pppoe.c

基于LINUX环境下的PPPOE协议源代码

	    /* Existing session: "sess:xx:yy:zz:aa:bb:cc" where "sess" is
	       session-ID, and xx:yy:zz:aa:bb:cc is MAC-address of peer */
	    n = sscanf(optarg, "%u:%2x:%2x:%2x:%2x:%2x:%2x",
		       &s, &m[0], &m[1], &m[2], &m[3], &m[4], &m[5]);
	    if (n != 7) {
		fprintf(stderr, "Illegal argument to -e: Should be sess:xx:yy:zz:aa:bb:cc\n");
		exit(EXIT_FAILURE);
	    }

	    /* Copy MAC address of peer */
	    for (n=0; n<6; n++) {
		conn.peerEth[n] = (unsigned char) m[n];
	    }

	    /* Convert session */
	    conn.session = htons(s);

	    /* Skip discovery phase! */
	    conn.skipDiscovery = 1;
	    break;
		       
	case 'p':
	    pidfile = fopen(optarg, "w");
	    if (pidfile) {
		fprintf(pidfile, "%lu\n", (unsigned long) getpid());
		fclose(pidfile);
	    }
	    break;
	case 'S':
	    SET_STRING(conn.serviceName, optarg);
	    break;
	case 'C':
	    SET_STRING(conn.acName, optarg);
	    break;
	case 's':
	    conn.synchronous = 1;
	    break;
	case 'U':
	    conn.useHostUniq = 1;
	    break;
	case 'D':
	    conn.debugFile = fopen(optarg, "w");
	    if (!conn.debugFile) {
		fprintf(stderr, "Could not open %s: %s\n",
			optarg, strerror(errno));
		exit(EXIT_FAILURE);
	    }
	    fprintf(conn.debugFile, "rp-pppoe-%s\n", VERSION);
	    fflush(conn.debugFile);
	    break;
	case 'T':
	    optInactivityTimeout = (int) strtol(optarg, NULL, 10);
	    if (optInactivityTimeout < 0) {
		optInactivityTimeout = 0;
	    }
	    break;
	case 'm':
	    optClampMSS = (int) strtol(optarg, NULL, 10);
	    if (optClampMSS < 536) {
		fprintf(stderr, "-m: %d is too low (min 536)\n", optClampMSS);
		exit(EXIT_FAILURE);
	    }
	    if (optClampMSS > 1452) {
		fprintf(stderr, "-m: %d is too high (max 1452)\n", optClampMSS);
		exit(EXIT_FAILURE);
	    }
	    break;
	case 'I':
	    SET_STRING(conn.ifName, optarg);
	    break;
	case 'V':
	    printf("Roaring Penguin PPPoE Version %s\n", VERSION);
	    exit(EXIT_SUCCESS);
	case 'A':
	    conn.printACNames = 1;
	    break;
	case 'h':
	    usage(argv[0]);
	    break;
	default:
	    usage(argv[0]);
	}
    }

    /* Pick a default interface name */
    if (!conn.ifName) {
#ifdef USE_BPF
	fprintf(stderr, "No interface specified (-I option)\n");
	exit(EXIT_FAILURE);
#else
	SET_STRING(conn.ifName, DEFAULT_IF);
#endif
    }

    /* Set signal handlers: send PADT on TERM, HUP and INT */
    if (!conn.printACNames) {
	signal(SIGTERM, sigPADT);
	signal(SIGHUP, sigPADT);
	signal(SIGINT, sigPADT);

#ifdef HAVE_N_HDLC
	if (conn.synchronous) {
	    if (ioctl(0, TIOCSETD, &disc) < 0) {
		printErr("Unable to set line discipline to N_HDLC -- synchronous mode probably will fail");
	    } else {
		syslog(LOG_INFO,
		       "Changed pty line discipline to N_HDLC for synchronous mode");
	    }
	    /* There is a bug in Linux's select which returns a descriptor
	     * as readable if N_HDLC line discipline is on, even if
	     * it isn't really readable.  This return happens only when
	     * select() times out.  To avoid blocking forever in read(),
	     * make descriptor 0 non-blocking */
	    flags = fcntl(0, F_GETFL);
	    if (flags < 0) fatalSys("fcntl(F_GETFL)");
	    if (fcntl(0, F_SETFL, (long) flags | O_NONBLOCK) < 0) {
		fatalSys("fcntl(F_SETFL)");
	    }
	}
#endif

