new goodies

src/cmd/ip/dhcpd/db.c

@@ -0,0 +1,452 @@
+#include <u.h>
+#include <libc.h>
+#include <ip.h>
+#include <bio.h>
+#include <ndb.h>
+#include <ctype.h>
+#include "dat.h"
+
+/*
+ *  format of a binding entry:
+ *	char ipaddr[32];
+ *	char id[32];
+ *	char hwa[32];
+ *	char otime[10];
+ */
+Binding *bcache;
+uchar bfirst[IPaddrlen];
+char *binddir = nil;
+char *xbinddir = "#9/ndb/dhcp";
+
+/*
+ *  convert a byte array to hex
+ */
+static char
+hex(int x)
+{
+	if(x < 10)
+		return x + '0';
+	return x - 10 + 'a';
+}
+extern char*
+tohex(char *hdr, uchar *p, int len)
+{
+	char *s, *sp;
+	int hlen;
+
+	hlen = strlen(hdr);
+	s = malloc(hlen + 2*len + 1);
+	sp = s;
+	strcpy(sp, hdr);
+	sp += hlen;
+	for(; len > 0; len--){
+		*sp++ = hex(*p>>4);
+		*sp++ = hex(*p & 0xf);
+		p++;
+	}
+	*sp = 0;
+	return s;
+}
+
+/*
+ *  convert a client id to a string.  If it's already
+ *  ascii, leave it be.  Otherwise, convert it to hex.
+ */
+extern char*
+toid(uchar *p, int n)
+{
+	int i;
+	char *s;
+
+	for(i = 0; i < n; i++)
+		if(!isprint(p[i]))
+			return tohex("id", p, n);
+	s = malloc(n + 1);
+	memmove(s, p, n);
+	s[n] = 0;
+	return s;
+}
+
+/*
+ *  increment an ip address
+ */
+static void
+incip(uchar *ip)
+{
+	int i, x;
+
+	for(i = IPaddrlen-1; i >= 0; i--){
+		x = ip[i];
+		x++;
+		ip[i] = x;
+		if((x & 0x100) == 0)
+			break;
+	}
+}
+
+/*
+ *  find a binding for an id or hardware address
+ */
+static int
+lockopen(char *file)
+{
+	char err[ERRMAX];
+	int fd, tries;
+
+	for(tries = 0; tries < 5; tries++){
+		fd = open(file, OLOCK|ORDWR);
+		if(fd >= 0)
+			return fd;
+print("open %s: %r\n", file);
+		errstr(err, sizeof err);
+		if(strstr(err, "lock")){
+			/* wait for other process to let go of lock */
+			sleep(250);
+
+			/* try again */
+			continue;
+		}
+		if(strstr(err, "exist") || strstr(err, "No such")){
+			/* no file, create an exclusive access file */
+			fd = create(file, ORDWR, DMEXCL|0666);
+			chmod(file, 0666);
+			if(fd >= 0)
+				return fd;
+		}
+	}
+	return -1;
+}
+
+void
+setbinding(Binding *b, char *id, long t)
+{
+	if(b->boundto)
+		free(b->boundto);
+
+	b->boundto = strdup(id);
+	b->lease = t;
+}
+
+static void
+parsebinding(Binding *b, char *buf)
+{
+	long t;
+	char *id, *p;
+
+	/* parse */
+	t = atoi(buf);
+	id = strchr(buf, '\n');
+	if(id){
+		*id++ = 0;
+		p = strchr(id, '\n');
+		if(p)
+			*p = 0;
+	} else
+		id = "";
+
+	/* replace any past info */
+	setbinding(b, id, t);
+}
+
+static int
+writebinding(int fd, Binding *b)
+{
+	Dir *d;
+
+	seek(fd, 0, 0);
+	if(fprint(fd, "%ld\n%s\n", b->lease, b->boundto) < 0)
+		return -1;
+	d = dirfstat(fd);
+	if(d == nil)
+		return -1;
+	b->q.type = d->qid.type;
+	b->q.path = d->qid.path;
+	b->q.vers = d->qid.vers;
+	free(d);
+	return 0;
+}
+
+/*
+ *  synchronize cached binding with file.  the file always wins.
