pptp_ctrl.c

/* pptp_ctrl.c ... handle PPTP control connection.
 *                 C. Scott Ananian <cananian@alumni.princeton.edu>
 *
 * $Id: pptp_ctrl.c,v 1.1 2009-01-07 09:47:37 steven Exp $
 */

#include <errno.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <stdlib.h>
#include <assert.h>
#include <signal.h>
#include <string.h>
#include <ctype.h>
#include <fcntl.h>
#include "pptp_msg.h"
#include "pptp_ctrl.h"
#include "pptp_options.h"
#include "vector.h"
#include "util.h"
#include "pptp_quirks.h"

/* BECAUSE OF SIGNAL LIMITATIONS, EACH PROCESS CAN ONLY MANAGE ONE
 * CONNECTION.  SO THIS 'PPTP_CONN' STRUCTURE IS A BIT MISLEADING.
 * WE'LL KEEP CONNECTION-SPECIFIC INFORMATION IN THERE ANYWAY (AS
 * OPPOSED TO USING GLOBAL VARIABLES), BUT BEWARE THAT THE ENTIRE
 * UNIX SIGNAL-HANDLING SEMANTICS WOULD HAVE TO CHANGE (OR THE
 * TIME-OUT CODE DRASTICALLY REWRITTEN) BEFORE YOU COULD DO A
 * PPTP_CONN_OPEN MORE THAN ONCE PER PROCESS AND GET AWAY WITH IT.
 */

/* This structure contains connection-specific information that the
 * signal handler needs to see.  Thus, it needs to be in a global
 * variable.  If you end up using pthreads or something (why not
 * just processes?), this would have to be placed in a thread-specific
 * data area, using pthread_get|set_specific, etc., so I've
 * conveniently encapsulated it for you.
 * [linux threads will have to support thread-specific signals
 *  before this would work at all, which, as of this writing
 *  (linux-threads v0.6, linux kernel 2.1.72), it does not.]
 */

/* Globals */

/* control the number of times echo packets will be logged */
static int nlogecho = 10;

static struct thread_specific {
    struct sigaction old_sigaction; /* evil signals */
    PPTP_CONN * conn;
} global;

#define INITIAL_BUFSIZE 512 /* initial i/o buffer size. */

struct PPTP_CONN {
    int inet_sock;
    /* Connection States */
    enum {
        CONN_IDLE, CONN_WAIT_CTL_REPLY, CONN_WAIT_STOP_REPLY, CONN_ESTABLISHED
    } conn_state; /* on startup: CONN_IDLE */
    /* Keep-alive states */
    enum {
        KA_NONE, KA_OUTSTANDING
    } ka_state;  /* on startup: KA_NONE */
    /* Keep-alive ID; monotonically increasing (watch wrap-around!) */
    u_int32_t ka_id; /* on startup: 1 */
    /* Other properties. */
    u_int16_t version;
    u_int16_t firmware_rev;
    u_int8_t  hostname[64], vendor[64];
    /* XXX these are only PNS properties, currently XXX */
    /* Call assignment information. */
    u_int16_t call_serial_number;
    VECTOR *call;
    void * closure;
    pptp_conn_cb callback;
    /******* IO buffers ******/
    char * read_buffer, *write_buffer;
    size_t read_alloc,   write_alloc;
    size_t read_size,    write_size;
};

struct PPTP_CALL {
    /* Call properties */
    enum {
        PPTP_CALL_PAC, PPTP_CALL_PNS
    } call_type;
    union {
        enum pptp_pac_state {
            PAC_IDLE, PAC_WAIT_REPLY, PAC_ESTABLISHED, PAC_WAIT_CS_ANS
        } pac;
        enum pptp_pns_state {
            PNS_IDLE, PNS_WAIT_REPLY, PNS_ESTABLISHED, PNS_WAIT_DISCONNECT
        } pns;
    } state;
    u_int16_t call_id, peer_call_id;
    u_int16_t sernum;
    u_int32_t speed;
    /* For user data: */
    pptp_call_cb callback;
    void * closure;
};


/* PPTP error codes: ----------------------------------------------*/

/* (General Error Codes) */
static const struct {
    const char *name, *desc;
} pptp_general_errors[] = {
#define PPTP_GENERAL_ERROR_NONE                 0
    { "(None)", "No general error" },
#define PPTP_GENERAL_ERROR_NOT_CONNECTED        1
    { "(Not-Connected)", "No control connection exists yet for this "
        "PAC-PNS pair" },
#define PPTP_GENERAL_ERROR_BAD_FORMAT           2
    { "(Bad-Format)", "Length is wrong or Magic Cookie value is incorrect" },
#define PPTP_GENERAL_ERROR_BAD_VALUE            3
    { "(Bad-Value)", "One of the field values was out of range or "
            "reserved field was non-zero" },
#define PPTP_GENERAL_ERROR_NO_RESOURCE          4
    { "(No-Resource)", "Insufficient resources to handle this command now" },
#define PPTP_GENERAL_ERROR_BAD_CALLID           5
    { "(Bad-Call ID)", "The Call ID is invalid in this context" },
#define PPTP_GENERAL_ERROR_PAC_ERROR            6
    { "(PAC-Error)", "A generic vendor-specific error occured in the PAC" }
};

#define  MAX_GENERAL_ERROR ( sizeof(pptp_general_errors) / \
        sizeof(pptp_general_errors[0]) - 1)

/* Outgoing Call Reply Result Codes */
static const char *pptp_out_call_reply_result[] = {
/* 0 */	"Unknown Result Code",
/* 1 */	"Connected",
/* 2 */	"General Error",
/* 3 */	"No Carrier Detected",
/* 4 */	"Busy Signal",
/* 5 */	"No Dial Tone",
/* 6 */	"Time Out",
/* 7 */	"Not Accepted, Call is administratively prohibited" };

