/net/arp and /net/iproute were world-writable.  Changed to be only
writable by the hostowner (Eve?).

The formal permissions (which were of no effect before, either) are
changed from 666 to:

--rw-rw-r-- I   0 network bootes  0 Oct  6 12:05 /net/arp
--rw-rw-r-- I   0 network bootes  0 Oct  6 12:05 /net/iproute

In fact, only the hostowner can write to them.  (The checking of group
membership is harder than checking ownership for the host).

Reference: /n/sources/patch/applied/permissions-iproute-arp
Date: Fri Oct  6 12:53:08 CES 2006
Signed-off-by: hdd@voidness.de

--- /sys/src/9/ip/devip.c	Fri Oct  6 12:52:52 2006
+++ /sys/src/9/ip/devip.c	Fri Oct  6 12:52:46 2006
@@ -142,6 +142,7 @@
 		return -1;
 	case Qarp:
 		p = "arp";
+		prot = 0664;
 		break;
 	case Qbootp:
 		p = "bootp";
@@ -153,6 +154,7 @@
 		break;
 	case Qiproute:
 		p = "iproute";
+		prot = 0664;
 		break;
 	case Qipselftab:
 		p = "ipselftab";
@@ -377,6 +379,12 @@
 		netlogopen(f);
 		break;
 	case Qiproute:
+		if(omode != OREAD && !iseve())
+			error(Eperm);
+		break;
+	case Qarp:
+		if(omode != OREAD && !iseve())
+			error(Eperm);
 		break;
 	case Qtopdir:
 	case Qprotodir: