Check checksum on CH11 under KLH10

Author: bictorv

src/system/chaos.291

@@ -2426,29 +2426,49 @@ BBLK
 	 JRST [	AOS CHNLOS	;No buffers, lose this packet
 		JRST CHXBK1 ]
 	HRLI A,-%CPKDT		;Copy out the packet header
+IFN KLH10P,[
+;; The KLH10P-marked code is a workaround for a bug in the 
+;; KLH10 implementation of the CH11. It seems to be a synchronization
+;; bug which results in packets being corrupted after being received
+;; from the net, and before being read by the 10.
+;; The workaround is to compute the checksum here, and verify it.
+;; When someone either fixes the CH11 bug or simply reimplements it,
+;; this code should be taken out again.
+;; Note that the performance impact is very small.
+;; /BV November 2024.
+;; (Side note: is "ADDI J,(B)" faster than "ADD J,B"?)
+IFN KLH10P,SETZ J,		; Clear checksum
 CHSRC1:	IORDI B,CAIRBF
+IFN KLH10P,ADD J,B
 	IORDI C,CAIRBF
+IFN KLH10P,ADD J,C
 	PACK16 B,(A)
 	AOBJN A,CHSRC1
 	PUSHJ P,CHSHDR		;Decode the header
 	 JRST CHSRC4		;No byte swapping
 	JUMPGE D,CHSRC3
 CHSRC2:	IORDI B,CAIRBF		;Read out the data, byte-swapped
+IFN KLH10P,ADD J,B
 	IORDI C,CAIRBF
+IFN KLH10P,ADD J,C
 	PACK8 B,(D)
 	AOBJN D,CHSRC2
 CHSRC3:	JUMPGE H,CHSRC7		;Jump if even packet length
 	IORDI B,CAIRBF		;Residual halfword
+IFN KLH10P,ADD J,B
 	SETZ C,			;Somebody depends on zero here
 	PACK8 B,(D)
 	AOJA D,CHSRC7
 
 CHSRC4:	JUMPGE D,CHSRC6
 CHSRC5:	IORDI B,CAIRBF		;Read out the data, halfwords
+IFN KLH10P,ADD J,B
 	IORDI C,CAIRBF
+IFN KLH10P,ADD J,C
 	PACK16 B,(D)
 	AOBJN D,CHSRC5
 CHSRC6:	JUMPL H,[ IORDI B,CAIRBF	;Residual halfword
+IFN KLH10P,	  ADD J,B
 		  SETZ C,		;Somebody depends on zero here
 		  PACK16 B,(D)
 		  AOJA D,CHSRC7 ]
@@ -2457,8 +2477,23 @@ CHSRC7:	SUB D,R			;AOBJN pointer minus number of words in packet
 	 JRST [	AOS CHNPLE	;Packet length disagrees with hardware length
 		JRST CHXBK2 ]
 	IORDI T,CAIRBF		;Read the three hardware header words
+IFN KLH10P,ADD J,T
 	IORDI T,CAIRBF
+IFN KLH10P,ADD J,T
 	IORDI T,CAIRBF
+IFN KLH10P,ADD J,T
+IFN KLH10P,[			; Wrap it up - see IPCKS3
+CHSRCZ::CAILE J,177777		; Does the checksum fit?
+	 JRST [	LDB Q,[202400,,J]	; No, get overflow bits
+		ANDI J,177777	; then clear them
+		ADDI J,(Q)	; and add at low end
+		JRST CHSRCZ ]
+	ANDCAI J,177777		; Make ones complement
+	JUMPE J,CHSRCY		; No problem
+	AOS CHNCR2		; CRC checksum error after reading
+	;; BUG CHECK,[Chaos: CRC error - cks =],OCT,J
+	JRST CHXBK2
+CHSRCY::]
 	IORDI T,CAICSR
 	TRNE T,%CAERR		;Make sure packet came out of RAM okay
 	 JRST [	AOS CHNCR2	;Garbage, try again