#define MAX_OUT_CALL_REPLY_RESULT 7

/* Call Disconnect Notify  Result Codes */
static const char *pptp_call_disc_ntfy[] = {
/* 0 */	"Unknown Result Code",
/* 1 */	"Lost Carrier",
/* 2 */	"General Error",
/* 3 */	"Administrative Shutdown",
/* 4 */	"(your) Request" };

#define MAX_CALL_DISC_NTFY 4

/* Call Disconnect Notify  Result Codes */
static const char *pptp_start_ctrl_conn_rply[] = {
/* 0 */	"Unknown Result Code",
/* 1 */	"Successful Channel Establishment",
/* 2 */	"General Error",
/* 3 */	"Command Channel Already Exists",
/* 4 */	"Requester is not Authorized" };

#define MAX_START_CTRL_CONN_REPLY 4

/* timing options */
int idle_wait = PPTP_TIMEOUT;
int max_echo_wait = PPTP_TIMEOUT;

/* Local prototypes */
static void pptp_reset_timer(void);
static void pptp_handle_timer();
/* Write/read as much as we can without blocking. */
int pptp_write_some(PPTP_CONN * conn);
int pptp_read_some(PPTP_CONN * conn);
/* Make valid packets from read_buffer */
int pptp_make_packet(PPTP_CONN * conn, void **buf, size_t *size);
/* Add packet to write_buffer */
int pptp_send_ctrl_packet(PPTP_CONN * conn, void * buffer, size_t size);
/* Dispatch packets (general) */
int pptp_dispatch_packet(PPTP_CONN * conn, void * buffer, size_t size);
/* Dispatch packets (control messages) */
int ctrlp_disp(PPTP_CONN * conn, void * buffer, size_t size);
/* Set link info, for pptp servers that need it.
   this is a noop, unless the user specified a quirk and
   there's a set_link hook defined in the quirks table
   for that quirk */
void pptp_set_link(PPTP_CONN * conn, int peer_call_id);

/*** log error information in control packets *********************************/
static void ctrlp_error( int result, int error, int cause,
        const char *result_text[], int max_result)
{
    if( cause >= 0)
        log("Result code is %d '%s'. Error code is %d, Cause code is %d",
                result, result_text[result <= max_result ?  result : 0], error,
                cause );
    else
        log("Reply result code is %d '%s'. Error code is %d",
                result, result_text[result <= max_result ?  result : 0], error);
    if ((error > 0) && (error <= MAX_GENERAL_ERROR)){
        if( result != PPTP_RESULT_GENERAL_ERROR )
            log("Result code is something else then \"general error\", "
                    "so the following error is probably bogus.");
        log("Error is '%s', Error message: '%s'",
                pptp_general_errors[error].name,
                pptp_general_errors[error].desc);
    }
}

static const char *ctrl_msg_types[] = {
         "invalid control message type",
/*         (Control Connection Management) */
         "Start-Control-Connection-Request",            /* 1 */
         "Start-Control-Connection-Reply",              /* 2 */
         "Stop-Control-Connection-Request",             /* 3 */
         "Stop-Control-Connection-Reply",               /* 4 */
         "Echo-Request",                                /* 5 */
         "Echo-Reply",                                  /* 6 */
/*         (Call Management) */
         "Outgoing-Call-Request",                       /* 7 */
         "Outgoing-Call-Reply",                         /* 8 */
         "Incoming-Call-Request",                       /* 9 */
         "Incoming-Call-Reply",                        /* 10 */
         "Incoming-Call-Connected",                    /* 11 */
         "Call-Clear-Request",                         /* 12 */
         "Call-Disconnect-Notify",                     /* 13 */
/*         (Error Reporting) */
         "WAN-Error-Notify",                           /* 14 */
/*         (PPP Session Control) */
         "Set-Link-Info"                              /* 15 */
};
#define MAX_CTRLMSG_TYPE 15

/*** report a sent packet ****************************************************/
static void ctrlp_rep( void * buffer, int size, int isbuff)
{
    struct pptp_header *packet = buffer;
    unsigned int type;
    if(size < sizeof(struct pptp_header)) return;
    type = ntoh16(packet->ctrl_type);
    /* FIXME: do not report sending echo requests as long as they are
     * sent in a signal handler. This may dead lock as the syslog call
     * is not reentrant */
    if( type ==  PPTP_ECHO_RQST ) return;
    /* don't keep reporting sending of echo's */
    if( (type == PPTP_ECHO_RQST || type == PPTP_ECHO_RPLY) && nlogecho <= 0 ) return;
    log("%s control packet type is %d '%s'\n",isbuff ? "Buffered" : "Sent",
            type, ctrl_msg_types[type <= MAX_CTRLMSG_TYPE ? type : 0]);

