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PDP10, PDP11, VAX: Added the DDCMP corruption troll to the DDCMP laye…
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…r and removed it from the KDP device.

Now all DDCMP capable devices KDP, DUP and DMC/DMR have access to packet corruption generation to simulate real world imperfect data lines for protocol testing.
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@markpizz
markpizz committed Feb 11, 2014
1 parent d7690ce commit b1fb809
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Showing 5 changed files with 396 additions and 212 deletions.
109 changes: 95 additions & 14 deletions PDP11/pdp11_ddcmp.h
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Expand Up @@ -173,6 +173,81 @@ if (sim_deb && dptr && (reason & dptr->dctrl)) {

uint16 ddcmp_crc16(uint16 crc, const void* vbuf, size_t len);

/* Data corruption troll, which simulates imperfect links.
*/

/* Evaluate the corruption troll's appetite.
*
* A message can be eaten (dropped), nibbled (corrupted) or spared.
*
* The probability of a message not being spared is trollHungerLevel,
* expressed in milli-gulps - 0.1%. The troll selects which action
* to taken on selected messages with equal probability.
*
* Nibbled messages' CRCs are changed when possible to simplify
* identifying them when debugging. When it's too much work to
* find the CRC, the first byte of data is changed. The change
* is an XOR to make it possible to reconstruct the original data.
*
* A particularly unfortunate message can be nibbled by both
* the transmitter and receiver; thus the troll applies a direction-
* dependent pattern.
*
* Return TRUE if the troll ate the message.
* Return FALSE if the message was nibbled or spared.
*/
static t_bool ddcmp_feedCorruptionTroll (TMLN *lp, uint8 *msg, t_bool rx, int32 trollHungerLevel)
{
double r, rmax;
char msgbuf[80];

if (trollHungerLevel == 0)
return FALSE;
#if defined(_POSIX_VERSION) || defined (_XOPEN_VERSION)
r = (double)random();
rmax = (double)0x7fffffff;
#else
r = rand();
rmax = (double)RAND_MAX;
#endif
if (msg[0] == DDCMP_ENQ) {
int eat = 0 + (int) (2000.0 * (r / rmax));

if (eat <= (trollHungerLevel * 2)) { /* Hungry? */
if (eat <= trollHungerLevel) { /* Eat the packet */
sprintf (msgbuf, "troll ate a %s control message", rx ? "RCV" : "XMT");
tmxr_debug_msg (rx ? DDCMP_DBG_PRCV : DDCMP_DBG_PXMT, lp, msgbuf);
return TRUE;
}
sprintf (msgbuf, "troll bit a %s control message", rx ? "RCV" : "XMT");
tmxr_debug_msg (rx ? DDCMP_DBG_PRCV : DDCMP_DBG_PXMT, lp, msgbuf);
msg[6] ^= rx? 0114: 0154; /* Eat the CRC */
}
}
else {
int eat = 0 + (int) (3000.0 * (r / rmax));

if (eat <= (trollHungerLevel * 3)) { /* Hungry? */
if (eat <= trollHungerLevel) { /* Eat the packet */
sprintf (msgbuf, "troll ate a %s %s message", rx ? "RCV" : "XMT", (msg[0] == DDCMP_SOH)? "data" : "maintenance");
tmxr_debug_msg (rx ? DDCMP_DBG_PRCV : DDCMP_DBG_PXMT, lp, msgbuf);
return TRUE;
}
if (eat <= (trollHungerLevel * 2)) { /* HCRC */
sprintf (msgbuf, "troll bit a %s %s message", rx ? "RCV" : "XMT", (msg[0] == DDCMP_SOH)? "data" : "maintenance");
tmxr_debug_msg (rx ? DDCMP_DBG_PRCV : DDCMP_DBG_PXMT, lp, msgbuf);
msg[6] ^= rx? 0124: 0164;
}
else { /* DCRC */
sprintf (msgbuf, "troll bit %s %s DCRC\n", (rx? "RCV" : "XMT"), ((msg[0] == DDCMP_SOH)? "data" : "maintenance"));
tmxr_debug_msg (rx ? DDCMP_DBG_PRCV : DDCMP_DBG_PXMT, lp, msgbuf);
msg[8] ^= rx? 0114: 0154; /* Rather than find the CRC, the first data byte will do */
}
}
}
return FALSE;
}

