tdnsquery.c - plan9port - [fork] Plan 9 from user space
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tdnsquery.c (2837B)
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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*
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 vwhoi*/
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 close(fd);
66 return t;
67 }
68
69 /*
70 * convert address into a reverse lookup address
71 */
72 static void
73 mkptrname(char *ip, char *rip, int rlen)
74 {
75 char buf[128];
76 char *p, *np;
77 int len;
78
79 if(strstr(ip, "in-addr.arpa") || strstr(ip, "IN-ADDR.ARPA")){
80 nstrcpy(rip, ip, rlen);
81 return;
82 }
83
84 nstrcpy(buf, ip, sizeof buf);
85 for(p = buf; *p; p++)
86 ;
87 *p = '.';
88 np = rip;
89 len = 0;
90 while(p >= buf){
91 len++;
92 p--;
93 if(*p == '.'){
94 memmove(np, p+1, len);
95 np += len;
96 len = 0;
97 }
98 }
99 memmove(np, p+1, len);
100 np += len;
101 strcpy(np, "in-addr.arpa");
102 }
103
104 static void
105 nstrcpy(char *to, char *from, int len)
106 {
107 strncpy(to, from, len);
108 to[len-1] = 0;
109 }
110
111 static Ndbtuple*
112 doquery(int fd, char *dn, char *type)
113 {
114 char buf[1024];
115 int n;
116 Ndbtuple *t, *first, *last;
117
118 seek(fd, 0, 0);
119 snprint(buf, sizeof(buf), "!%s %s", dn, type);
120 if(write(fd, buf, strlen(buf)) < 0)
121 return nil;
122
123 seek(fd, 0, 0);
124
125 first = last = nil;
126
127 for(;;){
128 n = read(fd, buf, sizeof(buf)-2);
129 if(n <= 0)
130 break;
131 if(buf[n-1] != '\n')
132 buf[n++] = '\n'; /* ndbparsline needs a trailing new line */
133 buf[n] = 0;
134
135 /* check for the error condition */
136 if(buf[0] == '!'){
137 werrstr("%s", buf+1);
138 return nil;
139 }
140
141 t = _ndbparseline(buf);
142 if(t != nil){
143 if(first)
144 last->entry = t;
145 else
146 first = t;
147 last = t;
148
149 while(last->entry)
150 last = last->entry;
151 }
152 }
153
154 setmalloctag(first, getcallerpc(&fd));
155 return first;
156 }