Re: [Qemu-devel] [PATCH v2 1/2] net: assert that tx packets have nonzero size

[Jason Wang]

On 2019/7/22 下午9:24, Oleinik, Alexander wrote:
> Virtual devices should not try to send zero-sized packets. The caller
> should check the size prior to calling qemu_sendv_packet_async.
>
> Signed-off-by: Alexander Oleinik <address@hidden>
> ---
> v2:
>    * Improve the comment to explain the rationale for adding the assert.
>   net/net.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/net/net.c b/net/net.c
> index 7d4098254f..4ad21df36f 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -741,6 +741,15 @@ ssize_t qemu_sendv_packet_async(NetClientState *sender,
>       size_t size = iov_size(iov, iovcnt);
>       int ret;
>   
> +    /*
> +     * Since this function returns the size of the sent packets, and a return
> +     * value of zero indicates that the packet will be sent asynchronously,
> +     * there is currently no way to report that a 0-sized packet has been sent
> +     * successfully. Forbid it for now, and if someone needs this functionality
> +     * later, the API will require a change.
> +     */
> +    assert(size);


This probably will make the assertion triggerable from guest. Is this 
better to warn and return NET_BUFSIZE + 1 here?

Thanks


> +
>       if (size > NET_BUFSIZE) {
>           return size;
>       }