dhcpcd-discuss

On 03/04/2020 17:50, Alarig Le Lay wrote:
> Hi,
>
> I’m facing a router that isn’t very friendly with NDP:
>
> Apr  3 18:12:55 core01-arendal dhcpcd[2833]: enp2s0: Router Advertisement from fe80::5e5e:abff:fe43:1ece
> Apr  3 18:12:55 core01-arendal dhcpcd[2833]: enp2s0: adding default route via fe80::5e5e:abff:fe43:1ece
> Apr  3 18:13:03 core01-arendal dhcpcd[2833]: enp2s0: fe80::5e5e:abff:fe43:1ece is unreachable
> Apr  3 18:13:04 core01-arendal dhcpcd[2833]: enp2s0: soliciting an IPv6 router
> Apr  3 18:13:16 core01-arendal dhcpcd[2833]: enp2s0: no IPv6 Routers available
> Apr  3 18:13:20 core01-arendal dhcpcd[2833]: enp2s0: Router Advertisement from fe80::5e5e:abff:fe43:1ece
> Apr  3 18:13:28 core01-arendal dhcpcd[2833]: enp2s0: fe80::5e5e:abff:fe43:1ece is unreachable
> Apr  3 18:13:29 core01-arendal dhcpcd[2833]: enp2s0: soliciting an IPv6 router
>
> and so on…
>
> If fixed the issue with this command:
> core01-arendal ~ # ip -6 neigh replace $(ip neigh show dev enp2s0 | awk '/router/ { print $1 }') dev enp2s0 lladdr $(ip neigh show dev enp2s0 | awk '/router/ { print $3 }')
>
> It’s not a bug in dhcpcd, the NDP itself is dropped from the kernel.
> So, my question is: Is it a good idea to put this command in a post-up
> hook (and a similar one in post-down), or is there a better way?

Could be a dhcpcd bug!
Does this patch help?

Roy

diff --git a/src/if-linux.c b/src/if-linux.c
index fe39dcb6..6b81197c 100644
--- a/src/if-linux.c
+++ b/src/if-linux.c
@@ -811,7 +811,7 @@ link_neigh(struct dhcpcd_ctx *ctx, __unused struct interface *ifp,
 	struct rtattr *rta;
 	size_t len;
 
-	if (nlm->nlmsg_type != RTM_NEWNEIGH && nlm->nlmsg_type != RTM_DELNEIGH)
+	if (nlm->nlmsg_type != RTM_NEWNEIGH)
 		return 0;
 	if (nlm->nlmsg_len < sizeof(*r))
 		return -1;
@@ -820,13 +820,11 @@ link_neigh(struct dhcpcd_ctx *ctx, __unused struct interface *ifp,
 	rta = RTM_RTA(r);
 	len = RTM_PAYLOAD(nlm);
         if (r->ndm_family == AF_INET6) {
-		bool reachable;
+		bool unreachable;
 		struct in6_addr addr6;
 
-		reachable = (nlm->nlmsg_type == RTM_NEWNEIGH &&
-		    r->ndm_state &
-		    (NUD_REACHABLE | NUD_STALE | NUD_DELAY | NUD_PROBE |
-		     NUD_PERMANENT));
+		unreachable = (nlm->nlmsg_type == RTM_NEWNEIGH &&
+		    r->ndm_state & NUD_FAILED);
 		memset(&addr6, 0, sizeof(addr6));
 		for (; RTA_OK(rta, len); rta = RTA_NEXT(rta, len)) {
 			switch (rta->rta_type) {
@@ -836,7 +834,7 @@ link_neigh(struct dhcpcd_ctx *ctx, __unused struct interface *ifp,
 				break;
 			}
 		}
-		ipv6nd_neighbour(ctx, &addr6, reachable);
+		ipv6nd_neighbour(ctx, &addr6, !unreachable);
 	}
 
 	return 0;