O/H Nick Kossifidis έγραψε:
Hello ppl ;-) Exw kairo na sas grapsw gia tis ekselikseis sto linux pou aforoun to kommati twn wireless drivers kai tou 802.11 protocol stack alla trexw me diafora. Τon Ioulio pou perase eixame to kathieromeno mas summit sto Berolino sta plaisia tou FudCon/LinuxTag 2009 kai htan ap' ta pleon paragogika summits ths omadas. Ayth th fora hmastan poio organomenoi kai etsi exoume ftiaksei mia selida sto wiki opou mporeite na katevasete tis diafores parousiaseis (sth diathesh sas an xreiasteite kapoia dieykrinish) , th selida mporeite na th vreite sto http://wireless.kernel.org/en/developers/Summits/Berlin-2009 Gia osous endiafereste akolouthei katevato :P Power saving -------------------- Eixame ektenh syzhthsh gia to power saving kai tis diafores texnikes pou xrhsimopoiountai kai o Kale mas edeikse pws oi diafores methodoi epirreazoun to power consumption sta chipakia twn Nokia (epeidh paizoun se kinhta exoun dwsei poly varos sto power saving, th parousiash tha th vreite sto parapanw link). To power saving genikws einai arketa endiaferon thema kai sxetizetai me diaforous timers pou vriskontai sthn karta kai sygxronizontai me to TSF (Time Sync Factor) pou vlepete sto scan. To TSF loipon vrisketai se kathe beacon pou stelnei to AP h to kathe IBSS (ad-hoc) node. Oloi oi clients sygronizontai (exei 64bit resolution) kai katopin xrhsimopoioun tous timers gia na ksypnane kai na koimountai (perissoteres plhrofories edw -> http://wireless.kernel.org/en/developers/Documentation/ieee80211/power-savings). Info: To TSF epishs xrhsimopoieitai sto IBSS gia na kathorizetai poios ksekinhse to IBSS cell afou opoios ksekinhsei prwtos ena IBSS diktyo exei metalytero TSF ap' tous ypoloipous kai ara oi ypoloipoi kanoun join to sygekrimeno cell (yiothetoun to IBSS id tou) anti na kanoun create to diko tous. Mac80211 --------------- Syzhtisame arketa to thema tou roaming kai diaforwn extensions pou yparxoun (oxi mono to 802.11r dld). Arxika xreiazomaste enan kalo algorithmo gia bg scan kai kapoia metrics gia na apofasizoume se poio AP tha pesoume, proteiname to signal strength pou einai to profanes alla epipleon proteina mazi me kapoia alla paidia na kratame ena packet loss count isws se synergasia me ton rate control algorithmo (afou krataei ayta ta stats outws h allws gia na dialeksei rate). Milwntas gia rate control fainetai oti o minstrel pou exoume ayth th stigmh ws default algoritmo einai poly varys gia embedded systhmata kai fainetai pws exoume kanei kapoia patata giati ston madwifi de shkwnei toso load (yparxoun kapoia patches apo tote kai genikws to psaxnoume). Epishs o minstrel den einai ftiagmenos gia 802.11n rates, syzhtisame to endexomeno na ton kanoume extend (thelei omws arketh douleia) etsi wste na xrhsimopoioume enan generic algorithmo kai na mhn xrhsimopoioume vendor-specific algorithmous opws ginetai ston ath9k h stous drivers ths intel klp. Telos symfwnisame oti to rate control prepei na perilamvanei kai to multicast traffic (oxi ta beacons ennoeitai afou afta stelnontai sto basic rate) gia na einai poio apodotikos. cfg80211/nl80211 -------------------------- Opws sas exw pei kai sta prohgoumena post skopos mas einai na ksefortothoume ta wireless extensions kai na doulevoume apokleistika me to kainourio api (cfg80211) pou xrhsimopoiei ena custom netlink socket (nl80211) kai oxi ta deprecated ioctl calls. Mexri twra loipon mas eleipan kapoies vasikes leitourgies me poio vasikh thn entolh connect dld na orizeis ena essid px. kai na les sto protocol stack na kanei join ayto to BSS network (px. iwconfig wlan0 essid <tade>) kai thn antistoixh entolh gia na kaneis join/create ena IBSS network (ypenthimizw pws gia na sthseis AP xreiazetai o hostapd afou tis leitourgies tou AP tis kanoume handle sto userspace). Prosfata loipon oloklhrwthike h ylopoihsh twn parapanw opote mporeite na xrhsimopoieisete to cfg80211 gia na kanete sxedon ta panta pleon me to ergaleio iw. Mporeite dhladh osoi xrhsimopoieite kapoion ap' tous kainourious mac80211-based drivers na petaksete ta wireless-tools kai na xrhsimopoieitai to iw ! Ta teleytaia bits pou leipoun ap to cfg80211 kai kata synepeia to iw einai to na mporeis na theteis rate (iwconfig wlan0 rate <tade>), tx power kai na mporeis na vlepeis to status (iwconfig wlan0) - to opoio omws mporeis na to deis me dmesg an kaneis enable ta vasika debug features tou mac80211/cfg80211 sto kernel config. Gia to rate control API arxika skefthkame na orizoume oxi ena memonomeno rate opws twra alla ena rate bitmask, etsi wste na mporoume na poume ston rate contorl algorithmo na perioristei se sygekrimena rates (px. na tou poume na paizei mono sta 18-38Mbit) kai profanws an theloume na kleidwsei se ena mono rate afinoume sto bitmask