I edited the example for simplicity, frame->n_vectors is incremented on
each iteration of the main loop. maybe that is the issue?
Here is the code with more context:
while (n_left_from > 0)
> {
> u32 bi0;
> bi0 = from[0];
> from++;
> n_left_from--;
> to_frame = vlib_get_frame_to_node (vm, node_index);
> to_next = vlib_frame_vector_args (to_frame);
> // 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;
> // 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
> intf_host_to_next[0] = cbi0[1];
> vlib_put_frame_to_node (vm, host_interface_node_index,
> host_if_frame);
> to_next[0] = bi0;
> to_next++;
> to_frame->n_vectors++;
> }
> vlib_put_frame_to_node (vm, node_index, to_frame);
> return from_frame->n_vectors;
On Thu, Apr 8, 2021 at 2:35 PM Damjan Marion <[email protected]> wrote:
>
> Setting frame->n_vectors may help :)
>
> —
> Damjan
>
> On 08.04.2021., at 13:11, David Gohberg <[email protected]> wrote:
>
> 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
>> >
>> >
>> >
>>
>>
>
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