On 28/05/2018 16:42, Loftus, Ciara wrote:
>>
>> The dp_packet_put*() function - dp_packet_put_uninit(), dp_packet_put()
>> and dp_packet_put_zeros() - are, in their current implementation,
>> operating on the data buffer of a dp_packet as if it were contiguous,
>> which in the case of multi-segment mbufs means they operate on the first
>> mbuf in the chain. However, in the case of dp_packet_put_uninit(), for
>> example, it is the data length of the last mbuf in the mbuf chain that
>> should be adjusted. These functions have thus been modified to support
>> multi-segment mbufs.
>>
>> Additionally, most of the core logic in dp_pcket_put_uninit() was moved
>> to a new helper function, dp_packet_put_uninit()_, to abstract the
>> implementation details from the API, since in the case of multi-seg
>> mbufs a new struct is returned that holds the mbuf and offset that
>> constitute the tail. For the single mbuf case a pointer to the byte that
>> constitute the tail still returned.
>>
>> Co-authored-by: Mark Kavanagh <[email protected]>
>>
>> Signed-off-by: Mark Kavanagh <[email protected]>
>> Signed-off-by: Tiago Lam <[email protected]>
>> ---
>> lib/dp-packet.c | 97
>> +++++++++++++++++++++++++++++++++++++++++++++++++--------
>> lib/dp-packet.h | 5 +++
>> 2 files changed, 89 insertions(+), 13 deletions(-)
>>
>> diff --git a/lib/dp-packet.c b/lib/dp-packet.c
>> index 782e7c2..1b39946 100644
>> --- a/lib/dp-packet.c
>> +++ b/lib/dp-packet.c
>> @@ -312,27 +312,66 @@ dp_packet_shift(struct dp_packet *b, int delta)
>> }
>> }
>>
>> -/* Appends 'size' bytes of data to the tail end of 'b', reallocating and
>> - * copying its data if necessary. Returns a pointer to the first byte of
>> the
>> - * new data, which is left uninitialized. */
>
> Is the function rte_pktmbuf_append()
> (http://dpdk.org/doc/api/rte__mbuf_8h.html#ad5b0cd686ad3bcbb83416ca8395a080b)
> of any use here?
>
Unfortunately most of the functions in rte_mbuf.h operate at the mbuf
level. In this case `rte_pktmbuf_append()` wouldn't allocate any more
data and would just return NULL if there's not enough tail room. To deal
with this why `dp_packet_resize__()` has been worked on to allocate more
mbufs when necessary.
>> -void *
>> -dp_packet_put_uninit(struct dp_packet *b, size_t size)
>> +static void *
>> +dp_packet_put_uninit_(struct dp_packet *b, size_t size)
>> {
>> void *p;
>> dp_packet_prealloc_tailroom(b, size);
>> +#ifdef DPDK_NETDEV
>> + p = dp_packet_mbuf_tail(b);
>> + /* In the case of multi-segment mbufs, the data length of the last mbuf
>> + * should be adjusted by 'size' bytes. The packet length of the entire
>> + * mbuf chain (stored in the first mbuf of said chain) is adjusted in
>> + * the normal execution path below.
