tests: fix isis_lsp_bits_topo1 race condition

Level 2 adjacency list is not supposed to be always set.

> #0  raise (sig=<optimized out>) at ../sysdeps/unix/sysv/linux/raise.c:50
> #1  0x00007f9f0353274f in core_handler (signo=6, siginfo=0x7ffe95260770, context=0x7ffe95260640) at lib/sigevent.c:258
> #2  <signal handler called>
> FRRouting#3  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
> FRRouting#4  0x00007f9f0324e537 in __GI_abort () at abort.c:79
> FRRouting#5  0x00007f9f035744ea in _zlog_assert_failed (xref=0x7f9f0362c6c0 <_xref.15>, extra=0x0) at lib/zlog.c:789
> FRRouting#6  0x00007f9f034d25ee in listnode_head (list=0x0) at lib/linklist.c:316
> FRRouting#7  0x000055cd65aaa481 in lib_interface_state_isis_adjacencies_adjacency_get_next (args=0x7ffe95261730) at isisd/isis_nb_state.c:101
> FRRouting#8  0x00007f9f034feadd in nb_callback_get_next (nb_node=0x55cd673c0190, parent_list_entry=0x55cd67570d30, list_entry=0x55cd6758f8a0) at lib/northbound.c:1748
> FRRouting#9  0x00007f9f0350bf07 in __walk (ys=0x55cd675782b0, is_resume=false) at lib/northbound_oper.c:1264
> FRRouting#10 0x00007f9f0350deaa in nb_op_walk_start (ys=0x55cd675782b0) at lib/northbound_oper.c:1741
> FRRouting#11 0x00007f9f0350e079 in nb_oper_iterate_legacy (xpath=0x55cd67595c60 "/frr-interface:lib", translator=0x0, flags=0, cb=0x0, cb_arg=0x0, tree=0x7ffe952621b0) at lib/northbound_oper.c:1803
> FRRouting#12 0x00007f9f03507661 in show_yang_operational_data_magic (self=0x7f9f03634a80 <show_yang_operational_data_cmd>, vty=0x55cd675a61f0, argc=4, argv=0x55cd6758eab0,
>     xpath=0x55cd67595c60 "/frr-interface:lib", json=0x0, xml=0x0, translator_family=0x0, with_config=0x0) at lib/northbound_cli.c:1576
> FRRouting#13 0x00007f9f035037f0 in show_yang_operational_data (self=0x7f9f03634a80 <show_yang_operational_data_cmd>, vty=0x55cd675a61f0, argc=4, argv=0x55cd6758eab0)
>     at ./lib/northbound_cli_clippy.c:906
> FRRouting#14 0x00007f9f0349435d in cmd_execute_command_real (vline=0x55cd6758e490, vty=0x55cd675a61f0, cmd=0x0, up_level=0) at lib/command.c:1003
> FRRouting#15 0x00007f9f03494477 in cmd_execute_command (vline=0x55cd67585340, vty=0x55cd675a61f0, cmd=0x0, vtysh=0) at lib/command.c:1053
> FRRouting#16 0x00007f9f03494a0c in cmd_execute (vty=0x55cd675a61f0, cmd=0x55cd67579040 "do show yang operational-data /frr-interface:lib", matched=0x0, vtysh=0) at lib/command.c:1228
> FRRouting#17 0x00007f9f0355239d in vty_command (vty=0x55cd675a61f0, buf=0x55cd67579040 "do show yang operational-data /frr-interface:lib") at lib/vty.c:625
> FRRouting#18 0x00007f9f03554136 in vty_execute (vty=0x55cd675a61f0) at lib/vty.c:1388
> FRRouting#19 0x00007f9f0355634c in vtysh_read (thread=0x7ffe952647a0) at lib/vty.c:2400
> FRRouting#20 0x00007f9f0354b6f6 in event_call (thread=0x7ffe952647a0) at lib/event.c:1996
> FRRouting#21 0x00007f9f034d1365 in frr_run (master=0x55cd67204da0) at lib/libfrr.c:1231
> FRRouting#22 0x000055cd65a3236e in main (argc=7, argv=0x7ffe952649c8, envp=0x7ffe95264a08) at isisd/isis_main.c:354

Fixes: 2a1c520 ("isisd: split northbound callbacks into multiple files")
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>

isisd/isis_nb_state.c

@@ -98,6 +98,8 @@ const void *lib_interface_state_isis_adjacencies_adjacency_get_next(
 			 * adjacencies list.
 			 */
 			list = circuit->u.bc.adjdb[ISIS_LEVEL2 - 1];
+			if (!list)
+				break;
 			adj_next = listnode_head(list);
 		}
 		break;