ref: 733c5d6645b133b60d304c38fcb1398f94d0618c
dir: /sys/src/cmd/ndb/dnserver.c/
#include <u.h> #include <libc.h> #include <ip.h> #include "dns.h" static RR* doextquery(DNSmsg*, Request*, int); static void hint(RR**, RR*); /* * answer a dns request */ void dnserver(DNSmsg *reqp, DNSmsg *repp, Request *req, uchar *srcip, int rcode) { char tname[32], *cp; DN *nsdp; Area *myarea; RR *rp, *neg; repp->id = reqp->id; repp->flags = Fresp | (reqp->flags & Omask); setercode(repp, Rok); /* move one question from reqp to repp */ rp = reqp->qd; reqp->qd = rp->next; rp->next = nil; repp->qd = rp; if(rcode != Rok || (reqp->flags & Omask) != Oquery){ dnslog("%d: server: response code %d %s, req from %I", req->id, rcode, rcname(rcode), srcip); /* provide feedback to clients who send us trash */ setercode(repp, rcode); return; } if(repp->qd->type == Topt || !rrsupported(repp->qd->type)){ if(debug) dnslog("%d: server: unsupported request %s from %I", req->id, rrname(repp->qd->type, tname, sizeof tname), srcip); setercode(repp, Runimplimented); return; } if(repp->qd->owner->class != Cin){ if(debug) dnslog("%d: server: unsupported class %d from %I", req->id, repp->qd->owner->class, srcip); setercode(repp, Runimplimented); return; } myarea = inmyarea(repp->qd->owner->name); if(myarea){ if(repp->qd->type == Tixfr || repp->qd->type == Taxfr){ if(debug) dnslog("%d: server: unsupported xfr request %s for %s from %I", req->id, rrname(repp->qd->type, tname, sizeof tname), repp->qd->owner->name, srcip); setercode(repp, Runimplimented); return; } repp->flags |= Fauth; neg = doextquery(repp, req, Dontrecurse); } else { if(cfg.nonrecursive || cfg.localrecursive && !localip(srcip)){ /* we don't recurse and we're not authoritative */ neg = nil; } else { repp->flags |= Fcanrec; if(reqp->flags & Frecurse){ neg = doextquery(repp, req, Recurse); /* pass on error codes */ if(repp->an == nil && repp->qd->owner->rr == nil){ repp->flags |= Fauth; setercode(repp, repp->qd->owner->respcode); } } else neg = doextquery(repp, req, Dontrecurse); /* authority is transitive */ if(repp->an && repp->an->auth) repp->flags |= Fauth; } /* * add name server if we know */ for(cp = repp->qd->owner->name; cp; cp = walkup(cp)){ nsdp = dnlookup(cp, repp->qd->owner->class, 0); if(nsdp == nil) continue; repp->ns = rrlookup(nsdp, Tns, OKneg); if(repp->ns){ /* don't pass on anything we know is wrong */ if(repp->ns->negative){ rp = repp->ns; repp->ns = nil; rrfreelist(rp); } break; } repp->ns = dblookup(cp, repp->qd->owner->class, Tns, 0, 0); if(repp->ns) break; } } /* * add ip addresses as hints */ if(repp->qd->type != Taxfr && repp->qd->type != Tixfr){ for(rp = repp->ns; rp; rp = rp->next) hint(&repp->ar, rp); for(rp = repp->an; rp; rp = rp->next) hint(&repp->ar, rp); } /* * add an soa to the authority section to help client * with negative caching */ if(repp->an == nil){ if(myarea){ rrcopy(myarea->soarr, &rp); rrcat(&repp->ns, rp); } else if(neg != nil) { if(neg->negsoaowner != nil) { rp = rrlookup(neg->negsoaowner, Tsoa, NOneg); rrcat(&repp->ns, rp); } setercode(repp, neg->negrcode); } } /* * get rid of duplicates */ unique(repp->an); unique(repp->ns); unique(repp->ar); rrfreelist(neg); } /* * satisfy a recursive request. dnlookup will handle cnames. */ static RR* doextquery(DNSmsg *mp, Request *req, int recurse) { ushort type; char *name; RR *rp, *neg; name = mp->qd->owner->name; type = mp->qd->type; rp = dnresolve(name, Cin, type, req, &mp->an, 0, recurse, 1, nil); /* don't return soa hints as answers, it's wrong */ if(rp && rp->db && !rp->auth && rp->type == Tsoa) { rrfreelist(rp); rp = nil; } /* don't let negative cached entries escape */ neg = rrremneg(&rp); rrcat(&mp->an, rp); return neg; } static void hint(RR **last, RR *rp) { RR *hp; switch(rp->type){ case Tns: case Tmx: case Tmb: case Tmf: case Tmd: hp = rrlookup(rp->host, Ta, NOneg); if(hp == nil) hp = dblookup(rp->host->name, Cin, Ta, 0, 0); if(hp == nil) hp = rrlookup(rp->host, Taaaa, NOneg); if(hp == nil) hp = dblookup(rp->host->name, Cin, Taaaa, 0, 0); if (hp && strncmp(hp->owner->name, "local#", 6) == 0) dnslog("returning %s as hint", hp->owner->name); rrcat(last, hp); break; } }