script: don't ignore RA with zero router lifetime

As per RFC 4861 (section 4.2), 0 is a valid value for
Router Lifetime field in Router Advertisement messages.
To quote from the RFC:

> A Lifetime of 0 indicates that the router is not a
> default router and SHOULD NOT appear on the default
> router list.

In fact, this is the mechanism by which a router,
previously advertising itself as a default router must
invalidate itself. From the RFC 7084 (4.1, G-5):

> By default, if the IPv6 CE router is an advertising
> router and loses its IPv6 default router(s) and/or
> detects loss of connectivity on the WAN interface,
> it MUST explicitly invalidate itself as an IPv6
> default router on each of its advertising interfaces
> by immediately transmitting one or more Router
> Advertisement messages with the "Router Lifetime"
> field set to zero [RFC4861].

Given that Router Lifetime is stored in the `valid`
field of the `struct odhcp6c_entry`, entries with
the field set to 0 shouldn't be ignored when entry
type is `ENTRY_ROUTE`.

Signed-off-by: Gasper Stukelj <gstukelj@plume.com>
Link: https://github.com/openwrt/odhcp6c/pull/84
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/src/script.c b/src/script.c
index bb93a53..4b06c69 100644
--- a/src/script.c
+++ b/src/script.c
@@ -180,11 +180,14 @@ static void entry_to_env(const char *name, const void *data, size_t len, enum en
 
 	for (size_t i = 0; i < len / sizeof(*e); ++i) {
 		/*
-		 * The only invalid entries allowed to be passed to the script are prefix entries.
-		 * This will allow immediate removal of the old ipv6-prefix-assignment that might
-		 * otherwise be kept for up to 2 hours (see L-13 requirement of RFC 7084).
+		 * The only invalid entries allowed to be passed to the script are prefix and RA
+		 * entries. This will allow immediate removal of the old ipv6-prefix-assignment
+		 * that might otherwise be kept for up to 2 hours (see L-13 requirement of RFC 7084).
+		 * Similarly, a RA with router lifetime set to 0 indicates that the advertising
+		 * router "is not a default router and SHOULD NOT appear on the default router list"
+		 * (see RFC 4861, section 4.2).
 		 */
-		if (!e[i].valid && type != ENTRY_PREFIX)
+		if (!e[i].valid && type != ENTRY_PREFIX && type != ENTRY_ROUTE)
 			continue;
 
 		inet_ntop(AF_INET6, &e[i].target, &buf[buf_len], INET6_ADDRSTRLEN);