Changeset 1708aa8

Timestamp:

09/05/07 11:41:27 (14 years ago)

Author:

Scott Raynel <smr26@…>

Branches:

4.0.1-hotfixes, cachetimestamps, develop, dpdk-ndag, etsilive, getfragoff, help, libtrace4, master, ndag_format, pfring, rc-4.0.1, rc-4.0.2, rc-4.0.3, rc-4.0.4, ringdecrementfix, ringperformance, ringtimestampfixes

Children:

34e22d1

Parents:

27bd348

Message:

Fix trace_get_source_mac() for wireless frames. Returns NULL if the frame
does not contain a source MAC, otherwise returns addr2 in all other cases.

Fixes #253

File:

• lib/protocols.c (modified) (1 diff)

lib/protocols.c

@@ -695 +695 @@
 }
 
+/* Take a pointer to the start of an IEEE 802.11 MAC frame and return a pointer
+ * to the source MAC address.  
+ * If the frame does not contain a sender address, e.g. ACK frame, return NULL.
+ * If the frame is a 4-address WDS frame, return TA, i.e. addr2.
+ * NB: This function decodes the 802.11 header, so it assumes that there are no
+ * bit-errors. If there are, all bets are off.
+ */
+static
+uint8_t *get_source_mac_from_wifi(void *wifi) {
+        if (wifi == NULL) return NULL;
+        struct libtrace_80211_t *w = (struct libtrace_80211_t *) wifi;
+        
+        /* If the frame is of type CTRL */
+        if (w->type == 0x1) 
+                /* If bit 2 of the subtype field is zero, this indicates that
+                 * there is no transmitter address, i.e. the frame is either an
+                 * ACK or a CTS frame */
+                if ((w->subtype & 0x2) == 0)
+                        return NULL;
+
+        /* Always return the address of the transmitter, i.e. address 2 */
+        return (uint8_t *) &w->mac2;
+}
 
 uint8_t *trace_get_source_mac(libtrace_packet_t *packet) {
         void *link = trace_get_link(packet);
-        libtrace_80211_t *wifi;
         libtrace_ether_t *ethptr = (libtrace_ether_t*)link;
         if (!link)
                 return NULL;
         switch (trace_get_link_type(packet)) {
+                case TRACE_TYPE_80211_RADIO:
+                        link = trace_get_payload_from_radiotap(
+                                        link, NULL, NULL);
+                        /* Fall through for 802.11 */
                 case TRACE_TYPE_80211:
-                        wifi=(libtrace_80211_t*)link;
-                        return (uint8_t*)&wifi->mac2;
-                case TRACE_TYPE_80211_RADIO:
-                        wifi=(libtrace_80211_t*)trace_get_payload_from_radiotap(
-                                        link,NULL,NULL);
-                        return (uint8_t*)&wifi->mac1;
+                        return get_source_mac_from_wifi(link);
                 case TRACE_TYPE_80211_PRISM:
-                        wifi=(libtrace_80211_t*)((char*)link+144);
-                        return (uint8_t*)&wifi->mac2;
+                        link = ((char*)link+144);
+                        return get_source_mac_from_wifi(link);
                 case TRACE_TYPE_ETH:
                         return (uint8_t*)&ethptr->ether_shost;