new

src/libndb/dnsquery.c

@@ -0,0 +1,156 @@
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+#include <ndb.h>
+#include <ndbhf.h>
+
+static void nstrcpy(char*, char*, int);
+static void mkptrname(char*, char*, int);
+static Ndbtuple *doquery(int, char *dn, char *type);
+
+/*
+ *  search for a tuple that has the given 'attr=val' and also 'rattr=x'.
+ *  copy 'x' into 'buf' and return the whole tuple.
+ *
+ *  return 0 if not found.
+ */
+Ndbtuple*
+dnsquery(char *net, char *val, char *type)
+{
+	char rip[128];
+	char *p;
+	Ndbtuple *t;
+	int fd;
+
+	/* if the address is V4 or V6 null address, give up early vwhoi*/
+	if(strcmp(val, "::") == 0 || strcmp(val, "0.0.0.0") == 0)
+		return nil;
+
+	if(net == nil)
+		net = "/net";
+	snprint(rip, sizeof(rip), "%s/dns", net);
+	fd = open(rip, ORDWR);
+	if(fd < 0){
+		if(strcmp(net, "/net") == 0)
+			snprint(rip, sizeof(rip), "/srv/dns");
+		else {
+			snprint(rip, sizeof(rip), "/srv/dns%s", net);
+			p = strrchr(rip, '/');
+			*p = '_';
+		}
+		fd = open(rip, ORDWR);
+		if(fd < 0)
+			return nil;
+		if(mount(fd, -1, net, MBEFORE, "") < 0){
+			close(fd);
+			return nil;
+		}
+		/* fd is now closed */
+		snprint(rip, sizeof(rip), "%s/dns", net);
+		fd = open(rip, ORDWR);
+		if(fd < 0)
+			return nil;
+	}
+
+	/* zero out the error string */
+	werrstr("");
+
+	/* if this is a reverse lookup, first lookup the domain name */
+	if(strcmp(type, "ptr") == 0){
+		mkptrname(val, rip, sizeof rip);
+		t = doquery(fd, rip, "ptr");
+	} else
+		t = doquery(fd, val, type);
+
+	close(fd);
+	return t;
+}
+
+/*
+ *  convert address into a reverse lookup address
+ */
+static void
+mkptrname(char *ip, char *rip, int rlen)
+{
+	char buf[128];
+	char *p, *np;
+	int len;
+
+	if(strstr(ip, "in-addr.arpa") || strstr(ip, "IN-ADDR.ARPA")){
+		nstrcpy(rip, ip, rlen);
+		return;
+	}
+
+	nstrcpy(buf, ip, sizeof buf);
+	for(p = buf; *p; p++)
+		;
+	*p = '.';
+	np = rip;
+	len = 0;
+	while(p >= buf){
+		len++;
+		p--;
+		if(*p == '.'){
+			memmove(np, p+1, len);
+			np += len;
+			len = 0;
+		}
+	}
+	memmove(np, p+1, len);
+	np += len;
+	strcpy(np, "in-addr.arpa");
+}
+
+static void
+nstrcpy(char *to, char *from, int len)
+{
+	strncpy(to, from, len);
+	to[len-1] = 0;
+}
+
+static Ndbtuple*
+doquery(int fd, char *dn, char *type)
+{
+	char buf[1024];
+	int n;
+	Ndbtuple *t, *first, *last;
+
+	seek(fd, 0, 0);
+	snprint(buf, sizeof(buf), "!%s %s", dn, type);
+	if(write(fd, buf, strlen(buf)) < 0)
+		return nil;
+		
+	seek(fd, 0, 0);
+
+	first = last = nil;
+	
+	for(;;){
+		n = read(fd, buf, sizeof(buf)-2);
+		if(n <= 0)
+			break;
+		if(buf[n-1] != '\n')
+			buf[n++] = '\n';	/* ndbparsline needs a trailing new line */
+		buf[n] = 0;
+
+		/* check for the error condition */
+		if(buf[0] == '!'){
+			werrstr("%s", buf+1);
+			return nil;
+		}
+
+		t = _ndbparseline(buf);
+		if(t != nil){
+			if(first)
+				last->entry = t;
+			else
+				first = t;
+			last = t;
+
+			while(last->entry)
+				last = last->entry;
+		}
+	}
+
+	setmalloctag(first, getcallerpc(&fd));
+	return first;
+}