Difference between revisions of "Bus snooping/sniffing"

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==External Links==
 
==External Links==
 
* [[Wikipedia:Bus sniffing|Wikipedia's Bus sniffing article]]; note that the [[Wikipedia:Cache coherency|Cache coherency]] article is a probably a little less vague or more enlightening
 
* [[Wikipedia:Bus sniffing|Wikipedia's Bus sniffing article]]; note that the [[Wikipedia:Cache coherency|Cache coherency]] article is a probably a little less vague or more enlightening
 +
[[Category:Development]]

Revision as of 01:06, 3 May 2009

Purpose and relevance to development work -- description coming soon

PCI / PCIe

Snooping Utilities:

USB

Snooping Utilities:

  • usbsnoop - a Windows based utility for sniffing/monitoring communications traffic for a USB device. Note: In case usbsnoop/SniffUSB doesn't work for you, here are a few time limited apps that should work under Vista:
  • SnoopyPro - Windows based snoop for USB device communications traffic
  • usbsnoop/SniffUSB - Windows based snoop for USB device communications traffic
  • usbmon - Linux kernel module which can snoop USB device communications traffic
    • Wireshark - logs usbmon output, via libpcap
    • USBMon - logs usbmon output

Log parsers, format etc

...

Snooping Procedures:

  • Use a Snopping utility to get the log.
  • Group URB transactions into a shorter log by using a parser
  • Identify the URB transactions at the control endpoint. URB transactions look like those:

40 02 00 00 ba 00 03 00 >>> 20 11 00

URB fields
Byte Meaning
1 bit 7 = 1 - IN / 0 - OUT

bit 6 = 1 - Vendor Class

2 URB Request
3-4 URB Value in big endian
5-6 URB Index in big endian
7-8 URB message size in big endian

For example, let's analyse the folowing URB's:

control URB examples
URB sequence log (URB setup + URB IN or OUT) Byte 1 Byte 2 Bytes 3-4 Bytes 5-6 Bytes 7-8 Message
40 00 00 00 08 00 01 00 >>> 3d USB OUT, Vendor Class Req = 0x00 Value = 0x0000 Index = 0x0008 Size = 0x0001 { 0x3d }
40 02 00 00 ba 00 03 00 >>> 20 11 00 USB OUT, Vendor Class Req = 0x02 Value = 0x0000 Index = 0x00ba Size = 0x0003 { 0x20, 0x11, 0x00 }
c0 00 00 00 15 00 01 00 <<< 00 USB IN, Vendor Class Req = 0x00 Value = 0x0000 Index = 0x0015 Size = 0x0001 { 0x00 }


After getting the log, you should analyse and understand the meaning of each of URB fields on your device.

For example, in the case of em28xx, Req is used to indicate internal registers or I2C, Value is always 0 and Index indicates what device register is being used.

On em28xx, the [em28xx log parser] could be used in order to proccess the URBs and the driver dmesg dumps (in the compact format as shown above) and print them into a more human way, generating C like statements that can be added at em28xx source code (with a few adaptations, in the case of i2c messages):

 em28xx_write_reg(dev, EM28XX_R08_GPIO, 0x3d);
 i2c_master_send(0xba>>1, { 20 11 00  }, 0x03);
 em28xx_read_reg(dev, EM28XX_R15_RGAIN);         /* read 0x00 */

Command Playback Utilities:

  • usb-robot - plays back USB Snoopy capture logs
  • usbreplay - plays back usbsnoop capture logs

i2c

External Links