}



/* Open new pptp_connection.  Returns NULL on failure. */
PPTP_CONN * pptp_conn_open(int inet_sock, int isclient, pptp_conn_cb callback)
{
    PPTP_CONN *conn;
    /* Allocate structure */
    if ((conn = malloc(sizeof(*conn))) == NULL) return NULL;
    if ((conn->call = vector_create()) == NULL) { free(conn); return NULL; }
    /* Initialize */
    conn->inet_sock = inet_sock;
    conn->conn_state = CONN_IDLE;
    conn->ka_state  = KA_NONE;
    conn->ka_id     = 1;
    conn->call_serial_number = 0;
    conn->callback  = callback;
    /* Create I/O buffers */
    conn->read_size = conn->write_size = 0;
    conn->read_alloc = conn->write_alloc = INITIAL_BUFSIZE;
    conn->read_buffer =
        malloc(sizeof(*(conn->read_buffer)) * conn->read_alloc);
    conn->write_buffer =
        malloc(sizeof(*(conn->write_buffer)) * conn->write_alloc);
    if (conn->read_buffer == NULL || conn->write_buffer == NULL) {
        if (conn->read_buffer  != NULL) free(conn->read_buffer);
        if (conn->write_buffer != NULL) free(conn->write_buffer);
        vector_destroy(conn->call); free(conn); return NULL;
    }
    /* Make this socket non-blocking. */
    fcntl(conn->inet_sock, F_SETFL, O_NONBLOCK);
    /* Request connection from server, if this is a client */
    if (isclient) {
        struct pptp_start_ctrl_conn packet = {
            PPTP_HEADER_CTRL(PPTP_START_CTRL_CONN_RQST),
            hton16(PPTP_VERSION), 0, 0,
            hton32(PPTP_FRAME_CAP), hton32(PPTP_BEARER_CAP),
            hton16(PPTP_MAX_CHANNELS), hton16(PPTP_FIRMWARE_VERSION),
            PPTP_HOSTNAME, PPTP_VENDOR
        };
        /* fix this packet, if necessary */
        int idx, rc;
        idx = get_quirk_index();
        if (idx != -1 && pptp_fixups[idx].start_ctrl_conn) {
            if ((rc = pptp_fixups[idx].start_ctrl_conn(&packet)))
                warn("calling the start_ctrl_conn hook failed (%d)", rc);
        }
        if (pptp_send_ctrl_packet(conn, &packet, sizeof(packet)))
            conn->conn_state = CONN_WAIT_CTL_REPLY;
        else
            return NULL; /* could not send initial start request. */
    }
    /* Set up interval/keep-alive timer */
    /*   First, register handler for SIGALRM */
    sigpipe_create();
    sigpipe_assign(SIGALRM);
    global.conn = conn;
    /* Reset event timer */
    pptp_reset_timer();
    /* all done. */
    return conn;
}

int pptp_conn_established(PPTP_CONN *conn) {
  return (conn->conn_state == CONN_ESTABLISHED);
}

/* This currently *only* works for client call requests.
 * We need to do something else to allocate calls for incoming requests.
 */
PPTP_CALL * pptp_call_open(PPTP_CONN * conn, int call_id,pptp_call_cb callback,
        char *phonenr,int window)
{
    PPTP_CALL * call;
    int idx, rc;
    /* Send off the call request */
    struct pptp_out_call_rqst packet = {
        PPTP_HEADER_CTRL(PPTP_OUT_CALL_RQST),
        0,0, /*call_id, sernum */
        hton32(PPTP_BPS_MIN), hton32(PPTP_BPS_MAX),
        hton32(PPTP_BEARER_CAP), hton32(PPTP_FRAME_CAP),
        hton16(window), 0, 0, 0, {0}, {0}
    };
    assert(conn && conn->call);
    assert(conn->conn_state == CONN_ESTABLISHED);
    /* Assign call id */
    if (!call_id && !vector_scan(conn->call, 0, PPTP_MAX_CHANNELS - 1, &call_id))
        /* no more calls available! */
        return NULL;
    /* allocate structure. */
    if ((call = malloc(sizeof(*call))) == NULL) return NULL;
    /* Initialize call structure */
    call->call_type = PPTP_CALL_PNS;
    call->state.pns = PNS_IDLE;
    call->call_id   = (u_int16_t) call_id;
    call->sernum    = conn->call_serial_number++;
    call->callback  = callback;
    call->closure   = NULL;
    packet.call_id = htons(call->call_id);
    packet.call_sernum = htons(call->sernum);
    /* if we have a quirk, build a new packet to fit it */
    idx = get_quirk_index();
    if (idx != -1 && pptp_fixups[idx].out_call_rqst_hook) {
        if ((rc = pptp_fixups[idx].out_call_rqst_hook(&packet)))
            warn("calling the out_call_rqst hook failed (%d)", rc);
    }
    /* fill in the phone number if it was specified */
    if (phonenr) {
        strncpy(packet.phone_num, phonenr, sizeof(packet.phone_num));
        packet.phone_len = strlen(phonenr);
        if( packet.phone_len > sizeof(packet.phone_num))
            packet.phone_len = sizeof(packet.phone_num);
        packet.phone_len = hton16 (packet.phone_len);
    }
    if (pptp_send_ctrl_packet(conn, &packet, sizeof(packet))) {
        pptp_reset_timer();
        call->state.pns = PNS_WAIT_REPLY;
        /* and add it to the call vector */
        vector_insert(conn->call, call_id, call);
        return call;
    } else { /* oops, unsuccessful. Deallocate. */
        free(call);
        return NULL;
    }
}

/*** pptp_call_close **********************************************************/
void pptp_call_close(PPTP_CONN * conn, PPTP_CALL * call)
{
    struct pptp_call_clear_rqst rqst = {
        PPTP_HEADER_CTRL(PPTP_CALL_CLEAR_RQST), 0, 0
    };
    assert(conn && conn->call); assert(call);
    assert(vector_contains(conn->call, call->call_id));
    /* haven't thought about PAC yet */
    assert(call->call_type == PPTP_CALL_PNS);
    assert(call->state.pns != PNS_IDLE);
    rqst.call_id = hton16(call->call_id);
    /* don't check state against WAIT_DISCONNECT... allow multiple disconnect
     * requests to be made.
     */
    pptp_send_ctrl_packet(conn, &rqst, sizeof(rqst));
    pptp_reset_timer();
    call->state.pns = PNS_WAIT_DISCONNECT;
    /* call structure will be freed when we have confirmation of disconnect. */
}

