1 #include <u.h>
2 #include <libc.h>
3 #include <bio.h>
4 #include <ndb.h>
5 #include <ndbhf.h>
6
7 static void nstrcpy(char*, char*, int);
8 static void mkptrname(char*, char*, int);
9 static Ndbtuple *doquery(int, char *dn, char *type);
10
11 /*
12 * search for a tuple that has the given 'attr=val' and also 'rattr=x'.
13 * copy 'x' into 'buf' and return the whole tuple.
14 *
15 * return 0 if not found.
16 */
17 Ndbtuple*
dnsquery(char * net,char * val,char * type)18 dnsquery(char *net, char *val, char *type)
19 {
20 char rip[128];
21 char *p;
22 Ndbtuple *t;
23 int fd;
24
25 /* if the address is V4 or V6 null address, give up early */
26 if(strcmp(val, "::") == 0 || strcmp(val, "0.0.0.0") == 0)
27 return nil;
28
29 if(net == nil)
30 net = "/net";
31 snprint(rip, sizeof(rip), "%s/dns", net);
32 fd = open(rip, ORDWR);
33 if(fd < 0){
34 if(strcmp(net, "/net") == 0)
35 snprint(rip, sizeof(rip), "/srv/dns");
36 else {
37 snprint(rip, sizeof(rip), "/srv/dns%s", net);
38 p = strrchr(rip, '/');
39 *p = '_';
40 }
41 fd = open(rip, ORDWR);
42 if(fd < 0)
43 return nil;
44 if(mount(fd, -1, net, MBEFORE, "") < 0){
45 close(fd);
46 return nil;
47 }
48 /* fd is now closed */
49 snprint(rip, sizeof(rip), "%s/dns", net);
50 fd = open(rip, ORDWR);
51 if(fd < 0)
52 return nil;
53 }
54
55 /* zero out the error string */
56 werrstr("");
57
58 /* if this is a reverse lookup, first lookup the domain name */
59 if(strcmp(type, "ptr") == 0){
60 mkptrname(val, rip, sizeof rip);
61 t = doquery(fd, rip, "ptr");
62 } else
63 t = doquery(fd, val, type);
64
65 /*
66 * TODO: make fd static and keep it open to reduce 9P traffic
67 * walking to /net*^/dns. Must be prepared to re-open it on error.
68 */
69 close(fd);
70 ndbsetmalloctag(t, getcallerpc(&net));
71 return t;
72 }
73
74 /*
75 * convert address into a reverse lookup address
76 */
77 static void
mkptrname(char * ip,char * rip,int rlen)78 mkptrname(char *ip, char *rip, int rlen)
79 {
80 char buf[128];
81 char *p, *np;
82 int len;
83
84 if(cistrstr(ip, "in-addr.arpa") || cistrstr(ip, "ip6.arpa")){
85 nstrcpy(rip, ip, rlen);
86 return;
87 }
88
89 nstrcpy(buf, ip, sizeof buf);
90 for(p = buf; *p; p++)
91 ;
92 *p = '.';
93 np = rip;
94 len = 0;
95 while(p >= buf){
96 len++;
97 p--;
98 if(*p == '.'){
99 memmove(np, p+1, len);
100 np += len;
101 len = 0;
102 }
103 }
104 memmove(np, p+1, len);
105 np += len;
106 strcpy(np, "in-addr.arpa");
107 }
108
109 static void
nstrcpy(char * to,char * from,int len)110 nstrcpy(char *to, char *from, int len)
111 {
112 strncpy(to, from, len);
113 to[len-1] = 0;
114 }
115
116 static Ndbtuple*
doquery(int fd,char * dn,char * type)117 doquery(int fd, char *dn, char *type)
118 {
119 char buf[1024];
120 int n;
121 Ndbtuple *t, *first, *last;
122
123 seek(fd, 0, 0);
124 snprint(buf, sizeof(buf), "!%s %s", dn, type);
125 if(write(fd, buf, strlen(buf)) < 0)
126 return nil;
127
128 seek(fd, 0, 0);
129
130 first = last = nil;
131
132 for(;;){
133 n = read(fd, buf, sizeof(buf)-2);
134 if(n <= 0)
135 break;
136 if(buf[n-1] != '\n')
137 buf[n++] = '\n'; /* ndbparsline needs a trailing new line */
138 buf[n] = 0;
139
140 /* check for the error condition */
141 if(buf[0] == '!'){
142 werrstr("%s", buf+1);
143 return nil;
144 }
145
146 t = _ndbparseline(buf);
147 if(t != nil){
148 if(first)
149 last->entry = t;
150 else
151 first = t;
152 last = t;
153
154 while(last->entry)
155 last = last->entry;
156 }
157 }
158
159 ndbsetmalloctag(first, getcallerpc(&fd));
160 return first;
161 }
162