VLIB_BUFFER_TRACE_TRAJECTORY宏的作用

可以通过开启宏VLIB_BUFFER_TRACE_TRAJECTORY，在mbuf里记录mbuf经过的node个数以及所经过的node的index：

if (VLIB_BUFFER_TRACE_TRAJECTORY && frame)

{

int i;

int log_index;

u32 * from;

from = vlib_frame_vector_args (frame);

for (i = 0; i < frame->n_vectors; i++)

{

vlib_buffer_t *b = vlib_get_buffer (vm, from[i]);

ASSERT (b->pre_data[0] < 32);

log_index = b->pre_data[0]++ + 1;

b->pre_data[log_index] = node->node_index;

}

n = node->function (vm, node, frame);

}

用以下函数打印记录的node信息

void vlib_dump_context_trace (vlib_main_t*vm, u32 bi)

{

vlib_node_main_t * vnm = &vm->node_main;

vlib_buffer_t * b;

u8 i, n;

if (VLIB_BUFFER_TRACE_TRAJECTORY)

{

b = vlib_get_buffer (vm, bi);

n = b->pre_data[0];

fformat(stderr, "Context trace for bi %d b 0x%llx, visited%d\n",

bi, b, n);

if (n == 0 || n > 20)

{

fformat(stderr, "n is unreasonable\n");

return;

}

for (i = 0; i < n; i++)

{

u32 node_index;

node_index = b->pre_data[i+1];

if (node_index > vec_len (vnm->nodes))

{

fformat(stderr, "Skip bogusnode index %d\n", node_index);

continue;

}

fformat(stderr, "%v (%d)\n",vnm->nodes[node_index]->name,

node_index);

}

}

else

{

fformat(stderr,

"in vlib/buffers.h,#define VLIB_BUFFER_TRACE_TRAJECTORY 1\n");

}

}