wctc4xxp: Do not ACK response packets without a corresponding request.

Closes a small window of opportunity where system conditions prevent the
driver from servicing it's receive ring within the timeout period of a
request, and then in the middle of retrying the request (after the
request was already removed from the "waiting_for_response" list) the
driver process the response, it's possible for the driver to ACK the
response without ever pairing it up with the original request. The
result being that the DTE will then ignore our attempts to retry the
original request. DAHDI-430.

git-svn-id: http://svn.asterisk.org/svn/dahdi/linux/trunk@9035 a0bf4364-ded3-4de4-8d8a-66a801d63aff

1 files changed, 35 insertions, 12 deletions

diff --git a/drivers/dahdi/wctc4xxp/base.c b/drivers/dahdi/wctc4xxp/base.c
index 03eda38..0bd19c7 100644
--- a/drivers/dahdi/wctc4xxp/base.c
+++ b/drivers/dahdi/wctc4xxp/base.c
@@ -1,5 +1,4 @@
-/*
- * Wildcard TC400B Driver
+/* Wildcard TC400B Driver
  *
  * Copyright (C) 2006-2010, Digium, Inc.
  *
@@ -39,6 +38,8 @@
 #include <linux/etherdevice.h>
 #include <linux/timer.h>
 
+#include <stdbool.h>
+
 #include "dahdi/kernel.h"
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 18)
@@ -2217,19 +2218,18 @@ wctc4xxp_send_ack(struct wcdte *wc, u8 seqno, __be16 channel)
 	wctc4xxp_transmit_cmd(wc, cmd);
 }
 
-static void
-do_rx_response_packet(struct wcdte *wc, struct tcb *cmd)
+static bool do_rx_response_packet(struct wcdte *wc, struct tcb *cmd)
 {
 	const struct csm_encaps_hdr *listhdr, *rxhdr;
 	struct tcb *pos, *temp;
 	unsigned long flags;
-	u32 handled = 0;
+	bool handled = false;
 	rxhdr = cmd->data;
-	if (0xffff == rxhdr->channel) {
+	if (SUPERVISOR_CHANNEL == rxhdr->channel) {
 		/* We received a duplicate response. */
 		if (rxhdr->seq_num == wc->last_rx_seq_num) {
 			free_cmd(cmd);
-			return;
+			return false;
 		}
 		wc->last_rx_seq_num = rxhdr->seq_num;
 	}
@@ -2250,7 +2250,7 @@ do_rx_response_packet(struct wcdte *wc, struct tcb *cmd)
 			if (pos->flags & TX_COMPLETE)
 				complete(&pos->complete);
 			spin_unlock(&pos->lock);
-			handled = 1;
+			handled = true;
 
 			break;
 		}
@@ -2262,7 +2262,10 @@ do_rx_response_packet(struct wcdte *wc, struct tcb *cmd)
 			"Freeing unhandled response ch:(%04x)\n",
 			be16_to_cpu(rxhdr->channel));
 		free_cmd(cmd);
+		return false;
 	}
+
+	return true;
 }
 
 static void
@@ -2356,12 +2359,20 @@ receive_csm_encaps_packet(struct wcdte *wc, struct tcb *cmd)
 	const struct csm_encaps_hdr *hdr = cmd->data;
 
 	if (!(hdr->control & MESSAGE_PACKET)) {
-		if (!(hdr->control & SUPPRESS_ACK))
-			wctc4xxp_send_ack(wc, hdr->seq_num, hdr->channel);
-
+		const bool suppress_ack = ((hdr->control & SUPPRESS_ACK) > 0);
 		if (is_response(hdr)) {
-			do_rx_response_packet(wc, cmd);
+			u8 seq_num = hdr->seq_num;
+			__be16 channel = hdr->channel;
+
+			if (do_rx_response_packet(wc, cmd) && !suppress_ack)
+				wctc4xxp_send_ack(wc, seq_num, channel);
+
 		} else if (0xc1 == hdr->type) {
+			if (!suppress_ack) {
+				wctc4xxp_send_ack(wc, hdr->seq_num,
+						  hdr->channel);
+			}
+
 			if (0x75 == hdr->class) {
 				DTE_PRINTK(WARNING,
 				   "Received alert (0x%04x) from dsp\n",
@@ -2369,6 +2380,10 @@ receive_csm_encaps_packet(struct wcdte *wc, struct tcb *cmd)
 			}
 			free_cmd(cmd);
 		} else if (0xd4 == hdr->type) {
+			if (!suppress_ack) {
+				wctc4xxp_send_ack(wc, hdr->seq_num,
+						  hdr->channel);
+			}
 			if (hdr->params[0] != le16_to_cpu(0xffff)) {
 				DTE_PRINTK(WARNING,
 				   "DTE Failed self test (%04x).\n",
@@ -2384,10 +2399,18 @@ receive_csm_encaps_packet(struct wcdte *wc, struct tcb *cmd)
 			}
 			free_cmd(cmd);
 		} else if (MONITOR_LIVE_INDICATION_TYPE == hdr->type) {
+			if (!suppress_ack) {
+				wctc4xxp_send_ack(wc, hdr->seq_num,
+						  hdr->channel);
+			}
 			DTE_PRINTK(WARNING, "Received diagnostic message:\n");
 			print_command(wc, cmd);
 			free_cmd(cmd);
 		} else {
+			if (!suppress_ack) {
+				wctc4xxp_send_ack(wc, hdr->seq_num,
+						  hdr->channel);
+			}
 			DTE_PRINTK(WARNING,
 			  "Unknown command type received. %02x\n", hdr->type);
 			free_cmd(cmd);