mono ayto to rate (opote einai to idio pragma me to yparxon iwconfig wlan0 rate <tade>). Ayto einai arketa poio evelikto kai tha mporei na perilamvanei kai ta ht rates (802.11n) pou to iwconfig (wireless extensions API) den ypostirizei. Epishs eipame na exoume enan tropo na mporei o xrhsths na dialeksei metaksy twn diaforetikwn (px. vendor-specific) rate control algorithmwn kai etsi na yparxei akoma megalyterh eveliksia. Me aformh ta diafora private extensions pou yparxoun sta wireless extensions (kai ta kaneis get/set me to iwpriv) syzhtisame kapoia common pragmata pou tha mporousame na thetoume epipleon kai den yparxoun ayth th stigmh sto API (oute sto iwconfig oute sto iw). Katalhksame sto antenna setting gia arxh, opote kapoia stigmh tha deite sto iw th dynatothta na orisete rx/tx antenna opws px. kanate ston madwifi me ta /proc h iwpriv settings. Epishs eipame oti genikws den tha ypostiriksoume vendor-specific pragmata giati theloume na kratisoume to API kai to protocol stack katharo alla sthn extreme periptwsh pou kapoios thelei na ylopoihsh kapoia entolh pou einai hw/driver specific (px. to turbo mode stis Atheros) tha exoume kati stan to iwpriv alla mesw nl80211. Ayto to kati to onomasame test mode kai prokeitai gia mia generic entolh sto nl80211 pou mporoun na xrhsimopoihsoun oi developers gia na perasoun parametrous ston driver (me kapoio diko tous tool isws). Genikws pantws eipame oti tha kratisoume oso to dynaton makrya ta vendor specific/proprietary extensions. Oson afora px. ton ath5k apofasisame oti leitourgies opws to XR h to dynamic turbo den tha tis kanoume support, enw alles leitourgies opws to compression tha tis doume isws mesw tou test mode (alla xwris information elements sta beacons -IEs-, dld tha einai h enabled gia olous h disabled gia olous, den tha yparxei plhroforia sto beacon gia handling per-client klp). Gia ta fast frames epese h protash na kanoume ena standards-compliant msdu aggregation (oxi dld to proprietary fast frames aggregation ths Atheros) gia olous tous drivers, opote kai tha akolouthoume to protypo kai tha exoun oloi oi drivers kerdos apo ayto sto performance (arkei na mporoun na steiloun megala frames sto hw). Telos apofasisame na katarghsoume to noise reporting giati gia to protocol stack einai axristo kai sth pragmatikothta den yparxei kapoios standard tropos na metrhseis to noise (ousiastika osoi to metrame -px ston ath5k- metrame px. to noise floor ths kartas h kati antistoixo, den yparxei dld kapoios standard tropos na metriseis to noise sto kanali -to utilization ap thn allh mporeis na to metrhseis kai einai arketa xrhsimo alla out of scope gia thn wra-), eks allou to signal strength pou kanoun report oi kartes lamvanei ypopsh to noise (einai dbm panw ap' to thoryvo h kati antistoixo). Mexri loipon na vroume kapoio standard tropo na kanoume handle to noise kai ena logo gia na to xrhsimopoihsoume to petame ap' to API kai o kathe driver mporei na to xrhismopoiei internaly (opws kanoume px. ston ath5k/ath9k gia to calibration). Na kserete epishs oti to signal quality pou vlepete sto iwconfig kai to network manager einai psilomoufa kai apla xrhsimopoioume ena linear maping me to singal strength, gia na peite kati gia to quality prepei na kserete kai alla xarakthristika (px. to sensitivity ths kartas). Sth kalyterh periptwsh na exoume kapoia oria ap' ton vendor pou syndeoun to signal strength me to rate (px. mas leei o x vendor oti apo -68 kai panw h karta kleidwnei sta 54M opote px. kanoume report 100% link quality). Ekselikseis sto 802.11 --------------------------------- Eixame mia analytikh parousiash ap' ton Jouni gia tis ekselikseis sthn IEEE kai ta drafts pou erxontai kathos kai tis allages pou prepei na kanoume sto protocol stack gia na tis akolouthisoume. Gia leptomereies thn parousiash tou Jouni mporeite na th vreite ki ayth sto wiki (http://wireless.kernel.org/en/developers/Summits/Berlin-2009?action=AttachFile&do=view&target=ieee80211-activity.pdf), epigramatika anaferw oti exoume kainouries protaseis gia gigabit asyrmata diktya (wide band kata kyrio logo), to 802.11s (to mesh pou isws na gnwrizete ap' to OLPC) exei kolhsei kai o chairman ths epitrophs paraiththike (to draft mexri twra exei sovara provlhmata) enw yparxoun anhsyxies oti paei gia founto, exoume mia protash gia extension sto protokolo gia p2p links (dhladh oxi topologia BSS h IBSS alla mia nea topologia optimized gia point to point links) kai polla alla endiaferonta (de synexizw giati sas exw hdh priksei :P). Ws synhthws an exete kapoia aporia h thelete kapoia dieykrinhsh eimai sth diathesh sas. Elpizw na "paizoun" kala oi wireless drivers kai na eiste eyxaristhmenoi apo to olo project ;-)
eyxaristw gia to vathos ths enhmerwshs (keep it up) y.c.