    }

    if (optFloodDiscovery) {
	for (n=0; n < optFloodDiscovery; n++) {
	    if (conn.printACNames) {
		fprintf(stderr, "Sending discovery flood %d\n", n+1);
	    }
	    discovery(&conn);
	    conn.discoveryState = STATE_SENT_PADI;
	    close(conn.discoverySocket);
	}
	exit(EXIT_SUCCESS);
    }

    discovery(&conn);
    if (optSkipSession) {
	printf("%u:%02x:%02x:%02x:%02x:%02x:%02x\n",
	       ntohs(conn.session),
	       conn.peerEth[0],
	       conn.peerEth[1],
	       conn.peerEth[2],
	       conn.peerEth[3],
	       conn.peerEth[4],
	       conn.peerEth[5]);
	exit(EXIT_SUCCESS);
    }
    session(&conn);
    return 0;
}

/**********************************************************************
*%FUNCTION: fatalSys
*%ARGUMENTS:
* str -- error message
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Prints a message plus the errno value to stderr and syslog and exits.
***********************************************************************/
void
fatalSys(char const *str)
{
    char buf[1024];
    sprintf(buf, "%.256s: %.256s", str, strerror(errno));
    printErr(buf);
    sendPADT(Connection, "RP-PPPoE: System call error");
    exit(EXIT_FAILURE);
}

/**********************************************************************
*%FUNCTION: sysErr
*%ARGUMENTS:
* str -- error message
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Prints a message plus the errno value to syslog.
***********************************************************************/
void
sysErr(char const *str)
{
    char buf[1024];
    sprintf(buf, "%.256s: %.256s", str, strerror(errno));
    printErr(buf);
}

/**********************************************************************
*%FUNCTION: rp_fatal
*%ARGUMENTS:
* str -- error message
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Prints a message to stderr and syslog and exits.
***********************************************************************/
void
rp_fatal(char const *str)
{
    char buf[1024];
    printErr(str);
    sprintf(buf, "RP-PPPoE: %.256s", str);
    sendPADT(Connection, buf);
    exit(EXIT_FAILURE);
}

/**********************************************************************
*%FUNCTION: asyncReadFromEth
*%ARGUMENTS:
* conn -- PPPoE connection info
* sock -- Ethernet socket
* clampMss -- if non-zero, do MSS-clamping
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Reads a packet from the Ethernet interface and sends it to async PPP
* device.
***********************************************************************/
void
asyncReadFromEth(PPPoEConnection *conn, int sock, int clampMss)
{
    PPPoEPacket packet;
    int len;
    int plen;
    int i;
    unsigned char pppBuf[4096];
    unsigned char *ptr = pppBuf;
    unsigned char c;
    UINT16_t fcs;
    unsigned char header[2] /* = {FRAME_ADDR, FRAME_CTRL}*/ ;
    unsigned char tail[2];
#ifdef USE_BPF
    int type;
#endif

     header[0] = FRAME_ADDR;
     header[1] = FRAME_CTRL;

    if (receivePacket(sock, &packet, &len) < 0) {
	return;
    }

    /* Check length */
    if (ntohs(packet.length) + HDR_SIZE > len) {
	syslog(LOG_ERR, "Bogus PPPoE length field (%u)",
	       (unsigned int) ntohs(packet.length));
	return;
    }
    if (conn->debugFile) {
	dumpPacket(conn->debugFile, &packet, "RCVD");
	fprintf(conn->debugFile, "\n");
	fflush(conn->debugFile);
    }

#ifdef USE_BPF
    /* Make sure this is a session packet before processing further */
    type = etherType(&packet);
    if (type == Eth_PPPOE_Discovery) {
	sessionDiscoveryPacket(&packet);
    } else if (type != Eth_PPPOE_Session) {
	return;
    }
#endif

    /* Sanity check */
    if (packet.code != CODE_SESS) {
	syslog(LOG_ERR, "Unexpected packet code %d", (int) packet.code);
	return;
    }
    if (packet.ver != 1) {
	syslog(LOG_ERR, "Unexpected packet version %d", (int) packet.ver);
	return;
    }
    if (packet.type != 1) {
	syslog(LOG_ERR, "Unexpected packet type %d", (int) packet.type);
	return;
    }
    if (memcmp(packet.ethHdr.h_dest, conn->myEth, ETH_ALEN)) {
	return;
    }
    if (memcmp(packet.ethHdr.h_source, conn->peerEth, ETH_ALEN)) {
	/* Not for us -- must be another session.  This is not an error,
	   so don't log anything.  */
	return;
    }

    if (packet.session != conn->session) {
	/* Not for us -- must be another session.  This is not an error,
	   so don't log anything.  */
	return;
    }
    plen = ntohs(packet.length);
    if (plen + HDR_SIZE > len) {
	syslog(LOG_ERR, "Bogus length field in session packet %d (%d)",
	       (int) plen, (int) len);
	return;
    }

