ref: 2149600d129944f60cbc858bc669193af0523409
dir: /sys/src/cmd/ndb/dnudpserver.c/
#include <u.h> #include <libc.h> #include <ip.h> #include "dns.h" enum { Logqueries = 0, }; static int udpannounce(char*); static void reply(int, uchar*, DNSmsg*, Request*); typedef struct Inprogress Inprogress; struct Inprogress { int inuse; Udphdr uh; DN *owner; ushort type; int id; }; Inprogress inprog[Maxactive+2]; typedef struct Forwtarg Forwtarg; struct Forwtarg { char *host; uchar addr[IPaddrlen]; int fd; ulong lastdial; }; Forwtarg forwtarg[10]; int forwtcount; static char *hmsg = "headers"; /* * record client id and ignore retransmissions. * we're still single thread at this point. */ static Inprogress* clientrxmit(DNSmsg *req, uchar *buf) { Inprogress *p, *empty; Udphdr *uh; uh = (Udphdr *)buf; empty = nil; for(p = inprog; p < &inprog[Maxactive]; p++){ if(p->inuse == 0){ if(empty == nil) empty = p; continue; } if(req->id == p->id) if(req->qd->owner == p->owner) if(req->qd->type == p->type) if(memcmp(uh, &p->uh, Udphdrsize) == 0) return nil; } if(empty == nil) return nil; /* shouldn't happen: see slave() & Maxactive def'n */ empty->id = req->id; empty->owner = req->qd->owner; empty->type = req->qd->type; if (empty->type != req->qd->type) dnslog("clientrxmit: bogus req->qd->type %d", req->qd->type); memmove(&empty->uh, uh, Udphdrsize); empty->inuse = 1; return empty; } int addforwtarg(char *host) { Forwtarg *tp; if (forwtcount >= nelem(forwtarg)) { dnslog("too many forwarding targets"); return -1; } tp = forwtarg + forwtcount; if(parseip(tp->addr, host) == -1) { dnslog("can't parse ip %s", host); return -1; } tp->lastdial = time(nil); tp->fd = udpport(mntpt); if (tp->fd < 0) return -1; free(tp->host); tp->host = estrdup(host); forwtcount++; return 0; } /* * fast forwarding of incoming queries to other dns servers. * intended primarily for debugging. */ static void redistrib(uchar *buf, int len) { uchar save[Udphdrsize]; Forwtarg *tp; Udphdr *uh; memmove(save, buf, Udphdrsize); uh = (Udphdr *)buf; for (tp = forwtarg; tp < forwtarg + forwtcount; tp++) if (tp->fd >= 0) { memmove(uh->raddr, tp->addr, sizeof tp->addr); hnputs(uh->rport, 53); /* dns port */ if (write(tp->fd, buf, len) != len) { close(tp->fd); tp->fd = -1; } } else if (tp->host && time(nil) - tp->lastdial > 60) { tp->lastdial = time(nil); tp->fd = udpport(mntpt); } memmove(buf, save, Udphdrsize); } /* * a process to act as a dns server for outside reqeusts */ void dnudpserver(char *mntpt) { volatile int fd, len, op, rcode; char *volatile err; volatile char tname[32]; volatile uchar buf[Udphdrsize + Maxudp + 1024]; volatile DNSmsg reqmsg, repmsg; Inprogress *volatile p; volatile Request req; Udphdr *volatile uh; /* * fork sharing text, data, and bss with parent. * stay in the same note group. */ switch(rfork(RFPROC|RFMEM|RFNOWAIT)){ case -1: break; case 0: break; default: return; } fd = -1; restart: procsetname("udp server announcing"); if(fd >= 0) close(fd); while((fd = udpannounce(mntpt)) < 0) sleep(5000); // procsetname("udp server"); memset(&req, 0, sizeof req); if(setjmp(req.mret)) putactivity(0); req.isslave = 0; req.id = 0; req.aborttime = 0; /* loop on requests */ for(;; putactivity(0)){ procsetname("served %lud udp; %lud alarms", stats.qrecvdudp, stats.alarms); memset(&repmsg, 0, sizeof