1 #include <u.h>
2 #include <libc.h>
3 #include <ip.h>
4 #include <bio.h>
5 #include <ndb.h>
6 #include "dns.h"
7 
8 static int	udpannounce(char*);
9 static void	reply(int, uchar*, DNSmsg*, Request*);
10 
11 extern char *logfile;
12 
13 static void
14 ding(void *x, char *msg)
15 {
16 	USED(x);
17 	if(strcmp(msg, "alarm") == 0)
18 		noted(NCONT);
19 	else
20 		noted(NDFLT);
21 }
22 
23 typedef struct Inprogress Inprogress;
24 struct Inprogress
25 {
26 	int	inuse;
27 	OUdphdr	uh;
28 	DN	*owner;
29 	int	type;
30 	int	id;
31 };
32 Inprogress inprog[Maxactive+2];
33 
34 /*
35  *  record client id and ignore retransmissions.
36  *  we're still single thread at this point.
37  */
38 static Inprogress*
39 clientrxmit(DNSmsg *req, uchar *buf)
40 {
41 	Inprogress *p, *empty;
42 	OUdphdr *uh;
43 
44 	uh = (OUdphdr *)buf;
45 	empty = 0;
46 	for(p = inprog; p < &inprog[Maxactive]; p++){
47 		if(p->inuse == 0){
48 			if(empty == 0)
49 				empty = p;
50 			continue;
51 		}
52 		if(req->id == p->id)
53 		if(req->qd->owner == p->owner)
54 		if(req->qd->type == p->type)
55 		if(memcmp(uh, &p->uh, OUdphdrsize) == 0)
56 			return 0;
57 	}
58 	if(empty == 0)
59 		return 0;	/* shouldn't happen - see slave() and definition of Maxactive */
60 
61 	empty->id = req->id;
62 	empty->owner = req->qd->owner;
63 	empty->type = req->qd->type;
64 	memmove(&empty->uh, uh, OUdphdrsize);
65 	empty->inuse = 1;
66 	return empty;
67 }
68 
69 /*
70  *  a process to act as a dns server for outside reqeusts
71  */
72 void
73 dnudpserver(char *mntpt)
74 {
75 	int fd, len, op;
76 	Request req;
77 	DNSmsg reqmsg, repmsg;
78 	uchar buf[OUdphdrsize + Maxudp + 1024];
79 	char *err;
80 	Inprogress *p;
81 	char tname[32];
82 	OUdphdr *uh;
83 
84 	/* fork sharing text, data, and bss with parent */
85 	switch(rfork(RFPROC|RFNOTEG|RFMEM|RFNOWAIT)){
86 	case -1:
87 		break;
88 	case 0:
89 		break;
90 	default:
91 		return;
92 	}
93 
94 	fd = -1;
95 	notify(ding);
96 restart:
97 	if(fd >= 0)
98 		close(fd);
99 	while((fd = udpannounce(mntpt)) < 0)
100 		sleep(5000);
101 	if(setjmp(req.mret))
102 		putactivity();
103 	req.isslave = 0;
104 
105 	/* loop on requests */
106 	for(;; putactivity()){
107 		memset(&repmsg, 0, sizeof(repmsg));
108 		memset(&reqmsg, 0, sizeof(reqmsg));
109 		alarm(60*1000);
110 		len = udpread(fd, (OUdphdr*)buf, buf+OUdphdrsize, sizeof(buf)-OUdphdrsize);
111 		alarm(0);
112 		if(len <= 0)
113 			goto restart;
114 		uh = (OUdphdr*)buf;
115 		getactivity(&req);
116 		req.aborttime = now + 30;	/* don't spend more than 30 seconds */
117 		err = convM2DNS(&buf[OUdphdrsize], len, &reqmsg);
118 		if(err){
119 			syslog(0, logfile, "server: input error: %s from %I", err, buf);
120 			continue;
121 		}
122 		if(reqmsg.qdcount < 1){
123 			syslog(0, logfile, "server: no questions from %I", buf);
