Thanks Damjan, This clarifies things regarding the cloning mechanism. However using n_clones=2 and putting the 2nd clone in the frame still results in the buffer being sent only to the host interface, the flow I'm using is this: (minimal example)
// getting host interface node index from sw if index > vnet_hw_interface_t * host_intf = vnet_get_sup_hw_interface (vnm, > sw_if_index); > u32 host_interface_node_index = host_intf->tx_node_index; > > // original frame > vlib_frame_t *frame = vlib_get_frame_to_node(vm, node_index); > u32 *to_next = vlib_frame_vector_args (frame); > > // frame for the cloned packet > vlib_frame_t *host_if_frame = vlib_get_frame_to_node(vm, > host_interface_node_index); > u32 *intf_host_to_next = vlib_frame_vector_args (host_if_frame); > host_if_frame->n_vectors = 1; > > // cloning the buffer > u32 cbi0[2]; > u16 n_cloned = vlib_buffer_clone (vm, bi0, &cbi0, 2, > VLIB_BUFFER_CLONE_HEAD_SIZE); > > // enqueuing both packets to two different nodes > to_next[0] = bi0; > intf_host_to_next[0] = cbi0[1]; > vlib_put_frame_to_node (vm, node_index, frame); > vlib_put_frame_to_node (vm, host_interface_node_index, host_if_frame); > This results in the packet being sent only to host interface. I've checked vpp source code for similar use cases that use buffer cloning but didn't find a place when a node mirrors a packet and enqueues it to two different nodes. On Thu, Apr 8, 2021 at 1:04 PM Damjan Marion <[email protected]> wrote: > > You need to say n_clones = 2 to get 2. > ref_cnt is updated only on tail buffer if tail buffer(s) exists. > Head buffers always have ref_cnt = 1. > > Reason for that is that you actually never want to clone head buffer > simply as if packet goes to 2 > different interfaces it needs to have different L2 headers. > > So it works as follows: > > if n_clones = 1, simply return same buffer index > > if n_clones > 1 and packet size is < VLIB_BUFFER_CLONE_HEAD_SIZE: > - allocate (n_clones-1) new buffers > - memcpy whole payload from original buffer to each allocated buffer > > if n_clones > 1 and packet size is >= VLIB_BUFFER_CLONE_HEAD_SIZE > - allocate (n_clones) new buffers > - for each allocated buffer: > - memcpy first VLIB_BUFFER_CLONE_HEAD_SIZE bytes of payload from > original buffer > - set b->next_buffer_index to point to the original buffer > - advance b->current_data for VLIB_BUFFER_CLONE_HEAD_SIZE > - set b->ref_cnt of the original buffer (and all his tails) to be n_clones > > > Hope this explains… > > — > Damjan > > > > > > > On 08.04.2021., at 11:37, David Gohberg <[email protected]> wrote: > > > > Hi, > > > > In my node processing function, I want some buffers to be cloned and > sent to a specific host interface while also be sent to the "normal" > interface resolved in the node. > > At the end, the node should be able to send the buffers to two different > interfaces simultaneously. > > packet -> node -> interface 1 > > | > > V > > cloned packet > > to host interface > > > > In my single loop where I process the buffers I added a call to this > function: > > > > static inline void replicate_and_send_buffer(vnet_main_t *vnm, > vlib_main_t * vm, > > vlib_node_runtime_t * node, > > u32 bi0, > > u16 sw_if_index) > > { > > u32 cbi0; > > u16 n_cloned = vlib_buffer_clone (vm, bi0, &cbi0, 1, > VLIB_BUFFER_CLONE_HEAD_SIZE); > > vnet_hw_interface_t * host_intf = vnet_get_sup_hw_interface > (vnm, sw_if_index); > > u32 node_index = host_intf->tx_node_index; > > vlib_frame_t *host_if_frame = vlib_get_frame_to_node(vm, > node_index); > > host_if_frame->n_vectors = 1; > > u32 *to_next = vlib_frame_vector_args (host_if_frame); > > to_next[0] = cbi0; > > vlib_put_frame_to_node (vm, node_index, host_if_frame); > > } > > > > What is happening here is that I clone the original buffer and put it in > a frame corresponding to the host interface node (in addition to the frame > of the main loop pointing to a different node) > > Running this code leads me to double-free crash. > > > > I noticed that vlib_buffer_clone, when asked to create 1 clone, > presented me with a new buffer index that has the same address as the > original buffer, but the ref_count stays 1. Looking at the > vlib_buffer_clone confirms that it only copies the packet for n_clones > 1, > but still not updating the ref_count. So it looks like I'm missing > something wrt how the cloning works. > > > > I changed the code to create 2 clones and tried to use the 2nd clone in > the host interface frame. This resulted in the packet being sent only to > the host interface, but not to both of the interfaces. > > > > I'm probably doing something wrong, how can I achieve the desired > behavior? > > > > Thanks, > > David > > > > > > > >
-=-=-=-=-=-=-=-=-=-=-=- Links: You receive all messages sent to this group. View/Reply Online (#19144): https://lists.fd.io/g/vpp-dev/message/19144 Mute This Topic: https://lists.fd.io/mt/81938105/21656 Group Owner: [email protected] Unsubscribe: https://lists.fd.io/g/vpp-dev/unsub [[email protected]] -=-=-=-=-=-=-=-=-=-=-=-