/* Get packet from specific line
Inputs:
Expand All @@ -190,7 +265,7 @@ uint16 ddcmp_crc16(uint16 crc, const void* vbuf, size_t len);
NULL, but success (SCPE_OK) is returned
*/

static t_stat ddcmp_tmxr_get_packet_ln (TMLN *lp, const uint8 **pbuf, uint16 *psize)
static t_stat ddcmp_tmxr_get_packet_ln (TMLN *lp, const uint8 **pbuf, uint16 *psize, int32 corruptrate)
{
int32 c;
size_t payloadsize;
Expand Down Expand Up @@ -230,6 +305,8 @@ while (TMXR_VALID & (c = tmxr_getc_ln (lp))) {
else
strcpy (msg, "<<< RCV Packet");
ddcmp_packet_trace (DDCMP_DBG_PRCV, lp->mp->dptr, msg, lp->rxpb, *psize);
if (ddcmp_feedCorruptionTroll (lp, lp->rxpb, TRUE, corruptrate))
break;
return SCPE_OK;
}
payloadsize = ((lp->rxpb[2] & 0x3F) << 8)| lp->rxpb[1];
Expand All @@ -243,6 +320,8 @@ while (TMXR_VALID & (c = tmxr_getc_ln (lp))) {
strcpy (msg, "<<< RCV Packet");
ddcmp_packet_trace (DDCMP_DBG_PRCV, lp->mp->dptr, msg, lp->rxpb, *psize);
lp->rxpboffset = 0;
if (ddcmp_feedCorruptionTroll (lp, lp->rxpb, TRUE, corruptrate))
break;
return SCPE_OK;
}
}
Expand Down Expand Up @@ -270,7 +349,7 @@ return SCPE_LOST;
2. If prior packet transmission still in progress, SCPE_STALL is
returned and no packet data is stored. The caller must retry later.
*/
static t_stat ddcmp_tmxr_put_packet_ln (TMLN *lp, const uint8 *buf, size_t size)
static t_stat ddcmp_tmxr_put_packet_ln (TMLN *lp, const uint8 *buf, size_t size, int32 corruptrate)
{
t_stat r;
char msg[32];
Expand All @@ -293,15 +372,17 @@ if (lp->mp->lines > 1)
else
strcpy (msg, ">>> XMT Packet");
ddcmp_packet_trace (DDCMP_DBG_PXMT, lp->mp->dptr, msg, lp->txpb, lp->txppsize);
++lp->txpcnt;
while ((lp->txppoffset < lp->txppsize) &&
(SCPE_OK == (r = tmxr_putc_ln (lp, lp->txpb[lp->txppoffset]))))
++lp->txppoffset;
tmxr_send_buffered_data (lp);
if (!ddcmp_feedCorruptionTroll (lp, lp->txpb, FALSE, corruptrate)) {
++lp->txpcnt;
while ((lp->txppoffset < lp->txppsize) &&
(SCPE_OK == (r = tmxr_putc_ln (lp, lp->txpb[lp->txppoffset]))))
++lp->txppoffset;
tmxr_send_buffered_data (lp);
}
return lp->conn ? SCPE_OK : SCPE_LOST;
}

static t_stat ddcmp_tmxr_put_packet_crc_ln (TMLN *lp, uint8 *buf, size_t size)
static t_stat ddcmp_tmxr_put_packet_crc_ln (TMLN *lp, uint8 *buf, size_t size, int32 corruptrate)
{
uint16 hdr_crc16 = ddcmp_crc16(0, buf, DDCMP_HEADER_SIZE-DDCMP_CRC_SIZE);

