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IPv6.Mod
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IPv6.Mod
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MODULE IPv6; (** AUTHOR "Erwin Betschart"; PURPOSE "IP protocol version 6"; *)
IMPORT SYSTEM, Machine, Kernel, Objects, Modules, Strings, KernelLog, Network, IP, Plugins;
CONST
(* DEBUG *)
DEBUG = TRUE;
(* IP *)
EtherTypeIP* = 86DDH;
MinIPHdrLen*= 40;
MaxIPHdrLen* = 40;
MaxFragPacketSize* = 65536; (* Maximal size of a packet, which can be fragmented *)
(* Interface *)
V6RouterIntName = "v6Router";
V6OwnRouterIntName = "v6OwnRouter";
V6DHCPIntName = "v6DHCP";
(* Neighbor etc. cache *)
CacheSize = 256;
(* Neighbor cache reachablility states *)
Incomplete = 0;
Reachable = 1;
Stale = 2;
Delay = 3;
Probe = 4;
ReachableTime = 30000;
(* autoconfig states *)
TentativeInterface = 0;
PreferredInterface = 1;
DepricatedInterface = 2;
InvalidInterface = 3;
(* Next header types *)
IPv6FragmentType = 44;
IPv6RoutingHdrType = 43;
IPv6HopByHopHdrType = 0;
IPv6DestinationHdrType = 60;
ICMPv6Type = 58;
(* Header / Options Lengths *)
NeighborHdrLen* = 20;
RouterSolHdrLen* = 4;
RouterAdvHdrLen = 12;
LLAdrOptionLen* = 8; (* Source or Target Link-Layer address option len *)
FragmentHdrLen = 8; (* Fragmentation header length *)
RoutingHdrLen = 8; (* Routing header length *)
HopByHopHdrLen = 8; (* Hop-by-hop header length *)
DestinationHdrLen = 8; (* Destination header length *)
MaxPrefixOptions = 10;
(* Timers *)
ShortTimerTimeout = 3000; (* 3 sec *)
LongTimerTimeout = 600000; (* 10 min *)
(* ICMP codes *)
ICMPv6CodeHopLimitExc* = 0;
ICMPv6FragmentReassemblyExc* = 3;
(* router *)
MaxRtrAdvInterval = 600000; (* milliseconds; default from RFC 2461*)
MinRtrAdvInterval = 198000; (* milliseconds; default 0.33 * MaxRtrAdvInterval *)
RouterPrefHigh = 1;
RouterPrefMedium = 0;
RouterPrefLow = 3;
TYPE
(* List of incoming fragmented packets which should be reassembled *)
FragmentList = POINTER TO RECORD
fragmentID: LONGINT;
nextHeader: LONGINT;
srcAdr: IP.Adr;
dstAdr: IP.Adr;
packets: PacketFragment;
startedAt: Kernel.MilliTimer;
fragmentCount: LONGINT;
next: FragmentList;
END;
(* List of a packet which was fragmented *)
PacketFragment = POINTER TO RECORD
buffer: Network.Buffer;
fragmentOffset: LONGINT;
moreFragments: BOOLEAN;
next: PacketFragment;
prev: PacketFragment;
END;
(* List of devices *)
DeviceList = POINTER TO RECORD
device: Network.LinkDevice;
linkLocalInterface: Interface;
next: DeviceList;
END;
(* Router config *)
RouterConfig* = POINTER TO RECORD
Device*: Plugins.Name;
SendRouterAdvertisements*: BOOLEAN;
ManagedAddressConfig*: BOOLEAN;
OtherStatefulConfig*: BOOLEAN;
LinkMTU*: LONGINT;
ReachableTime*: LONGINT; (* in seconds *)
RetransTimer*: LONGINT; (* in seconds *)
CurrentHopLimit*: LONGINT;
Lifetime*: LONGINT; (* in seconds *)
Prefixes*: PrefixConfig;
next*: RouterConfig;
END;
(* Prefix config for router config *)
PrefixConfig* = POINTER TO RECORD
Prefix*: IP.Adr;
IsSitePrefix*: BOOLEAN;
ValidLifetime*: LONGINT; (* in seconds *)
OnLink*: BOOLEAN;
PreferredLifetime*: LONGINT;(* in seconds *)
Autonomous*: BOOLEAN;
