pptp_ctrl.c

pptp第二层隧道模块

/* pptp_ctrl.c ... handle PPTP control connection.
 *                 C. Scott Ananian <[e-mail]>
 *
 * $Id: pptp_ctrl.c,v 1.31 2005/03/31 07:42:39 quozl 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, pptp_call_cb callback,
        char *phonenr)
{
    PPTP_CALL * call;
    int i;
    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(PPTP_WINDOW), 0, 0, 0, {0}, {0}
    };
    assert(conn && conn->call);
    assert(conn->conn_state == CONN_ESTABLISHED);
    /* Assign call id */
    if (!vector_scan(conn->call, 0, PPTP_MAX_CHANNELS - 1, &i))
        /* 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) i;
    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);
    }