/*** hard close ***************************************************************/
void pptp_call_destroy(PPTP_CONN *conn, PPTP_CALL *call)
{
    assert(conn && conn->call); assert(call);
    assert(vector_contains(conn->call, call->call_id));
    /* notify */
    if (call->callback != NULL) call->callback(conn, call, CALL_CLOSE_DONE);
    /* deallocate */
    vector_remove(conn->call, call->call_id);
    free(call);
}

/*** this is a soft close *****************************************************/
void pptp_conn_close(PPTP_CONN * conn, u_int8_t close_reason)
{
    struct pptp_stop_ctrl_conn rqst = {
        PPTP_HEADER_CTRL(PPTP_STOP_CTRL_CONN_RQST),
        hton8(close_reason), 0, 0
    };
    int i;
    assert(conn && conn->call);
    /* avoid repeated close attempts */
    if (conn->conn_state == CONN_IDLE || conn->conn_state == CONN_WAIT_STOP_REPLY)
        return;
    /* close open calls, if any */
    for (i = 0; i < vector_size(conn->call); i++)
        pptp_call_close(conn, vector_get_Nth(conn->call, i));
    /* now close connection */
    log("Closing PPTP connection");
    pptp_send_ctrl_packet(conn, &rqst, sizeof(rqst));
    pptp_reset_timer(); /* wait 60 seconds for reply */
    conn->conn_state = CONN_WAIT_STOP_REPLY;
    return;
}

/*** this is a hard close *****************************************************/
void pptp_conn_destroy(PPTP_CONN * conn)
{
    int i;
    assert(conn != NULL); assert(conn->call != NULL);
    /* destroy all open calls */
    for (i = 0; i < vector_size(conn->call); i++)
        pptp_call_destroy(conn, vector_get_Nth(conn->call, i));
    /* notify */
    if (conn->callback != NULL) conn->callback(conn, CONN_CLOSE_DONE);
    sigpipe_close();
    close(conn->inet_sock);
    /* deallocate */
    vector_destroy(conn->call);
    free(conn);
}

/*** Deal with messages, in a non-blocking manner
 * Add file descriptors used by pptp to fd_set.
 */
void pptp_fd_set(PPTP_CONN * conn, fd_set * read_set, fd_set * write_set,
                 int * max_fd)
{
    assert(conn && conn->call);
    /* Add fd to write_set if there are outstanding writes. */
    if (conn->write_size > 0)
        FD_SET(conn->inet_sock, write_set);
    /* Always add fd to read_set. (always want something to read) */
    FD_SET(conn->inet_sock, read_set);
    if (*max_fd < conn->inet_sock) *max_fd = conn->inet_sock;
    /* Add signal pipe file descriptor to set */
    int sig_fd = sigpipe_fd();
    FD_SET(sig_fd, read_set);
    if (*max_fd < sig_fd) *max_fd = sig_fd;
}

/*** handle any pptp file descriptors set in fd_set, and clear them ***********/
int pptp_dispatch(PPTP_CONN * conn, fd_set * read_set, fd_set * write_set)
{
    int r = 0;
    assert(conn && conn->call);
    /* Check for signals */
    if (FD_ISSET(sigpipe_fd(), read_set)) {
        if (sigpipe_read() == SIGALRM) pptp_handle_timer();
	FD_CLR(sigpipe_fd(), read_set);
    }
    /* Check write_set could be set. */
    if (FD_ISSET(conn->inet_sock, write_set)) {
        FD_CLR(conn->inet_sock, write_set);
        if (conn->write_size > 0)
            r = pptp_write_some(conn);/* write as much as we can without blocking */
    }
    /* Check read_set */
    if (r >= 0 && FD_ISSET(conn->inet_sock, read_set)) {
        void *buffer; size_t size;
        FD_CLR(conn->inet_sock, read_set);
        r = pptp_read_some(conn); /* read as much as we can without blocking */
	if (r < 0)
	    return r;
        /* make packets of the buffer, while we can. */
        while (r >= 0 && pptp_make_packet(conn, &buffer, &size)) {
            r = pptp_dispatch_packet(conn, buffer, size);
            free(buffer);
        }
    }
    /* That's all, folks.  Simple, eh? */
    return r;
}

/*** Non-blocking write *******************************************************/
int pptp_write_some(PPTP_CONN * conn) {
    ssize_t retval;
    assert(conn && conn->call);
    retval = write(conn->inet_sock, conn->write_buffer, conn->write_size);
    if (retval < 0) { /* error. */
        if (errno == EAGAIN || errno == EINTR) {
            return 0;
        } else { /* a real error */
            log("write error: %s", strerror(errno));
	    return -1;
        }
    }
    assert(retval <= conn->write_size);
    conn->write_size -= retval;
    memmove(conn->write_buffer, conn->write_buffer + retval, conn->write_size);
    ctrlp_rep(conn->write_buffer, retval, 0);
    return 0;
}

/*** Non-blocking read ********************************************************/
int pptp_read_some(PPTP_CONN * conn)
{
    ssize_t retval;
    assert(conn && conn->call);
    if (conn->read_size == conn->read_alloc) { /* need to alloc more memory */
        char *new_buffer = realloc(conn->read_buffer,
                sizeof(*(conn->read_buffer)) * conn->read_alloc * 2);
        if (new_buffer == NULL) {
            log("Out of memory"); return -1;
        }
        conn->read_alloc *= 2;
        conn->read_buffer = new_buffer;
    }
    retval = read(conn->inet_sock, conn->read_buffer + conn->read_size,
            conn->read_alloc  - conn->read_size);
    if (retval == 0) {
        log("read returned zero, peer has closed");
        return -1;
    }
    if (retval < 0) {
        if (errno == EINTR || errno == EAGAIN)
	    return 0;
        else { /* a real error */
            log("read error: %s", strerror(errno));
            return -1;
        }
    }
    conn->read_size += retval;
    assert(conn->read_size <= conn->read_alloc);
    return 0;
}

/*** Packet formation *********************************************************/
int pptp_make_packet(PPTP_CONN * conn, void **buf, size_t *size)
{
    struct pptp_header *header;
    size_t bad_bytes = 0;
    assert(conn && conn->call); assert(buf != NULL); assert(size != NULL);
    /* Give up unless there are at least sizeof(pptp_header) bytes */
    while ((conn->read_size-bad_bytes) >= sizeof(struct pptp_header)) {
        /* Throw out bytes until we have a valid header. */
        header = (struct pptp_header *) (conn->read_buffer + bad_bytes);
        if (ntoh32(header->magic) != PPTP_MAGIC) goto throwitout;
        if (ntoh16(header->reserved0) != 0)
            log("reserved0 field is not zero! (0x%x) Cisco feature? \n",
                    ntoh16(header->reserved0));
        if (ntoh16(header->length) < sizeof(struct pptp_header)) goto throwitout;
        if (ntoh16(header->length) > PPTP_CTRL_SIZE_MAX) goto throwitout;
        /* well.  I guess it's good. Let's see if we've got it all. */
        if (ntoh16(header->length) > (conn->read_size-bad_bytes))
            /* nope.  Let's wait until we've got it, then. */
            goto flushbadbytes;
        /* One last check: */
        if ((ntoh16(header->pptp_type) == PPTP_MESSAGE_CONTROL) &&
                (ntoh16(header->length) !=
                         PPTP_CTRL_SIZE(ntoh16(header->ctrl_type))))
            goto throwitout;
        /* well, I guess we've got it. */
        *size = ntoh16(header->length);
        *buf = malloc(*size);
        if (*buf == NULL) { log("Out of memory."); return 0; /* ack! */ }
        memcpy(*buf, conn->read_buffer + bad_bytes, *size);
        /* Delete this packet from the read_buffer. */
        conn->read_size -= (bad_bytes + *size);
        memmove(conn->read_buffer, conn->read_buffer + bad_bytes + *size,
                conn->read_size);
        if (bad_bytes > 0)
            log("%lu bad bytes thrown away.", (unsigned long) bad_bytes);
        return 1;
throwitout:
        bad_bytes++;
    }
flushbadbytes:
    /* no more packets.  Let's get rid of those bad bytes */
    conn->read_size -= bad_bytes;
    memmove(conn->read_buffer, conn->read_buffer + bad_bytes, conn->read_size);
    if (bad_bytes > 0)
        log("%lu bad bytes thrown away.", (unsigned long) bad_bytes);
    return 0;
}

/*** pptp_send_ctrl_packet ****************************************************/
int pptp_send_ctrl_packet(PPTP_CONN * conn, void * buffer, size_t size)
{
    assert(conn && conn->call); assert(buffer);
    if( conn->write_size > 0) pptp_write_some( conn);
    if( conn->write_size == 0) {
        ssize_t retval;
        retval = write(conn->inet_sock, buffer, size);
        if (retval < 0) { /* error. */
            if (errno == EAGAIN || errno == EINTR) {
                /* ignore */;
                retval = 0;
            } else { /* a real error */
                log("write error: %s", strerror(errno));
                pptp_conn_destroy(conn); /* shut down fast. */
                return 0;
            }
        }
        ctrlp_rep( buffer, retval, 0);
        size -= retval;
        if( size <= 0) return 1;
    }
    /* Shove anything not written into the write buffer */
    if (conn->write_size + size > conn->write_alloc) { /* need more memory */
        char *new_buffer = realloc(conn->write_buffer,
                sizeof(*(conn->write_buffer)) * conn->write_alloc * 2);
        if (new_buffer == NULL) {
            log("Out of memory"); return 0;
        }
        conn->write_alloc *= 2;
        conn->write_buffer = new_buffer;
    }
    memcpy(conn->write_buffer + conn->write_size, buffer, size);
    conn->write_size += size;
    ctrlp_rep( buffer,size,1);
    return 1;
}

/*** Packet Dispatch **********************************************************/
int pptp_dispatch_packet(PPTP_CONN * conn, void * buffer, size_t size)
{
    int r = 0;
    struct pptp_header *header = (struct pptp_header *)buffer;
    assert(conn && conn->call); assert(buffer);
    assert(ntoh32(header->magic) == PPTP_MAGIC);
    assert(ntoh16(header->length) == size);
    switch (ntoh16(header->pptp_type)) {
        case PPTP_MESSAGE_CONTROL:
            r = ctrlp_disp(conn, buffer, size);
            break;
        case PPTP_MESSAGE_MANAGE:
            /* MANAGEMENT messages aren't even part of the spec right now. */
            log("PPTP management message received, but not understood.");
            break;
        default:
            log("Unknown PPTP control message type received: %u",
                    (unsigned int) ntoh16(header->pptp_type));
            break;
    }
    return r;
}

/*** log echo request/replies *************************************************/
static void logecho( int type)
{
    /* hack to stop flooding the log files (the most interesting part is right
     * after the connection built-up) */
    if( nlogecho > 0) {
        log( "Echo Re%s received.", type == PPTP_ECHO_RQST ? "quest" :"ply");
        if( --nlogecho == 0)
            log("no more Echo Reply/Request packets will be reported.");
    }
}

