ref: a291bbdeddfd41a2f0907ecbd7b819f0eedffdaf
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) < 0) {
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 %d udp; %d 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");
}