From d2585d6da2d30f116ef99339f79ce502f78697d4 Mon Sep 17 00:00:00 2001
From: Richard Mudgett <rmudgett@digium.com>
Date: Fri, 1 Jul 2016 13:07:17 -0500
Subject: [PATCH] q931.c: Lucent switch implementation bug workaround.

A bug in a Lucent switch implementation sets the Connected Number
information element octet 3 extension bit.  When set that means octet 3 is
complete and thus there is no optional octet 3a.  However, the buggy
switch still sends octet 3a.  The unexpected octet 3a is interpreted as
the first octet 4 and thus the first character in the connected line
number is a garbage character.

* Work around the switch bug by checking octet 3 and the potential octet
3a extension bits.  If they are both set then assume that octet 3a is
actually present for the buggy switch types.

PRI-183 #close
Reported by: Richard Mudgett

Change-Id: I378af37bfd852737a0bfe6263ef3473ea6acfbad
---
 q931.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 53 insertions(+), 2 deletions(-)

diff --git a/q931.c b/q931.c
index b25e951..98d6596 100644
--- a/q931.c
+++ b/q931.c
@@ -2351,7 +2351,30 @@ static int receive_connected_number(int full_ie, struct pri *ctrl, q931_call *ca
 		switch (i) {
 		case 0:
 			call->remote_id.number.plan = ie->data[i] & 0x7f;
-			break;
+
+			/*
+			 * Work around a bug in a Lucent switch implementation that
+			 * sets the extension bit in octet 3 even though octet 3a
+			 * is present.
+			 */
+			if (ie->data[i] & 0x80) {
+				/* Octet 3 extension bit is set */
+				if (ctrl->switchtype != PRI_SWITCH_LUCENT5E
+					&& ctrl->switchtype != PRI_SWITCH_ATT4ESS) {
+					/* Not a potentially buggy switch type. */
+					break;
+				}
+				if (!(ie->data[i + 1] & 0x80)) {
+					/*
+					 * The possible octet 3a doesn't have the extension
+					 * bit set.  It is likely not the erroneous octet 3a.
+					 */
+					break;
+				}
+			}
+			/* Octet 3a is present */
+			++i;
+			/* Fall through */
 		case 1:
 			/* Keep only the presentation and screening fields */
 			call->remote_id.number.presentation =
@@ -2393,7 +2416,35 @@ static void dump_connected_number(int full_ie, struct pri *ctrl, q931_ie *ie, in
 				prefix, ie2str(full_ie), len, ie->data[0] >> 7,
 				ton2str((ie->data[0] >> 4) & 0x07), (ie->data[0] >> 4) & 0x07,
 				npi2str(ie->data[0] & 0x0f), ie->data[0] & 0x0f);
-			break;
+
+			/*
+			 * Work around a bug in a Lucent switch implementation that
+			 * sets the extension bit in octet 3 even though octet 3a
+			 * is present.
+			 */
+			if (ie->data[i] & 0x80) {
+				/* Octet 3 extension bit is set */
+				if (ctrl->switchtype != PRI_SWITCH_LUCENT5E
+					&& ctrl->switchtype != PRI_SWITCH_ATT4ESS) {
+					/* Not a potentially buggy switch type. */
+					break;
+				}
+				if (!(ie->data[i + 1] & 0x80)) {
+					/*
+					 * The possible octet 3a doesn't have the extension
+					 * bit set.  It is likely not the erroneous octet 3a.
+					 */
+					break;
+				}
+				pri_message(ctrl, "\n");
+				pri_message(ctrl, "%c                             Switch bug workaround.\n",
+					prefix);
+				pri_message(ctrl, "%c                             Assuming octet 3a is present.",
+					prefix);
+			}
+			/* Octet 3a is present */
+			++i;
+			/* Fall through */
 		case 1: /* Octet 3a */
 			pri_message(ctrl, "\n");
 			pri_message(ctrl, "%c                             Ext: %d  Presentation: %s (%d)",