bfdd: don't allow link-local without interface

When using link-local addresses we must provide scope-id to the
operating system so it knows where to send packets.

Spotted by Pavel Ivashchenko (@zays26).

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>

diff --git a/bfdd/bfdd_northbound.c b/bfdd/bfdd_northbound.c
index 7cd2fb6b9aebe49d36e9ee492466ac0e227c576d..6bcc5d66bbd183efd0ae1880f17a577c47d64a91 100644 (file)
--- a/bfdd/bfdd_northbound.c
+++ b/bfdd/bfdd_northbound.c
@@ -58,10 +58,39 @@ static int bfd_session_create(enum nb_event event, const struct lyd_node *dnode,
                              union nb_resource *resource, bool mhop)
 {
        struct bfd_session *bs;
+       const char *ifname;
        struct bfd_key bk;
+       struct in6_addr i6a;
 
        switch (event) {
        case NB_EV_VALIDATE:
+               /*
+                * When `dest-addr` is IPv6 and link-local we must
+                * require interface name, otherwise we can't figure
+                * which interface to use to send the packets.
+                *
+                * `memset` `i6a` in case address is IPv4 or non
+                * link-local IPv6, it should also avoid static
+                * analyzer warning about unset memory read.
+                */
+               memset(&i6a, 0, sizeof(i6a));
+               yang_dnode_get_ipv6(&i6a, dnode, "./dest-addr");
+
+               /*
+                * To support old FRR versions we must allow empty
+                * interface to be specified, however that should
+                * change in the future.
+                */
+               if (yang_dnode_exists(dnode, "./interface"))
+                       ifname = yang_dnode_get_string(dnode, "./interface");
+               else
+                       ifname = "";
+
+               if (IN6_IS_ADDR_LINKLOCAL(&i6a) && strlen(ifname) == 0) {
+                       zlog_warn("%s: when using link-local you must specify "
+                                 "an interface.", __func__);
+                       return NB_ERR_VALIDATION;
+               }
                break;
 
        case NB_EV_PREPARE: