CAN的安全隱患ppt課件

1、CAN的平安隱患An Undiscovered Safety Related Fault in CAN-消極報(bào)錯(cuò)節(jié)點(diǎn)不能正常收發(fā)Real bus off state of error passive node楊福宇 Fuyu Yang:yfy812163援用的規(guī)范援用的規(guī)范lISO/TC 22/SC3. International standard: ISO -11898-1, 2003,Road Vehicles-Controller Area Network (CAN) part1: Data link layer and physical signalinglISO/TC 22/SC3.

2、 International standard: ISO 16845, 2004 Road Vehicles-Controller Area Network (CAN)-Conformance test plan lRobert Bosch GmbH. CAN Specification Version 2.0, September 1991問題的根源在規(guī)范一問題的根源在規(guī)范一l In order to terminate an ERROR FRAME correctly, an error passive node may need the bus to be bus idle for at

3、 least 3 bit times (if there is a local error at an error passive receiver). Therefore the bus should not be loaded to 100%. -Bosch CAN 2.0A 3.1.3l即使負(fù)載率小，也無法保證3bit總線空閑問題的根源在規(guī)范二問題的根源在規(guī)范二l“A message, which is pending for transmission during the transmission of another message, is started in the first

4、bit following INTERMISSION. l最壞的情況是一切的音訊都掛起在那里等待發(fā)送問題的根源在規(guī)范三問題的根源在規(guī)范三消極報(bào)錯(cuò)幀分界符的長(zhǎng)度是消極報(bào)錯(cuò)幀分界符的長(zhǎng)度是8位隱位位隱位消極報(bào)錯(cuò)幀分界符內(nèi)的顯位是格式錯(cuò)，它要引起消極報(bào)錯(cuò)幀分界符內(nèi)的顯位是格式錯(cuò)，它要引起新的消極報(bào)錯(cuò)幀新的消極報(bào)錯(cuò)幀ISO 16845 :7.5.6 Form error in passive error delimiter (receiver)ISO 16845 :8.5.13 Form error in passive error delimiter (transmitter)7.5.6內(nèi)容內(nèi)容8.

5、5.13一樣一樣l7.5.6.1 Purpose and limits of test casel測(cè)試設(shè)備將報(bào)錯(cuò)分界符的8個(gè)隱位之一用顯位替代 The LT replace one of the eight recessive bits of the error delimiter by a dominant bit. l7.5.6.2 Test case organizationl 在接納報(bào)錯(cuò)分界符時(shí)測(cè)試設(shè)備按7.5.6.1款制造一個(gè)格式錯(cuò)，然后等6+7位再送一個(gè)顯位破壞報(bào)錯(cuò)分界符的最后一位，被測(cè)設(shè)備在測(cè)試設(shè)備送的最后一個(gè)顯位后開場(chǎng)一個(gè)過載幀During the reception of t

6、he error delimiter, the LT creates a form error according to 7.5.6.1.l After creating the form error, the LT waits for (6+7) bit time before sending a dominant bit, corrupting the last bit of the error delimiter. l The IUT shall generate an overload frame starting at the position following the last

7、dominant bit sent by LT.能夠呵斥此類缺點(diǎn)的情況超越能夠呵斥此類缺點(diǎn)的情況超越Bosch估計(jì)估計(jì)l消極報(bào)錯(cuò)接納節(jié)點(diǎn)的本地缺點(diǎn)引起消極報(bào)錯(cuò)接納節(jié)點(diǎn)的本地缺點(diǎn)引起B(yǎng)oschBosch提提到到l消極報(bào)錯(cuò)發(fā)送節(jié)點(diǎn)的本地缺點(diǎn)引起消極報(bào)錯(cuò)發(fā)送節(jié)點(diǎn)的本地缺點(diǎn)引起l偶爾自動(dòng)報(bào)錯(cuò)節(jié)點(diǎn)的本地缺點(diǎn)引起偶爾自動(dòng)報(bào)錯(cuò)節(jié)點(diǎn)的本地缺點(diǎn)引起l防止缺點(diǎn)要求的空閑時(shí)間要更多防止缺點(diǎn)要求的空閑時(shí)間要更多(10 bit (10 bit 而不而不是是3 bit)3 bit)出錯(cuò)情況舉例出錯(cuò)情況舉例l消極報(bào)錯(cuò)接納節(jié)點(diǎn)因本地缺點(diǎn)如干擾有誤判消極報(bào)錯(cuò)接納節(jié)點(diǎn)因本地缺點(diǎn)如干擾有誤判時(shí)時(shí)C R CRI. MP. E. D

8、eloverl appi ngError foundA C KnoFl ag8354D 7N ew Fram ePassi ve ErrorError foundN ew Error FoundSO FEO FError passi ve nodeError acti ve nodeD R R R R R R R RLocal faul t i n error passi ve recei cer Fi gure 1出錯(cuò)情況舉例出錯(cuò)情況舉例 消極報(bào)錯(cuò)接納節(jié)點(diǎn)有一次漏判時(shí)消極報(bào)錯(cuò)接納節(jié)點(diǎn)有一次漏判時(shí)7D4 538BBI. MP. E. Fl agP. E. D elA . E. D elA .

