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ip/ipconfig: properly handle ipv6 address deprecations

do not add default route when address is
deprecated (preflt == 0).

delete previous default route on router change.

implement rfc4862 section 5.5.3 processing rules
in regard to remaining valid lifetime.

--- a/sys/src/cmd/ip/ipconfig/ipv6.c

+++ b/sys/src/cmd/ip/ipconfig/ipv6.c

@@ -655,9 +655,10 @@

 	issuebasera6(&conf);

+	now = time(nil);

+

 	/* remove expired default routes */

 	m = 0;

-	now = time(nil);

 	for(rr = &routelist; (r = *rr) != nil;){

 		if(m > 100

 		|| r->prefixlt != ~0UL && r->prefixlt < now-r->time

@@ -671,7 +672,6 @@

 			free(r);

 			continue;

 		}

-

 		rr = &r->next;

 		m++;

 	}

@@ -699,8 +699,19 @@

 			continue;

 		conf.prefixlen = prfo->plen & 127;

+		if(conf.prefixlen < 1

+		|| conf.prefixlen > 64)

+			continue;

+

 		genipmkask(conf.mask, conf.prefixlen);

 		maskip(prfo->pref, conf.mask, conf.v6pref);

+		if(!validip(conf.v6pref)

+		|| isv4(conf.v6pref)

+		|| ipcmp(conf.v6pref, v6loopback) == 0

+		|| ISIPV6MCAST(conf.v6pref)

+		|| ISIPV6LINKLOCAL(conf.v6pref))

+			continue;

+

 		memmove(conf.laddr, conf.v6pref, 8);

 		memmove(conf.laddr+8, conf.lladdr+8, 8);

 		ipmove(conf.gaddr, (prfo->lar & RFMASK) != 0? prfo->pref: ra->src);

@@ -708,61 +719,71 @@

 		conf.autoflag = (prfo->lar & AFMASK) != 0;

 		conf.validlt = nhgetl(prfo->validlt);

 		conf.preflt = nhgetl(prfo->preflt);

+		if(conf.preflt > conf.validlt)

+			continue;

-		seen = 0;

+		if(conf.routerlt == 0

+		|| conf.preflt == 0

+		|| isula(conf.laddr)

+		|| ipcmp(conf.gaddr, conf.laddr) == 0

+		|| ipcmp(conf.gaddr, conf.lladdr) == 0)

+			ipmove(conf.gaddr, IPnoaddr);

+

 		sha1((uchar*)&conf, sizeof(conf), hash, nil);

 		for(rr = &routelist; (r = *rr) != nil; rr = &r->next){

 			if(ipcmp(r->src, ra->src) == 0

 			&& ipcmp(r->laddr, conf.laddr) == 0){

-				seen = memcmp(r->hash, hash, SHA1dlen) == 0;

 				*rr = r->next;

 				break;

 			}

 		}

-		if(r == nil)

+		if(r != nil){

+			/* rfc4862, section 5.5.3, e) */

+			ulong remaining = r->prefixlt != ~0UL ? r->time + r->prefixlt : ~0UL;

+			ulong signaled = conf.validlt != ~0UL ? now + conf.validlt : ~0UL;

+			ulong timeout = now + 2*60*60;	/* 2 horus from now */

+			if(signaled <= timeout && signaled <= remaining) {

+				if(remaining <= timeout)

+					conf.validlt = remaining - now;

+				else

+					conf.validlt = timeout - now;

+				if (conf.preflt > conf.validlt)

+					conf.preflt = conf.validlt;

+			}

+			seen = memcmp(r->hash, hash, SHA1dlen) == 0;

+			if(!seen && validip(r->gaddr) && ipcmp(r->gaddr, conf.gaddr) != 0){

+				DEBUG("changing router %I->%I", r->gaddr, conf.gaddr);

+				if(!noconfig)

+					deldefroute(r->gaddr, conf.lladdr, r->laddr, r->mask);

+			}

+		} else {

+			seen = 0;

+			if(conf.preflt == 0)

+				continue;

 			r = malloc(sizeof(*r));

-

+		}

 		memmove(r->hash, hash, SHA1dlen);

-		if(conf.routerlt == 0

-		|| isula(conf.laddr)

-		|| ipcmp(conf.gaddr, conf.laddr) == 0

-		|| ipcmp(conf.gaddr, conf.lladdr) == 0)

-			ipmove(conf.gaddr, IPnoaddr);

-

+		r->time = now;

+		r->routerlt = conf.routerlt;

+		r->prefixlt = conf.validlt;

 		ipmove(r->src, ra->src);

 		ipmove(r->gaddr, conf.gaddr);

 		ipmove(r->laddr, conf.laddr);

 		ipmove(r->mask, conf.mask);

-		r->time = now;

-		r->routerlt = conf.routerlt;

-		r->prefixlt = conf.validlt;

-

 		r->next = routelist;

 		routelist = r;

-		if(conf.prefixlen < 1

-		|| conf.prefixlen > 64

-		|| !validip(conf.v6pref)

-		|| isv4(conf.v6pref)

-		|| ipcmp(conf.v6pref, v6loopback) == 0

-		|| ISIPV6MCAST(conf.v6pref)

-		|| ISIPV6LINKLOCAL(conf.v6pref)){

-			if(!seen)

-				warning("igoring bogus prefix from %I on %s; pfx %I %M",

-					ra->src, conf.dev, conf.v6pref, conf.mask);

-

-			/* keep it arround so we wont comlain again */

-			r->prefixlt = r->routerlt = ~0UL;

-			continue;

-		}

-

 		/* add prefix and update parameters */

 		issueadd6(&conf);

-		/* report this prefix configuration only once */

+		/* report only once */

 		if(seen)

+			continue;

+

+		/* must not be deprecated */

+		if(conf.preflt == 0)

 			continue;

 		DEBUG("got RA from %I on %s; pfx %I %M",

-- 

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