122 lines
2.4 KiB
C
122 lines
2.4 KiB
C
#include <u.h>
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#include <libc.h>
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#include <bio.h>
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#include <ndb.h>
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#include <ndbhf.h>
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#include <ip.h>
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static void mkptrname(char*, char*, int);
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static Ndbtuple *doquery(int, char *dn, char *type);
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/*
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* search for a tuple that has the given 'attr=val' and also 'rattr=x'.
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* copy 'x' into 'buf' and return the whole tuple.
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*
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* return nil if not found.
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*/
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Ndbtuple*
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dnsquery(char *net, char *val, char *type)
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{
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char buf[128];
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Ndbtuple *t;
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int fd;
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/* if the address is V4 or V6 null address, give up early */
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if(strcmp(val, "::") == 0 || strcmp(val, "0.0.0.0") == 0)
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return nil;
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if(net == nil)
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net = "/net";
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snprint(buf, sizeof(buf), "%s/dns", net);
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if((fd = open(buf, ORDWR|OCEXEC)) < 0)
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return nil;
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/* zero out the error string */
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werrstr("");
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/* if this is a reverse lookup, first lookup the domain name */
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if(strcmp(type, "ptr") == 0){
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mkptrname(val, buf, sizeof buf);
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t = doquery(fd, buf, "ptr");
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} else
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t = doquery(fd, val, type);
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/*
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* TODO: make fd static and keep it open to reduce 9P traffic
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* walking to /net*^/dns.
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*/
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close(fd);
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ndbsetmalloctag(t, getcallerpc(&net));
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return t;
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}
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/*
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* convert address into a reverse lookup address
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*/
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static void
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mkptrname(char *ip, char *rip, int rlen)
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{
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uchar a[IPaddrlen];
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char *p, *e;
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int i;
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if(cistrstr(ip, "in-addr.arpa") || cistrstr(ip, "ip6.arpa") || parseip(a, ip) == -1)
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snprint(rip, rlen, "%s", ip);
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else if(isv4(a))
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snprint(rip, rlen, "%ud.%ud.%ud.%ud.in-addr.arpa",
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a[15], a[14], a[13], a[12]);
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else{
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p = rip;
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e = rip + rlen;
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for(i = 15; i >= 0; i--){
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p = seprint(p, e, "%ux.", a[i]&0xf);
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p = seprint(p, e, "%ux.", a[i]>>4);
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}
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seprint(p, e, "ip6.arpa");
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}
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}
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static Ndbtuple*
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doquery(int fd, char *dn, char *type)
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{
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char buf[1024];
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int n;
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Ndbtuple *t, *first, *last;
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snprint(buf, sizeof(buf), "!%s %s", dn, type);
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if(write(fd, buf, strlen(buf)) < 0)
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return nil;
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seek(fd, 0, 0);
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first = last = nil;
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for(;;){
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n = read(fd, buf, sizeof(buf)-2);
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if(n <= 0)
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break;
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if(buf[n-1] != '\n')
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buf[n++] = '\n'; /* ndbparsline needs a trailing new line */
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buf[n] = 0;
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/* check for the error condition */
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if(buf[0] == '!'){
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werrstr("%s", buf+1);
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return nil;
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}
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t = _ndbparseline(buf);
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if(t != nil){
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if(first != nil)
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last->entry = t;
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else
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first = t;
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last = t;
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while(last->entry != nil)
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last = last->entry;
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}
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}
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return first;
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}
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