Fix reading from pcap dumpfile

.gitignore

@@ -0,0 +1,3 @@
+*.o
+driftnet
+driftnet.1

driftnet.c

@@ -183,7 +183,10 @@ void dump_data(FILE *fp, const unsigned char *data, const unsigned int len) {
  * type. This is based on init_linktype in the libpcap distribution; I
  * don't know why libpcap doesn't expose the information directly. The
  * constants here are taken from 0.6.2, but I've added #ifdefs in the hope
- * that it will still compile with earlier versions. */
+ * that it will still compile with earlier versions.
+ * The return value _must_ be checked by the caller, since -1 will be returned for
+ * unknown link types!
+ */
 int get_link_level_hdr_length(int type)
 {
     switch (type) {
@@ -247,11 +250,32 @@ int get_link_level_hdr_length(int type)
         case DLT_IEEE802_11:
             return 32; /* 20030606 email from Nikhil Bobb */ /*44; */
 #endif
-
+
+#ifdef DLT_IEEE802_11_RADIO           /* radiotap (atheros monitoring) */
+        case DLT_IEEE802_11_RADIO:
+            /* actually, the header size can vary from packet to packet;
+             * we have to look at each packet separately
+             */
+            return 0;
+#endif
         default:;
     }
     fprintf(stderr, PROGNAME": unknown data link type %d", type);
-    exit(1);
+    return -1;
+}
+
+int get_frame_link_level_hdr_length(int type, const u_char *pkt) {
+	switch(type) {
+#ifdef DLT_IEEE802_11_RADIO
+		case DLT_IEEE802_11_RADIO:
+			/* determine the length of the variable header
+			 * and add the underlying part (we assume 802.11 for now)
+			 */
+			return *(uint16_t*)(pkt+2)+2+get_link_level_hdr_length(DLT_IEEE802_11);
+#endif
+		default:
+			return get_link_level_hdr_length(type);
+	};
 }
 
 
@@ -368,18 +392,24 @@ char *connection_string(const struct in_addr s, const unsigned short s_port, con
 
 /* process_packet:
  * Callback which processes a packet captured by libpcap. */
-int pkt_offset; /* offset of IP packet within wire packet */
 
 void process_packet(u_char *user, const struct pcap_pkthdr *hdr, const u_char *pkt) {
     struct ip ip;
     struct tcphdr tcp;
     struct in_addr s, d;
     int off, len, delta;
+    int pkt_offset;
     connection *C, c;
 
     if (verbose)
         fprintf(stderr, ".");
 
+    /* get the individual packet offset */
+    pkt_offset = get_frame_link_level_hdr_length( pcap_datalink(pc), pkt );
+    if (pkt_offset < 0) { /* something strange happened, we cannot handle this packet */
+        return;
+    }
+
     memcpy(&ip, pkt + pkt_offset, sizeof(ip));
     memcpy(&s, &ip.ip_src, sizeof(ip.ip_src));
     memcpy(&d, &ip.ip_dst, sizeof(ip.ip_dst));
@@ -656,14 +686,19 @@ int main(int argc, char *argv[]) {
     if (verbose) 
         fprintf(stderr, PROGNAME": using temporary file directory %s\n", tmpdir);
 
-    if (!interface && !(interface = pcap_lookupdev(ebuf))) {
+    if (!dumpfile && !interface && !(interface = pcap_lookupdev(ebuf))) {
         fprintf(stderr, PROGNAME": pcap_lookupdev: %s\n", ebuf);
         fprintf(stderr, PROGNAME": try specifying an interface with -i\n");
         return -1;
     }
 
-    if (verbose)
-        fprintf(stderr, PROGNAME": listening on %s%s\n", interface ? interface : "all interfaces", promisc ? " in promiscuous mode" : "");
+    if (verbose) {
+        if (interface) {
+            fprintf(stderr, PROGNAME": listening on %s%s\n", interface ? interface : "all interfaces", promisc ? " in promiscuous mode" : "");
+	} else if (dumpfile) {
+            fprintf(stderr, PROGNAME": processing packets from dumpfile '%s'\n", dumpfile);
+        }
+    }
 
     /* Build up filter. */
     if (optind < argc) {
@@ -756,12 +791,6 @@ int main(int argc, char *argv[]) {
         }
     }
 
-    /* Figure out the offset from the start of a returned packet to the data in
-     * it. */
-    pkt_offset = get_link_level_hdr_length(pcap_datalink(pc));
-    if (verbose)
-        fprintf(stderr, PROGNAME": link-level header length is %d bytes\n", pkt_offset);
-
     slotsused = 0;
     slotsalloc = 64;
     slots = (connection*)xcalloc(slotsalloc, sizeof(connection));