[VPP-1521] L2BD tests trigger assert in vlib/buffer.h

[vvalderrv]

The debug tests of l2bd triggers following crash:

make test-debug TEST=l2bd

 

#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51

#1  0x00007f5ad2d04801 in __GI_abort () at abort.c:79

#2  0x0000559e53c5d30f in os_exit (code=1) at /vpp/master/src/vpp/vnet/main.c:357

#3  0x00007f5ad38fdef0 in unix_signal_handler (signum=6, si=0x7f5a92bfd6b0, uc=0x7f5a92bfd580)

    at /vpp/master/src/vlib/unix/main.c:156

#4  <signal handler called>

#5  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51

#6  0x00007f5ad2d04801 in __GI_abort () at abort.c:79

#7  0x0000559e53c5d294 in os_panic () at /vpp/master/src/vpp/vnet/main.c:333

#8  0x00007f5ad30f2b77 in debugger () at /vpp/master/src/vppinfra/error.c:84

#9  0x00007f5ad30f2fb2 in _clib_error (how_to_die=2, function_name=0x0, line_number=0, 

    fmt=0x7f5ad494c3d0 "%s:%d (%s) assertion `%s' fails") at /vpp/master/src/vppinfra/error.c:143

#10 0x00007f5ad3e15cfd in vlib_buffer_advance (b=0x7f568d913a00, l=14) at /vpp/master/src/vlib/buffer.h:239

#11 0x00007f5ad3e17c08 in parse_header (variant=ETHERNET_INPUT_VARIANT_ETHERNET, b0=0x7f568d913a00, 

    type=0x7f5a92bfe734, orig_type=0x7f5a92bfe736, outer_id=0x7f5a92bfe73c, inner_id=0x7f5a92bfe73e, 

    match_flags=0x7f5a92bfe744) at /vpp/master/src/vnet/ethernet/node.c:122

#12 0x00007f5ad3e1a20f in ethernet_input_inline (vm=0x7f5ad3b2a340 <vlib_global_main>, node=0x7f5a9293acc0, 

    from=0x7f5a92823230, n_packets=256, variant=ETHERNET_INPUT_VARIANT_ETHERNET)

    at /vpp/master/src/vnet/ethernet/node.c:856

#13 0x00007f5ad3e1b800 in ethernet_input_node_fn_avx512 (vm=0x7f5ad3b2a340 <vlib_global_main>, 

    node=0x7f5a9293acc0, frame=0x7f5a92823200) at /vpp/master/src/vnet/ethernet/node.c:1274

#14 0x00007f5ad38a0c2b in dispatch_node (vm=0x7f5ad3b2a340 <vlib_global_main>, node=0x7f5a9293acc0, 

    type=VLIB_NODE_TYPE_INTERNAL, dispatch_state=VLIB_NODE_STATE_POLLING, frame=0x7f5a92823200,