9、E. Fl agRRRRRRRRDDDDDDError acti ve nodeError passi ve nodeError FoundSO FN ew Error FoundError foundN ew Fram eG l obal bi t stuffi ng error wi th l ocal faul t i n error passi ve recei cer Fi gure 2出錯(cuò)情況舉例出錯(cuò)情況舉例l消極報(bào)錯(cuò)接納節(jié)點(diǎn)誤判發(fā)生在消極報(bào)錯(cuò)接納節(jié)點(diǎn)誤判發(fā)生在EOFEOF域，至少域，至少10bit10bit總線空閑才干使它與其它節(jié)點(diǎn)同步總線空閑才干使它與其它節(jié)點(diǎn)同步P. E. F

10、ram eC R CDRRR R R DR R R R R R RSO Fnew fram eB B B B654321EO FForm Error foundA C KError acti ve nodeserror not foundI. M .BBEO FA C KBBFi gure 3 Local faul t i n error passi ve recei ver onl y出錯(cuò)情況舉例出錯(cuò)情況舉例l消極報(bào)錯(cuò)發(fā)送節(jié)點(diǎn)誤判消極報(bào)錯(cuò)發(fā)送節(jié)點(diǎn)誤判ACKACK位位I. M .BBBBnew fram eSO FRRRRRRRfoundA C K ErrorP. E. D elDRRRRR

11、RC R CP. E. Fl agB BA C KEO FB BI. M .Error acti ve nodeserror not foundfoundForm ErrorFi gure 4出錯(cuò)情況舉例出錯(cuò)情況舉例l消極報(bào)錯(cuò)發(fā)送節(jié)點(diǎn)在消極報(bào)錯(cuò)發(fā)送節(jié)點(diǎn)在CRCCRC分界符處誤判分界符處誤判foundForm ErrorError acti ve nodeserror not foundI. M .BBEO FA C KBBP. E. Fl agC R CDDRR R R DP. E. D elForm Error foundR R R R R R RSO Fnew fram eB B B BI

12、. M .Fi gure 5 Local faul t of error passi ve transm i tter onl y出錯(cuò)情況舉例出錯(cuò)情況舉例l消極報(bào)錯(cuò)發(fā)送節(jié)點(diǎn)在消極報(bào)錯(cuò)發(fā)送節(jié)點(diǎn)在ACKACK分界符有誤判分界符有誤判BBBBnew fram eSO FRRRRRRRfoundForm ErrorP. E. D elDRRRDR DC R CP. E. Fl agB BA C KEO FB BI. M .Error acti ve nodeserror not foundA C KfoundForm ErrorLocal faul t of error passi ve transm

13、 i tter onl yFi gure 6出錯(cuò)情況舉例出錯(cuò)情況舉例l當(dāng)系統(tǒng)小，只留下一個(gè)自動(dòng)報(bào)錯(cuò)節(jié)點(diǎn)時(shí)，它的誤判引起消極報(bào)錯(cuò)節(jié)點(diǎn)不同步A . E. D elA . E. Fl agR R RRRRRDnew fram eSO FRDDDDDDRRRI. M .BError acti ve nodeerror foundP. E. Fl agP. E. D elI. M .Error foundFi gure 7 l ocal faul t i n error acti ve node causes fai l ure i n error passi ve node.總的出錯(cuò)情況總的出錯(cuò)情況l

14、出錯(cuò)后消極報(bào)錯(cuò)節(jié)點(diǎn)與其它節(jié)點(diǎn)同步的情況有很多l(xiāng)出錯(cuò)情況呵斥消極報(bào)錯(cuò)節(jié)點(diǎn)不同步的例子還有很多消極報(bào)錯(cuò)節(jié)點(diǎn)不同步后續(xù)情形一o新幀中有全局錯(cuò)，節(jié)點(diǎn)在自動(dòng)報(bào)錯(cuò)幀終了時(shí)同新幀中有全局錯(cuò)，節(jié)點(diǎn)在自動(dòng)報(bào)錯(cuò)幀終了時(shí)同步步o延續(xù)出錯(cuò)的概率小，意味著此種情況概率小延續(xù)出錯(cuò)的概率小，意味著此種情況概率小Error foundA l l Error acti ve node B D D D D D D R RRRR R R RFi g. 8a)P. E. D elA . E. Fl agA . E. D elBB BBBI. MError foundError passi ve nodeN ew fram eover

15、l appi ngFl agPassi ve ErrorP. E. D elDSO FError passi ve node i s synchroni zed at an acti ve error fram eSO FN ew Fram e消極報(bào)錯(cuò)節(jié)點(diǎn)不同步后續(xù)情形二o新幀終了后空閑時(shí)間足夠長(zhǎng)后同步新幀終了后空閑時(shí)間足夠長(zhǎng)后同步o這是事件觸發(fā)協(xié)議無法保證的這是事件觸發(fā)協(xié)議無法保證的N ew fram eRI. MP. E . D eloverl appi ngE rror foundA C KnoFl ag8354D7B us Idl ePassi ve E rrorE rror foundSO FE O FE rror passi ve nodeE rror acti ve nodeD R R R R R R R RFi g. 8b)E rror passi ve node i s synchroni zed at bus i dl e ti m eP. E . D elSO FDO verl oad fram e requestM i n.6I. M消極報(bào)錯(cuò)節(jié)點(diǎn)不同步后續(xù)情形三o新幀正常終了后又有新幀新幀正常終了后又有新幀o只需掛起幀未送完，消極報(bào)錯(cuò)節(jié)點(diǎn)就不斷錯(cuò)只需掛起幀未送完，消極報(bào)錯(cuò)節(jié)點(diǎn)就不斷錯(cuò)Erro