relay.c

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    memcpy(cliHash->peerMac, cliMac, ETH_ALEN);
    cliHash->sesNum = sess->sesNum;
    cliHash->ses = sess;

    addHash(acHash);
    addHash(cliHash);

    /* Log */
    syslog(LOG_INFO,
	   "Opened session: server=%02x:%02x:%02x:%02x:%02x:%02x(%s:%d), client=%02x:%02x:%02x:%02x:%02x:%02x(%s:%d)",
	   acHash->peerMac[0], acHash->peerMac[1],
	   acHash->peerMac[2], acHash->peerMac[3],
	   acHash->peerMac[4], acHash->peerMac[5],
	   acHash->interface->name,
	   ntohs(acHash->sesNum),
	   cliHash->peerMac[0], cliHash->peerMac[1],
	   cliHash->peerMac[2], cliHash->peerMac[3],
	   cliHash->peerMac[4], cliHash->peerMac[5],
	   cliHash->interface->name,
	   ntohs(cliHash->sesNum));

    return sess;
}

/**********************************************************************
*%FUNCTION: freeSession
*%ARGUMENTS:
* ses -- session to free
* msg -- extra message to log on syslog.
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Frees data used by a PPPoE session -- adds hashes and session back
* to the free list
***********************************************************************/
void
freeSession(PPPoESession *ses, char const *msg)
{
    syslog(LOG_INFO,
	   "Closed session: server=%02x:%02x:%02x:%02x:%02x:%02x(%s:%d), client=%02x:%02x:%02x:%02x:%02x:%02x(%s:%d): %s",
	   ses->acHash->peerMac[0], ses->acHash->peerMac[1],
	   ses->acHash->peerMac[2], ses->acHash->peerMac[3],
	   ses->acHash->peerMac[4], ses->acHash->peerMac[5],
	   ses->acHash->interface->name,
	   ntohs(ses->acHash->sesNum),
	   ses->clientHash->peerMac[0], ses->clientHash->peerMac[1],
	   ses->clientHash->peerMac[2], ses->clientHash->peerMac[3],
	   ses->clientHash->peerMac[4], ses->clientHash->peerMac[5],
	   ses->clientHash->interface->name,
	   ntohs(ses->clientHash->sesNum), msg);

    /* Unlink from active sessions */
    if (ses->prev) {
	ses->prev->next = ses->next;
    } else {
	ActiveSessions = ses->next;
    }
    if (ses->next) {
	ses->next->prev = ses->prev;
    }

    /* Link onto free list -- this is a singly-linked list, so
       we do not care about prev */
    ses->next = FreeSessions;
    FreeSessions = ses;

    unhash(ses->acHash);
    unhash(ses->clientHash);
    NumSessions--;
}

/**********************************************************************
*%FUNCTION: unhash
*%ARGUMENTS:
* sh -- session hash to free
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Frees a session hash -- takes it out of hash table and puts it on
* free list.
***********************************************************************/
void
unhash(SessionHash *sh)
{
    unsigned int b = hash(sh->peerMac, sh->sesNum) % HASHTAB_SIZE;
    if (sh->prev) {
	sh->prev->next = sh->next;
    } else {
	Buckets[b] = sh->next;
    }

    if (sh->next) {
	sh->next->prev = sh->prev;
    }

    /* Add to free list (singly-linked) */
    sh->next = FreeHashes;
    FreeHashes = sh;
}

/**********************************************************************
*%FUNCTION: addHash
*%ARGUMENTS:
* sh -- a session hash
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Adds a SessionHash to the hash table
***********************************************************************/
void
addHash(SessionHash *sh)
{
    unsigned int b = hash(sh->peerMac, sh->sesNum) % HASHTAB_SIZE;
    sh->next = Buckets[b];
    sh->prev = NULL;
    if (sh->next) {
	sh->next->prev = sh;
    }
    Buckets[b] = sh;
}

/**********************************************************************
*%FUNCTION: hash
*%ARGUMENTS:
* mac -- an Ethernet address
* sesNum -- a session number
*%RETURNS:
* A hash value combining Ethernet address with session number.
* Currently very simplistic; we may need to experiment with different
* hash values.
***********************************************************************/
unsigned int
hash(unsigned char const *mac, UINT16_t sesNum)
{
    unsigned int ans1 =
	((unsigned int) mac[0]) |
	(((unsigned int) mac[1]) << 8) |
	(((unsigned int) mac[2]) << 16) |
	(((unsigned int) mac[3]) << 24);
    unsigned int ans2 =
	((unsigned int) sesNum) |
	(((unsigned int) mac[4]) << 16) |
	(((unsigned int) mac[5]) << 24);
    return ans1 ^ ans2;
}

