pimd: fix crash on non-existent interface

Fix the following crash when pim options are (un)configured on an
non-existent interface.

> r1(config)# int fgljdsf
> r1(config-if)# no ip pim unicast-bsm
> vtysh: error reading from pimd: Connection reset by peer (104)Warning: closing connection to pimd because of an I/O error!

> #0  raise (sig=<optimized out>) at ../sysdeps/unix/sysv/linux/raise.c:50
> #1  0x00007f70c8f32249 in core_handler (signo=11, siginfo=0x7fffff88e4f0, context=0x7fffff88e3c0) at lib/sigevent.c:258
> #2  <signal handler called>
> #3  0x0000556cfdd9b16d in lib_interface_pim_address_family_unicast_bsm_modify (args=0x7fffff88f130) at pimd/pim_nb_config.c:1910
> #4  0x00007f70c8efdcb5 in nb_callback_modify (context=0x556d00032b60, nb_node=0x556cffeeb9b0, event=NB_EV_APPLY, dnode=0x556d00031670, resource=0x556d00032b48, errmsg=0x7fffff88f710 "", errmsg_len=8192)
>     at lib/northbound.c:1538
> #5  0x00007f70c8efe949 in nb_callback_configuration (context=0x556d00032b60, event=NB_EV_APPLY, change=0x556d00032b10, errmsg=0x7fffff88f710 "", errmsg_len=8192) at lib/northbound.c:1888
> #6  0x00007f70c8efee82 in nb_transaction_process (event=NB_EV_APPLY, transaction=0x556d00032b60, errmsg=0x7fffff88f710 "", errmsg_len=8192) at lib/northbound.c:2016
> #7  0x00007f70c8efd658 in nb_candidate_commit_apply (transaction=0x556d00032b60, save_transaction=true, transaction_id=0x0, errmsg=0x7fffff88f710 "", errmsg_len=8192) at lib/northbound.c:1356
> #8  0x00007f70c8efd78e in nb_candidate_commit (context=..., candidate=0x556cffeb0e80, save_transaction=true, comment=0x0, transaction_id=0x0, errmsg=0x7fffff88f710 "", errmsg_len=8192) at lib/northbound.c:1389
> #9  0x00007f70c8f03e58 in nb_cli_classic_commit (vty=0x556d00025a80) at lib/northbound_cli.c:51
> #10 0x00007f70c8f043f8 in nb_cli_apply_changes_internal (vty=0x556d00025a80,
>     xpath_base=0x7fffff893bb0 "/frr-interface:lib/interface[name='fgljdsf']/frr-pim:pim/address-family[address-family='frr-routing:ipv4']", clear_pending=false) at lib/northbound_cli.c:178
> #11 0x00007f70c8f0475d in nb_cli_apply_changes (vty=0x556d00025a80, xpath_base_fmt=0x556cfdde9fe0 "./frr-pim:pim/address-family[address-family='%s']") at lib/northbound_cli.c:234
> #12 0x0000556cfdd8298f in pim_process_no_unicast_bsm_cmd (vty=0x556d00025a80) at pimd/pim_cmd_common.c:3493
> #13 0x0000556cfddcf782 in no_ip_pim_ucast_bsm (self=0x556cfde40b20 <no_ip_pim_ucast_bsm_cmd>, vty=0x556d00025a80, argc=4, argv=0x556d00031500) at pimd/pim_cmd.c:4950
> #14 0x00007f70c8e942f0 in cmd_execute_command_real (vline=0x556d00032070, vty=0x556d00025a80, cmd=0x0, up_level=0) at lib/command.c:1002
> #15 0x00007f70c8e94451 in cmd_execute_command (vline=0x556d00032070, vty=0x556d00025a80, cmd=0x0, vtysh=0) at lib/command.c:1061
> #16 0x00007f70c8e9499f in cmd_execute (vty=0x556d00025a80, cmd=0x556d00030320 "no ip pim unicast-bsm", matched=0x0, vtysh=0) at lib/command.c:1227
> #17 0x00007f70c8f51e44 in vty_command (vty=0x556d00025a80, buf=0x556d00030320 "no ip pim unicast-bsm") at lib/vty.c:616
> #18 0x00007f70c8f53bdd in vty_execute (vty=0x556d00025a80) at lib/vty.c:1379
> #19 0x00007f70c8f55d59 in vtysh_read (thread=0x7fffff896600) at lib/vty.c:2374
> #20 0x00007f70c8f4b209 in event_call (thread=0x7fffff896600) at lib/event.c:2011
> #21 0x00007f70c8ed109e in frr_run (master=0x556cffdb4ea0) at lib/libfrr.c:1217
> #22 0x0000556cfdddec12 in main (argc=2, argv=0x7fffff896828, envp=0x7fffff896840) at pimd/pim_main.c:165
> (gdb) f 3
> #3  0x0000556cfdd9b16d in lib_interface_pim_address_family_unicast_bsm_modify (args=0x7fffff88f130) at pimd/pim_nb_config.c:1910
> 1910			pim_ifp->ucast_bsm_accept =
> (gdb) list
> 1905		case NB_EV_ABORT:
> 1906			break;
> 1907		case NB_EV_APPLY:
> 1908			ifp = nb_running_get_entry(args->dnode, NULL, true);
> 1909			pim_ifp = ifp->info;
> 1910			pim_ifp->ucast_bsm_accept =
> 1911				yang_dnode_get_bool(args->dnode, NULL);
> 1912
> 1913			break;
> 1914		}
> (gdb) p pim_ifp
> $1 = (struct pim_interface *) 0x0

Fixes: 3bb513c ("lib: adapt to version 2 of libyang")
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
(cherry picked from commit 6952bea)

pimd/pim_nb_config.c

@@ -1504,11 +1504,19 @@ int routing_control_plane_protocols_control_plane_protocol_pim_address_family_re
  */
 int lib_interface_pim_address_family_create(struct nb_cb_create_args *args)
 {
+	struct interface *ifp;
+
 	switch (args->event) {
 	case NB_EV_VALIDATE:
-	case NB_EV_PREPARE:
-	case NB_EV_ABORT:
 	case NB_EV_APPLY:
+	case NB_EV_ABORT:
+		break;
+	case NB_EV_PREPARE:
+		ifp = nb_running_get_entry(args->dnode, NULL, true);
+		if (ifp->info)
+			return NB_OK;
+
+		pim_if_new(ifp, false, false, false, false);
 		break;
 	}