Re: [Qemu-devel] [PATCH v4 2/2] colo: compare the packet based on the tcp sequence number

[Thomas Huth]

On 2017-12-25 03:54, Mao Zhongyi wrote:
> Packet size some time different or when network is busy.
> Based on same payload size, but TCP protocol can not
> guarantee send the same one packet in the same way,
[...]
> Signed-off-by: Mao Zhongyi <address@hidden>
> Signed-off-by: Li Zhijian <address@hidden>
> Signed-off-by: Zhang Chen <address@hidden>
> Reviewed-by: Zhang Chen <address@hidden>
> Tested-by: Zhang Chen <address@hidden>
> ---
>  net/colo-compare.c | 343 
> +++++++++++++++++++++++++++++++++++------------------
>  net/colo.c         |   9 ++
>  net/colo.h         |  15 +++
>  net/trace-events   |   2 +-
>  4 files changed, 250 insertions(+), 119 deletions(-)
> 
> diff --git a/net/colo-compare.c b/net/colo-compare.c
> index f39ca02..8622b0b 100644
> --- a/net/colo-compare.c
> +++ b/net/colo-compare.c
[...]
> @@ -214,104 +254,175 @@ static int colo_compare_packet_payload(Packet *ppkt,
>  }
>  
>  /*
> - * Called from the compare thread on the primary
> - * for compare tcp packet
> - * compare_tcp copied from Dr. David Alan Gilbert's branch
> - */
> -static int colo_packet_compare_tcp(Packet *spkt, Packet *ppkt)
> + * return true means that the payload is consist and
> + * need to make the next comparison, false means do
> + * the checkpoint
> +*/
> +static bool colo_mark_tcp_pkt(Packet *ppkt, Packet *spkt,
> +                              int8_t *mark, uint32_t max_ack)
>  {
> -    struct tcphdr *ptcp, *stcp;
> -    int res;
> +    *mark = 0;
> +
> +    if (ppkt->tcp_seq == spkt->tcp_seq && ppkt->seq_end == spkt->seq_end) {
> +        if (colo_compare_packet_payload(ppkt, spkt,
> +                                        ppkt->header_size, spkt->header_size,
> +                                        ppkt->payload_size)) {
> +            *mark = COLO_COMPARE_FREE_SECONDARY | COLO_COMPARE_FREE_PRIMARY;
> +            return true;
> +        }
> +    }
> +    if (ppkt->tcp_seq == spkt->tcp_seq && ppkt->seq_end == spkt->seq_end) {
> +        if (colo_compare_packet_payload(ppkt, spkt,
> +                                        ppkt->header_size, spkt->header_size,
> +                                        ppkt->payload_size)) {
> +            *mark = COLO_COMPARE_FREE_SECONDARY | COLO_COMPARE_FREE_PRIMARY;
> +            return true;
> +        }
> +    }

 Hi,

seems like this patch introduced some duplicated code, see this bug
ticket here:

 https://bugs.launchpad.net/qemu/+bug/1811499

Is the second if-statement here on purpose? If yes, maybe you could add
a comment here? If no, could you please send a patch to remove it?

 Thanks,
  Thomas