next*: PrefixConfig;
END;
(* A queue of packets used in neighbor cache to store pending packets *)
PacketQueue = POINTER TO RECORD
l3hdr: POINTER TO ARRAY OF CHAR;
l4hdr: POINTER TO ARRAY OF CHAR;
data: POINTER TO ARRAY OF CHAR;
h3len: LONGINT;
h4len: LONGINT;
dofs: LONGINT;
dlen: LONGINT;
next: PacketQueue;
END;
(* Entry in the neighbor cache *)
NeighborCacheEntry* = POINTER TO RECORD
next: NeighborCacheEntry;
neighborIP: IP.Adr;
linkAdr: Network.LinkAdr;
reachability: LONGINT; (* either Incomplete, Reachable, Stale, Delay or Probe *)
isRouter: BOOLEAN;
queuedPackets: PacketQueue;
probes: LONGINT; (* number of unanswered probes *)
lastConfirmation: Kernel.MilliTimer;
END;
(* Entry in the destination cache *)
DestCacheEntry = POINTER TO RECORD
next: DestCacheEntry;
dest: IP.Adr;
nextHop: IP.Adr;
pmtu: LONGINT;
END;
(* Entry in the prefix list *)
PrefixesEntry = POINTER TO RECORD
next: PrefixesEntry;
prefix: IP.Adr;
lifetime: Kernel.MilliTimer; (* time, when a prefix becomes invalid *)
END;
(* Entry in the default router list *)
RoutersEntry = POINTER TO RECORD
next: RoutersEntry;
router: NeighborCacheEntry;
routerLifetime: Kernel.MilliTimer;
END;
(* Entry in the local address cache *)
LocalAdrCacheEntry = POINTER TO RECORD
next: LocalAdrCacheEntry;
localAdr: IP.Adr;
interface: Interface;
created: Kernel.MilliTimer;
END;
TYPE
(** Destination cache *)
DestCache = OBJECT
VAR
(* Array which holds linked lists of destination cache entries. The last byte of the destination address
is the key to find a entry in this array *)
destArray: ARRAY CacheSize OF DestCacheEntry;
interface: Interface; (* Interface on which this cache operates *)
(** Constructor: Initializes destinations array.*)
PROCEDURE &Constr*(int: Interface; prefixes: Prefixes);
VAR
i: LONGINT;
BEGIN
FOR i := 0 TO 255 DO
destArray[i] := NIL;
END;
interface := int;
END Constr;
(** Add a new dest entry *)
PROCEDURE Add(destAdr, nextHop: IP.Adr);
VAR
newDestItem: DestCacheEntry;
destItem: DestCacheEntry;
BEGIN {EXCLUSIVE}
(* look if entry already exists *)
destItem := destArray[ORD(destAdr.ipv6Adr[15])];
WHILE (destItem # NIL) & (~IP.AdrsEqual(destItem.dest, destAdr)) DO
destItem := destItem.next;
END;
IF destItem = NIL THEN
(* Add new entry *)
NEW(newDestItem);
newDestItem.next := NIL;
newDestItem.dest := destAdr;
newDestItem.nextHop := nextHop;
newDestItem.pmtu := interface.linkMTU;
(* put in array *)
destItem := destArray[ORD(destAdr.ipv6Adr[15])];
IF destItem = NIL THEN
(* first element *)
destArray[ORD(destAdr.ipv6Adr[15])] := newDestItem;
ELSE
WHILE destItem.next # NIL DO
destItem := destItem.next;
END;
destItem.next := newDestItem;
END;
END;
END Add;
(** Remove a destination entry *)
PROCEDURE Remove(destAdr: IP.Adr);
VAR
destItem: DestCacheEntry;
BEGIN {EXCLUSIVE}
destItem := destArray[ORD(destAdr.ipv6Adr[15])];
IF destItem # NIL THEN
IF IP.AdrsEqual(destItem.dest, destAdr) THEN
(* remove first element *)
destArray[ORD(destAdr.ipv6Adr[15])] := destItem.next;
ELSIF destItem.next # NIL THEN
(* search for elem *)
WHILE (destItem.next.next # NIL) & (~IP.AdrsEqual(destItem.next.dest, destAdr)) DO
destItem := destItem.next;
