From: Uwe Kleine-König <uwe@kleine-koenig.org>
Date: Wed, 20 Nov 2019 18:11:31 +0000 (+0100)
Subject: interface: warn if ip6hint is truncated
X-Git-Url: http://git.openwrt.org/?p=project%2Fnetifd.git;a=commitdiff_plain;h=e45b1408284c05984b38a910a1f0a07d6c761397

interface: warn if ip6hint is truncated

When for example a /60 is assigned to a network the last 4 bits of the
ip6hint are unused. Emit a warning if any of these unused bits is set as
it indicates that someone didn't understand how the hint is used. (As I
did earlier today resulting in spending some time understanding the
code.)

Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>
---

diff --git a/interface.c b/interface.c
index 028dc6c..2fa0613 100644
--- a/interface.c
+++ b/interface.c
@@ -863,9 +863,15 @@ interface_alloc(const char *name, struct blob_attr *config, bool dynamic)
 	}
 
 	iface->assignment_hint = -1;
-	if ((cur = tb[IFACE_ATTR_IP6HINT]))
-		iface->assignment_hint = strtol(blobmsg_get_string(cur), NULL, 16) &
-				~((1 << (64 - iface->assignment_length)) - 1);
+	if ((cur = tb[IFACE_ATTR_IP6HINT])) {
+		int32_t assignment_hint = strtol(blobmsg_get_string(cur), NULL, 16);
+
+		iface->assignment_hint = assignment_hint & ~((1 << (64 - iface->assignment_length)) - 1);
+
+		if (iface->assignment_hint != assignment_hint)
+			netifd_log_message(L_WARNING, "Using truncated assignment hint %d (0x%x) for interface '%s'\n",
+					   iface->assignment_hint, iface->assignment_hint, iface->name);
+	}
 
 	if ((cur = tb[IFACE_ATTR_IP6CLASS]))
 		interface_add_assignment_classes(iface, cur);