Re: [Qemu-devel] [PATCH V12 07/10] colo-compare: add TCP, UDP, ICMP packet comparison

[Jason Wang <jasowang@redhat.com>]

On 2016年09月01日 13:00, Zhang Chen wrote:
>>> +    /*
>>> +     * The 'identification' field in the IP header is *very* random
>>> +     * it almost never matches.  Fudge this by ignoring differences in
>>> +     * unfragmented packets; they'll normally sort themselves out 
>>> if different
>>> +     * anyway, and it should recover at the TCP level.
>>> +     * An alternative would be to get both the primary and 
>>> secondary to rewrite
>>> +     * somehow; but that would need some sync traffic to sync the 
>>> state
>>> +     */
>>> +    if (ntohs(ppkt->ip->ip_off) & IP_DF) {
>>> +        spkt->ip->ip_id = ppkt->ip->ip_id;
>>> +        /* and the sum will be different if the IDs were different */
>>> +        spkt->ip->ip_sum = ppkt->ip->ip_sum;
>>> +    }
>>> +
>>> +    res = memcmp(ppkt->data + ETH_HLEN, spkt->data + ETH_HLEN,
>>> +                (spkt->size - ETH_HLEN));
>>
>> This may work but I worry about whether or not tagged packet can work 
>> here. Looks like parse_packet_early() can recognize vlan tag, but 
>> fill_connection_key() can not. This looks can result queuing wrong 
>> packets into wrong connection.
>
> Currently COLO proxy can't support vlan, we will add this feature in 
> the future.

Looks like current code can still queue vlan packets, please make sure 
it can't.

Thanks