END;
IF destItem.next # NIL THEN
(* found the right elem *)
destItem.next := destItem.next.next;
END;
END;
END;
END Remove;
(* Changes a PMTU of a cache entry *)
PROCEDURE ChangePMTU(adr: IP.Adr; newPMTU: LONGINT);
VAR
destItem: DestCacheEntry;
BEGIN
destItem := destArray[ORD(adr.ipv6Adr[15])];
IF destItem # NIL THEN
(* search for right element *)
WHILE (destItem # NIL) & (~IP.AdrsEqual(destItem.dest, adr)) DO
destItem := destItem.next;
END;
IF destItem # NIL THEN
destItem.pmtu := newPMTU;
END;
END;
END ChangePMTU;
(** Get next hop address *)
PROCEDURE GetNextHop(destAdr: IP.Adr): IP.Adr;
VAR
nextHop: IP.Adr;
destItem: DestCacheEntry;
BEGIN
IF interface.IsMulticast(destAdr) THEN
(* Multicast packets are considered to be on-link *)
nextHop := destAdr;
ELSE
nextHop := IP.NilAdr;
destItem := destArray[ORD(destAdr.ipv6Adr[15])];
WHILE (destItem # NIL) & (~IP.AdrsEqual(destAdr, destItem.dest)) DO
destItem := destItem.next;
END;
IF destItem # NIL THEN
nextHop := destItem.nextHop;
ELSE
nextHop := NextHopDetermination(destAdr);
IF IP.IsNilAdr(nextHop) THEN
(* assume destination is link-local *)
nextHop := destAdr;
END;
(* Save results of NextHopDetermination *)
Add(destAdr, nextHop);
END;
END;
RETURN nextHop;
END GetNextHop;
(** Get PMTU of a address *)
PROCEDURE GetPMTU(adr: IP.Adr): LONGINT;
VAR
destItem: DestCacheEntry;
pmtu: LONGINT;
BEGIN
destItem := destArray[ORD(adr.ipv6Adr[15])];
WHILE (destItem # NIL) & (~IP.AdrsEqual(adr, destItem.dest)) DO
destItem := destItem.next;
END;
IF destItem # NIL THEN
pmtu := destItem.pmtu;
ELSE
pmtu := interface.linkMTU;
END;
RETURN pmtu;
END GetPMTU;
(** Next hop determination *)
PROCEDURE NextHopDetermination(destAdr: IP.Adr): IP.Adr;
VAR
longestPrefix: PrefixesEntry;
nextHop: IP.Adr;
BEGIN
(* perform longest prefix match against prefix list *)
longestPrefix := interface.prefixes.FindLongestMatch(destAdr);
IF longestPrefix = NIL THEN
(* select a router from the Default Router list *)
nextHop := interface.routers.GetRouter();
IF IP.IsNilAdr(nextHop) THEN
(* no default router is found assume destAdr is on-link, therefore
next hop = destination address *)
nextHop := destAdr;
END;
ELSE
(* destination is on-link: nextHop is same as destination *)
nextHop := destAdr;
END;
RETURN nextHop;
END NextHopDetermination;
(** When a router become invalid update all affected entries *)
PROCEDURE ChangeDests(fromAdr: IP.Adr; toAdr: IP.Adr);
VAR
destItem: DestCacheEntry;
i: LONGINT;
BEGIN
FOR i := 0 TO CacheSize DO
destItem := destArray[i];
WHILE destItem # NIL DO
IF IP.AdrsEqual(fromAdr, destItem.dest) THEN
destItem.dest := toAdr;
END;
destItem := destItem.next;
END;
END;
END ChangeDests;
(** Clears the destination cache *)
PROCEDURE Clear;
VAR
i: LONGINT;
BEGIN
FOR i := 0 TO CacheSize - 1 DO
destArray[i] := NIL;
END;
END Clear;
END DestCache;
TYPE
(** Neighbor cache. *)
NeighborCache = OBJECT
VAR
neighbors: ARRAY CacheSize OF NeighborCacheEntry;
(* Array which holds all neighbor entries. The last byte of the neighbor IP is the index
of the array *)
interface: Interface; (* Interface the neighbor cache operates on *)
(** Constructor: Initializes neighbor array.*)
