Return status code
 */
static int udp_open_common ( struct interface *xfer,
                             struct sockaddr *peer, struct sockaddr *local,
                             int promisc ) {
        struct sockaddr_tcpip *st_peer = ( struct sockaddr_tcpip * ) peer;
        struct sockaddr_tcpip *st_local = ( struct sockaddr_tcpip * ) local;
        struct udp_connection *udp;
        int port;
        int rc;

        /* Allocate and initialise structure */
        udp = zalloc ( sizeof ( *udp ) );
        if ( ! udp )
                return -ENOMEM;
        DBGC ( udp, "UDP %p allocated\n", udp );
        ref_init ( &udp->refcnt, NULL );
        intf_init ( &udp->xfer, &udp_xfer_desc, &udp->refcnt );
        if ( st_peer )
                memcpy ( &udp->peer, st_peer, sizeof ( udp->peer ) );
        if ( st_local )
                memcpy ( &udp->local, st_local, sizeof ( udp->local ) );

        /* Bind to local port */
        if ( ! promisc ) {
                port = tcpip_bind ( st_local, udp_port_available );
                if ( port < 0 ) {
                        rc = port;
                        DBGC ( udp, "UDP %p could not bind: %s\n",
                               udp, strerror ( rc ) );
                        goto err;
                }
                udp->local.st_port = htons ( port );
                DBGC ( udp, "UDP %p bound to port %d\n",
                       udp, ntohs ( udp->local.st_port ) );
        }

        /* Attach parent interface, transfer reference to connection
         * list and return
         */
        intf_plug_plug ( &udp->xfer, xfer );
        list_add ( &udp->list, &udp_conns );
        return 0;

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

/**
 * Open a UDP connection
 *
 * @v xfer              Data transfer interface
 * @v peer              Peer socket address
 * @v local             Local socket address, or NULL
 * @ret rc              Return status code
 */
int udp_open ( struct interface *xfer, struct sockaddr *peer,
               struct sockaddr *local ) {
        return udp_open_common ( xfer, peer, local, 0 );
}

/**
 * Open a promiscuous UDP connection
 *
 * @v xfer              Data transfer interface
 * @ret rc              Return status code
 *
 * Promiscuous UDP connections are required in order to support the
 * PXE API.
 */
int udp_open_promisc ( struct interface *xfer ) {
        return udp_open_common ( xfer, NULL, NULL, 1 );
}

/**
 * Close a UDP connection
 *
 * @v udp               UDP connection
 * @v rc                Reason for close
 */
static void udp_close ( struct udp_connection *udp, int rc ) {

        /* Close data transfer interface */
        intf_shutdown ( &udp->xfer, rc );

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

        DBGC ( udp, "UDP %p closed\n", udp );
}

/**
 * Transmit data via a UDP connection to a specified address
 *
 * @v udp               UDP connection
 * @v iobuf             I/O buffer
 * @v src               Source address, or NULL to use default
 * @v dest              Destination address, or NULL to use default
 * @v netdev            Network device, or NULL to use default
 * @ret rc              Return status code
 */
static int udp_tx ( struct udp_connection *udp, struct io_buffer *iobuf,
                    struct sockaddr_tcpip *src, struct sockaddr_tcpip *dest,
                    struct net_device *netdev ) {
        struct udp_header *udphdr;
        size_t len;
        int rc;

        /* Check we can accommodate the header */
        if ( ( rc = iob_ensure_headroom ( iobuf,
                                          MAX_LL_NET_HEADER_LEN ) ) != 0 ) {
                free_iob ( iobuf );
                return rc;
        }

        /* Fill in default values if not explicitly provided */
        if ( ! src )
                src = &udp->local;
        if ( ! dest )
                dest = &udp->peer;

        /* Add the UDP header */
        udphdr = iob_push ( iobuf, sizeof ( *udphdr ) );
        len = iob_len ( iobuf );
        udphdr->dest = dest->st_port;
        udphdr->src = src->st_port;
        udphdr->len = htons ( len );
        udphdr->chksum = 0;
        udphdr->chksum = tcpip_chksum ( udphdr, len );

