libpcap: don't generate a fake interface for LINKTYPE_ERF files.

The ERF code will generate interfaces based on the ERF records in the
file, so don't bother adding an additional dummy interface.

wiretap/libpcap.c

@@ -603,25 +603,16 @@ done:
 	if (wth->file_encap == WTAP_ENCAP_ERF) {
 		/*Reset the ERF interface lookup table*/
 		libpcap->encap_priv = erf_priv_create();
+	} else {
+		/*
+		 * Add an IDB; we don't know how many interfaces were
+		 * involved, so we just say one interface, about which
+		 * we only know the link-layer type, snapshot length,
+		 * and time stamp resolution.
+		 */
+		wtap_add_generated_idb(wth);
 	}
 
-	/*
-	 * Add an IDB; we don't know how many interfaces were involved,
-	 * so we just say one interface, about which we only know
-	 * the link-layer type, snapshot length, and time stamp
-	 * resolution.
-	 *
-	 * XXX - this will be a bit weird if you're trying to convert
-	 * a LINKTYPE_ERF pcap file to a pcapng file; it'll have a
-	 * placeholder interface added here, *plus* interfaces
-	 * added from the ERF records.  Ideally, at some point in
-	 * the future, libpcap will have a more pcapng-friendly API
-	 * for capturing, and the DAG capture code will use it, so that
-	 * if you're capturing on more than one interface, they'll all
-	 * get regular IDBs, with no need for the placeholder.
-	 */
-	wtap_add_generated_idb(wth);
-
 	return WTAP_OPEN_MINE;
 }