| | 1 | [wiki:WikiStart Orbit] > [wiki:Documentation/OTG OTG] > [wiki:Documentation/OTG/FuncSpec Function Specifications] > Using LIBMAC |
| | 2 | |
| | 3 | = Use LIBMAC in OTR Program = |
| | 4 | |
| | 5 | == Introduction to LIBMAC == |
| | 6 | Libmac is a user-space C library that brings the wireless driver application program interface (API) into user space allowing one to get or set values of driver parameters. This library supports operation for a variable number of parameters per call. Currently, the documentation of LIBMAC is created by Doxygen tool and can be found in |
| | 7 | http://www.winlab.rutgers.edu/~kishore/libmac_docs/index.html |
| | 8 | |
| | 9 | List of libmac function used by OTR program: |
| | 10 | * mac_get_ifinfo |
| | 11 | * mac_append_params |
| | 12 | * mac_recv |
| | 13 | |
| | 14 | Some information about Libmac recv interface |
| | 15 | 1. mac_append_params is the function to determine which parameters shouls be reported by the driver |
| | 16 | 1. mac_recv is the "receive" function |
| | 17 | 1. libmac does not use IP address at all |
| | 18 | |
| | 19 | == Gate with LIBMAC support == |
| | 20 | |
| | 21 | At both ends of the OTG-OTR connection, regular sockets are opened. However, at the receiving end, in addition to regular sockets, we could use ''mac_recv'' of Libmac which is also waiting to hear from the interface. Two copies of the incoming frame are made by the kernel for pcap, one of which is given to the application on top of the listening socket and the other to mac_recv. mac_recv, extracts the RSSI value using its regular magic and reports to OML. |
| | 22 | |
| | 23 | To suppport this functionality for various Gate types, I defined LibmacRX class. LibmacRX is an encapsulation of all LIBMAC Related methods to retreiving MAC/PHY parameters. |
| | 24 | I defined three custom Gate classes which inherits the LibmacRX class. |
| | 25 | |
| | 26 | http://www.winlab.rutgers.edu/~zhibinwu/image/classLibmacRX.png |
| | 27 | |
| | 28 | The major purpose to use LibmacRX class is to call mac_recv function to extract some parameters supported by Libmac-customized driver. In order to do this: |
| | 29 | |
| | 30 | Init: |
| | 31 | 1. Get interface information by ''mac_get_ifinfo'' |
| | 32 | 1. finding the wireless dev interface. either by ''pickInterfacebyName'' or ''pickInterfacebyIPAddr'' |
| | 33 | 1. set "dst host" as libpcap filter |
| | 34 | 1. determine whihc PHY/MAC parameters are needed and call ''mac_append_params'' |
| | 35 | |
| | 36 | When packet is received. |
| | 37 | 1. use ''mac_recv'' to fetch parameters one by one. |
| | 38 | |
| | 39 | |
| | 40 | == Rate Conversion == |
| | 41 | This is used only for Intel driver which does not do proper rate mapping from "signal field value" to actual rate value |
| | 42 | {{{ |
| | 43 | short LibmacRX::rateMapping(unsigned short signal_bits) |
| | 44 | { |
| | 45 | short val; |
| | 46 | switch (signal_bits){ |
| | 47 | case 13: val = 60; |
| | 48 | break; |
| | 49 | case 15: val = 90; |
| | 50 | break; |
| | 51 | case 5: val = 120; |
| | 52 | break; |
| | 53 | case 7: val = 180; |
| | 54 | break; |
| | 55 | case 9: val = 240; |
| | 56 | break; |
| | 57 | case 11: val = 360; |
| | 58 | break; |
| | 59 | case 1: val = 480; |
| | 60 | break; |
| | 61 | case 3: val = 540; |
| | 62 | break; |
| | 63 | default: val = (short)signal_bits; |
| | 64 | //for 802.11b , no need to map (10,20,55,110) |
| | 65 | } |
| | 66 | return val; |
| | 67 | } |
| | 68 | |
| | 69 | }}} |
| | 70 | |