        /* Dump debugging information */
        DBGC2 ( udp, "UDP %p TX %d->%d len %d\n", udp,
                ntohs ( udphdr->src ), ntohs ( udphdr->dest ),
                ntohs ( udphdr->len ) );

        /* Send it to the next layer for processing */
        if ( ( rc = tcpip_tx ( iobuf, &udp_protocol, src, dest, netdev,
                               &udphdr->chksum ) ) != 0 ) {
                DBGC ( udp, "UDP %p could not transmit packet: %s\n",
                       udp, strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Identify UDP connection by local address
 *
 * @v local             Local address
 * @ret udp             UDP connection, or NULL
 */
static struct udp_connection * udp_demux ( struct sockaddr_tcpip *local ) {
        static const struct sockaddr_tcpip empty_sockaddr = { .pad = { 0, } };
        struct udp_connection *udp;

        list_for_each_entry ( udp, &udp_conns, list ) {
                if ( ( ( udp->local.st_family == local->st_family ) ||
                       ( udp->local.st_family == 0 ) ) &&
                     ( ( udp->local.st_port == local->st_port ) ||
                       ( udp->local.st_port == 0 ) ) &&
                     ( ( memcmp ( udp->local.pad, local->pad,
                                  sizeof ( udp->local.pad ) ) == 0 ) ||
                       ( memcmp ( udp->local.pad, empty_sockaddr.pad,
                                  sizeof ( udp->local.pad ) ) == 0 ) ) ) {
                        return udp;
                }
        }
        return NULL;
}

/**
 * Process a received packet
 *
 * @v iobuf             I/O buffer
 * @v netdev            Network device
 * @v st_src            Partially-filled source address
 * @v st_dest           Partially-filled destination address
 * @v pshdr_csum        Pseudo-header checksum
 * @ret rc              Return status code
 */
static int udp_rx ( struct io_buffer *iobuf,
                    struct net_device *netdev __unused,
                    struct sockaddr_tcpip *st_src,
                    struct sockaddr_tcpip *st_dest, uint16_t pshdr_csum ) {
        struct udp_header *udphdr = iobuf->data;
        struct udp_connection *udp;
        struct xfer_metadata meta;
        size_t ulen;
        unsigned int csum;
        int rc = 0;

        /* Sanity check packet */
        if ( iob_len ( iobuf ) < sizeof ( *udphdr ) ) {
                DBG ( "UDP packet too short at %zd bytes (min %zd bytes)\n",
                      iob_len ( iobuf ), sizeof ( *udphdr ) );
                
                rc = -EINVAL;
                goto done;
        }
        ulen = ntohs ( udphdr->len );
        if ( ulen < sizeof ( *udphdr ) ) {
                DBG ( "UDP length too short at %zd bytes "
                      "(header is %zd bytes)\n", ulen, sizeof ( *udphdr ) );
                rc = -EINVAL;
                goto done;
        }
        if ( ulen > iob_len ( iobuf ) ) {
                DBG ( "UDP length too long at %zd bytes (packet is %zd "
                      "bytes)\n", ulen, iob_len ( iobuf ) );
                rc = -EINVAL;
                goto done;
        }
        if ( udphdr->chksum ) {
                csum = tcpip_continue_chksum ( pshdr_csum, iobuf->data, ulen );
                if ( csum != 0 ) {
                        DBG ( "UDP checksum incorrect (is %04x including "
                              "checksum field, should be 0000)\n", csum );
                        rc = -EINVAL;
                        goto done;
                }
        }

        /* Parse parameters from header and strip header */
        st_src->st_port = udphdr->src;
        st_dest->st_port = udphdr->dest;
        udp = udp_demux ( st_dest );
        iob_unput ( iobuf, ( iob_len ( iobuf ) - ulen ) );
        iob_pull ( iobuf, sizeof ( *udphdr ) );

        /* Dump debugging information */
        DBGC2 ( udp, "UDP %p RX %d<-%d len %zd\n", udp,
                ntohs ( udphdr->dest ), ntohs ( udphdr->src ), ulen );