/*** pptp_dispatch_ctrl_packet ************************************************/
int ctrlp_disp(PPTP_CONN * conn, void * buffer, size_t size)
{
    struct pptp_header *header = (struct pptp_header *)buffer;
    u_int8_t close_reason = PPTP_STOP_NONE;
    assert(conn && conn->call); assert(buffer);
    assert(ntoh32(header->magic) == PPTP_MAGIC);
    assert(ntoh16(header->length) == size);
    assert(ntoh16(header->pptp_type) == PPTP_MESSAGE_CONTROL);
    if (size < PPTP_CTRL_SIZE(ntoh16(header->ctrl_type))) {
        log("Invalid packet received [type: %d; length: %d].",
                (int) ntoh16(header->ctrl_type), (int) size);
        return 0;
    }
    switch (ntoh16(header->ctrl_type)) {
        /* ----------- STANDARD Start-Session MESSAGES ------------ */
        case PPTP_START_CTRL_CONN_RQST:
        {
            struct pptp_start_ctrl_conn *packet =
                (struct pptp_start_ctrl_conn *) buffer;
            struct pptp_start_ctrl_conn reply = {
                PPTP_HEADER_CTRL(PPTP_START_CTRL_CONN_RPLY),
                hton16(PPTP_VERSION), 0, 0,
                hton32(PPTP_FRAME_CAP), hton32(PPTP_BEARER_CAP),
                hton16(PPTP_MAX_CHANNELS), hton16(PPTP_FIRMWARE_VERSION),
                PPTP_HOSTNAME, PPTP_VENDOR };
            int idx, rc;
            log("Received Start Control Connection Request");
            /* fix this packet, if necessary */
            idx = get_quirk_index();
            if (idx != -1 && pptp_fixups[idx].start_ctrl_conn) {
                if ((rc = pptp_fixups[idx].start_ctrl_conn(&reply)))
                    warn("calling the start_ctrl_conn hook failed (%d)", rc);
            }
            if (conn->conn_state == CONN_IDLE) {
                if (ntoh16(packet->version) < PPTP_VERSION) {
                    /* Can't support this (earlier) PPTP_VERSION */
                    reply.version = packet->version;
                    /* protocol version not supported */
                    reply.result_code = hton8(5);
                    pptp_send_ctrl_packet(conn, &reply, sizeof(reply));
                    pptp_reset_timer(); /* give sender a chance for a retry */
                } else { /* same or greater version */
                    if (pptp_send_ctrl_packet(conn, &reply, sizeof(reply))) {
                        conn->conn_state = CONN_ESTABLISHED;
                        log("server connection ESTABLISHED.");
                        pptp_reset_timer();
                    }
                }
            }
            break;
        }
        case PPTP_START_CTRL_CONN_RPLY:
        {
            struct pptp_start_ctrl_conn *packet =
                (struct pptp_start_ctrl_conn *) buffer;
            log("Received Start Control Connection Reply");
            if (conn->conn_state == CONN_WAIT_CTL_REPLY) {
                /* XXX handle collision XXX [see rfc] */
                if (ntoh16(packet->version) != PPTP_VERSION) {
                    if (conn->callback != NULL)
                        conn->callback(conn, CONN_OPEN_FAIL);
                    close_reason = PPTP_STOP_PROTOCOL;
                    goto pptp_conn_close;
                }
                if (ntoh8(packet->result_code) != 1 &&
                    /* J'ai change le if () afin que la connection ne se ferme
                     * pas pour un "rien" :p adel@cybercable.fr -
                     *
                     * Don't close the connection if the result code is zero
                     * (feature found in certain ADSL modems)
                     */
                        ntoh8(packet->result_code) != 0) {
                    log("Negative reply received to our Start Control "
                            "Connection Request");
                    ctrlp_error(packet->result_code, packet->error_code,
                            -1, pptp_start_ctrl_conn_rply,
                            MAX_START_CTRL_CONN_REPLY);
                    if (conn->callback != NULL)
                        conn->callback(conn, CONN_OPEN_FAIL);
                    close_reason = PPTP_STOP_PROTOCOL;
                    goto pptp_conn_close;
                }
                conn->conn_state = CONN_ESTABLISHED;
                /* log session properties */
                conn->version      = ntoh16(packet->version);
                conn->firmware_rev = ntoh16(packet->firmware_rev);
                memcpy(conn->hostname, packet->hostname, sizeof(conn->hostname));
                memcpy(conn->vendor, packet->vendor, sizeof(conn->vendor));
                pptp_reset_timer(); /* 60 seconds until keep-alive */
                log("Client connection established.");
                if (conn->callback != NULL)
                    conn->callback(conn, CONN_OPEN_DONE);
            } /* else goto pptp_conn_close; */
            break;
        }
            /* ----------- STANDARD Stop-Session MESSAGES ------------ */
        case PPTP_STOP_CTRL_CONN_RQST:
        {
            /* conn_state should be CONN_ESTABLISHED, but it could be
             * something else */
            struct pptp_stop_ctrl_conn reply = {
                PPTP_HEADER_CTRL(PPTP_STOP_CTRL_CONN_RPLY),
                hton8(1), hton8(PPTP_GENERAL_ERROR_NONE), 0
            };
            log("Received Stop Control Connection Request.");
            if (conn->conn_state == CONN_IDLE) break;
            if (pptp_send_ctrl_packet(conn, &reply, sizeof(reply))) {
                if (conn->callback != NULL)
                    conn->callback(conn, CONN_CLOSE_RQST);
                conn->conn_state = CONN_IDLE;
		return -1;
            }
            break;
        }
        case PPTP_STOP_CTRL_CONN_RPLY:
        {
            log("Received Stop Control Connection Reply.");
            /* conn_state should be CONN_WAIT_STOP_REPLY, but it
             * could be something else */
            if (conn->conn_state == CONN_IDLE) break;
            conn->conn_state = CONN_IDLE;
	    return -1;
        }
            /* ----------- STANDARD Echo/Keepalive MESSAGES ------------ */
        case PPTP_ECHO_RPLY:
        {
            struct pptp_echo_rply *packet =
                (struct pptp_echo_rply *) buffer;
            logecho( PPTP_ECHO_RPLY);
            if ((conn->ka_state == KA_OUTSTANDING) &&
                    (ntoh32(packet->identifier) == conn->ka_id)) {
                conn->ka_id++;
                conn->ka_state = KA_NONE;
                pptp_reset_timer();
            }
            break;
        }
        case PPTP_ECHO_RQST:
        {
            struct pptp_echo_rqst *packet =
                (struct pptp_echo_rqst *) buffer;
