accf_nameaccept

AcceptFiltersMikeSilbersackAcceptFilters:RationaleAcceptfiltersservetoreducethenumberofunnecessarywakeupsatypicalserverwillsee.
–Socketsarenotpassedtotheapplicationviaaccept()untiltheacceptfilter'scriteriahasbeenmet.
AcceptfiltersshippedwithFreeBSD:–accf_data:Anydataisreceivedonthesocket.
–accf_http:AhttpHEADorGETrequesthasbeenreceivedonthesocket.
IfastringnotstartingwithGorHisdetected,thesocketisimmediatelyhandedtotheapplication.
Otheracceptfilterideas:–Afilterthatemitsabanner–Wouldanacceptandread()syscallbeusefulAcceptFilters:TheAPIstructaccept_filter{characcf_name[16];void(*accf_callback)(structsocket*so,void*arg,intwaitflag);void*(*accf_create)(structsocket*so,char*arg);void(*accf_destroy)(structsocket*so);SLIST_ENTRY(accept_filter)accf_next;/*nextonthelist*/};accf_dataandaccf_httpuseonlyaccf_callback.
accf_createandaccf_destroymaynotbewelltested.
Filterscanbedynamicallyloaded.
Dynamicunloadcanbeenabled,butitwillprobablybreakyoursystem.
Acceptfilters:uipc_accf.
cHandlesloadingandunloadingofacceptfiltermodules,enablinganddisablingofacceptfilterspersocket.
Note:accept_filter_mtx.
Thisisusedonlytosynchronizeloadingandunloadingoffiltermodules,notforanyruntimelockingofacceptfilters.
AcceptFilters:hooksintothesocketlayeruipc_socket.
c:–sosetoptandsogetoptallowprogramstoset/getthestatusofacceptfilteringonasocket.
sodeallocremovesacceptfiltersduringsocketdestruction.
–soisconnectediscalledwhenthe3WHScompletesIfnoacceptfiltering,thesocketismovedfromso_incomptoso_compIfacceptfilteringisenabled,thesocketcontinuestoliveonso_incomp.
so_upcallandSB_UPCALLaresetforthatsocket.
so_upcalliscalled.
–Keepingthesocketonso_incompisprobablyamistake,duetohowwehandleincompoverflowsinsonewconn.
Overflowsduetowaitingonacceptfilteringshouldprobablybekickeduptotheapplicationratherthandropped.
–sowakeupwillcallso_upcallwhennewdataarrivesifSB_UPCALLisset.
AcceptFilters:accf_data.
cSimple,yeteffective.
staticvoidsohasdata(structsocket*so,void*arg,intwaitflag){if(!
soreadable(so))return;so->so_upcall=NULL;so->so_rcv.
sb_flags&=~SB_UPCALL;soisconnected(so);return;}AcceptFilters:accf_http.
csohashttpgethandlesparsingtheincomingdata.
–EarlyexitifthestringdoesnotstartwithGorH–Notimeoutmechanism,someIISwormsdonottriggerthecompletioncriteriaandgetstuckinhere.