PupEthernetTranslation.mesa
Copyright © 1986 by Xerox Corporation. All rights reserved.
Demers, February 5, 1986 5:04:32 pm PST
Hal Murray, April 3, 1986 7:47:02 pm PST
Very freely adapted from translation code in: Cedar6.0>OISCP>EthernetOneDriver.mesa
Birrell on: 9-Oct-81 16:43:32
BLyon on: March 13, 1981 10:47 PM
Levin, August 9, 1983 9:28 am
Russ Atkinson (RRA) February 19, 1985 7:44:43 pm PST
DIRECTORY
Basics USING [bytesPerWord],
BasicTime USING [GetClockPulses, MicrosecondsToPulses, Pulses],
CommBuffer USING [Overhead],
Driver USING [AllocBuffer, Buffer, FreeBuffer, GetNetworkChain, InsertReceiveProc, Network, RecvProc],
DriverType USING [Encapsulation, ethernetOneBroadcastHost],
NS USING [broadcastHost, GetThisHost, Host, unknownHost],
Process USING [SecondsToTicks, SetPriority, SetTimeout, Ticks],
Pup USING [allHosts, Host];
PupEthernetTranslation:
CEDAR
MONITOR
LOCKS cH USING cH: Cache
IMPORTS BasicTime, Driver, NS, Process
EXPORTS CommBuffer
~ {
BYTE: TYPE ~ [0..100H);
bytesPerWord: NAT ~ Basics.bytesPerWord;
Buffer: TYPE ~ Driver.Buffer;
Network: TYPE ~ Driver.Network;
Encapsulation: PUBLIC TYPE ~ DriverType.Encapsulation; -- exported to CommBuffer
thisHost: NS.Host ~ NS.GetThisHost[];
Time
Pulses: TYPE ~ BasicTime.Pulses;
MSecsToPulses:
PROC [n:
LONG
CARDINAL]
RETURNS[Pulses] ~
INLINE {
RETURN [BasicTime.MicrosecondsToPulses[1000*n]] };
PulsesSince:
PROC [then: Pulses]
RETURNS[Pulses] ~
INLINE {
RETURN [BasicTime.GetClockPulses[] - then] };
Translation Request / Reply Packets
TranslationType: TYPE ~ MACHINE DEPENDENT RECORD [a, b: BYTE];
requestType: TranslationType ~ [010H, 041H];
replyType: TranslationType ~ [00eH, 038H];
HostPair:
TYPE ~
MACHINE
DEPENDENT
RECORD [
nsHost: NS.Host,
pupHost: Pup.Host,
filler: BYTE];
hostPairBytes:
CARDINAL ~ bytesPerWord*
SIZE[HostPair];
-- Should be BYTES[HostPair]
TranslationPacketObject: TYPE ~
MACHINE
DEPENDENT
RECORD [
translationType: TranslationType,
replier: HostPair,
requestor: HostPair];
translationPacketBytes: CARDINAL ~ bytesPerWord*SIZE[TranslationPacketObject]; -- Should be BYTES[TranslationPacketObject]; Must be even!
translationShortPacketBytes:
CARDINAL ~ translationPacketBytes - hostPairBytes;
-- CROCK: some old implementations send reply packets without the requestor field
TranslationBuffer: TYPE ~ REF TranslationBufferObject;
TranslationBufferObject:
TYPE ~
MACHINE
DEPENDENT
RECORD [
ovh: CommBuffer.Overhead,
translationType: TranslationType,
replier: HostPair,
requestor: HostPair];
Translation Entry Cache
For the Pup world, the number of hash headers has been set to the size of the Pup Host space. The hash table chained overflow code is not exercised, and could be discarded. If you want to reduce the number of hash headers, replace the Identity hash function with something like the MOD function in the comment below.
