relay.c

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    if (!loc) {
	tag.type = htons(TAG_RELAY_SESSION_ID);
	tag.length = htons(MY_RELAY_TAG_LEN);
	memcpy(tag.payload, &ifIndex, sizeof(ifIndex));
	memcpy(tag.payload+sizeof(ifIndex), packet->ethHdr.h_source, ETH_ALEN);
	/* Add a relay tag if there's room */
	r = addTag(packet, &tag);
	if (r < 0) return;
	size += r;
    } else {
	/* We do not re-use relay-id tags.  Drop the frame.  The RFC says the
	   relay agent SHOULD return a Generic-Error tag, but this does not
	   make sense for PADI packets. */
	return;
    }

    /* Broadcast the PADI on all AC-capable interfaces except the interface
       on which it came */
    for (i=0; i < NumInterfaces; i++) {
	if (iface == &Interfaces[i]) continue;
	if (!Interfaces[i].acOK) continue;
	memcpy(packet->ethHdr.h_source, Interfaces[i].mac, ETH_ALEN);
	sendPacket(NULL, Interfaces[i].discoverySock, packet, size);
    }

}

/**********************************************************************
*%FUNCTION: relayHandlePADO
*%ARGUMENTS:
* iface -- interface on which packet was received
* packet -- the PADO packet
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Receives and processes a PADO packet.
***********************************************************************/
void
relayHandlePADO(PPPoEInterface const *iface,
		PPPoEPacket *packet,
		int size)
{
    PPPoETag tag;
    unsigned char *loc;
    int ifIndex;
    int acIndex;

    /* Can a server legally be behind this interface? */
    if (!iface->acOK) {
	syslog(LOG_ERR,
	       "PADO packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s not permitted",
	       packet->ethHdr.h_source[0],
	       packet->ethHdr.h_source[1],
	       packet->ethHdr.h_source[2],
	       packet->ethHdr.h_source[3],
	       packet->ethHdr.h_source[4],
	       packet->ethHdr.h_source[5],
	       iface->name);
	return;
    }

    acIndex = iface - Interfaces;

    /* Source address must be unicast */
    if (NOT_UNICAST(packet->ethHdr.h_source)) {
	syslog(LOG_ERR,
	       "PADO packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s not from a unicast address",
	       packet->ethHdr.h_source[0],
	       packet->ethHdr.h_source[1],
	       packet->ethHdr.h_source[2],
	       packet->ethHdr.h_source[3],
	       packet->ethHdr.h_source[4],
	       packet->ethHdr.h_source[5],
	       iface->name);
	return;
    }

    /* Destination address must be interface's MAC address */
    if (memcmp(packet->ethHdr.h_dest, iface->mac, ETH_ALEN)) {
	return;
    }

    /* Find relay tag */
    loc = findTag(packet, TAG_RELAY_SESSION_ID, &tag);
    if (!loc) {
	syslog(LOG_ERR,
	       "PADO packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s does not have Relay-Session-Id tag",
	       packet->ethHdr.h_source[0],
	       packet->ethHdr.h_source[1],
	       packet->ethHdr.h_source[2],
	       packet->ethHdr.h_source[3],
	       packet->ethHdr.h_source[4],
	       packet->ethHdr.h_source[5],
	       iface->name);
	return;
    }

    /* If it's the wrong length, ignore it */
    if (ntohs(tag.length) != MY_RELAY_TAG_LEN) {
	syslog(LOG_ERR,
	       "PADO packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s does not have correct length Relay-Session-Id tag",
	       packet->ethHdr.h_source[0],
	       packet->ethHdr.h_source[1],
	       packet->ethHdr.h_source[2],
	       packet->ethHdr.h_source[3],
	       packet->ethHdr.h_source[4],
	       packet->ethHdr.h_source[5],
	       iface->name);
	return;
    }

    /* Extract interface index */
    memcpy(&ifIndex, tag.payload, sizeof(ifIndex));

    if (ifIndex < 0 || ifIndex >= NumInterfaces ||
	!Interfaces[ifIndex].clientOK ||
	iface == &Interfaces[ifIndex]) {
	syslog(LOG_ERR,
	       "PADO packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s has invalid interface in Relay-Session-Id tag",
	       packet->ethHdr.h_source[0],
	       packet->ethHdr.h_source[1],
	       packet->ethHdr.h_source[2],
	       packet->ethHdr.h_source[3],
	       packet->ethHdr.h_source[4],
	       packet->ethHdr.h_source[5],
	       iface->name);
	return;
    }