            struct pptp_echo_rply reply = {
                PPTP_HEADER_CTRL(PPTP_ECHO_RPLY),
                packet->identifier, /* skip hton32(ntoh32(id)) */
                hton8(1), hton8(PPTP_GENERAL_ERROR_NONE), 0
            };
            logecho( PPTP_ECHO_RQST);
            pptp_send_ctrl_packet(conn, &reply, sizeof(reply));
            pptp_reset_timer();
            break;
        }
            /* ----------- OUTGOING CALL MESSAGES ------------ */
        case PPTP_OUT_CALL_RQST:
        {
            struct pptp_out_call_rqst *packet =
                (struct pptp_out_call_rqst *)buffer;
            struct pptp_out_call_rply reply = {
                PPTP_HEADER_CTRL(PPTP_OUT_CALL_RPLY),
                0 /* callid */, packet->call_id, 1, PPTP_GENERAL_ERROR_NONE, 0,
                hton32(PPTP_CONNECT_SPEED),
                hton16(PPTP_WINDOW), hton16(PPTP_DELAY), 0
            };
            log("Received Outgoing Call Request.");
            /* XXX PAC: eventually this should make an outgoing call. XXX */
            reply.result_code = hton8(7); /* outgoing calls verboten */
            pptp_send_ctrl_packet(conn, &reply, sizeof(reply));
            break;
        }
        case PPTP_OUT_CALL_RPLY:
        {
            struct pptp_out_call_rply *packet =
                (struct pptp_out_call_rply *)buffer;
            PPTP_CALL * call;
            u_int16_t callid = ntoh16(packet->call_id_peer);
            log("Received Outgoing Call Reply.");
            if (!vector_search(conn->call, (int) callid, &call)) {
                log("PPTP_OUT_CALL_RPLY received for non-existant call: "
                        "peer call ID (us)  %d call ID (them) %d.",
                        callid, ntoh16(packet->call_id));
                break;
            }
            if (call->call_type != PPTP_CALL_PNS) {
                log("Ack!  How did this call_type get here?"); /* XXX? */
                break;
            }
            if (call->state.pns != PNS_WAIT_REPLY) {
                warn("Unexpected(?) Outgoing Call Reply will be ignored.");
                break;
            }
            /* check for errors */
            if (packet->result_code != 1) {
                /* An error.  Log it verbosely. */
                log("Our outgoing call request [callid %d] has not been "
                        "accepted.", (int) callid);
                ctrlp_error(packet->result_code, packet->error_code,
                        packet->cause_code, pptp_out_call_reply_result,
                        MAX_OUT_CALL_REPLY_RESULT);
                call->state.pns = PNS_IDLE;
                if (call->callback != NULL)
                    call->callback(conn, call, CALL_OPEN_FAIL);
                pptp_call_destroy(conn, call);
            } else {
                /* connection established */
                call->state.pns = PNS_ESTABLISHED;
                call->peer_call_id = ntoh16(packet->call_id);
                call->speed        = ntoh32(packet->speed);
                pptp_reset_timer();
                /* call pptp_set_link. unless the user specified a quirk
                   and this quirk has a set_link hook, this is a noop */
                pptp_set_link(conn, call->peer_call_id);
                if (call->callback != NULL)
                    call->callback(conn, call, CALL_OPEN_DONE);
                log("Outgoing call established (call ID %u, peer's "
                        "call ID %u).\n", call->call_id, call->peer_call_id);
            }
            break;
        }
            /* ----------- INCOMING CALL MESSAGES ------------ */
            /* XXX write me XXX */
            /* ----------- CALL CONTROL MESSAGES ------------ */
        case PPTP_CALL_CLEAR_RQST:
        {
            struct pptp_call_clear_rqst *packet =
                (struct pptp_call_clear_rqst *)buffer;
            struct pptp_call_clear_ntfy reply = {
                PPTP_HEADER_CTRL(PPTP_CALL_CLEAR_NTFY), packet->call_id,
                1, PPTP_GENERAL_ERROR_NONE, 0, 0, {0}
            };
            log("Received Call Clear Request.");
            if (vector_contains(conn->call, ntoh16(packet->call_id))) {
                PPTP_CALL * call;
                vector_search(conn->call, ntoh16(packet->call_id), &call);
                if (call->callback != NULL)
                    call->callback(conn, call, CALL_CLOSE_RQST);
                pptp_send_ctrl_packet(conn, &reply, sizeof(reply));
                pptp_call_destroy(conn, call);
                log("Call closed (RQST) (call id %d)", (int) call->call_id);
            }
            break;
        }
        case PPTP_CALL_CLEAR_NTFY:
        {
            struct pptp_call_clear_ntfy *packet =
                (struct pptp_call_clear_ntfy *)buffer;
            log("Call disconnect notification received (call id %d)",
                    ntoh16(packet->call_id));
            if (vector_contains(conn->call, ntoh16(packet->call_id))) {
                PPTP_CALL * call;
                ctrlp_error(packet->result_code, packet->error_code,
                        packet->cause_code, pptp_call_disc_ntfy,
                        MAX_CALL_DISC_NTFY);
                vector_search(conn->call, ntoh16(packet->call_id), &call);
                pptp_call_destroy(conn, call);
            }
            /* XXX we could log call stats here XXX */
            /* XXX not all servers send this XXX */
            break;
        }
        case PPTP_SET_LINK_INFO:
        {
            /* I HAVE NO CLUE WHAT TO DO IF send_accm IS NOT 0! */
            /* this is really dealt with in the HDLC deencapsulation, anyway. */
            struct pptp_set_link_info *packet =
                (struct pptp_set_link_info *)buffer;
            /* log it. */
            log("PPTP_SET_LINK_INFO received from peer_callid %u",
                    (unsigned int) ntoh16(packet->call_id_peer));
            log("  send_accm is %08lX, recv_accm is %08lX",
                    (unsigned long) ntoh32(packet->send_accm),
                    (unsigned long) ntoh32(packet->recv_accm));
            if (!(ntoh32(packet->send_accm) == 0 &&
                    ntoh32(packet->recv_accm) == 0))
                warn("Non-zero Async Control Character Maps are not supported!");
            break;
        }
        default:
            log("Unrecognized Packet %d received.",
                    (int) ntoh16(((struct pptp_header *)buffer)->ctrl_type));
            /* goto pptp_conn_close; */
            break;
    }
    return 0;
pptp_conn_close:
    warn("pptp_conn_close(%d)", (int) close_reason);
    pptp_conn_close(conn, close_reason);
    return 0;
}