    /* Clamp MSS */
    if (clampMss) {
	clampMSS(&packet, "incoming", clampMss);
    }

    /* Compute FCS */
    fcs = pppFCS16(PPPINITFCS16, header, 2);
    fcs = pppFCS16(fcs, packet.payload, plen) ^ 0xffff;
    tail[0] = fcs & 0x00ff;
    tail[1] = (fcs >> 8) & 0x00ff;

    /* Build a buffer to send to PPP */
    *ptr++ = FRAME_FLAG;
    *ptr++ = FRAME_ADDR;
    *ptr++ = FRAME_ESC;
    *ptr++ = FRAME_CTRL ^ FRAME_ENC;

    for (i=0; i<plen; i++) {
	c = packet.payload[i];
	if (c == FRAME_FLAG || c == FRAME_ADDR || c == FRAME_ESC || c < 0x20) {
	    *ptr++ = FRAME_ESC;
	    *ptr++ = c ^ FRAME_ENC;
	} else {
	    *ptr++ = c;
	}
    }
    for (i=0; i<2; i++) {
	c = tail[i];
	if (c == FRAME_FLAG || c == FRAME_ADDR || c == FRAME_ESC || c < 0x20) {
	    *ptr++ = FRAME_ESC;
	    *ptr++ = c ^ FRAME_ENC;
	} else {
	    *ptr++ = c;
	}
    }
    *ptr++ = FRAME_FLAG;

    /* Ship it out */
    if (write(1, pppBuf, (ptr-pppBuf)) < 0) {
	fatalSys("asyncReadFromEth: write");
    }
}

/**********************************************************************
*%FUNCTION: syncReadFromEth
*%ARGUMENTS:
* conn -- PPPoE connection info
* sock -- Ethernet socket
* clampMss -- if true, clamp MSS.
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Reads a packet from the Ethernet interface and sends it to sync PPP
* device.
***********************************************************************/
void
syncReadFromEth(PPPoEConnection *conn, int sock, int clampMss)
{
    PPPoEPacket packet;
    int len;
    int plen;
    struct iovec vec[2];
    unsigned char dummy[2];
#ifdef USE_BPF
    int type;
#endif

    if (receivePacket(sock, &packet, &len) < 0) {
	return;
    }

    /* Check length */
    if (ntohs(packet.length) + HDR_SIZE > len) {
	syslog(LOG_ERR, "Bogus PPPoE length field (%u)",
	       (unsigned int) ntohs(packet.length));
	return;
    }
    if (conn->debugFile) {
	dumpPacket(conn->debugFile, &packet, "RCVD");
	fprintf(conn->debugFile, "\n");
	fflush(conn->debugFile);
    }

#ifdef USE_BPF
    /* Make sure this is a session packet before processing further */
    type = etherType(&packet);
    if (type == Eth_PPPOE_Discovery) {
	sessionDiscoveryPacket(&packet);
    } else if (type != Eth_PPPOE_Session) {
	return;
    }
#endif

    /* Sanity check */
    if (packet.code != CODE_SESS) {
	syslog(LOG_ERR, "Unexpected packet code %d", (int) packet.code);
	return;
    }
    if (packet.ver != 1) {
	syslog(LOG_ERR, "Unexpected packet version %d", (int) packet.ver);
	return;
    }
    if (packet.type != 1) {
	syslog(LOG_ERR, "Unexpected packet type %d", (int) packet.type);
	return;
    }
    if (memcmp(packet.ethHdr.h_dest, conn->myEth, ETH_ALEN)) {
	/* Not for us -- must be another session.  This is not an error,
	   so don't log anything.  */
	return;
    }
    if (memcmp(packet.ethHdr.h_source, conn->peerEth, ETH_ALEN)) {
	/* Not for us -- must be another session.  This is not an error,
	   so don't log anything.  */
	return;
    }
    if (packet.session != conn->session) {
	/* Not for us -- must be another session.  This is not an error,
	   so don't log anything.  */
	return;
    }
    plen = ntohs(packet.length);
    if (plen + HDR_SIZE > len) {
	syslog(LOG_ERR, "Bogus length field in session packet %d (%d)",
	       (int) plen, (int) len);
	return;
    }

    /* Clamp MSS */
    if (clampMss) {
	clampMSS(&packet, "incoming", clampMss);
    }

    /* Ship it out */
    vec[0].iov_base = (void *) dummy;
    dummy[0] = FRAME_ADDR;
    dummy[1] = FRAME_CTRL;
    vec[0].iov_len = 2;
    vec[1].iov_base = (void *) packet.payload;
    vec[1].iov_len = plen;

    if (writev(1, vec, 2) < 0) {
	fatalSys("syncReadFromEth: write");
    }
}