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

[Jason Wang]

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