Allow the hostname used in inform records to
be overridden using a tuple in /lib/ndb/local.

Reference: /n/sources/patch/applied/inform-update
Date: Wed May 18 19:05:21 CES 2011
Signed-off-by: steve@auintile.net

--- /sys/src/cmd/ndb/inform.c	Wed May 18 19:04:40 2011
+++ /sys/src/cmd/ndb/inform.c	Wed May 18 19:04:36 2011
@@ -24,11 +24,6 @@
 	[10] "domain name not in zone",
 };
 
-char *dnsrch[] = {
-	"dnsdomain",
-	"dom",
-};
-
 void
 usage(void)
 {
@@ -98,12 +93,12 @@
 {
 	int debug, len, fd;
 	uint err;
-	char *sysname, *dnsdomain, *dom, *ns, net[32];
+	char *sysname, *dnsdomain, *dom, *inform, *ns, net[32];
 	uchar *p, buf[4096], addr[IPv4addrlen], v6addr[IPaddrlen];
 	ushort txid;
 	Ndb *db;
 	Ndbtuple *t, *tt;
-	static char *query[] = { "dom", "dnsdomain", "ns", };
+	static char *query[] = { "dom", "dnsdomain", "ns", "inform" };
 
 	fmtinstall('I', eipfmt);
 	fmtinstall('V', eipfmt);
@@ -112,6 +107,7 @@
 	debug = 0;
 	ns = nil;
 	dom = nil;
+	inform = nil;
 	dnsdomain = nil;
 	ARGBEGIN{
 	case 'd':
@@ -133,16 +129,22 @@
 	if((db = ndbopen(nil)) == nil)
 		sysfatal("can't open ndb: %r");
 	tt = ndbipinfo(db, "sys", sysname, query, nelem(query));
-	for(t = tt; t; t = t->entry)
+	for(t = tt; t; t = t->entry){
 		if(strcmp(t->attr, "ns") == 0)
 			ns = t->val;
 		else if(strcmp(t->attr, "dom") == 0)
 			dom = t->val;
 		else if(strcmp(t->attr, "dnsdomain") == 0)
 			dnsdomain = t->val;
+		else if(strcmp(t->attr, "inform") == 0)
+			inform = t->val;
+	}
+
 	ndbfree(tt);
 	ndbclose(db);
 
+	if(inform)
+		dom = inform;
 	if(!ns)
 		sysfatal("no relevant ns=");
 	if(!dom)
--- /sys/man/8/ndb	Wed May 18 19:04:47 2011
+++ /sys/man/8/ndb	Wed May 18 19:04:42 2011
@@ -169,6 +169,8 @@
 packet to a nameserver to associate the host's IPv4 address with its DNS name.
 This is required if the domain's nameserver is
 a Microsoft Windows Active Directory controller.
+The host's FQDN will be sent to the AD controller unless 
+a tuple of the form inform=xxx is found in the hosts NDB entry.
 .SS "Database maintenance"
 .I Ndb/mkhash
 creates a hash file for all entries with attribute