Petri Savolainen(psavol) replied on github web page:
@@ -401,30 +401,39 @@ uint32_t odp_packet_buf_len(odp_packet_t pkt);
* Packet data pointer
- * Returns the current packet data pointer. When a packet is received
- * from packet input, this points to the first byte of the received
- * packet. Packet level offsets are calculated relative to this position.
+ * Returns pointer to the first byte of packet data. When packet is segmented,
+ * only a portion of packet data follows the pointer. When unsure, use e.g.
+ * odp_packet_seg_len() to check the data length following the pointer. Packet
+ * level offsets are calculated relative to this position.
- * User can adjust the data pointer with head_push/head_pull (does not modify
- * segmentation) and add_data/rem_data calls (may modify segmentation).
+ * When a packet is received from packet input, this points to the first byte
+ * of the received packet. Pool configuration parameters may be used to ensure
+ * that the first packet segment contains all/most of the data relevant to the
+ * application.
+ * User can adjust the data pointer with e.g. push_head/pull_head (does not
+ * modify segmentation) and extend_head/trunc_head (may modify segmentation)
+ * calls.
* @param pkt Packet handle
* @return Pointer to the packet data
- * @see odp_packet_l2_ptr(), odp_packet_seg_len()
+ * @see odp_packet_seg_len(), odp_packet_push_head(), odp_packet_extend_head()
seg_len / push_head / extend_head are mentioned above. Packet_offset is not
specialized for handling first N bytes of packet, so it's not directly related
to these ones.
> Petri Savolainen(psavol) wrote:
> packet_offset is for different purpose (access data on arbitrary offset),
> these calls are optimized for the common case (offset zero). Also
> odp_packet_seg_data_len(), the new data_seg_len(), odp_packet_l2_ptr(),
> odp_packet_l3_ptr() and odp_packet_l4_ptr() output seg len, but we don't
> need to list all possible ways to get it. It's enough that the reader
> understands that a packet may have segments and segment length is different
> thing than total packet length
>> Dmitry Eremin-Solenikov(lumag) wrote:
>> And here too, please.
>>> Dmitry Eremin-Solenikov(lumag) wrote:
>>> odp_packet_seg_len() **or odp_packet_offset()**, if you don't mind.
updated_at 2018-02-23 07:36:58