/*** pptp_set_link **************************************************************/
void pptp_set_link(PPTP_CONN* conn, int peer_call_id)
{
    int idx, rc;
    /* if we need to send a set_link packet because of buggy
       hardware or pptp server, do it now */
    if ((idx = get_quirk_index()) != -1 && pptp_fixups[idx].set_link_hook) {
        struct pptp_set_link_info packet;
        if ((rc = pptp_fixups[idx].set_link_hook(&packet, peer_call_id)))
            warn("calling the set_link hook failed (%d)", rc);
        if (pptp_send_ctrl_packet(conn, &packet, sizeof(packet))) {
            pptp_reset_timer();
        }
    }
}

/*** Get info from call structure *********************************************/
/* NOTE: The peer_call_id is undefined until we get a server response. */
void pptp_call_get_ids(PPTP_CONN * conn, PPTP_CALL * call,
		       u_int16_t * call_id, u_int16_t * peer_call_id)
{
    assert(conn != NULL); assert(call != NULL);
    *call_id = call->call_id;
    *peer_call_id = call->peer_call_id;
}

/*** pptp_call_closure_put ****************************************************/
void   pptp_call_closure_put(PPTP_CONN * conn, PPTP_CALL * call, void *cl)
{
    assert(conn != NULL); assert(call != NULL);
    call->closure = cl;
}

/*** pptp_call_closure_get ****************************************************/
void * pptp_call_closure_get(PPTP_CONN * conn, PPTP_CALL * call)
{
    assert(conn != NULL); assert(call != NULL);
    return call->closure;
}

/*** pptp_conn_closure_put ****************************************************/
void   pptp_conn_closure_put(PPTP_CONN * conn, void *cl)
{
    assert(conn != NULL);
    conn->closure = cl;
}

/*** pptp_conn_closure_get ****************************************************/
void * pptp_conn_closure_get(PPTP_CONN * conn)
{
    assert(conn != NULL);
    return conn->closure;
}

/*** Reset keep-alive timer ***************************************************/
static void pptp_reset_timer(void)
{
    const struct itimerval tv = { {  0, 0 },   /* stop on time-out */
        { idle_wait, 0 } };
    if (idle_wait) setitimer(ITIMER_REAL, &tv, NULL);
}


/*** Handle keep-alive timer **************************************************/
static void pptp_handle_timer()
{
    int i;
    /* "Keep Alives and Timers, 1": check connection state */
    if (global.conn->conn_state != CONN_ESTABLISHED) {
        if (global.conn->conn_state == CONN_WAIT_STOP_REPLY)
            /* hard close. */
            pptp_conn_destroy(global.conn);
        else /* soft close */
            pptp_conn_close(global.conn, PPTP_STOP_NONE);
    }
    /* "Keep Alives and Timers, 2": check echo status */
    if (global.conn->ka_state == KA_OUTSTANDING) {
        /* no response to keep-alive */
        log ("closing control connection due to missing echo reply");
	pptp_conn_close(global.conn, PPTP_STOP_NONE);
    } else { /* ka_state == NONE */ /* send keep-alive */
        struct pptp_echo_rqst rqst = {
            PPTP_HEADER_CTRL(PPTP_ECHO_RQST), hton32(global.conn->ka_id) };
        pptp_send_ctrl_packet(global.conn, &rqst, sizeof(rqst));
        global.conn->ka_state = KA_OUTSTANDING;
    }
    /* check incoming/outgoing call states for !IDLE && !ESTABLISHED */
    for (i = 0; i < vector_size(global.conn->call); i++) {
        PPTP_CALL * call = vector_get_Nth(global.conn->call, i);
        if (call->call_type == PPTP_CALL_PNS) {
            if (call->state.pns == PNS_WAIT_REPLY) {
                /* send close request */
                pptp_call_close(global.conn, call);
                assert(call->state.pns == PNS_WAIT_DISCONNECT);
            } else if (call->state.pns == PNS_WAIT_DISCONNECT) {
                /* hard-close the call */
                pptp_call_destroy(global.conn, call);
            }
        } else if (call->call_type == PPTP_CALL_PAC) {
            if (call->state.pac == PAC_WAIT_REPLY) {
                /* XXX FIXME -- drop the PAC connection XXX */
            } else if (call->state.pac == PAC_WAIT_CS_ANS) {
                /* XXX FIXME -- drop the PAC connection XXX */
            }
        }
    }
    pptp_reset_timer();
}