repmsg); memset(&reqmsg, 0, sizeof reqmsg); alarm(60*1000); len = read(fd, buf, sizeof buf); alarm(0); if(len <= Udphdrsize) goto restart; if(forwtcount > 0) redistrib(buf, len); uh = (Udphdr*)buf; len -= Udphdrsize; // dnslog("read received UDP from %I to %I", // ((Udphdr*)buf)->raddr, ((Udphdr*)buf)->laddr); getactivity(&req, 0); req.aborttime = timems() + Maxreqtm; req.from = smprint("%I", buf); rcode = 0; stats.qrecvdudp++; err = convM2DNS(&buf[Udphdrsize], len, &reqmsg, &rcode); if(err){ /* first bytes in buf are source IP addr */ dnslog("server: input error: %s from %I", err, buf); free(err); goto freereq; } if (rcode == 0) if(reqmsg.qdcount < 1){ dnslog("server: no questions from %I", buf); goto freereq; } else if(reqmsg.flags & Fresp){ dnslog("server: reply not request from %I", buf); goto freereq; } op = reqmsg.flags & Omask; if(op != Oquery && op != Onotify){ dnslog("server: op %d from %I", reqmsg.flags & Omask, buf); goto freereq; } if(reqmsg.qd == nil){ dnslog("server: no question RR from %I", buf); goto freereq; } if(debug || (trace && subsume(trace, reqmsg.qd->owner->name))) dnslog("%d: serve (%I/%d) %d %s %s", req.id, buf, uh->rport[0]<<8 | uh->rport[1], reqmsg.id, reqmsg.qd->owner->name, rrname(reqmsg.qd->type, tname, sizeof tname)); p = clientrxmit(&reqmsg, buf); if(p == nil){ if(debug) dnslog("%d: duplicate", req.id); goto freereq; } if (Logqueries) { RR *rr; for (rr = reqmsg.qd; rr; rr = rr->next) syslog(0, "dnsq", "id %d: (%I/%d) %d %s %s", req.id, buf, uh->rport[0]<<8 | uh->rport[1], reqmsg.id, reqmsg.qd->owner->name, rrname(reqmsg.qd->type, tname, sizeof tname)); } /* loop through each question */ while(reqmsg.qd){ memset(&repmsg, 0, sizeof repmsg); switch(op){ case Oquery: dnserver(&reqmsg, &repmsg, &req, buf, rcode); break; case Onotify: dnnotify(&reqmsg, &repmsg, &req); break; } /* send reply on fd to address in buf's udp hdr */ reply(fd, buf, &repmsg, &req); freeanswers(&repmsg); } p->inuse = 0; freereq: free(req.from); req.from = nil; freeanswers(&reqmsg); if(req.isslave){ putactivity(0); _exits(0); } } } /* * announce on well-known dns udp port and set message style interface */ static int udpannounce(char *mntpt) { int data, ctl; char dir[64], datafile[64+6]; static int whined; /* get a udp port */ sprint(datafile, "%s/udp!*!dns", mntpt); ctl = announce(datafile, dir); if(ctl < 0){ if(!whined++) warning("can't announce on %s", datafile); return -1; } /* turn on header style interface */ if(write(ctl, hmsg, strlen(hmsg)) != strlen(hmsg)){ close(ctl); if(!whined++) warning("can't enable headers on %s", datafile); return -1; } snprint(datafile, sizeof(datafile), "%s/data", dir); data = open(datafile, ORDWR); if(data < 0){ close(ctl); if(!whined++) warning("can't open %s to announce on dns udp port", datafile); return -1; } close(ctl); return data; } static void reply(int fd, uchar *buf, DNSmsg *rep, Request *reqp) { int len; char tname[32]; if(debug || (trace && subsume(trace, rep->qd->owner->name))) dnslog("%d: reply (%I/%d) %d %s %s qd %R an %R ns %R ar %R", reqp->id, buf, buf[4]<<8 | buf[5], rep->id, rep->qd->owner->name, rrname(rep->qd->type, tname, sizeof tname), rep->qd, rep->an, rep->ns, rep->ar); len = convDNS2M(rep, &buf[Udphdrsize], Maxudp); len += Udphdrsize; if(write(fd, buf, len) != len) dnslog("error sending reply: %r"); }