numHashHeaders: CARDINAL ~ 256;
HashIndex: TYPE ~ [0..numHashHeaders);
Hash:
PROC [pupHost: Pup.Host]
RETURNS [HashIndex] ~
INLINE {
RETURN [pupHost] };
Hash: PROC [pupHost: Pup.Host] RETURNS [HashIndex] ~ INLINE {
RETURN [ pupHost MOD numHashHeaders ] };
Cache: TYPE ~ REF CacheObject;
CacheObject:
TYPE ~
MONITORED
RECORD [
daemon: PROCESS,
event: CONDITION,
newPendingEntry: BOOL ← FALSE,
sweepCheckTime: Pulses ← 0,
sweepChecksUntilSweep: CARDINAL ← sweepChecksPerSweep,
sendHead, sendTail: Buffer,
broadcastHostEntry: CacheEntry,
thisHostEntry: CacheEntry,
pendingEntries: CacheEntry,
validEntries: ARRAY HashIndex OF CacheEntry];
CacheEntry: TYPE ~ REF CacheEntryObject;
CacheEntryObject:
TYPE ~
RECORD [
next: CacheEntry,
hosts: HostPair,
referenced: BOOL,
timeStamp: Pulses,
tries: CARDINAL
];
Timeouts
pulsesPerSweepCheck: Pulses ~ MSecsToPulses[59500];
sweepCheckTimeout: Process.Ticks ~ Process.SecondsToTicks[60];
sweepChecksPerSweep: CARDINAL ~ 5;
pulsesPerResend: Pulses ~ MSecsToPulses[1500];
resendTimeout: Process.Ticks ← Process.SecondsToTicks[1];
maxTries: CARDINAL ~ 8;
Encapsulating Pup Packets
Statistics
noTranslation: INT ← 0;
notQuick: INT ← 0;
GetEncapsulation:
PROC [network: Network, pupHost: Pup.Host]
RETURNS [Encapsulation] ~ {
cH: Cache ~ NARROW[network.pup.translation];
eH: CacheEntry ← NIL;
hashIndex: HashIndex ~ Hash[pupHost];
BEGIN
Quick check of first couple of entries without acquiring ML.
IF (eH ← cH.validEntries[hashIndex]) #
NIL
THEN {
IF eH.hosts.pupHost = pupHost THEN GOTO Found;
IF (eH ← eH.next) #
NIL
THEN {
IF eH.hosts.pupHost = pupHost THEN GOTO Found;
NULL; -- more checks would go here ...
};
};
IF pupHost = Pup.allHosts THEN { eH ← cH.broadcastHostEntry; GOTO Found };
IF pupHost = network.pup.host THEN { eH ← cH.thisHostEntry; GOTO Found };
notQuick ← notQuick.SUCC;
IF (eH ← GetCacheEntry[cH, hashIndex, pupHost]) # NIL THEN GOTO Found;
GOTO NotFound;
EXITS
Found => {
eH.referenced ← TRUE;
TRUSTED { RETURN[ [ethernet[ethernetDest~eH.hosts.nsHost, ethernetSource~thisHost, ethernetType~oldPup]] ] }
};
NotFound => {
noTranslation ← noTranslation.SUCC;
TRUSTED { RETURN[ [ethernet[ethernetDest~NS.unknownHost, ethernetSource~thisHost, ethernetType~translationFailed]] ] }
};
END;
};
GetCacheEntry:
ENTRY
PROC [cH: Cache, hashIndex: HashIndex, pupHost: Pup.Host]
RETURNS [CacheEntry] ~ {
Search for a valid cache entry for the given nsHost. If a valid entry is found, return it; otherwise return NIL and arrange for an entry to be added.
eH, prevH: CacheEntry;
eH ← cH.validEntries[hashIndex]; prevH ← NIL;
WHILE eH #
NIL
DO
IF eH.hosts.pupHost = pupHost
THEN {
Move entry to head of list.
IF prevH #
NIL
THEN {
prevH.next ← eH.next;
eH.next ← cH.validEntries[hashIndex];
cH.validEntries[hashIndex] ← eH };
RETURN[eH] };
prevH ← eH; eH ← eH.next
ENDLOOP;
FOR eH ← cH.pendingEntries, eH.next
WHILE eH #
NIL
DO
IF eH.hosts.pupHost = pupHost THEN RETURN[NIL];
ENDLOOP;
TRUSTED { cH.pendingEntries ← NEW[ CacheEntryObject ← [next~cH.pendingEntries, hosts~[nsHost~NS.unknownHost, pupHost~pupHost, filler~], referenced~TRUE, timeStamp~BasicTime.GetClockPulses[], tries~0] ] };
cH.newPendingEntry ← TRUE; NOTIFY cH.event;
RETURN[NIL] };
Building Request / Reply Packets
MakeRequest:
PROC [cH: Cache, pupHost: Pup.Host, sendTo:
NS.Host ← NS.broadcastHost]
RETURNS [b: Buffer] ~ {
Allocate a buffer, build a request packet in it, and return it.
The sendTo parameter is the NS Host to which the request packet will be sent. It should be broadcastHost for a normal request.
bH: TranslationBuffer;
b ← Driver.AllocBuffer[];
TRUSTED { bH ← LOOPHOLE[b] };
bH.translationType ← requestType;
bH.replier ← [nsHost~NS.unknownHost, pupHost~pupHost, filler~0];
bH.requestor ← cH.thisHostEntry.hosts;
TRUSTED { bH.ovh.encap ← Encapsulation[ethernet[ethernetDest~sendTo, ethernetSource~thisHost, ethernetType~oldPupTranslation]] };
};
ConvertToReply:
PROC [cH: Cache, bH: TranslationBuffer] ~ {
Given a request buffer, convert it to the corresponding reply.
Fill in the encapsulation part here, so the buffer can be sent using network.sendTranslate rather than network.return.
bH.translationType ← replyType;
bH.replier ← cH.thisHostEntry.hosts;
TRUSTED { bH.ovh.encap ← Encapsulation[ethernet[ethernetDest~bH.requestor.nsHost, ethernetSource~thisHost, ethernetType~oldPupTranslation]] };
};
Processing Received Translation Packets
AddTranslation:
ENTRY
PROC [cH: Cache, hosts: HostPair] ~ {
eH, prevH: CacheEntry;
i: HashIndex ~ Hash[hosts.pupHost];
Look for a pending entry.
eH ← cH.pendingEntries; prevH ← NIL;
WHILE eH #
NIL
DO
IF eH.hosts.pupHost = hosts.pupHost
THEN {
IF prevH = NIL THEN cH.pendingEntries ← eH.next ELSE prevH.next ← eH.next;
eH.hosts.nsHost ← hosts.nsHost;
EXIT };
prevH ← eH; eH ← eH.next
ENDLOOP;
If no pending entry, look for a valid one.
IF eH =
NIL
THEN {
eH ← cH.validEntries[i]; prevH ← NIL;
WHILE eH #
NIL
DO
IF eH.hosts.pupHost = hosts.pupHost
THEN {
IF prevH = NIL THEN cH.validEntries[i] ← eH.next ELSE prevH.next ← eH.next;
If existing entry is incorrect, drop it on the floor ...
IF eH.hosts.nsHost # hosts.nsHost THEN eH ← NIL;
EXIT };
prevH ← eH; eH ← eH.next
ENDLOOP;
};
IF eH =
NIL
THEN cH.validEntries[i] ← NEW[ CacheEntryObject ← [next~cH.validEntries[i], hosts~hosts, referenced~TRUE, timeStamp~BasicTime.GetClockPulses[], tries~0] ]
ELSE { eH.next ← cH.validEntries[i]; cH.validEntries[i] ← eH };
};
Receive Statistics
requestsReceived: INT ← 0;
repliesReceived: INT ← 0;
tooShort: INT ← 0;
badProtocol: INT ← 0;
RecvTranslation: Driver.RecvProc
[network: Network, buffer: Buffer, bytes: NAT] RETURNS [Buffer]
~ {
cH: Cache ~ NARROW[network.pup.translation];
bH: TranslationBuffer;
CROCK: the following test should be "< translationPacketBytes", but some old implementations send reply packets without the requestor field. Eventually, when the old implementations go away, fix it by moving the other CROCK (below) up to this position.
IF bytes < translationShortPacketBytes
THEN {
tooShort ← tooShort.SUCC;
RETURN [buffer] };
TRUSTED { bH ← LOOPHOLE[buffer] };
SELECT
TRUE
FROM
bH.translationType = requestType => {
CROCK: the following test should be moved up to replace the previous CROCK.
IF bytes < translationPacketBytes
THEN {
tooShort ← tooShort.SUCC;
RETURN [buffer] };
IF bH.replier.pupHost = network.pup.host
THEN {
requestsReceived ← requestsReceived.SUCC;
AddTranslation[cH, bH.requestor];
ConvertToReply[cH, bH];
EnqueueForSending[cH, buffer];
buffer ← NIL;
};
};
bH.translationType = replyType => {
repliesReceived ← repliesReceived.SUCC;
AddTranslation[cH, bH.replier];
};
ENDCASE => {
badProtocol ← badProtocol.SUCC };
RETURN[buffer];
};
Daemon Process
EnqueueForSending:
ENTRY PROC [cH: Cache, b: Buffer] ~ {
IF cH.sendHead = NIL THEN cH.sendHead ← b ELSE cH.sendTail.ovh.next ← b;
cH.sendTail ← b;
b.ovh.next ← NIL;
NOTIFY cH.event };
InternalEnqueueForSending:
INTERNAL PROC [cH: Cache, b: Buffer] ~ {
IF cH.sendHead = NIL THEN cH.sendHead ← b ELSE cH.sendTail.ovh.next ← b;
cH.sendTail ← b;
b.ovh.next ← NIL;
NOTIFY cH.event };
DequeueForSending:
ENTRY
PROC [cH: Cache]
RETURNS [b: Buffer] ~ {
IF (b ← cH.sendHead) = NIL THEN RETURN;
IF (cH.sendHead ← NARROW[b.ovh.next]) = NIL THEN cH.sendTail ← NIL;
};
InternalSendQueueIsEmpty:
INTERNAL
PROC [cH: Cache]
RETURNS [
BOOL] ~
INLINE {
RETURN [cH.sendHead = NIL] };
WaitAndScanCache:
ENTRY
PROC [cH: Cache] ~ {
eH, prevH: CacheEntry;
IF InternalSendQueueIsEmpty[cH]
AND
NOT cH.newPendingEntry
THEN {
TRUSTED {
IF cH.pendingEntries #
NIL
THEN Process.SetTimeout[@cH.event, resendTimeout]
ELSE Process.SetTimeout[@cH.event, sweepCheckTimeout] };
WAIT cH.event };
prevH ← NIL; eH ← cH.pendingEntries;
WHILE eH #
NIL
DO
IF PulsesSince[eH.timeStamp] >= pulsesPerResend
THEN {
IF eH.tries >= maxTries
THEN
{
Delete the entry.