+ */
+int
+syncbinding(Binding *b, int returnfd)
+{
+	char buf[512];
+	int i, fd;
+	Dir *d;
+
+	if(binddir == nil)
+		binddir = unsharp(xbinddir);
+
+	snprint(buf, sizeof(buf), "%s/%I", binddir, b->ip);
+	fd = lockopen(buf);
+	if(fd < 0){
+		/* assume someone else is using it */
+		b->lease = time(0) + OfferTimeout;
+		return -1;
+	}
+
+	/* reread if changed */
+	d = dirfstat(fd);
+	if(d != nil)	/* BUG? */
+	if(d->qid.type != b->q.type || d->qid.path != b->q.path || d->qid.vers != b->q.vers){
+		i = read(fd, buf, sizeof(buf)-1);
+		if(i < 0)
+			i = 0;
+		buf[i] = 0;
+		parsebinding(b, buf);
+		b->lasttouched = d->mtime;
+		b->q.path = d->qid.path;
+		b->q.vers = d->qid.vers;
+	}
+
+	free(d);
+
+	if(returnfd)
+		return fd;
+
+	close(fd);
+	return 0;
+}
+
+extern int
+samenet(uchar *ip, Info *iip)
+{
+	uchar x[IPaddrlen];
+
+	maskip(iip->ipmask, ip, x);
+	return ipcmp(x, iip->ipnet) == 0;
+}
+
+/*
+ *  create a record for each binding
+ */
+extern void
+initbinding(uchar *first, int n)
+{
+	while(n-- > 0){
+		iptobinding(first, 1);
+		incip(first);
+	}
+}
+
+/*
+ *  find a binding for a specific ip address
+ */
+extern Binding*
+iptobinding(uchar *ip, int mk)
+{
+	Binding *b;
+
+	for(b = bcache; b; b = b->next){
+		if(ipcmp(b->ip, ip) == 0){
+			syncbinding(b, 0);
+			return b;
+		}
+	}
+
+	if(mk == 0)
+		return 0;
+	b = malloc(sizeof(*b));
+	memset(b, 0, sizeof(*b));
+	ipmove(b->ip, ip);
+	b->next = bcache;
+	bcache = b;
+	syncbinding(b, 0);
+	return b;
+}
+
+static void
+lognolease(Binding *b)
+{
+	/* renew the old binding, and hope it eventually goes away */
+	b->offer = 5*60;
+	commitbinding(b);
+
+	/* complain if we haven't in the last 5 minutes */
+	if(now - b->lastcomplained < 5*60)
+		return;
+	syslog(0, blog, "dhcp: lease for %I to %s ended at %ld but still in use\n",
+		b->ip, b->boundto != nil ? b->boundto : "?", b->lease);
+	b->lastcomplained = now;
+}
+
+/*
+ *  find a free binding for a hw addr or id on the same network as iip
+ */
+extern Binding*
+idtobinding(char *id, Info *iip, int ping)
+{
+	Binding *b, *oldest;
+	int oldesttime;
+
+	/*
+	 *  first look for an old binding that matches.  that way
+	 *  clients will tend to keep the same ip addresses.
