> In its current implementation dp_packet_shift() is also unaware of multi-
> seg mbufs (that holds data in memory non-contiguously) and assumes that
> data exists contiguously in memory, memmove'ing data to perform the shift.
> 
> To add support for multi-seg mbuds a new set of functions was introduced,
> dp_packet_mbuf_shift() and dp_packet_mbuf_write(). These functions are
> used by dp_packet_shift(), when handling multi-seg mbufs, to shift and
> write data within a chain of mbufs.
> 

Hi Tiago,

After applying this patch I see the following error during compilation.

lib/conntrack.c: In function 'handle_ftp_ctl':
lib/conntrack.c:3154:11: error: 'addr_offset_from_ftp_data_start' may be used 
uninitialized in this function [-Werror=maybe-uninitialized]
     char *pkt_addr_str = ftp_data_start + addr_offset_from_ftp_data_start;
           ^~~~~~~~~~~~
lib/conntrack.c:3173:12: note: 'addr_offset_from_ftp_data_start' was declared 
here
     size_t addr_offset_from_ftp_data_start;

It can be fixed with the following incremental.

diff --git a/lib/conntrack.c b/lib/conntrack.c
index 974f985..7cd1fc9 100644
--- a/lib/conntrack.c
+++ b/lib/conntrack.c
@@ -3170,7 +3170,7 @@ handle_ftp_ctl(struct conntrack *ct, const struct 
conn_lookup_ctx *ctx,
     struct ip_header *l3_hdr = dp_packet_l3(pkt);
     ovs_be32 v4_addr_rep = 0;
     struct ct_addr v6_addr_rep;
-    size_t addr_offset_from_ftp_data_start;
+    size_t addr_offset_from_ftp_data_start = 0;
     size_t addr_size = 0;
     char *ftp_data_start;
     bool do_seq_skew_adj = true;

If there are no objections I can roll this into the patch upon application to 
dpdk merge.

