lib, zebra: Allow for zebra to recognize that a route has gotten desynced

FRR does not use the NLM_F_APPEND semantics ( in fact I would argue that
the NLM_F_APPEND semantics just introduce pain for all parties involved )
I would also argue that most people who use the kernel netlink api
have recognized that NLM_F_APPEND for a route is a recipe for disaster
that is well documented and as such it is not used as anything other
than a curiousity by operators.

See:
https://bugzilla.redhat.com/show_bug.cgi?id=1337855
https://github.com/thom311/libnl/issues/226

Are 2 great examples of how confusing it is for anyone in user
space to know what the correct thing to do is.  Given that
new fields can be added with no semantics to allow us to know
what has resulted in a change or not.

In an attempt to recognize this, let's note that FRR
believes it has gotten out of sync with the kernel.
Future commits will react to the desynchronized route
and request from the kernel a reload of that specific
route if possible.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>

diff --git a/lib/zclient.h b/lib/zclient.h
index fb5da9aad2a9f293264ca643d98588b9d9d713c2..e6920d533f3412efa0ef1aefb294373d2b3f4fb2 100644 (file)
--- a/lib/zclient.h
+++ b/lib/zclient.h
@@ -540,6 +540,13 @@ struct zapi_route {
  */
 #define ZEBRA_FLAG_OFFLOAD_FAILED     0x200
 
+/*
+ * This flag lets us know that we think the route entry
+ * received has caused us to be out of sync with the
+ * kernel (NLM_F_APPEND at the very least )
+ */
+#define ZEBRA_FLAG_OUTOFSYNC          0x400
+
        /* The older XXX_MESSAGE flags live here */
        uint32_t message;
 

diff --git a/zebra/rt_netlink.c b/zebra/rt_netlink.c
index 3a8f5264f42133c3e5df3ee62e1b6965b2744021..d02cc93f5f738672133f13311a16267e4470fe94 100644 (file)
--- a/zebra/rt_netlink.c
+++ b/zebra/rt_netlink.c
@@ -803,6 +803,9 @@ static int netlink_route_change_read_unicast(struct nlmsghdr *h, ns_id_t ns_id,
        if (rtm->rtm_flags & RTM_F_OFFLOAD_FAILED)
                flags |= ZEBRA_FLAG_OFFLOAD_FAILED;
 
+       if (h->nlmsg_flags & NLM_F_APPEND)
+               flags |= ZEBRA_FLAG_OUTOFSYNC;
+
        /* Route which inserted by Zebra. */
        if (selfroute) {
                flags |= ZEBRA_FLAG_SELFROUTE;

diff --git a/zebra/zebra_vty.c b/zebra/zebra_vty.c
index f68a656710f3b86df230bf0087f5263cc7a5f890..6526cc1ae7b4e31450e301203beb61de567e8ebc 100644 (file)
--- a/zebra/zebra_vty.c
+++ b/zebra/zebra_vty.c
@@ -222,6 +222,9 @@ static char re_status_output_char(const struct route_entry *re,
                    && CHECK_FLAG(re->flags, ZEBRA_FLAG_OFFLOAD_FAILED))
                        return 'o';
 
+               if (CHECK_FLAG(re->flags, ZEBRA_FLAG_OUTOFSYNC))
+                       return 'd';
+
                if (star_p)
                        return '*';
                else