PROCEDURE &Constr *(int: Interface);
VAR
i: LONGINT;
BEGIN
interface := int;
FOR i := 0 TO (CacheSize - 1) DO
neighbors[i] := NIL;
END;
END Constr;
(** Add an IP to the neighbor cache *)
PROCEDURE Add(neighborIP: IP.Adr);
VAR
newNeighborEntry: NeighborCacheEntry;
neighborItem: NeighborCacheEntry;
BEGIN {EXCLUSIVE}
(* look if already an entry exists *)
newNeighborEntry := Get(neighborIP);
IF newNeighborEntry = NIL THEN
NEW(newNeighborEntry);
(* initialize neighbor cache entry to incomplete*)
newNeighborEntry.next := NIL;
newNeighborEntry.neighborIP := neighborIP;
newNeighborEntry.reachability := Incomplete;
newNeighborEntry.isRouter := FALSE;
newNeighborEntry.queuedPackets := NIL;
newNeighborEntry.probes := 0;
Kernel.SetTimer(newNeighborEntry.lastConfirmation, 0);
(* put into neighbor cache *)
neighborItem := neighbors[ORD(neighborIP.ipv6Adr[15])];
IF neighborItem = NIL THEN
neighbors[ORD(neighborIP.ipv6Adr[15])] := newNeighborEntry;
ELSE
WHILE (neighborItem.next # NIL) DO
neighborItem := neighborItem.next
END;
neighborItem.next := newNeighborEntry;
END;
END;
END Add;
(* Remove *)
PROCEDURE Remove(neighborIP: IP.Adr);
VAR
neighborItem: NeighborCacheEntry;
BEGIN {EXCLUSIVE}
neighborItem := neighbors[ORD(neighborIP.ipv6Adr[15])];
(* first element *)
IF IP.AdrsEqual(neighborItem.neighborIP, neighborIP) THEN
neighbors[ORD(neighborIP.ipv6Adr[15])] := neighborItem.next;
ELSE
WHILE (neighborItem.next # NIL) & (~IP.AdrsEqual(neighborItem.neighborIP, neighborIP)) DO
neighborItem := neighborItem.next;
END;
IF neighborItem.next # NIL THEN
(* found *)
neighborItem.next := neighborItem.next.next;
END;
END;
END Remove;
(** Delete expired neighbor entries *)
PROCEDURE ClearExpired;
VAR
neighborItem: NeighborCacheEntry;
neighborItemPrev: NeighborCacheEntry;
i: LONGINT;
BEGIN {EXCLUSIVE}
FOR i := 0 TO CacheSize - 1 DO
neighborItem := neighbors[i];
WHILE neighborItem # NIL DO
IF Kernel.Expired(neighborItem.lastConfirmation) THEN
IF neighborItemPrev = NIL THEN
(* first item *)
neighbors[i] := neighborItem.next;
ELSE
neighborItemPrev.next := neighborItem.next;
END;
END;
IF (neighborItem.next # NIL) & (neighborItem.next # neighbors[i]) THEN
neighborItemPrev := neighborItem;
ELSE
neighborItemPrev := NIL;
END;
neighborItem := neighborItem.next;
END;
END;
END ClearExpired;
(* Deliver a neighbor cache entry *)
PROCEDURE Get*(adr: IP.Adr): NeighborCacheEntry;
VAR
neighborItem: NeighborCacheEntry;
BEGIN
neighborItem := neighbors[ORD(adr.ipv6Adr[15])];
WHILE (neighborItem # NIL) & (~IP.AdrsEqual(neighborItem.neighborIP, adr)) DO
neighborItem := neighborItem.next;
END;
RETURN neighborItem;
END Get;
(* Return link-layer address of a IP address *)
PROCEDURE GetLinkLayerAdr(adr: IP.Adr; VAR linkAdr: Network.LinkAdr): BOOLEAN;
VAR
neighborItem: NeighborCacheEntry;
found: BOOLEAN;
BEGIN
neighborItem := neighbors[ORD(adr.ipv6Adr[15])];
WHILE (neighborItem # NIL) & (~IP.AdrsEqual(neighborItem.neighborIP, adr)) DO
neighborItem := neighborItem.next;
END;
IF (neighborItem # NIL) & (neighborItem.reachability # Incomplete) THEN
(* check timers *)
IF Kernel.Expired(neighborItem.lastConfirmation) THEN