        /* Ignore if no matching connection found */
        if ( ! udp ) {
                DBG ( "No UDP connection listening on port %d\n",
                      ntohs ( udphdr->dest ) );
                rc = -ENOTCONN;
                goto done;
        }

        /* Pass data to application */
        memset ( &meta, 0, sizeof ( meta ) );
        meta.src = ( struct sockaddr * ) st_src;
        meta.dest = ( struct sockaddr * ) st_dest;
        rc = xfer_deliver ( &udp->xfer, iob_disown ( iobuf ), &meta );

 done:
        free_iob ( iobuf );
        return rc;
}

struct tcpip_protocol udp_protocol __tcpip_protocol = {
        .name = "UDP",
        .rx = udp_rx,
        .zero_csum = TCPIP_NEGATIVE_ZERO_CSUM,
        .tcpip_proto = IP_UDP,
};

/***************************************************************************
 *
 * Data transfer interface
 *
 ***************************************************************************
 */

/**
 * Allocate I/O buffer for UDP
 *
 * @v udp               UDP connection
 * @v len               Payload size
 * @ret iobuf           I/O buffer, or NULL
 */
static struct io_buffer * udp_xfer_alloc_iob ( struct udp_connection *udp,
                                               size_t len ) {
        struct io_buffer *iobuf;

        iobuf = alloc_iob ( MAX_LL_NET_HEADER_LEN + len );
        if ( ! iobuf ) {
                DBGC ( udp, "UDP %p cannot allocate buffer of length %zd\n",
                       udp, len );
                return NULL;
        }
        iob_reserve ( iobuf, MAX_LL_NET_HEADER_LEN );
        return iobuf;
}

/**
 * Deliver datagram as I/O buffer
 *
 * @v udp               UDP connection
 * @v iobuf             Datagram I/O buffer
 * @v meta              Data transfer metadata
 * @ret rc              Return status code
 */
static int udp_xfer_deliver ( struct udp_connection *udp,
                              struct io_buffer *iobuf,
                              struct xfer_metadata *meta ) {

        /* Transmit data, if possible */
        return udp_tx ( udp, iobuf, ( ( struct sockaddr_tcpip * ) meta->src ),
                        ( ( struct sockaddr_tcpip * ) meta->dest ),
                        meta->netdev );
}

/** UDP data transfer interface operations */
static struct interface_operation udp_xfer_operations[] = {
        INTF_OP ( xfer_deliver, struct udp_connection *, udp_xfer_deliver ),
        INTF_OP ( xfer_alloc_iob, struct udp_connection *, udp_xfer_alloc_iob ),
        INTF_OP ( intf_close, struct udp_connection *, udp_close ),
};

/** UDP data transfer interface descriptor */
static struct interface_descriptor udp_xfer_desc =
        INTF_DESC ( struct udp_connection, xfer, udp_xfer_operations );

/***************************************************************************
 *
 * Openers
 *
 ***************************************************************************
 */

/** UDP socket opener */
struct socket_opener udp_socket_opener __socket_opener = {
        .semantics      = UDP_SOCK_DGRAM,
        .open           = udp_open,
};

/** Linkage hack */
int udp_sock_dgram = UDP_SOCK_DGRAM;

/**
 * Open UDP URI
 *
 * @v xfer              Data transfer interface
 * @v uri               URI
 * @ret rc              Return status code
 */
static int udp_open_uri ( struct interface *xfer, struct uri *uri ) {
        struct sockaddr_tcpip peer;

        /* Sanity check */
        if ( ! uri->host )
                return -EINVAL;

        memset ( &peer, 0, sizeof ( peer ) );
        peer.st_port = htons ( uri_port ( uri, 0 ) );
        return xfer_open_named_socket ( xfer, SOCK_DGRAM,
                                        ( struct sockaddr * ) &peer,
                                        uri->host, NULL );
}

/** UDP URI opener */
struct uri_opener udp_uri_opener __uri_opener = {
        .scheme         = "udp",
        .open           = udp_open_uri,
};