gsm: fix CMGS PDU mode length calculation

The first byte of the PDU is the SMSC length, but it's not
the padded SMSC length.  So we need to subtract the actual
byte index of the start of the message from length of the
PDU, and since the PDU creation function knows all about
where the SMSC address stops and the message begins, just
have it return that length instead of making the callers
calculate it.

src/mm-generic-gsm.c

@@ -4770,16 +4770,14 @@ sms_send (MMModemGsmSms *modem,
 
     if (priv->sms_pdu_mode) {
         guint8 *pdu;
-        guint pdulen = 0;
-        guint smsclen = 0;
+        guint pdulen = 0, msgstart = 0;
         char *hex;
 
-        pdu = sms_create_submit_pdu (number, text, smsc, validity, class, &pdulen, &info->error);
+        pdu = sms_create_submit_pdu (number, text, smsc, validity, class, &pdulen, &msgstart, &info->error);
         if (!pdu) {
             mm_callback_info_schedule (info);
             return;
         }
-        smsclen = pdu[0];
 
         hex = utils_bin2hexstr (pdu, pdulen);
         g_free (pdu);
@@ -4793,7 +4791,7 @@ sms_send (MMModemGsmSms *modem,
         }
 
         /* CMGS length is the size of the PDU without SMSC information */
-        command = g_strdup_printf ("+CMGS=%d\r%s\x1a", pdulen - smsclen, hex);
+        command = g_strdup_printf ("+CMGS=%d\r%s\x1a", pdulen - msgstart, hex);
         g_free (hex);
     } else
         command = g_strdup_printf ("+CMGS=\"%s\"\r%s\x1a", number, text);

src/mm-sms-utils.c

@@ -600,6 +600,8 @@ validity_to_relative (guint validity)
  *  suitable default
  * @class: unused
  * @out_pdulen: on success, the size of the returned PDU in bytes
+ * @out_msgstart: on success, the byte index in the returned PDU where the
+ *  message starts (ie, skipping the SMSC length byte and address, if present)
  * @error: on error, filled with the error that occurred
  *
  * Constructs a single-part SMS message with the given details, preferring to
@@ -615,6 +617,7 @@ sms_create_submit_pdu (const char *number,
                        guint validity,
                        guint class,
                        guint *out_pdulen,
+                       guint *out_msgstart,
                        GError **error)
 {
     guint8 *pdu;
@@ -668,6 +671,9 @@ sms_create_submit_pdu (const char *number,
         pdu[offset++] = 0x00;
     }
 
+    if (out_msgstart)
+        *out_msgstart = offset;
+
     if (validity > 0)
         pdu[offset] = 1 << 4; /* TP-VP present; format RELATIVE */
     else

src/mm-sms-utils.h

@@ -28,6 +28,7 @@ guint8 *sms_create_submit_pdu (const char *number,
                                guint validity,
                                guint class,
                                guint *out_pdulen,
+                               guint *out_msgstart,
                                GError **error);
 
 /* For testcases only */

src/tests/test-sms.c

@@ -488,14 +488,15 @@ test_create_pdu_ucs2_with_smsc (void *f, gpointer d)
         0x04, 0x42, 0x04, 0x3A, 0x04, 0x30, 0x00, 0x21
     };
     guint8 *pdu;
-    guint len = 0;
+    guint len = 0, msgstart = 0;
     GError *error = NULL;
 
-    pdu = sms_create_submit_pdu (number, text, smsc, 1, 0, &len, &error);
+    pdu = sms_create_submit_pdu (number, text, smsc, 1, 0, &len, &msgstart, &error);
     g_assert_no_error (error);
     g_assert (pdu);
     g_assert_cmpint (len, ==, sizeof (expected));
     g_assert_cmpint (memcmp (pdu, expected, len), ==, 0);
+    g_assert_cmpint (msgstart, ==, 8);
 }
 
 static void
@@ -513,14 +514,15 @@ test_create_pdu_ucs2_no_smsc (void *f, gpointer d)
         0x21
     };
     guint8 *pdu;
-    guint len = 0;
+    guint len = 0, msgstart = 0;
     GError *error = NULL;
 
-    pdu = sms_create_submit_pdu (number, text, NULL, 1, 0, &len, &error);
+    pdu = sms_create_submit_pdu (number, text, NULL, 1, 0, &len, &msgstart, &error);
     g_assert_no_error (error);
     g_assert (pdu);
     g_assert_cmpint (len, ==, sizeof (expected));
     g_assert_cmpint (memcmp (pdu, expected, len), ==, 0);
+    g_assert_cmpint (msgstart, ==, 1);
 }
 
 static void
@@ -538,14 +540,15 @@ test_create_pdu_gsm_with_smsc (void *f, gpointer d)
         0x49, 0x5D, 0xC5, 0x52, 0x20, 0x08, 0x04, 0x02, 0x81, 0x00
     };
     guint8 *pdu;
-    guint len = 0;
+    guint len = 0, msgstart = 0;
     GError *error = NULL;
 
-    pdu = sms_create_submit_pdu (number, text, smsc, 1, 0, &len, &error);
+    pdu = sms_create_submit_pdu (number, text, smsc, 1, 0, &len, &msgstart, &error);
     g_assert_no_error (error);
     g_assert (pdu);
     g_assert_cmpint (len, ==, sizeof (expected));
     g_assert_cmpint (memcmp (pdu, expected, len), ==, 0);
+    g_assert_cmpint (msgstart, ==, 8);
 }
 
 static void
@@ -562,14 +565,15 @@ test_create_pdu_gsm_no_smsc (void *f, gpointer d)
         0x02, 0x81, 0x00
     };
     guint8 *pdu;
-    guint len = 0;
+    guint len = 0, msgstart = 0;
     GError *error = NULL;
 
-    pdu = sms_create_submit_pdu (number, text, NULL, 1, 0, &len, &error);
+    pdu = sms_create_submit_pdu (number, text, NULL, 1, 0, &len, &msgstart, &error);
     g_assert_no_error (error);
     g_assert (pdu);
     g_assert_cmpint (len, ==, sizeof (expected));
     g_assert_cmpint (memcmp (pdu, expected, len), ==, 0);
+    g_assert_cmpint (msgstart, ==, 1);
 }
 
 static void
@@ -584,7 +588,7 @@ test_create_pdu_gsm_3 (void *f, gpointer d)
         0x10
     };
     guint8 *pdu;
-    guint len = 0;
+    guint len = 0, msgstart = 0;
     GError *error = NULL;
 
     /* Tests that a 25-character message (where the last septet is packed into
@@ -593,11 +597,12 @@ test_create_pdu_gsm_3 (void *f, gpointer d)
      * leave off the last octet.
      */
 
-    pdu = sms_create_submit_pdu (number, text, NULL, 1, 0, &len, &error);
+    pdu = sms_create_submit_pdu (number, text, NULL, 1, 0, &len, &msgstart, &error);
     g_assert_no_error (error);
     g_assert (pdu);
     g_assert_cmpint (len, ==, sizeof (expected));
     g_assert_cmpint (memcmp (pdu, expected, len), ==, 0);
+    g_assert_cmpint (msgstart, ==, 1);
 }
 
 #if 0