(* Send a Neighbor Solicitation message *)
sendNeighborSolicitation(interface, neighborItem.linkAdr, adr, FALSE);
END;
linkAdr := neighborItem.linkAdr;
found := TRUE;
ELSE
found := FALSE;
END;
RETURN found;
END GetLinkLayerAdr;
(* Initiate address resolution *)
PROCEDURE AddressResolution(neighborIP: IP.Adr; VAR l3hdr, l4hdr, data: ARRAY OF CHAR; h3len, h4len, dofs, dlen: LONGINT);
VAR
neighborEntry: NeighborCacheEntry;
packetQueue: PacketQueue;
packetQueueItem: PacketQueue;
linkDst: Network.LinkAdr;
i: LONGINT;
BEGIN
(* create a new neighbor cache entry *)
Add(neighborIP);
neighborEntry := Get(neighborIP);
IF neighborEntry # NIL THEN
(* Queue packet *)
NEW(packetQueueItem);
NEW(packetQueueItem.l3hdr, LEN(l3hdr));
FOR i := 0 TO LEN(l3hdr) - 1 DO
packetQueueItem.l3hdr[i] := l3hdr[i];
END;
NEW(packetQueueItem.l4hdr, LEN(l4hdr));
FOR i := 0 TO LEN(l4hdr) - 1 DO
packetQueueItem.l4hdr[i] := l4hdr[i];
END;
NEW(packetQueueItem.data, LEN(data));
FOR i := 0 TO LEN(data) - 1 DO
packetQueueItem.data[i] := data[i];
END;
packetQueueItem.h3len := h3len;
packetQueueItem.h4len := h4len;
packetQueueItem.dofs := dofs;
packetQueueItem.dlen := dlen;
packetQueue := neighborEntry.queuedPackets;
packetQueueItem.next := packetQueue;
neighborEntry.queuedPackets := packetQueueItem;
(* link and IP destination addresses are the solicited node addresses *)
linkDst := linkMulticastAllNodesAdr;
linkDst[2] := 0FFX;
linkDst[3] := neighborIP.ipv6Adr[13];
linkDst[4] := neighborIP.ipv6Adr[14];
linkDst[5] := neighborIP.ipv6Adr[15];
(* Send a Neighbor Solicitation message *)
sendNeighborSolicitation(interface, linkDst, neighborIP, TRUE);
END;
END AddressResolution;
(* Send queued Packets *)
PROCEDURE SendQueuedPackets(neighborCacheEntry: NeighborCacheEntry);
VAR
queuedPacket: PacketQueue;
pmtu: LONGINT;
toFragment: BOOLEAN;
BEGIN {EXCLUSIVE}
toFragment := FALSE;
queuedPacket := neighborCacheEntry.queuedPackets;
WHILE queuedPacket # NIL DO
pmtu := interface.destCache.GetPMTU(neighborCacheEntry.neighborIP);
IF queuedPacket.h3len+queuedPacket.h4len+queuedPacket.dlen > pmtu THEN
(* fragment packet *)
toFragment := TRUE;
END;
IF ~toFragment THEN
interface.dev.Send(neighborCacheEntry.linkAdr,
EtherTypeIP,
queuedPacket.l3hdr^,
queuedPacket.l4hdr^,
queuedPacket.data^,
queuedPacket.h3len,
queuedPacket.h4len,
queuedPacket.dofs,
queuedPacket.dlen,
FALSE);
ELSE
interface.DoFragAndSend(pmtu,
neighborCacheEntry.linkAdr,
queuedPacket.l3hdr^,
queuedPacket.l4hdr^,
queuedPacket.data^,
queuedPacket.h3len,
queuedPacket.h4len,
queuedPacket.dofs,
queuedPacket.dlen);
END;
queuedPacket := queuedPacket.next;
END;
neighborCacheEntry.queuedPackets := NIL;
END SendQueuedPackets;
END NeighborCache;
TYPE
(* Prefix list *)
Prefixes = OBJECT
VAR
prefixes: PrefixesEntry;
(* Constructor: Initializes prefixes.*)
PROCEDURE &Constr*;
BEGIN
prefixes := NIL;
END Constr;
(* Add a prefix. Lifetime in seconds *)
PROCEDURE Add(prefix: IP.Adr; lifetime: LONGINT);
VAR
prefixItem: PrefixesEntry;
BEGIN {EXCLUSIVE}
NEW(prefixItem);
prefixItem.prefix := prefix;
Kernel.SetTimer(prefixItem.lifetime, lifetime * 1000); (* Milliseconds *)
