Some fixes for smsc usb ethernet and kernel etherusb driver (useful for Raspberry Pi):
- don't assume etherusb is #l0 (so it can coexist with another ether adapter)
- enable multicast by default for etherusb, since there's no interface available
  yet to turn it on dynamically (so ipv6 will work)
- implement promiscuous and multicast modes for smsc

Reference: /n/sources/patch/usbether-rpi
Date: Sun May 29 16:09:35 CES 2016
Signed-off-by: miller@hamnavoe.com

--- /sys/src/cmd/usb/ether/ether.c	Sun May 29 16:05:43 2016
+++ /sys/src/cmd/usb/ether/ether.c	Sun May 29 16:05:39 2016
@@ -1145,29 +1145,34 @@
 static int
 kernelproxy(Ether *e)
 {
-	int ctlfd, n;
+	int ctlfd, n, i;
+	char ename[20];
 	char eaddr[13];
 
-	ctlfd = open("#l0/ether0/clone", ORDWR);
-	if(ctlfd < 0){
-		deprint(2, "%s: etherusb bind #l0: %r\n", argv0);
-		return -1;
-	}
 	close(e->epin->dfd);
 	close(e->epout->dfd);
-	seprintaddr(eaddr, eaddr+sizeof(eaddr), e->addr);
-	n = fprint(ctlfd, "bind %s #u/usb/ep%d.%d/data #u/usb/ep%d.%d/data %s %d %d",
-		e->name, e->dev->id, e->epin->id, e->dev->id, e->epout->id,
-		eaddr, e->bufsize, e->epout->maxpkt);
-	if(n < 0){
-		deprint(2, "%s: etherusb bind #l0: %r\n", argv0);
-		opendevdata(e->epin, OREAD);
-		opendevdata(e->epout, OWRITE);
+	for(i = 0; i < 10; i++){
+		sprint(ename, "#l%d/ether%d/clone", i, i);
+		ctlfd = open(ename, ORDWR);
+		if(ctlfd < 0){
+			deprint(2, "%s: etherusb bind %.3s: %r\n", argv0, ename);
+			break;
+		}
+		seprintaddr(eaddr, eaddr+sizeof(eaddr), e->addr);
+		n = fprint(ctlfd, "bind %s #u/usb/ep%d.%d/data #u/usb/ep%d.%d/data %s %d %d",
+			e->name, e->dev->id, e->epin->id, e->dev->id, e->epout->id,
+			eaddr, e->bufsize, e->epout->maxpkt);
+		if(n < 0){
+			deprint(2, "%s: etherusb bind %.3s: %r\n", argv0, ename);
+			close(ctlfd);
+			continue;
+		}
 		close(ctlfd);
-		return -1;
+		return 0;
 	}
-	close(ctlfd);
-	return 0;
+	opendevdata(e->epin, OREAD);
+	opendevdata(e->epout, OWRITE);
+	return -1;
 }
 
 int
@@ -1222,8 +1227,18 @@
 
 	if(openeps(e, epin, epout) < 0)
 		return -1;
-	if(kernelproxy(e) == 0)
+	if(kernelproxy(e) == 0){
+		if(e->multicast != nil){
+			/*
+			 * Until there is an interface for the kernel etherusb driver
+			 * to write to usb/ether ctl file, multicast needs to be on
+			 * by default so ipv6 will work.
+			 */
+			e->nmcasts++;
+			e->multicast(e, nil, 1);
+		}
 		return 0;
+	}
 	e->fs = etherfs;
 	snprint(e->fs.name, sizeof(e->fs.name), "etherU%d", devid);
 	e->fs.dev = dev;
--- /sys/src/cmd/usb/ether/smsc.c	Sun May 29 16:05:47 2016
+++ /sys/src/cmd/usb/ether/smsc.c	Sun May 29 16:05:45 2016
@@ -323,38 +323,34 @@
 static int
 smscpromiscuous(Ether *e, int on)
 {
-	USED(on, e);
-#ifdef TODO		/* copied from asix */
+	Dev *d;
 	int rxctl;
 
-	deprint(2, "%s: smscpromiscuous %d\n", argv0, on);
-	rxctl = getrxctl(e->dev);
-	if(on != 0)
-		rxctl |= Rxctlprom;
+	d = e->dev;
+	rxctl = rr(d, Maccr);
+	if(on)
+		rxctl |= Prms;
 	else
-		rxctl &= ~Rxctlprom;
-	return wr(e->dev, Cwrxctl, rxctl);
-#endif
-	return -1;
+		rxctl &= ~Prms;
+	return wr(d, Maccr, rxctl);
 }
 
 static int
 smscmulticast(Ether *e, uchar *addr, int on)
 {
-	USED(addr, on, e);
-#ifdef TODO		/* needed for ipv6; copied from asix */
 	int rxctl;
+	Dev *d;
 
+	USED(addr, on);
 	/* BUG: should write multicast filter */
-	rxctl = getrxctl(e->dev);
+	d = e->dev;
+	rxctl = rr(d, Maccr);
 	if(e->nmcasts != 0)
-		rxctl |= Rxctlamall;
+		rxctl |= Mcpas;
 	else
-		rxctl &= ~Rxctlamall;
+		rxctl &= ~Mcpas;
 	deprint(2, "%s: smscmulticast %d\n", argv0, e->nmcasts);
-	return wr(e->dev, Cwrxctl, rxctl);
-#endif
-	return -1;
+	return wr(d, Maccr, rxctl);
 }
 
 static void