>> + */
>> +
>> + struct rte_mbuf *tmbuf = (struct rte_mbuf *) p;
>> + struct mbuf_tail *mbuf_tail = xmalloc(sizeof(*mbuf_tail));
>> + size_t pkt_len = size;
>> +
>> + mbuf_tail->mbuf = tmbuf;
>> + mbuf_tail->ofs = tmbuf->data_len;
>> +
>> + /* Adjust size of intermediate mbufs from current tail to end */
>> + while (tmbuf && pkt_len > 0) {
>> + tmbuf->data_len = MIN(pkt_len, tmbuf->buf_len - tmbuf->data_off);
>> + pkt_len -= tmbuf->data_len;
>> +
>> + tmbuf = tmbuf->next;
>> + }
>> +
>> + p = (void *) mbuf_tail;
>> +#else
>> p = dp_packet_tail(b);
>> +#endif
>> dp_packet_set_size(b, dp_packet_size(b) + size);
>> +
>> return p;
>> }
>>
>> -/* Appends 'size' zeroed bytes to the tail end of 'b'. Data in 'b' is
>> - * reallocated and copied if necessary. Returns a pointer to the first
>> byte of
>> - * the data's location in the dp_packet. */
>> +static void *
>> +dp_packet_tail_to_addr(struct dp_packet *b OVS_UNUSED, void *p) {
>> +#ifdef DPDK_NETDEV
>> + struct mbuf_tail *mbuf_tail = (struct mbuf_tail *) p;
>> + p = (void *) rte_pktmbuf_mtod_offset(mbuf_tail->mbuf, void *,
>> + mbuf_tail->ofs);
>> +#endif
>> +
>> + return p;
>> +}
>> +
>> +/* Appends 'size' bytes of data to the tail end of 'b', reallocating and
>> + * copying its data if necessary. Returns a pointer to the first byte of
>> the
>> + * new data, which is left uninitialized. */
>> void *
>> -dp_packet_put_zeros(struct dp_packet *b, size_t size)
>> +dp_packet_put_uninit(struct dp_packet *b, size_t size)
>> {
>> - void *dst = dp_packet_put_uninit(b, size);
>> - memset(dst, 0, size);
>> + void *tail = dp_packet_put_uninit_(b, size);
>> +
>> + void *dst = dp_packet_tail_to_addr(b, tail);
>> +
>> + free(tail);
>
> For the !DPDK_NETDEV case, the code remains the same (as it should) except
> this call to free(). It could maybe cause a problem.
>
This is a nice spot! It was indeed leading to memory corruption.
>> +
>> return dst;
>> }
>>
>> @@ -342,8 +381,40 @@ dp_packet_put_zeros(struct dp_packet *b, size_t
>> size)
>> void *
>> dp_packet_put(struct dp_packet *b, const void *p, size_t size)
>> {
>> - void *dst = dp_packet_put_uninit(b, size);
>> - memcpy(dst, p, size);
>> + void *tail = dp_packet_put_uninit_(b, size);
>> +#ifdef DPDK_NETDEV
>> + struct mbuf_tail *mbuf_tail = (struct mbuf_tail *) tail;
>> +
>> + dp_packet_mbuf_write(mbuf_tail->mbuf, mbuf_tail->ofs, size, p);
>
> This function doesn't exist yet.
>
It is included in the next patch in the series (07/13). But it was meant
to be here... I'll rebase to include it here for the next iteration.
Tiago.
>> +#else
>> + memcpy(tail, p, size);
>> +#endif
>> +
>> + void *dst = dp_packet_tail_to_addr(b, tail);
>> +
>> + free(tail);
>> +
>> + return dst;
>> +}
>> +
>> +/* Appends 'size' zeroed bytes to the tail end of 'b'. Data in 'b' is
>> + * reallocated and copied if necessary. Returns a pointer to the first
>> byte of
>> + * the data's location in the dp_packet. */
>> +void *
>> +dp_packet_put_zeros(struct dp_packet *b, size_t size)
>> +{
>> + void *dst;
>> +#ifdef DPDK_NETDEV
>> + char zeros[size];
>> + memset(zeros, 0, size);
>> +
>> + dst = dp_packet_put(b, zeros, size);
>> +
>> + return dst;
>> +#endif
>> + dst = dp_packet_put_uninit(b, size);
>> + memset(dst, 0, size);
>> +
>> return dst;
>> }
>>
>> diff --git a/lib/dp-packet.h b/lib/dp-packet.h
>> index 4d4b420..2fa6205 100644
>> --- a/lib/dp-packet.h
>> +++ b/lib/dp-packet.h
>> @@ -83,6 +83,11 @@ struct dp_packet {
>> #ifdef DPDK_NETDEV
>> #define MBUF_BUF_END(BUF_ADDR, BUF_LEN) \
>> (char *) (((char *) BUF_ADDR) + BUF_LEN)
>> +
>> +struct mbuf_tail {
>> + struct rte_mbuf *mbuf;
>> + uint16_t ofs;
>> +};
>> #endif
>>
>> static inline void *dp_packet_data(const struct dp_packet *);
>> --
>> 2.7.4
>>
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