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ip: generalize Rproxy route handling, allowing non point-to-point arp proxy

Generalize the arp proxy code, so one can create
specific routes for ip ranges that we want to arp
proxy for, not just for point-to-point interface
routes.

as we have source specific routes, this also
gives some control over which requester we will
reply to.

one example for this is a vps where we booked
another ip address on the ethernet, that we want
to route into a vpn tunnel. the new ip is in
subnet of the public ethernet interface, so all
we now need todo is add a route for that ip into
the vpn tunnel and set the proxy flag "y", and
we will respond to arp for that ip on the public
ethernet interface.

--- a/sys/src/9/ip/arp.c

+++ b/sys/src/9/ip/arp.c

@@ -383,7 +383,43 @@

 	return 1;

 }

+/*

+ * arpforme() checks if we should respond to arp/ndp on a specific interface.

+ * 

+ * returns Runi if targ is a non-tentative local address on ifc.

+ * returns Rproxy if we have a proxy route for targ to another interface.

+ */

 int

+arpforme(Fs *fs, int version, uchar *targ, uchar *src, Ipifc *ifc)

+{

+	uchar ipv6[IPaddrlen];

+	Iplifc *lifc;

+	Route *r;

+

+	if(version == V4) {

+		v4tov6(ipv6, targ);

+		targ = ipv6;

+	}

+	lifc = iplocalonifc(ifc, targ);

+	if(lifc != nil){

+		if(lifc->tentative)

+			return 0;

+		return Runi;

+	}

+	if(ipremoteonifc(ifc, targ) == nil)

+		return 0;

+	if(version == V4){

+		targ += IPv4off;

+		r = v4lookup(fs, targ, src, nil);

+	} else {

+		r = v6lookup(fs, targ, src, nil);

+	}

+	if(r == nil || r->ifc == ifc && r->ifcid == ifc->ifcid)

+		return 0;

+	return r->type & Rproxy;

+}

+

+int

 arpwrite(Fs *fs, char *s, int len)

 {

 	int n;

@@ -552,8 +588,7 @@

 	if(a->last != nil){

 		ipmove(src, ((Ip6hdr*)a->last->rp)->src);

 		arpcontinue(f->arp, a);

-

-		if(iplocalonifc(ifc, src) != nil || ipproxyifc(f, ifc, src))

+		if(arpforme(f, V6, src, targ, ifc))

 			goto send;

 	} else {

 		arpcontinue(f->arp, a);

--- a/sys/src/9/ip/ethermedium.c

+++ b/sys/src/9/ip/ethermedium.c

@@ -508,7 +508,6 @@

 	int forme;

 	Block *ebp, *rbp;

 	Etherarp *e, *r;

-	uchar ip[IPaddrlen];

 	static uchar eprinted[4];

 	Etherrock *er = ifc->arg;

@@ -529,8 +528,7 @@

 			break;

 		/* check for machine using my ip address */

-		v4tov6(ip, e->spa);

-		if(iplocalonifc(ifc, ip) != nil || ipproxyifc(er->f, ifc, ip)){

+		if(arpforme(er->f, V4, e->spa, e->tpa, ifc)){

 			if(memcmp(e->sha, ifc->mac, sizeof(e->sha)) != 0){

 				print("arprep: 0x%E/0x%E also has ip addr %V\n",

 					e->s, e->sha, e->spa);

@@ -552,8 +550,7 @@

 			break;

 		/* check for machine using my ip or ether address */

-		v4tov6(ip, e->spa);

-		if(iplocalonifc(ifc, ip) != nil || ipproxyifc(er->f, ifc, ip)){

+		if(arpforme(er->f, V4, e->spa, e->tpa, ifc)){

 			if(memcmp(e->sha, ifc->mac, sizeof(e->sha)) != 0){

 				if(memcmp(eprinted, e->spa, sizeof(e->spa)) != 0){

 					/* print only once */

@@ -576,8 +573,7 @@

 		 * enter senders address into arp table and reply, otherwise just

 		 * refresh the senders address.

 		 */

-		v4tov6(ip, e->tpa);

-		forme = iplocalonifc(ifc, ip) != nil || ipproxyifc(er->f, ifc, ip);

+		forme = arpforme(er->f, V4, e->tpa, e->spa, ifc);

 		if(arpenter(er->f, V4, e->spa, e->sha, sizeof(e->sha), e->tpa, ifc, !forme) < 0 || !forme)

 			break;

--- a/sys/src/9/ip/icmp6.c

+++ b/sys/src/9/ip/icmp6.c

@@ -636,21 +636,6 @@

 	return 0;

 }

-static int

-targettype(Fs *f, Ipifc *ifc, uchar *target)

-{

-	Iplifc *lifc;

-	int t;

-

-	if((lifc = iplocalonifc(ifc, target)) != nil)

-		t = lifc->tentative? Tunitent: Tunirany;

-	else if(ipproxyifc(f, ifc, target))

-		t = Tuniproxy;

-	else

-		t = 0;

-	return t;

-}

-

 static void

 icmpiput6(Proto *icmp, Ipifc *ifc, Block *bp)

 {

@@ -745,12 +730,11 @@

 		pktflags = 0;

 		if(ifc->sendra6)

 			pktflags |= Rflag;