/**********************************************************************
*%FUNCTION: findSession
*%ARGUMENTS:
* mac -- an Ethernet address
* sesNum -- a session number
*%RETURNS:
* The session hash for peer address "mac", session number sesNum
***********************************************************************/
SessionHash *
findSession(unsigned char const *mac, UINT16_t sesNum)
{
    unsigned int b = hash(mac, sesNum) % HASHTAB_SIZE;
    SessionHash *sh = Buckets[b];
    while(sh) {
	if (!memcmp(mac, sh->peerMac, ETH_ALEN) && sesNum == sh->sesNum) {
	    return sh;
	}
	sh = sh->next;
    }
    return NULL;
}

/**********************************************************************
*%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);
    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)
{
    printErr(str);
    exit(EXIT_FAILURE);
}

/**********************************************************************
*%FUNCTION: relayLoop
*%ARGUMENTS:
* None
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Runs the relay loop.  This function never returns
***********************************************************************/
void
relayLoop()
{
    fd_set readable, readableCopy;
    int maxFD;
    int i, r;
    int sock;

    /* Build the select set */
    FD_ZERO(&readable);
    maxFD = 0;
    for (i=0; i<NumInterfaces; i++) {
	sock = Interfaces[i].discoverySock;
	if (sock > maxFD) maxFD = sock;
	FD_SET(sock, &readable);
	sock = Interfaces[i].sessionSock;
	if (sock > maxFD) maxFD = sock;
	FD_SET(sock, &readable);
	if (CleanPipe[0] > maxFD) maxFD = CleanPipe[0];
	FD_SET(CleanPipe[0], &readable);
    }
    maxFD++;
    for(;;) {
	readableCopy = readable;
	for(;;) {
	    r = select(maxFD, &readableCopy, NULL, NULL, NULL);
	    if (r >= 0 || errno != EINTR) break;
	}
	if (r < 0) {
	    sysErr("select (relayLoop)");
	    continue;
	}

	/* Handle session packets first */
	for (i=0; i<NumInterfaces; i++) {
	    if (FD_ISSET(Interfaces[i].sessionSock, &readableCopy)) {
		relayGotSessionPacket(&Interfaces[i]);
	    }
	}

	/* Now handle discovery packets */
	for (i=0; i<NumInterfaces; i++) {
	    if (FD_ISSET(Interfaces[i].discoverySock, &readableCopy)) {
		relayGotDiscoveryPacket(&Interfaces[i]);
	    }
	}

	/* Handle the session-cleaning process */
	if (FD_ISSET(CleanPipe[0], &readableCopy)) {
	    char dummy;
	    CleanCounter = 0;
	    read(CleanPipe[0], &dummy, 1);
	    if (IdleTimeout) cleanSessions();
	}
    }
}

/**********************************************************************
*%FUNCTION: relayGotDiscoveryPacket
*%ARGUMENTS:
* iface -- interface on which packet is waiting
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Receives and processes a discovery packet.
***********************************************************************/
void
relayGotDiscoveryPacket(PPPoEInterface const *iface)
{
    PPPoEPacket packet;
    int size;

    if (receivePacket(iface->discoverySock, &packet, &size) < 0) {
	return;
    }
    /* Ignore unknown code/version */
    if (packet.ver != 1 || packet.type != 1) {
	return;
    }

    /* Validate length */
    if (ntohs(packet.length) + HDR_SIZE > size) {
	syslog(LOG_ERR, "Bogus PPPoE length field (%u)",
	       (unsigned int) ntohs(packet.length));
	return;
    }

    /* Drop Ethernet frame padding */
    if (size > ntohs(packet.length) + HDR_SIZE) {
	size = ntohs(packet.length) + HDR_SIZE;
    }

    switch(packet.code) {
    case CODE_PADT:
	relayHandlePADT(iface, &packet, size);
	break;
    case CODE_PADI:
	relayHandlePADI(iface, &packet, size);
	break;
    case CODE_PADO:
	relayHandlePADO(iface, &packet, size);
	break;
    case CODE_PADR:
	relayHandlePADR(iface, &packet, size);
	break;
    case CODE_PADS:
	relayHandlePADS(iface, &packet, size);
	break;
    default:
	syslog(LOG_ERR, "Discovery packet on %s with unknown code %d",
	       iface->name, (int) packet.code);
    }
}

