ref: 733c5d6645b133b60d304c38fcb1398f94d0618c
dir: /sys/src/cmd/ndb/dnudpserver.c/
#include <u.h> #include <libc.h> #include <ip.h> #include "dns.h" static int udpannounce(char*, char*); static void reply(int, uchar*, int, DNSmsg*, Request*); typedef struct Inprogress Inprogress; struct Inprogress { int inuse; Udphdr uh; DN *owner; ushort type; ushort id; }; static Inprogress inprog[Maxactive+2]; /* * record client id and ignore retransmissions. * we're still single thread at this point. */ static Inprogress* clientrxmit(DNSmsg *mp, Udphdr *uh, Request *req) { Inprogress *p, *empty; empty = nil; for(p = inprog; p < &inprog[Maxactive]; p++){ if(p->inuse == 0){ if(empty == nil) empty = p; continue; } if(mp->id == p->id) if(mp->qd->owner == p->owner) if(mp->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 = mp->id; empty->owner = mp->qd->owner; empty->type = mp->qd->type; if(empty->type != mp->qd->type) dnslog("%d: clientrxmit: bogus req->qd->type %d", req->id, mp->qd->type); memmove(&empty->uh, uh, Udphdrsize); empty->inuse = 1; return empty; } /* * a process to act as a dns server for outside reqeusts */ void dnudpserver(char *mntpt, char *addr) { volatile int fd, len, op, rcode, served; char *volatile err; volatile char caller[64]; volatile uchar pkt[Udphdrsize + Maxudp]; volatile DNSmsg reqmsg, repmsg; Inprogress *volatile p; volatile RR *edns; 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; } served = 0; restart: procsetname("%s: udp server announcing %s", mntpt, addr); if((fd = udpannounce(mntpt, addr)) < 0){ warning("can't announce %s on %s: %r", addr, mntpt); do { sleep(5000); } while((fd = udpannounce(mntpt, addr)) < 0); } memset(&req, 0, sizeof req); setjmp(req.mret); req.isslave = 0; /* loop on requests */ for(;; putactivity(&req)){ memset(&reqmsg, 0, sizeof reqmsg); edns = nil; procsetname("%s: udp server %s: served %d", mntpt, addr, served); len = read(fd, pkt, sizeof pkt); if(len <= Udphdrsize){ close(fd); goto restart; } uh = (Udphdr*)pkt; len -= Udphdrsize; snprint(caller, sizeof(caller), "%I", uh->raddr); getactivity(&req); req.aborttime = timems() + Maxreqtm; req.from = caller; served++; stats.qrecvdudp++; rcode = Rok; err = convM2DNS(&pkt[Udphdrsize], len, &reqmsg, &rcode); if(err){ /* first bytes in buf are source IP addr */ dnslog("%d: server: input err, len %d: %s from %s", req.id, len, err, caller); free(err); goto freereq; } if(rcode == Rok) if(reqmsg.qdcount < 1){ dnslog("%d: server: no questions from %s", req.id, caller); goto freereq; } else if(reqmsg.flags & Fresp){ dnslog("%d: server: reply not request from %s", req.id, caller); goto freereq; } op = reqmsg.flags & Omask; if(op != Oquery && op != Onotify){ dnslog("%d: server: op %d from %s", req.id, reqmsg.flags & Omask, caller); goto freereq; } if(reqmsg.qd == nil){ dnslog("%d: server: no question RR from %s", req.id, caller); goto freereq; } p = clientrxmit(&reqmsg, uh, &req); if(p == nil) goto freereq; logrequest(req.id, 0, "rcvd", uh->raddr, caller, reqmsg.qd->owner->name, reqmsg.qd->type); /* determine response size */ len = 512; /* default */ if(rcode == Rok) if((reqmsg.edns = getednsopt(&reqmsg, &rcode)) != nil){ edns = mkednsopt(); len = Maxudp; if(edns->udpsize < len) len = edns->udpsize; if(reqmsg.edns->udpsize < len) len = reqmsg.edns->udpsize; } /* loop through each question */ while(reqmsg.qd){ memset(&repmsg, 0, sizeof repmsg); repmsg.edns = edns; if(rcode == Rok && op == Onotify) dnnotify(&reqmsg, &repmsg, &req); else dnserver(&reqmsg, &repmsg, &req, uh->raddr, rcode); reply(fd, pkt, len, &repmsg, &req); freeanswers(&repmsg); } rrfreelist(edns); p->inuse = 0; freereq: rrfreelist(reqmsg.edns); freeanswers(&reqmsg); if(req.isslave){ putactivity(&req); _exits(0); } } } static void reply(int fd, uchar *pkt, int len, DNSmsg *rep, Request *req) { logreply(req->id, "send", pkt, rep); len = convDNS2M(rep, &pkt[Udphdrsize], len); len += Udphdrsize; if(write(fd, pkt, len) != len) dnslog("%d: error sending reply to %I: %r", req->id, pkt); } /* * announce on well-known dns udp port and set message style interface */ static int udpannounce(char *mntpt, char *addr) { static char hmsg[] = "headers"; static char imsg[] = "ignoreadvice"; char adir[NETPATHLEN], buf[NETPATHLEN]; int data, ctl; snprint(buf, sizeof(buf), "%s/udp!%s!53", mntpt, addr); ctl = announce(buf, adir); if(ctl < 0) return -1; /* turn on header style interface */ if(write(ctl, hmsg, sizeof(hmsg)-1) < 0){ warning("can't enable %s on %s: %r", hmsg, adir); close(ctl); return -1; } /* ignore ICMP advice */ write(ctl, imsg, sizeof(imsg)-1); snprint(buf, sizeof(buf), "%s/data", adir); data = open(buf, ORDWR|OCEXEC); if(data < 0) warning("can't open udp port %s: %r", adir); close(ctl); return data; }