Re: [PATCH v5 06/29] packet: Add packet_data()

[Stefano Brivio <sbrivio@redhat.com>]

On Thu, 17 Apr 2025 18:51:13 +0200
Laurent Vivier <lvivier@redhat.com> wrote:

> packet_data() gets the data range from a packet descriptor from a
> given pool.
> 
> It uses iov_tail to return the packet memory.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
>  packet.c | 41 +++++++++++++++++++++++++++++++++++++++++
>  packet.h |  5 +++++
>  2 files changed, 46 insertions(+)
> 
> diff --git a/packet.c b/packet.c
> index 98ded4e27aae..675bccf4d787 100644
> --- a/packet.c
> +++ b/packet.c
> @@ -190,6 +190,47 @@ void *packet_get_do(const struct pool *p, const size_t idx,
>  	return r;
>  }
>  
> +/**
> + * packet_data_do() - Get data range from packet descriptor from given pool

All the code changes here make sense to me, but the name itself,
packet_data_do(), is rather cryptic, in the sense that 'data' is not a
verb.

Was this supposed to be a temporary name to use before removing
packet_get_do() later in the series?

> + * @p:		Packet pool
> + * @idx:	Index of packet descriptor in pool
> + * @data:	IOV tail to store the address of the data (output)
> + * @func:	For tracing: name of calling function, NULL means no trace()
> + * @line:	For tracing: caller line of function call
> + *
> + * Return: true if @data contains valid data, false otherwise

I think it's not so much about "valid" data (how do we define data
validity here?): we return false if the packet index is invalid.

If there's something wrong with @data, we don't return at all.

> + */
> +/* cppcheck-suppress unusedFunction */
> +bool packet_data_do(const struct pool *p, size_t idx,
> +		    struct iov_tail *data,
> +		    const char *func, int line)
> +{
> +	size_t i;
> +
> +	ASSERT_WITH_MSG(p->count <= p->size,
> +			"Corrupt pool count: %zu, size: %zu, %s:%i",
> +			p->count, p->size, func, line);
> +
> +	if (idx >= p->count) {
> +		debug("packet %zu from pool size: %zu, count: %zu, "
> +		      "%s:%i", idx, p->size, p->count, func, line);
> +		return false;
> +	}
> +
> +	data->cnt = 1;
> +	data->off = 0;
> +	data->iov = &p->pkt[idx];
> +
> +	for (i = 0; i < data->cnt; i++) {
> +		ASSERT_WITH_MSG(!packet_check_range(p, data->iov[i].iov_base,
> +						    data->iov[i].iov_len,
> +						    func, line),
> +				"Corrupt packet pool, %s:%i", func, line);

I think "Corrupted" is a bit more common in computing, but I guess it's
correct either way.

> +	}
> +
> +	return true;
> +}
> +
>  /**
>   * pool_flush() - Flush a packet pool
>   * @p:		Pointer to packet pool
> diff --git a/packet.h b/packet.h
> index af40b39b5251..062afb978124 100644
> --- a/packet.h
> +++ b/packet.h
> @@ -39,6 +39,9 @@ void *packet_get_try_do(const struct pool *p, const size_t idx,
>  void *packet_get_do(const struct pool *p, const size_t idx,
>  		    size_t offset, size_t len, size_t *left,
>  		    const char *func, int line);
> +bool packet_data_do(const struct pool *p, const size_t idx,
> +		    struct iov_tail *data,
> +		    const char *func, int line);
>  bool pool_full(const struct pool *p);
>  void pool_flush(struct pool *p);
>  
> @@ -49,6 +52,8 @@ void pool_flush(struct pool *p);
>  	packet_get_try_do(p, idx, offset, len, left, __func__, __LINE__)
>  #define packet_get(p, idx, offset, len, left)				\
>  	packet_get_do(p, idx, offset, len, left, __func__, __LINE__)
> +#define packet_data(p, idx, data)					\
> +	packet_data_do(p, idx, data, __func__, __LINE__)
>  
>  #define PACKET_POOL_DECL(_name, _size, _buf)				\
>  struct _name ## _t {							\

-- 
Stefano