Ian

> Signed-off-by: Tiago Lam <[email protected]>
> Acked-by: Eelco Chaudron <[email protected]>
> ---
>  lib/dp-packet.c | 97
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  lib/dp-packet.h | 10 ++++++
>  2 files changed, 107 insertions(+)
> 
> diff --git a/lib/dp-packet.c b/lib/dp-packet.c index 2aaeaae..d6e19eb
> 100644
> --- a/lib/dp-packet.c
> +++ b/lib/dp-packet.c
> @@ -294,6 +294,97 @@ dp_packet_prealloc_headroom(struct dp_packet *b,
> size_t size)
>      }
>  }
> 
> +#ifdef DPDK_NETDEV
> +/* Write len data bytes in a mbuf at specified offset.
> + *
> + * 'mbuf', pointer to the destination mbuf where 'ofs' is, and the mbuf
> +where
> + * the data will first be written.
> + * 'ofs', the offset within the provided 'mbuf' where 'data' is to be
> written.
> + * 'len', the size of the to be written 'data'.
> + * 'data', pointer to the to be written bytes.
> + *
> + * XXX: This function is the counterpart of the `rte_pktmbuf_read()`
> +function
> + * available with DPDK, in the rte_mbuf.h */ void
> +dp_packet_mbuf_write(struct rte_mbuf *mbuf, int16_t ofs, uint32_t len,
> +                     const void *data)
> +{
> +    char *dst_addr;
> +    uint16_t data_len;
> +    int len_copy;
> +    while (mbuf) {
> +        if (len == 0) {
> +            break;
> +        }
> +
> +        dst_addr = rte_pktmbuf_mtod_offset(mbuf, char *, ofs);
> +        data_len = MBUF_BUF_END(mbuf->buf_addr, mbuf->buf_len) -
> + dst_addr;
> +
> +        len_copy = MIN(len, data_len);
> +        /* We don't know if 'data' is the result of a rte_pktmbuf_read()
> call,
> +         * in which case we may end up writing to the same region of
> memory we
> +         * are reading from and overlapping. Hence the use of memmove()
> here */
> +        memmove(dst_addr, data, len_copy);
> +
> +        data = ((char *) data) + len_copy;
> +        len -= len_copy;
> +        ofs = 0;
> +
> +        mbuf = mbuf->next;
> +    }
> +}
> +
> +static void
> +dp_packet_mbuf_shift_(struct rte_mbuf *dbuf, int16_t dst_ofs,
> +                      const struct rte_mbuf *sbuf, uint16_t src_ofs,
> +int len) {
> +    char rd[len];
> +    const char *wd = rte_pktmbuf_read(sbuf, src_ofs, len, rd);
> +
> +    ovs_assert(wd);
> +
> +    dp_packet_mbuf_write(dbuf, dst_ofs, len, wd); }
> +
> +/* Similarly to dp_packet_shift(), shifts the data within the mbufs of
> +a
> + * dp_packet of DPBUF_DPDK source by 'delta' bytes.
> + * Caller must make sure of the following conditions:
> + * - When shifting left, delta can't be bigger than the data_len
> available in
> + *   the last mbuf;
> + * - When shifting right, delta can't be bigger than the space available
> in the
> + *   first mbuf (buf_len - data_off).
> + * Both these conditions guarantee that a shift operation doesn't fall
> +outside
> + * the bounds of the existing mbufs, so that the first and last mbufs
> +(when
> + * using multi-segment mbufs), remain the same. */ static void
> +dp_packet_mbuf_shift(struct dp_packet *b, int delta) {
> +    uint16_t src_ofs;
> +    int16_t dst_ofs;
> +
> +    struct rte_mbuf *mbuf = CONST_CAST(struct rte_mbuf *, &b->mbuf);
> +    struct rte_mbuf *tmbuf = rte_pktmbuf_lastseg(mbuf);
> +
> +    if (delta < 0) {
> +        ovs_assert(-delta <= tmbuf->data_len);
> +    } else {
> +        ovs_assert(delta < (mbuf->buf_len - mbuf->data_off));
> +    }
> +
> +    /* Set the destination and source offsets to copy to */
> +    dst_ofs = delta;
> +    src_ofs = 0;
> +
> +    /* Shift data from src mbuf and offset to dst mbuf and offset */
> +    dp_packet_mbuf_shift_(mbuf, dst_ofs, mbuf, src_ofs,
> +                          rte_pktmbuf_pkt_len(mbuf));
> +
> +    /* Update mbufs' properties, and if using multi-segment mbufs, first
> and
> +     * last mbuf's data_len also needs to be adjusted */
> +    mbuf->data_off = mbuf->data_off + dst_ofs; } #endif
> +
>  /* Shifts all of the data within the allocated space in 'b' by 'delta'
> bytes.
>   * For example, a 'delta' of 1 would cause each byte of data to move one
> byte
>   * forward (from address 'p' to 'p+1'), and a 'delta' of -1 would cause
> each @@ -306,6 +397,12 @@ dp_packet_shift(struct dp_packet *b, int delta)
>                 : true);
> 
>      if (delta != 0) {
> +#ifdef DPDK_NETDEV
> +        if (b->source == DPBUF_DPDK) {
> +            dp_packet_mbuf_shift(b, delta);
> +            return;
> +        }
> +#endif
>          char *dst = (char *) dp_packet_data(b) + delta;
>          memmove(dst, dp_packet_data(b), dp_packet_size(b));
>          dp_packet_set_data(b, dst);
> diff --git a/lib/dp-packet.h b/lib/dp-packet.h index 14e2551..6ca4e98
> 100644
> --- a/lib/dp-packet.h
> +++ b/lib/dp-packet.h
> @@ -80,6 +80,11 @@ struct dp_packet {
>      };
>  };
> 
> +#ifdef DPDK_NETDEV
> +#define MBUF_BUF_END(BUF_ADDR, BUF_LEN) \
> +    (char *) (((char *) BUF_ADDR) + BUF_LEN) #endif
> +
>  static inline void *dp_packet_data(const struct dp_packet *);  static
> inline void dp_packet_set_data(struct dp_packet *, void *);  static inline
> void *dp_packet_base(const struct dp_packet *); @@ -133,6 +138,11 @@
> static inline void *dp_packet_at(const struct dp_packet *, size_t offset,
>                                   size_t size);  static inline void
> *dp_packet_at_assert(const struct dp_packet *,
>                                          size_t offset, size_t size);
> +#ifdef DPDK_NETDEV
> +void
> +dp_packet_mbuf_write(struct rte_mbuf *mbuf, int16_t ofs, uint32_t len,
> +                     const void *data); #endif
>  static inline void *dp_packet_tail(const struct dp_packet *);  static
> inline void *dp_packet_end(const struct dp_packet *);
> 
> --
> 2.7.4

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