Hi all, I'd like some feedback about the VLIB_BUFFER_TRACE_TRAJECTORY debug feature in VPP. The goal of this feature is to save the nodes traversed by a buffer in the buffer metadata (opaque2->trajectory) for debug purpose.
As far as I can see, it is broken as soon as the buffer is copied/cloned or similar, as the pointer to the vector used to save the trajectory is now shared by multiple buffers. Basically anything copying opaque2 blindly will break it, eg. - vlib_buffer_copy() and friends, eg. https://git.fd.io/vpp/tree/src/vlib/buffer_funcs.h#n1071 - arp/ipv6 nd nodes: https://git.fd.io/vpp/tree/src/vnet/ip-neighbor/ip4_neighbor.c#n225 and https://git.fd.io/vpp/tree/src/vnet/ip-neighbor/ip6_neighbor.c#n221 Any idea? Maybe the easiest way to fix it would be to grow the vlib_buffer_t metadata when it is enabled, so that we can stash the node indices directly in the buffer metadata instead of relying on an external vector? Best ben
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