pimd: Ensure new generation_id is different from previous
The RFC states that an interfaces generation_id must be changed
if it experiences an if down. From 4.3.1:
The GenID option contains a randomly generated
32-bit value that is regenerated each time PIM forwarding is started
or restarted on the interface, including when the router itself
restarts.
Since we are only grabbing a new generation_id without comparing
it to the previous generation_id, it is possible that random
can generate the exact same number.
Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
diff --git a/pimd/pim_pim.c b/pimd/pim_pim.c
index 7dcb501..41c26a8 100644
--- a/pimd/pim_pim.c
+++ b/pimd/pim_pim.c
@@ -698,6 +698,7 @@
{
struct pim_interface *pim_ifp;
struct in_addr ifaddr;
+ uint32_t old_genid;
pim_ifp = ifp->info;
zassert(pim_ifp);
@@ -720,7 +721,18 @@
pim_ifp->t_pim_sock_read = 0;
pim_ifp->pim_sock_creation = pim_time_monotonic_sec();
- pim_ifp->pim_generation_id = random();
+ /*
+ * Just ensure that the new generation id
+ * actually chooses something different.
+ * Actually ran across a case where this
+ * happened, pre-switch to random().
+ * While this is unlikely to happen now
+ * let's make sure it doesn't.
+ */
+ old_genid = pim_ifp->pim_generation_id;
+
+ while (old_genid == pim_ifp->pim_generation_id)
+ pim_ifp->pim_generation_id = random();
zlog_info("PIM INTERFACE UP: on interface %s ifindex=%d",
ifp->name, ifp->ifindex);