    /* Replace Relay-ID tag with opposite-direction tag */
    memcpy(loc+TAG_HDR_SIZE, &acIndex, sizeof(acIndex));
    memcpy(loc+TAG_HDR_SIZE+sizeof(ifIndex), packet->ethHdr.h_source, ETH_ALEN);

    /* Set destination address to MAC address in relay ID */
    memcpy(packet->ethHdr.h_dest, tag.payload + sizeof(ifIndex), ETH_ALEN);

    /* Set source address to MAC address of interface */
    memcpy(packet->ethHdr.h_source, Interfaces[ifIndex].mac, ETH_ALEN);

    /* Send the PADO to the proper client */
    sendPacket(NULL, Interfaces[ifIndex].discoverySock, packet, size);
}

/**********************************************************************
*%FUNCTION: relayHandlePADR
*%ARGUMENTS:
* iface -- interface on which packet was received
* packet -- the PADR packet
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Receives and processes a PADR packet.
***********************************************************************/
void
relayHandlePADR(PPPoEInterface const *iface,
		PPPoEPacket *packet,
		int size)
{
    PPPoETag tag;
    unsigned char *loc;
    int ifIndex;
    int cliIndex;

    /* Can a client legally be behind this interface? */
    if (!iface->clientOK) {
	syslog(LOG_ERR,
	       "PADR packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s not permitted",
	       packet->ethHdr.h_source[0],
	       packet->ethHdr.h_source[1],
	       packet->ethHdr.h_source[2],
	       packet->ethHdr.h_source[3],
	       packet->ethHdr.h_source[4],
	       packet->ethHdr.h_source[5],
	       iface->name);
	return;
    }

    cliIndex = iface - Interfaces;

    /* Source address must be unicast */
    if (NOT_UNICAST(packet->ethHdr.h_source)) {
	syslog(LOG_ERR,
	       "PADR packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s not from a unicast address",
	       packet->ethHdr.h_source[0],
	       packet->ethHdr.h_source[1],
	       packet->ethHdr.h_source[2],
	       packet->ethHdr.h_source[3],
	       packet->ethHdr.h_source[4],
	       packet->ethHdr.h_source[5],
	       iface->name);
	return;
    }

    /* Destination address must be interface's MAC address */
    if (memcmp(packet->ethHdr.h_dest, iface->mac, ETH_ALEN)) {
	return;
    }

    /* Find relay tag */
    loc = findTag(packet, TAG_RELAY_SESSION_ID, &tag);
    if (!loc) {
	syslog(LOG_ERR,
	       "PADR packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s does not have Relay-Session-Id tag",
	       packet->ethHdr.h_source[0],
	       packet->ethHdr.h_source[1],
	       packet->ethHdr.h_source[2],
	       packet->ethHdr.h_source[3],
	       packet->ethHdr.h_source[4],
	       packet->ethHdr.h_source[5],
	       iface->name);
	return;
    }

    /* If it's the wrong length, ignore it */
    if (ntohs(tag.length) != MY_RELAY_TAG_LEN) {
	syslog(LOG_ERR,
	       "PADR packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s does not have correct length Relay-Session-Id tag",
	       packet->ethHdr.h_source[0],
	       packet->ethHdr.h_source[1],
	       packet->ethHdr.h_source[2],
	       packet->ethHdr.h_source[3],
	       packet->ethHdr.h_source[4],
	       packet->ethHdr.h_source[5],
	       iface->name);
	return;
    }

    /* Extract interface index */
    memcpy(&ifIndex, tag.payload, sizeof(ifIndex));

    if (ifIndex < 0 || ifIndex >= NumInterfaces ||
	!Interfaces[ifIndex].acOK ||
	iface == &Interfaces[ifIndex]) {
	syslog(LOG_ERR,
	       "PADR packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s has invalid interface in Relay-Session-Id tag",
	       packet->ethHdr.h_source[0],
	       packet->ethHdr.h_source[1],
	       packet->ethHdr.h_source[2],
	       packet->ethHdr.h_source[3],
	       packet->ethHdr.h_source[4],
	       packet->ethHdr.h_source[5],
	       iface->name);
	return;
    }

    /* Replace Relay-ID tag with opposite-direction tag */
    memcpy(loc+TAG_HDR_SIZE, &cliIndex, sizeof(cliIndex));
    memcpy(loc+TAG_HDR_SIZE+sizeof(ifIndex), packet->ethHdr.h_source, ETH_ALEN);

    /* Set destination address to MAC address in relay ID */
    memcpy(packet->ethHdr.h_dest, tag.payload + sizeof(ifIndex), ETH_ALEN);

    /* Set source address to MAC address of interface */
    memcpy(packet->ethHdr.h_source, Interfaces[ifIndex].mac, ETH_ALEN);

