pinctrl: Fix segfault seen when creating mac_binding for local GARPs.

Segfault is seen with the below trace.  This patch fixes the issue by
checking 'ovnsb_idl_txn' is not NULL before continuing in the function
send_garp_locally().

    #0  ovsdb_idl_txn_insert (txn=0x0, class=0x64b170 <sbrec_table_classes+816>, uuid=0x0) at ../lib/ovsdb-idl.c:3504
    #1  0x000000000041b068 in mac_binding_add (ovnsb_idl_txn=ovnsb_idl_txn@entry=0x0,
    sbrec_mac_binding_by_lport_ip=sbrec_mac_binding_by_lport_ip@entry=0xf6a7e0, logical_port=0xfd0d70 "lr0-pub", dp=0xfd0f20,
    ea=..., ip=0xf67be0 "172.24.4.221") at ../controller/pinctrl.c:3877
    #2  0x000000000041b18b in send_garp_locally (ovnsb_idl_txn=ovnsb_idl_txn@entry=0x0,
    sbrec_mac_binding_by_lport_ip=sbrec_mac_binding_by_lport_ip@entry=0xf6a7e0, local_datapaths=local_datapaths@entry=0xf766f0,
    in_pb=in_pb@entry=0xfd3370, ea=..., ip=3708033196) at ../controller/pinctrl.c:3913
    #3  0x000000000041d1be in send_garp_rarp_update (ovnsb_idl_txn=ovnsb_idl_txn@entry=0x0,
    sbrec_mac_binding_by_lport_ip=sbrec_mac_binding_by_lport_ip@entry=0xf6a7e0, local_datapaths=local_datapaths@entry=0xf766f0,
    binding_rec=0xfd3370, nat_addresses=nat_addresses@entry=0x7ffdb9295b80) at ../controller/pinctrl.c:4118
    #4  0x0000000000425c88 in send_garp_rarp_prepare (active_tunnels=0xf76770, local_datapaths=0xf766f0, chassis=0xfdb4e0,
    br_int=<optimized out>, sbrec_mac_binding_by_lport_ip=0xf6a7e0, sbrec_port_binding_by_name=0xf6a090,
    sbrec_port_binding_by_datapath=<optimized out>, ovnsb_idl_txn=0x0) at ../controller/pinctrl.c:5491
    #5  pinctrl_run (ovnsb_idl_txn=0x0, sbrec_datapath_binding_by_key=<optimized out>,
    sbrec_port_binding_by_datapath=<optimized out>, sbrec_port_binding_by_key=<optimized out>,
    sbrec_port_binding_by_name=0xf6a090, sbrec_mac_binding_by_lport_ip=0xf6a7e0, sbrec_igmp_groups=0xf6ab90,
    sbrec_ip_multicast_opts=0xf6a9c0, dns_table=0xf33960, ce_table=0xf33960, svc_mon_table=0xf33960, br_int=0xf67d50,
    chassis=0xfdb4e0, local_datapaths=0xf766f0, active_tunnels=0xf76770) at ../controller/pinctrl.c:3169
    #6  0x0000000000408e91 in main (argc=<optimized out>, argv=<optimized out>) at ../controller/ovn-controller.c:2789

Fixes: a2b88dc("pinctrl: Directly update MAC_Bindings created by self originated GARPs.")
Signed-off-by: Numan Siddique <[email protected]>
Acked-by: Dumitru Ceara <[email protected]>

controller/pinctrl.c

@@ -3859,7 +3859,8 @@ mac_binding_lookup(struct ovsdb_idl_index *sbrec_mac_binding_by_lport_ip,
     return retval;
 }
 
-/* Update or add an IP-MAC binding for 'logical_port'. */
+/* Update or add an IP-MAC binding for 'logical_port'.
+ * Caller should make sure that 'ovnsb_idl_txn' is valid. */
 static void
 mac_binding_add(struct ovsdb_idl_txn *ovnsb_idl_txn,
                 struct ovsdb_idl_index *sbrec_mac_binding_by_lport_ip,
@@ -3894,6 +3895,10 @@ send_garp_locally(struct ovsdb_idl_txn *ovnsb_idl_txn,
                   const struct sbrec_port_binding *in_pb,
                   struct eth_addr ea, ovs_be32 ip)
 {
+    if (!ovnsb_idl_txn) {
+        return;
+    }
+
     const struct local_datapath *ldp =
         get_local_datapath(local_datapaths, in_pb->datapath->tunnel_key);