eH ← eH.next;
IF prevH = NIL THEN cH.pendingEntries ← eH ELSE prevH.next ← eH;
LOOP };
eH.tries ← eH.tries + 1;
eH.timeStamp ← BasicTime.GetClockPulses[];
{ buffer: Buffer ~ MakeRequest[cH, eH.hosts.pupHost];
InternalEnqueueForSending[cH, buffer] };
};
prevH ← eH; eH ← eH.next;
ENDLOOP;
cH.newPendingEntry ← FALSE;
IF PulsesSince[cH.sweepCheckTime] >= pulsesPerSweepCheck
THEN {
Do a sweep check ...
cH.sweepCheckTime ← BasicTime.GetClockPulses[];
IF cH.sweepChecksUntilSweep = 0
THEN {
Do a sweep ...
FOR i: HashIndex
IN [0..numHashHeaders)
DO
eH ← cH.validEntries[i]; prevH ← NIL;
WHILE eH #
NIL
DO
IF eH.referenced
THEN {
eH.referenced ← FALSE;
prevH ← eH; eH ← eH.next }
ELSE {
Delete the entry.
eH ← eH.next;
IF prevH = NIL THEN cH.validEntries[i] ← eH ELSE prevH.next ← eH };
ENDLOOP;
ENDLOOP;
cH.sweepChecksUntilSweep ← sweepChecksPerSweep;
}
ELSE {
cH.sweepChecksUntilSweep ← cH.sweepChecksUntilSweep - 1;
};
};
};
Daemon:
PROC [network: Network] ~ {
cH: Cache ~ NARROW[ network.pup.translation ];
buffer: Buffer;
Process.SetPriority[3]; -- ???
DO
WaitAndScanCache[cH];
WHILE (buffer ← DequeueForSending[cH]) #
NIL
DO
network.pup.sendTranslate[network, buffer, translationPacketBytes];
Driver.FreeBuffer[buffer];
ENDLOOP;
ENDLOOP;
};
Initialization
Init:
PROC = {
Install a cache (and start a daemon) for each ethernet on the chain.
cH: Cache;
FOR network: Network ← Driver.GetNetworkChain[], network.next
UNTIL network =
NIL
DO
IF network.type # ethernet THEN LOOP;
cH ← NEW[ CacheObject ← [] ];
cH.broadcastHostEntry ← NEW[ CacheEntryObject ← [hosts~[nsHost~NS.broadcastHost, pupHost~DriverType.ethernetOneBroadcastHost, filler~], referenced~, timeStamp~, tries~] ];
cH.thisHostEntry ← NEW[ CacheEntryObject ← [hosts~[nsHost~thisHost, pupHost~network.pup.host, filler~], referenced~, timeStamp~, tries~] ];
network.pup.translation ← cH;
network.pup.getEncapsulation ← GetEncapsulation;
Driver.InsertReceiveProc[network~network, type~pupTranslate, proc~RecvTranslation];
cH.daemon ← FORK Daemon[network];
ENDLOOP;
};
Hack for debugging use from the Interpreter:
TryHost:
PROC [pupHost: Pup.Host] ~ {
FOR network: Network ← Driver.GetNetworkChain[], network.next
UNTIL network =
NIL
DO
IF network.type = ethernet
THEN {
[] ← GetEncapsulation[network, pupHost]; EXIT };
ENDLOOP;
};
Init[];
}.