prefixItem.next := prefixes;
prefixes := prefixItem;
END Add;
(* Remove a prefix *)
PROCEDURE Remove(prefix: IP.Adr);
VAR
prefixItem: PrefixesEntry;
BEGIN {EXCLUSIVE}
prefixItem := prefixes;
IF prefixItem # NIL THEN
(* first element? *)
IF IP.AdrsEqual(prefix, prefixItem.prefix) THEN
prefixes := prefixItem.next;
ELSE
WHILE (prefixItem.next # NIL) & (~IP.AdrsEqual(prefix, prefixItem.next.prefix)) DO
prefixItem := prefixItem.next;
END;
IF prefixItem # NIL THEN
(* remove item from list *)
prefixItem.next := prefixItem.next.next;
END;
END;
END;
END Remove;
(** Delete expired prefixes *)
PROCEDURE ClearExpired;
VAR
prefixItem: PrefixesEntry;
prefixItemPrev: PrefixesEntry;
BEGIN {EXCLUSIVE}
prefixItem := prefixes;
WHILE prefixItem # NIL DO
IF Kernel.Expired(prefixItem.lifetime) THEN
IF prefixItemPrev = NIL THEN
(* first item *)
prefixes := prefixItem.next;
ELSE
prefixItemPrev.next := prefixItem.next;
END;
END;
IF (prefixItem.next # NIL) & (prefixItem.next # prefixes) THEN
prefixItemPrev := prefixItem;
ELSE
prefixItemPrev := NIL;
END;
prefixItem := prefixItem.next;
END;
END ClearExpired;
(* Deliver a specific prefix entry *)
PROCEDURE Get(prefix: IP.Adr): PrefixesEntry;
VAR
prefixItem: PrefixesEntry;
BEGIN
prefixItem := prefixes;
WHILE ((prefixItem # NIL) & (~IP.AdrsEqual(prefix, prefixItem.prefix)) & (~(prefix.data = prefixItem.prefix.data))) DO
prefixItem := prefixItem.next;
END;
RETURN prefixItem;
END Get;
(* Is there a prefix which matches adr *)
PROCEDURE FindLongestMatch(adr: IP.Adr): PrefixesEntry;
VAR
prefixItem: PrefixesEntry;
longestPrefixItem: PrefixesEntry;
longestPrefix: LONGINT;
BEGIN
prefixItem := prefixes;
longestPrefixItem := NIL;
longestPrefix := 0;
WHILE (prefixItem # NIL) DO
IF IP.MatchPrefix (adr, prefixItem.prefix) THEN
IF prefixItem.prefix.data > longestPrefix THEN
longestPrefix := prefixItem.prefix.data;
longestPrefixItem := prefixItem;
END;
END;
prefixItem := prefixItem.next;
END;
IF longestPrefixItem # NIL THEN
RETURN longestPrefixItem;
END;
RETURN NIL;
END FindLongestMatch;
END Prefixes;
TYPE
(* Default Router List *)
Routers = OBJECT
VAR
routers: RoutersEntry;
lastRobinRouter: RoutersEntry; (* last choosen Router with round robin *)
interface: Interface;
(* Constructor: Initializes routers.*)
PROCEDURE &Constr*(int: Interface);
BEGIN
routers := NIL;
lastRobinRouter := routers;
interface := int;
END Constr;
(* Add a default router *)
PROCEDURE Add(routerIP: IP.Adr; routerLinkAdr: Network.LinkAdr; lifetime: LONGINT): RoutersEntry;
VAR
router: RoutersEntry;
neighbor: NeighborCacheEntry;
BEGIN {EXCLUSIVE}
lifetime := lifetime * 1000; (* lifetime in milliseconds *)
router := Get(routerIP);
IF router = NIL THEN
(* default routers does not exist *)
NEW(router);
router.next := routers;
routers := router;
END;
Kernel.SetTimer(router.routerLifetime, lifetime);
neighbor := interface.neighborCache.Get(routerIP);
IF neighbor = NIL THEN
interface.neighborCache.Add(routerIP);
neighbor := interface.neighborCache.Get(routerIP);
neighbor.linkAdr := routerLinkAdr;
neighbor.reachability := Stale;
neighbor.isRouter := TRUE;
neighbor.probes := 0;
Kernel.SetTimer(neighbor.lastConfirmation, lifetime);