/**********************************************************************
*%FUNCTION: relayGotSessionPacket
*%ARGUMENTS:
* iface -- interface on which packet is waiting
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Receives and processes a session packet.
***********************************************************************/
void
relayGotSessionPacket(PPPoEInterface const *iface)
{
    PPPoEPacket packet;
    int size;
    SessionHash *sh;
    PPPoESession *ses;

    if (receivePacket(iface->sessionSock, &packet, &size) < 0) {
	return;
    }

    /* Ignore unknown code/version */
    if (packet.ver != 1 || packet.type != 1) {
	return;
    }

    /* Must be a session packet */
    if (packet.code != CODE_SESS) {
	syslog(LOG_ERR, "Session packet with code %d", (int) packet.code);
	return;
    }

    /* Ignore session packets whose destination address isn't ours */
    if (memcmp(packet.ethHdr.h_dest, iface->mac, ETH_ALEN)) {
	return;
    }

    /* Validate length */
    if (ntohs(packet.length) + HDR_SIZE > size) {
	syslog(LOG_ERR, "Bogus PPPoE length field (%u)",
	       (unsigned int) ntohs(packet.length));
	return;
    }

    /* Drop Ethernet frame padding */
    if (size > ntohs(packet.length) + HDR_SIZE) {
	size = ntohs(packet.length) + HDR_SIZE;
    }

    /* We're in business!  Find the hash */
    sh = findSession(packet.ethHdr.h_source, packet.session);
    if (!sh) {
	/* Don't log this.  Someone could be running the client and the
	   relay on the same box. */
	return;
    }

    /* Relay it */
    ses = sh->ses;
    ses->epoch = Epoch;
    sh = sh->peer;
    packet.session = sh->sesNum;
    memcpy(packet.ethHdr.h_source, sh->interface->mac, ETH_ALEN);
    memcpy(packet.ethHdr.h_dest, sh->peerMac, ETH_ALEN);
#if 0
    fprintf(stderr, "Relaying %02x:%02x:%02x:%02x:%02x:%02x(%s:%d) to %02x:%02x:%02x:%02x:%02x:%02x(%s:%d)\n",
	    sh->peer->peerMac[0], sh->peer->peerMac[1], sh->peer->peerMac[2],
	    sh->peer->peerMac[3], sh->peer->peerMac[4], sh->peer->peerMac[5],
	    sh->peer->interface->name, ntohs(sh->peer->sesNum),
	    sh->peerMac[0], sh->peerMac[1], sh->peerMac[2],
	    sh->peerMac[3], sh->peerMac[4], sh->peerMac[5],
	    sh->interface->name, ntohs(sh->sesNum));
#endif
    sendPacket(NULL, sh->interface->sessionSock, &packet, size);
}

/**********************************************************************
*%FUNCTION: relayHandlePADT
*%ARGUMENTS:
* iface -- interface on which packet was received
* packet -- the PADT packet
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Receives and processes a PADT packet.
***********************************************************************/
void
relayHandlePADT(PPPoEInterface const *iface,
		PPPoEPacket *packet,
		int size)
{
    SessionHash *sh;
    PPPoESession *ses;

    sh = findSession(packet->ethHdr.h_source, packet->session);
    if (!sh) {
	return;
    }
    /* Relay the PADT to the peer */
    sh = sh->peer;
    ses = sh->ses;
    packet->session = sh->sesNum;
    memcpy(packet->ethHdr.h_source, sh->interface->mac, ETH_ALEN);
    memcpy(packet->ethHdr.h_dest, sh->peerMac, ETH_ALEN);
    sendPacket(NULL, sh->interface->sessionSock, packet, size);

    /* Destroy the session */
    freeSession(ses, "Received PADT");
}

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

    int ifIndex;

    /* Can a client legally be behind this interface? */
    if (!iface->clientOK) {
	syslog(LOG_ERR,
	       "PADI 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;
    }

    /* Source address must be unicast */
    if (NOT_UNICAST(packet->ethHdr.h_source)) {
	syslog(LOG_ERR,
	       "PADI 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 broadcast */
    if (NOT_BROADCAST(packet->ethHdr.h_dest)) {
	syslog(LOG_ERR,
	       "PADI packet from %02x:%02x:%02x:%02x:%02x:%02x on interface %s not to a broadcast 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;
    }

    /* Get array index of interface */
    ifIndex = iface - Interfaces;

    loc = findTag(packet, TAG_RELAY_SESSION_ID, &tag);