    /* Send the PADR to the proper access concentrator */
    sendPacket(NULL, Interfaces[ifIndex].discoverySock, packet, size);
}

/**********************************************************************
*%FUNCTION: relayHandlePADS
*%ARGUMENTS:
* iface -- interface on which packet was received
* packet -- the PADS packet
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Receives and processes a PADS packet.
***********************************************************************/
void
relayHandlePADS(PPPoEInterface const *iface,
		PPPoEPacket *packet,
		int size)
{
    PPPoETag tag;
    unsigned char *loc;
    int ifIndex;
    int acIndex;
    PPPoESession *ses = NULL;
    SessionHash *sh;

    /* Can a server legally be behind this interface? */
    if (!iface->acOK) {
	syslog(LOG_ERR,
	       "PADS packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s not permitted",
	       packet->ethHdr.h_source[0],
	       packet->ethHdr.h_source[1],
	       packet->ethHdr.h_source[2],
	       packet->ethHdr.h_source[3],
	       packet->ethHdr.h_source[4],
	       packet->ethHdr.h_source[5],
	       iface->name);
	return;
    }

    acIndex = iface - Interfaces;

    /* Source address must be unicast */
    if (NOT_UNICAST(packet->ethHdr.h_source)) {
	syslog(LOG_ERR,
	       "PADS packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s not from a unicast address",
	       packet->ethHdr.h_source[0],
	       packet->ethHdr.h_source[1],
	       packet->ethHdr.h_source[2],
	       packet->ethHdr.h_source[3],
	       packet->ethHdr.h_source[4],
	       packet->ethHdr.h_source[5],
	       iface->name);
	return;
    }

    /* Destination address must be interface's MAC address */
    if (memcmp(packet->ethHdr.h_dest, iface->mac, ETH_ALEN)) {
	return;
    }

    /* Find relay tag */
    loc = findTag(packet, TAG_RELAY_SESSION_ID, &tag);
    if (!loc) {
	syslog(LOG_ERR,
	       "PADS packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s does not have Relay-Session-Id tag",
	       packet->ethHdr.h_source[0],
	       packet->ethHdr.h_source[1],
	       packet->ethHdr.h_source[2],
	       packet->ethHdr.h_source[3],
	       packet->ethHdr.h_source[4],
	       packet->ethHdr.h_source[5],
	       iface->name);
	return;
    }

    /* If it's the wrong length, ignore it */
    if (ntohs(tag.length) != MY_RELAY_TAG_LEN) {
	syslog(LOG_ERR,
	       "PADS packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s does not have correct length Relay-Session-Id tag",
	       packet->ethHdr.h_source[0],
	       packet->ethHdr.h_source[1],
	       packet->ethHdr.h_source[2],
	       packet->ethHdr.h_source[3],
	       packet->ethHdr.h_source[4],
	       packet->ethHdr.h_source[5],
	       iface->name);
	return;
    }

    /* Extract interface index */
    memcpy(&ifIndex, tag.payload, sizeof(ifIndex));

    if (ifIndex < 0 || ifIndex >= NumInterfaces ||
	!Interfaces[ifIndex].clientOK ||
	iface == &Interfaces[ifIndex]) {
	syslog(LOG_ERR,
	       "PADS packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s has invalid interface in Relay-Session-Id tag",
	       packet->ethHdr.h_source[0],
	       packet->ethHdr.h_source[1],
	       packet->ethHdr.h_source[2],
	       packet->ethHdr.h_source[3],
	       packet->ethHdr.h_source[4],
	       packet->ethHdr.h_source[5],
	       iface->name);
	return;
    }

    /* If session ID is zero, it's the AC respoding with an error.
       Just relay it; do not create a session */
    if (packet->session != htons(0)) {
	/* Check for existing session */
	sh = findSession(packet->ethHdr.h_source, packet->session);
	if (sh) ses = sh->ses;

	/* If already an existing session, assume it's a duplicate PADS.  Send
	   the frame, but do not create a new session.  Is this the right
	   thing to do?  Arguably, should send an error to the client and
	   a PADT to the server, because this could happen due to a
	   server crash and reboot. */

	if (!ses) {
	    /* Create a new session */
	    ses = createSession(iface, &Interfaces[ifIndex],
				packet->ethHdr.h_source,
				loc + TAG_HDR_SIZE + sizeof(ifIndex), packet->session);
	    if (!ses) {
		/* Can't allocate session -- send error PADS to client and
		   PADT to server */
		PPPoETag hostUniq, *hu;
		if (findTag(packet, TAG_HOST_UNIQ, &hostUniq)) {
		    hu = &hostUniq;
		} else {
		    hu = NULL;
		}
		relaySendError(CODE_PADS, htons(0), &Interfaces[ifIndex],
			       loc + TAG_HDR_SIZE + sizeof(ifIndex),
			       hu, "RP-PPPoE: Relay: Unable to allocate session");
		relaySendError(CODE_PADT, packet->session, iface,
			       packet->ethHdr.h_source, NULL,
			       "RP-PPPoE: Relay: Unable to allocate session");
		return;
	    }
	}
	/* Replace session number */
	packet->session = ses->sesNum;
    }