ELSE
Kernel.SetTimer(neighbor.lastConfirmation, lifetime);
END;
router.router := neighbor;
RETURN router;
END Add;
(* Remove a default router *)
PROCEDURE Remove(router: IP.Adr);
VAR
routerItem: RoutersEntry;
routerItemPrev: RoutersEntry;
BEGIN {EXCLUSIVE}
routerItem := routers;
WHILE (routerItem # NIL) & (~IP.AdrsEqual(routerItem.router.neighborIP, router)) DO
routerItemPrev := routerItem;
routerItem := routerItem.next;
END;
IF routerItem # NIL THEN
IF routerItemPrev = NIL THEN
(* first element *)
routers := routerItem.next;
ELSE
routerItemPrev.next := routerItem.next;
END;
END;
END Remove;
(* Deliver a specific router *)
PROCEDURE Get(routerIP: IP.Adr): RoutersEntry;
VAR
item: RoutersEntry;
BEGIN
item := routers;
WHILE (item # NIL) & (~IP.AdrsEqual(item.router.neighborIP, routerIP)) DO
item := item.next;
END;
RETURN item;
END Get;
(* Deliver a default router *)
PROCEDURE GetRouter(): IP.Adr;
VAR
routersItem: RoutersEntry;
routerAdr: IP.Adr;
searchReachable: BOOLEAN;
BEGIN
(* deliver router: first searched for REACHABLES then other in round robin fashion *)
routerAdr := IP.NilAdr;
IF routers # NIL THEN
IF lastRobinRouter = NIL THEN
lastRobinRouter := routers;
END;
routersItem := lastRobinRouter.next;
IF routersItem = NIL THEN
(* start from begin *)
routersItem := routers.next;
END;
searchReachable := TRUE;
LOOP
IF routersItem = NIL THEN
(* start from begin *)
routersItem := routers;
END;
IF (routersItem = lastRobinRouter) & ~searchReachable THEN
IF routersItem.router.reachability # Incomplete THEN
routerAdr := routersItem.router.neighborIP;
ELSE
(* searched for reachable and other found nothing *)
lastRobinRouter := NIL;
routerAdr := IP.NilAdr;
EXIT;
END;
END;
IF (routersItem = lastRobinRouter) & searchReachable THEN
(* searched for reachable found nothing *)
searchReachable := FALSE;
IF routersItem.router.reachability = Reachable THEN
(* only a single reachable router *)
EXIT;
END;
routersItem := routersItem.next;
IF routersItem = NIL THEN
routersItem := routers;
END;
END;
IF searchReachable & (routersItem.router.reachability = Reachable) THEN
(* found a reachable router *)
routerAdr := routersItem.router.neighborIP;
lastRobinRouter := routersItem;
EXIT;
END;
IF ~searchReachable & (routersItem.router.reachability # Incomplete) THEN
(* found a stale, delay or probe router *)
routerAdr := routersItem.router.neighborIP;
lastRobinRouter := routersItem;
EXIT;
END;
routersItem := routersItem.next;
END;
END;
RETURN routerAdr;
END GetRouter;
(** Delete expired routers *)
PROCEDURE ClearExpired;
VAR
routerItem: RoutersEntry;
routerItemPrev: RoutersEntry;
BEGIN {EXCLUSIVE}
routerItem := routers;
WHILE routerItem # NIL DO
IF Kernel.Expired(routerItem.routerLifetime) THEN
IF routerItemPrev = NIL THEN
(* first item *)
routers := routerItem.next;
ELSE
routerItemPrev.next := routerItem.next;
END;
END;
IF (routerItem.next # NIL) & (routerItem.next # routers) THEN
routerItemPrev := routerItem;
ELSE
routerItemPrev := NIL;
END;
routerItem := routerItem.next;
END;
END ClearExpired;
(** Writes all default routers *)
PROCEDURE OutRouters;
VAR
item: RoutersEntry;
BEGIN