+	 */
+	for(b = bcache; b; b = b->next){
+		if(b->boundto && strcmp(b->boundto, id) == 0){
+			if(!samenet(b->ip, iip))
+				continue;
+
+			/* check with the other servers */
+			syncbinding(b, 0);
+			if(strcmp(b->boundto, id) == 0)
+				return b;
+		}
+	}
+
+print("looking for old for %I\n", iip->ipnet);
+
+	/*
+	 *  look for oldest binding that we think is unused
+	 */
+	for(;;){
+		oldest = nil;
+		oldesttime = 0;
+		for(b = bcache; b; b = b->next){
+print("tried %d now %d lease %d exp %d %I\n", b->tried, now, b->lease, b->expoffer, b->ip);
+			if(b->tried != now)
+			if(b->lease < now && b->expoffer < now && samenet(b->ip, iip))
+			if(oldest == nil || b->lasttouched < oldesttime){
+				/* sync and check again */
+				syncbinding(b, 0);
+				if(b->lease < now && b->expoffer < now && samenet(b->ip, iip))
+				if(oldest == nil || b->lasttouched < oldesttime){
+					oldest = b;
+print("have oldest\n");
+					oldesttime = b->lasttouched;
+				}
+			}
+		}
+		if(oldest == nil)
+			break;
+
+		/* make sure noone is still using it */
+		oldest->tried = now;
+print("return oldest\n");
+		if(ping == 0 || icmpecho(oldest->ip) == 0)
+			return oldest;
+
+		lognolease(oldest);	/* sets lastcomplained */
+	}
+
+	/* try all bindings */
+	for(b = bcache; b; b = b->next){
+		syncbinding(b, 0);
+		if(b->tried != now)
+		if(b->lease < now && b->expoffer < now && samenet(b->ip, iip)){
+			b->tried = now;
+			if(ping == 0 || icmpecho(b->ip) == 0)
+				return b;
+
+			lognolease(b);
+		}
+	}
+
+	/* nothing worked, give up */
+	return 0;
+}
+
+/*
+ *  create an offer
+ */
+extern void
+mkoffer(Binding *b, char *id, long leasetime)
+{
+	if(leasetime <= 0){
+		if(b->lease > now + minlease)
+			leasetime = b->lease - now;
+		else
+			leasetime = minlease;
+	}
+	if(b->offeredto)
+		free(b->offeredto);
+	b->offeredto = strdup(id);
+	b->offer = leasetime;
+	b->expoffer = now + OfferTimeout;
+}
+
+/*
+ *  find an offer for this id
+ */
+extern Binding*
+idtooffer(char *id, Info *iip)
+{
+	Binding *b;
+
+	/* look for an offer to this id */
+	for(b = bcache; b; b = b->next){
+print("%I %I ? offeredto %s id %s\n", b->ip, iip->ipnet, b->offeredto, id);
+		if(b->offeredto && strcmp(b->offeredto, id) == 0 && samenet(b->ip, iip)){
+			/* make sure some other system hasn't stolen it */
+			syncbinding(b, 0);
+print("b->lease %d now %d boundto %s offered %s\n", b->lease, now, b->boundto, b->offeredto);
+			if(b->lease < now
+			|| (b->boundto && strcmp(b->boundto, b->offeredto) == 0))
+				return b;
+		}
+	}
+	return 0;
+}
+
+/*
+ *  commit a lease, this could fail
+ */
+extern int
+commitbinding(Binding *b)
+{
+	int fd;
+	long now;
+
+	now = time(0);
+
+	if(b->offeredto == 0)
+		return -1;
+	fd = syncbinding(b, 1);
+	if(fd < 0)
+		return -1;
+	if(b->lease > now && b->boundto && strcmp(b->boundto, b->offeredto) != 0){
+		close(fd);
+		return -1;
+	}
+	setbinding(b, b->offeredto, now + b->offer);
+	b->lasttouched = now;
+	
+	if(writebinding(fd, b) < 0){
+		close(fd);
+		return -1;
+	}
+	close(fd);
+	return 0;
+}
+
+/*
+ *  commit a lease, this could fail
+ */
+extern int
+releasebinding(Binding *b, char *id)
+{
+	int fd;
+	long now;
+
+	now = time(0);
+
+	fd = syncbinding(b, 1);
+	if(fd < 0)
+		return -1;
+	if(b->lease > now && b->boundto && strcmp(b->boundto, id) != 0){
+		close(fd);
+		return -1;
+	}
+	b->lease = 0;
+	b->expoffer = 0;
+	
+	if(writebinding(fd, b) < 0){
+		close(fd);
+		return -1;
+	}
+	close(fd);
+	return 0;
+}