    /* Remove relay-ID tag */
    removeBytes(packet, loc, MY_RELAY_TAG_LEN + TAG_HDR_SIZE);
    size -= (MY_RELAY_TAG_LEN + TAG_HDR_SIZE);

    /* Set destination address to MAC address in relay ID */
    memcpy(packet->ethHdr.h_dest, tag.payload + sizeof(ifIndex), ETH_ALEN);

    /* Set source address to MAC address of interface */
    memcpy(packet->ethHdr.h_source, Interfaces[ifIndex].mac, ETH_ALEN);

    /* Send the PADS to the proper client */
    sendPacket(NULL, Interfaces[ifIndex].discoverySock, packet, size);
}

/**********************************************************************
*%FUNCTION: relaySendError
*%ARGUMENTS:
* code -- PPPoE packet code (PADS or PADT, typically)
* session -- PPPoE session number
* iface -- interface on which to send frame
* mac -- Ethernet address to which frame should be sent
* hostUniq -- if non-NULL, a hostUniq tag to add to error frame
* errMsg -- error message to insert into Generic-Error tag.
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Sends either a PADS or PADT packet with a Generic-Error tag and an
* error message.
***********************************************************************/
void
relaySendError(unsigned char code,
	       UINT16_t session,
	       PPPoEInterface const *iface,
	       unsigned char const *mac,
	       PPPoETag const *hostUniq,
	       char const *errMsg)
{
    PPPoEPacket packet;
    PPPoETag errTag;
    int size;

    memcpy(packet.ethHdr.h_source, iface->mac, ETH_ALEN);
    memcpy(packet.ethHdr.h_dest, mac, ETH_ALEN);
    packet.ethHdr.h_proto = htons(Eth_PPPOE_Discovery);
    packet.type = 1;
    packet.ver = 1;
    packet.code = code;
    packet.session = session;
    packet.length = htons(0);
    if (hostUniq) {
	if (addTag(&packet, hostUniq) < 0) return;
    }
    errTag.type = htons(TAG_GENERIC_ERROR);
    errTag.length = htons(strlen(errMsg));
    strcpy((char *) errTag.payload, errMsg);
    if (addTag(&packet, &errTag) < 0) return;
    size = ntohs(packet.length) + HDR_SIZE;
    if (code == CODE_PADT) {
	sendPacket(NULL, iface->discoverySock, &packet, size);
    } else {
	sendPacket(NULL, iface->sessionSock, &packet, size);
    }
}

/**********************************************************************
*%FUNCTION: alarmHandler
*%ARGUMENTS:
* sig -- signal number
*%RETURNS:
* Nothing
*%DESCRIPTION:
* SIGALRM handler.  Increments Epoch; if necessary, writes a byte of
* data to the alarm pipe to trigger the stale-session cleaner.
***********************************************************************/
void
alarmHandler(int sig)
{
    alarm(1);
    Epoch++;
    CleanCounter++;
    if (CleanCounter == CleanPeriod) {
	write(CleanPipe[1], "", 1);
    }
}

/**********************************************************************
*%FUNCTION: cleanSessions
*%ARGUMENTS:
* None
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Goes through active sessions and cleans sessions idle for longer
* than IdleTimeout seconds.
***********************************************************************/
void cleanSessions(void)
{
    PPPoESession *cur, *next;
    cur = ActiveSessions;
    while(cur) {
	next = cur->next;
	if (Epoch - cur->epoch > IdleTimeout) {
	    /* Send PADT to each peer */
	    relaySendError(CODE_PADT, cur->acHash->sesNum,
			   cur->acHash->interface,
			   cur->acHash->peerMac, NULL,
			   "RP-PPPoE: Relay: Session exceeded idle timeout");
	    relaySendError(CODE_PADT, cur->clientHash->sesNum,
			   cur->clientHash->interface,
			   cur->clientHash->peerMac, NULL,
			   "RP-PPPoE: Relay: Session exceeded idle timeout");
	    freeSession(cur, "Idle Timeout");
	}
	cur = next;
    }
}