[ovs-dev] [PATCH v8 10/13] dp-packet: copy data from multi-seg. DPDK mbuf

Lam, Tiago tiago.lam at intel.com
Fri Jun 22 19:05:00 UTC 2018


On 18/06/2018 14:10, Eelco Chaudron wrote:
> 
> 
> On 11 Jun 2018, at 18:21, Tiago Lam wrote:
> 
>> From: Michael Qiu <qiudayu at chinac.com>
>>
>> When doing packet clone, if packet source is from DPDK driver,
>> multi-segment must be considered, and copy the segment's data one by
>> one.
>>
>> Also, lots of DPDK mbuf's info is missed during a copy, like packet
>> type, ol_flags, etc.  That information is very important for DPDK to 
>> do
>> packets processing.
>>
>> Co-authored-by: Mark Kavanagh <mark.b.kavanagh at intel.com>
>>
>> Signed-off-by: Michael Qiu <qiudayu at chinac.com>
>> Signed-off-by: Mark Kavanagh <mark.b.kavanagh at intel.com>
>> ---
>>  lib/dp-packet.c   | 76 
>> +++++++++++++++++++++++++++++++++++++++++++++++--------
>>  lib/dp-packet.h   |  3 +++
>>  lib/netdev-dpdk.c |  1 +
>>  3 files changed, 69 insertions(+), 11 deletions(-)
>>
>> diff --git a/lib/dp-packet.c b/lib/dp-packet.c
>> index d0fab94..2e65b82 100644
>> --- a/lib/dp-packet.c
>> +++ b/lib/dp-packet.c
>> @@ -48,6 +48,23 @@ dp_packet_use__(struct dp_packet *b, void *base, 
>> size_t allocated,
>>      dp_packet_set_size(b, 0);
>>  }
>>
>> +#ifdef DPDK_NETDEV
>> +void
>> +dp_packet_copy_mbuf_flags(struct dp_packet *dst, const struct 
>> dp_packet *src)
>> +{
>> +    ovs_assert(dst != NULL && src != NULL);
>> +    struct rte_mbuf *buf_dst = &(dst->mbuf);
>> +    struct rte_mbuf buf_src = src->mbuf;
>> +
>> +    buf_dst->nb_segs = buf_src.nb_segs;
>> +    buf_dst->ol_flags = buf_src.ol_flags;
>> +    buf_dst->packet_type = buf_src.packet_type;
>> +    buf_dst->tx_offload = buf_src.tx_offload;
>> +}
>> +#else
>> +#define dp_packet_copy_mbuf_flags(arg1, arg2)
>> +#endif
>> +
>>  /* Initializes 'b' as an empty dp_packet that contains the 
>> 'allocated' bytes of
>>   * memory starting at 'base'.  'base' should be the first byte of a 
>> region
>>   * obtained from malloc().  It will be freed (with free()) if 'b' is 
>> resized or
>> @@ -158,6 +175,50 @@ dp_packet_clone(const struct dp_packet *buffer)
>>      return dp_packet_clone_with_headroom(buffer, 0);
>>  }
>>
>> +#ifdef DPDK_NETDEV
>> +struct dp_packet *
>> +dp_packet_clone_with_headroom(const struct dp_packet *buffer,
>> +                              size_t headroom) {
>> +    struct dp_packet *new_buffer;
>> +    uint32_t pkt_len = dp_packet_size(buffer);
>> +
>> +    /* copy multi-seg data */
>> +    if (buffer->source == DPBUF_DPDK && buffer->mbuf.nb_segs > 1) {
>> +        uint32_t offset = 0;
>> +        void *dst = NULL;
>> +        struct rte_mbuf *tmbuf = CONST_CAST(struct rte_mbuf *,
>> +                                                &(buffer->mbuf));
>> +
>> +        new_buffer = dp_packet_new_with_headroom(pkt_len, headroom);
>> +        dp_packet_set_size(new_buffer, pkt_len + headroom);
>> +        dst = dp_packet_tail(new_buffer);
>> +
> 
> The dst is not pointing to the first data, but to the end of the data, 
> as dp_packet_set_size() has been called.  Why not just call dst = 
> dp_packet_put_uninit().

I'm taking your suggestion below, so this will be removed.

> 
>> +        while (tmbuf) {
>> +            rte_memcpy((char *)dst + offset,
>> +                       rte_pktmbuf_mtod(tmbuf, void *), 
>> tmbuf->data_len);
>> +            offset += tmbuf->data_len;
>> +            tmbuf = tmbuf->next;
> 
> Why not using rte_pktmbuf_read() here with a check its not a contiguous 
> read?
> 

Good point! We can use `rte_pktmbuf_read()` to read the data to
`new_buffer`. It should be OK since in this clause we have always more
than 1 mbuf in the chain.

Tiago.


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