Expand All @@ -312,7 +393,7 @@ if (size > DDCMP_HEADER_SIZE) {
buf[size-DDCMP_CRC_SIZE] = data_crc16 & 0xFF;
buf[size-DDCMP_CRC_SIZE+1] = (data_crc16>>8) & 0xFF;
}
return ddcmp_tmxr_put_packet_ln (lp, buf, size);
return ddcmp_tmxr_put_packet_ln (lp, buf, size, corruptrate);
}

static void ddcmp_build_data_packet (uint8 *buf, size_t size, uint8 flags, uint8 sequence, uint8 ack)
Expand All @@ -338,7 +419,7 @@ buf[5] = 1;
static t_stat ddcmp_tmxr_put_data_packet_ln (TMLN *lp, uint8 *buf, size_t size, uint8 flags, uint8 sequence, uint8 ack)
{
ddcmp_build_data_packet (buf, size, flags, sequence, ack);
return ddcmp_tmxr_put_packet_crc_ln (lp, buf, size);
return ddcmp_tmxr_put_packet_crc_ln (lp, buf, size, 0);
}

static void ddcmp_build_control_packet (uint8 *buf, uint8 type, uint8 subtype, uint8 flags, uint8 sndr, uint8 rcvr)
Expand All @@ -355,7 +436,7 @@ buf[5] = 1; /* ADDR */
static t_stat ddcmp_tmxr_put_control_packet_ln (TMLN *lp, uint8 *buf, uint8 type, uint8 subtype, uint8 flags, uint8 sndr, uint8 rcvr)
{
ddcmp_build_control_packet (buf, type, subtype, flags, sndr, rcvr);
return ddcmp_tmxr_put_packet_crc_ln (lp, buf, DDCMP_HEADER_SIZE);
return ddcmp_tmxr_put_packet_crc_ln (lp, buf, DDCMP_HEADER_SIZE, 0);
}

static void ddcmp_build_ack_packet (uint8 *buf, uint8 ack, uint8 flags)
Expand All @@ -366,7 +447,7 @@ ddcmp_build_control_packet (buf, DDCMP_CTL_ACK, 0, flags, 0, ack);
static t_stat ddcmp_tmxr_put_ack_packet_ln (TMLN *lp, uint8 *buf, uint8 ack, uint8 flags)
{
ddcmp_build_ack_packet (buf, ack, flags);
return ddcmp_tmxr_put_packet_crc_ln (lp, buf, DDCMP_HEADER_SIZE);
return ddcmp_tmxr_put_packet_crc_ln (lp, buf, DDCMP_HEADER_SIZE, 0);
}

static void ddcmp_build_nak_packet (uint8 *buf, uint8 reason, uint8 nack, uint8 flags)
Expand Down Expand Up @@ -397,7 +478,7 @@ ddcmp_build_control_packet (buf, DDCMP_CTL_STRT, 0, DDCMP_FLAG_SELECT|DDCMP_FLAG
static t_stat ddcmp_tmxr_put_start_packet_ln (TMLN *lp, uint8 *buf)
{
ddcmp_build_start_packet (buf);
return ddcmp_tmxr_put_packet_crc_ln (lp, buf, DDCMP_HEADER_SIZE);
return ddcmp_tmxr_put_packet_crc_ln (lp, buf, DDCMP_HEADER_SIZE, 0);
}

static void ddcmp_build_start_ack_packet (uint8 *buf)
Expand All @@ -408,7 +489,7 @@ ddcmp_build_control_packet (buf, DDCMP_CTL_STACK, 0, DDCMP_FLAG_SELECT|DDCMP_FLA
static t_stat ddcmp_tmxr_put_start_ack_packet_ln (TMLN *lp, uint8 *buf)
{
ddcmp_build_start_ack_packet (buf);
return ddcmp_tmxr_put_packet_crc_ln (lp, buf, DDCMP_HEADER_SIZE);
return ddcmp_tmxr_put_packet_crc_ln (lp, buf, DDCMP_HEADER_SIZE, 0);
}

#endif /* PDP11_DDCMP_H_ */

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