Access Violation in snaservr!snpugeti When Using PU Passthrough

SYMPTOMS

SNA Server may fail unexpectedly with an access violation when you use the PU Passthrough feature (new in SNA Server 4.0). This failure may occur when receiving XID messages from the downstream physical unit (for example, after the downstream PU is powered on).

If Drwtsn32.exe is configured as the default debugger on the SNA Server, the Drwtsn32.log file may contain an entry similar to the following when this access violation occurs:

   Application exception occurred:
   App: <path>snaservr.exe (pid=<process ID #>)
   When: <date> @ <time>
   Exception number: c0000005 (access violation)
   [...]

function: snpugeti
        0100a5ba 8d4e04   lea     ecx,[esi+0x4]      ds:012eea06=00000000
        0100a5bd 2bea     sub     ebp,edx
        0100a5bf 0fbfd7   movsx   edx,di
        0100a5c2 3bd5     cmp     edx,ebp
        0100a5c4 7e27     jle     snpugeti+0x4d (0100a5ed)
        0100a5c6 85f6     test    esi,esi
        0100a5c8 7427     jz      snpugeti+0x51 (0100a5f1)
        0100a5ca 668b09   mov     cx,[ecx]           ds:01f5fff4=0000
        0100a5cd 8b36     mov     esi,[esi]          ds:00000000=????????
        0100a5cf 662b08   sub     cx,[eax]           ds:01f56d8e=0016
FAULT ->0100a5d2 0fbf5606 movsx   edx,word ptr [esi+0x6] ds:012eea07=0000
        0100a5d6 0fbf6e04 movsx   ebp,word ptr [esi+0x4] ds:012eea07=0000
        0100a5da 8d7c0fff lea     edi,[edi+ecx-0x1]   ds:0324e9fb=????????
        0100a5de 8d4606   lea     eax,[esi+0x6]       ds:012eea06=00000000
        0100a5e1 8d4e04   lea     ecx,[esi+0x4]       ds:012eea06=00000000
        0100a5e4 2bd5     sub     edx,ebp
        0100a5e6 0fbfef   movsx   ebp,di
        0100a5e9 3bea     cmp     ebp,edx
        0100a5eb 7fd9     jg      snpugeti+0x26 (0100a5c6)
        0100a5ed 85f6     test    esi,esi
        0100a5ef 750f     jnz     snpugeti+0x60 (0100a600)
        0100a5f1 53       push    ebx

*----> Stack Back Trace <----*

FramePtr ReturnAd Param#1  Param#2  Param#3  Param#4  Function Name
011cfef8 010413fd 01f56d88 0000001a 01180011 011840cc snaservr!snpugeti
(FPO: [EBP 0x01f54908] [2,0,4])