124 			goto freereq;
125 		}
126 		if(reqmsg.flags & Fresp){
127 			syslog(0, logfile, "server: reply not request from %I", buf);
128 			goto freereq;
129 		}
130 		op = reqmsg.flags & Omask;
131 		if(op != Oquery && op != Onotify){
132 			syslog(0, logfile, "server: op %d from %I", reqmsg.flags & Omask, buf);
133 			goto freereq;
134 		}
135 
136 		if(debug || (trace && subsume(trace, reqmsg.qd->owner->name))){
137 			syslog(0, logfile, "%d: serve (%I/%d) %d %s %s",
138 				req.id, buf, ((uh->rport[0])<<8)+uh->rport[1],
139 				reqmsg.id,
140 				reqmsg.qd->owner->name,
141 				rrname(reqmsg.qd->type, tname, sizeof tname));
142 		}
143 
144 		p = clientrxmit(&reqmsg, buf);
145 		if(p == 0){
146 			if(debug)
147 				syslog(0, logfile, "%d: duplicate", req.id);
148 			goto freereq;
149 		}
150 
151 		/* loop through each question */
152 		while(reqmsg.qd){
153 			memset(&repmsg, 0, sizeof(repmsg));
154 			switch(op){
155 			case Oquery:
156 				dnserver(&reqmsg, &repmsg, &req);
157 				break;
158 			case Onotify:
159 				dnnotify(&reqmsg, &repmsg, &req);
160 				break;
161 			}
162 			reply(fd, buf, &repmsg, &req);
163 			rrfreelist(repmsg.qd);
164 			rrfreelist(repmsg.an);
165 			rrfreelist(repmsg.ns);
166 			rrfreelist(repmsg.ar);
167 		}
168 
169 		p->inuse = 0;
170 
171 freereq:
172 		rrfreelist(reqmsg.qd);
173 		rrfreelist(reqmsg.an);
174 		rrfreelist(reqmsg.ns);
175 		rrfreelist(reqmsg.ar);
176 
177 		if(req.isslave){
178 			putactivity();
179 			_exits(0);
180 		}
181 
182 	}
183 }
184 
185 /*
186  *  announce on udp port
187  */
188 static int
189 udpannounce(char *mntpt)
190 {
191 	int fd;
192 	char buf[40];
193 	
194 	USED(mntpt);
195 	
196 	if((fd=announce("udp!*!nameserver", buf)) < 0)
197 		warning("can't announce on dns udp port");
198 	return fd;
199 }
200 
201 static void
202 reply(int fd, uchar *buf, DNSmsg *rep, Request *reqp)
203 {
204 	int len;
205 	char tname[32];
206 	RR *rp;
207 
208 	if(debug || (trace && subsume(trace, rep->qd->owner->name)))
209 		syslog(0, logfile, "%d: reply (%I/%d) %d %s %s an %R ns %R ar %R",
210 			reqp->id, buf, ((buf[4])<<8)+buf[5],
211 			rep->id, rep->qd->owner->name,
212 			rrname(rep->qd->type, tname, sizeof tname), rep->an, rep->ns, rep->ar);
213 
214 	len = convDNS2M(rep, &buf[OUdphdrsize], Maxudp);
215 	if(len <= 0){
216 		syslog(0, logfile, "error converting reply: %s %d", rep->qd->owner->name,
217 			rep->qd->type);
218 		for(rp = rep->an; rp; rp = rp->next)
219 			syslog(0, logfile, "an %R", rp);
220 		for(rp = rep->ns; rp; rp = rp->next)
221 			syslog(0, logfile, "ns %R", rp);
222 		for(rp = rep->ar; rp; rp = rp->next)
223 			syslog(0, logfile, "ar %R", rp);
224 		return;
225 	}
226 	if(udpwrite(fd, (OUdphdr*)buf, buf+OUdphdrsize, len) != len)
227 		syslog(0, logfile, "error sending reply: %r");
228 }