-		switch (targettype(icmp->f, ifc, np->target)) {

-		case Tunirany:

+		switch(arpforme(icmp->f, V6, np->target, np->src, ifc)){

+		case Runi:

 			pktflags |= Oflag;

-			/* fall through */

-

-		case Tuniproxy:

+			/* wet floor */

+		case Rproxy:

 			if(ipv6local(ifc, ia, 0, np->src)) {

 				if(arpenter(icmp->f, V6, np->src, np->lnaddr, 8*np->olen-2, ia, ifc, 0) < 0)

 					break;

@@ -759,12 +743,6 @@

 				ipmove(ia, np->target);

 			icmpna6(icmp->f, ia, (pktflags & Sflag)? np->src: v6allnodesL,

 				np->target, ifc->mac, pktflags);

-			break;

-		case Tunitent:

-			/*

-			 * not clear what needs to be done. send up

-			 * an icmp mesg saying don't use this address?

-			 */

 			break;

 		}

 		freeblist(bp);

--- a/sys/src/9/ip/ip.h

+++ b/sys/src/9/ip/ip.h

@@ -668,6 +668,7 @@

 extern void	arpcontinue(Arp*, Arpent *a);

 extern Block*	arpresolve(Arp*, Arpent *a, uchar *mac, Routehint *rh);

 extern int	arpenter(Fs*, int version, uchar *ip, uchar *mac, int n, uchar *ia, Ipifc *ifc, int refresh);

+extern int	arpforme(Fs*, int version, uchar *targ, uchar *src, Ipifc *ifc);

 extern void	ndpsendsol(Fs*, Arpent*);

 /*

@@ -725,7 +726,6 @@

 extern int	ipv6local(Ipifc *ifc, uchar *local, int prefixlen, uchar *remote);

 extern Iplifc*	iplocalonifc(Ipifc *ifc, uchar *ip);

 extern Iplifc*	ipremoteonifc(Ipifc *ifc, uchar *ip);

-extern int	ipproxyifc(Fs *f, Ipifc *ifc, uchar *ip);

 extern Ipmulti*	ipifcgetmulti(Fs *f, Ipifc *ifc, uchar *ma);

 extern void	ipifcremmulti(Conv *c, uchar *ma, uchar *ia);

 extern void	ipifcaddmulti(Conv *c, uchar *ma, uchar *ia);

--- a/sys/src/9/ip/ipifc.c

+++ b/sys/src/9/ip/ipifc.c

@@ -569,7 +569,7 @@

 	addselfcache(f, ifc, lifc, ip, Runi);

-	/* register proxy */

+	/* register point-to-point proxy */

 	if(type & Rptpt){

 		if(type & Rproxy)

 			ipifcregisterproxy(f, ifc, rem, 1);

@@ -576,6 +576,10 @@

 		goto done;

 	}

+	/* register local ip if proxy */

+	if(type & Rproxy)

+		ipifcregisterproxy(f, ifc, ip, 1);

+

 	if(type & Rv4) {

 		/* add subnet directed broadcast address to the self cache */

 		for(i = 0; i < IPaddrlen; i++)

@@ -667,7 +671,7 @@

 				lifc->remote, lifc->type, ifc, tifc);

 	}

-	/* unregister proxy */

+	/* unregister point-to-point proxy */

 	if(lifc->type & Rptpt){

 		if(lifc->type & Rproxy)

 			ipifcregisterproxy(f, ifc, lifc->remote, 0);

@@ -674,6 +678,10 @@

 		goto done;

 	}

+	/* unregister local ip if proxy */

+	if(lifc->type & Rproxy)

+		ipifcregisterproxy(f, ifc, lifc->local, 0);

+

 	/* remove route for all nodes multicast */

 	if((lifc->type & Rv4) == 0){

 		if(ipcmp(lifc->local, v6loopback) == 0){

@@ -902,6 +910,7 @@

 	Ipself *p;

 	int h;

+	if(type == Runi) type |= (lifc->type & Rproxy);

 	type |= (lifc->type & Rv4);

 	qlock(f->self);

@@ -1448,22 +1457,6 @@

 			return lifc;

 	return nil;

-}

-

-/*

- *  See if we're proxying for this address on this interface

- */

-int

-ipproxyifc(Fs *f, Ipifc *ifc, uchar *ip)

-{

-	Route *r;

-

-	/* see if this is a direct connected pt to pt address */

-	r = v6lookup(f, ip, ip, nil);

-	if(r == nil || (r->type & (Rifc|Rproxy)) != (Rifc|Rproxy))

-		return 0;

-

-	return ipremoteonifc(ifc, ip) != nil;

 }

 /*

--- a/sys/src/9/ip/ipv6.h

+++ b/sys/src/9/ip/ipv6.h

@@ -94,10 +94,6 @@

 	TARG_UNI	= 2,

 	TARG_MULTI	= 3,

-	Tunitent	= 1,

-	Tuniproxy	= 2,

-	Tunirany	= 3,

-

 	/* Node constants */

 	MAX_MULTICAST_SOLICIT	= 3,

 	RETRANS_TIMER		= 1000,