Re: [Qemu-devel] [PULL V2 01/26] filter-rewriter: Add TCP state machine and fix memory leak in connection_track_table

[Zhang Chen]

On Tue, Oct 30, 2018 at 10:02 AM Jason Wang <address@hidden> wrote:

>
> On 2018/10/29 下午7:01, Peter Maydell wrote:
> > On 19 October 2018 at 04:22, Jason Wang <address@hidden> wrote:
> >> From: Zhang Chen <address@hidden>
> >>
> >> We add almost full TCP state machine in filter-rewriter, except
> >> TCPS_LISTEN and some simplify in VM active close FIN states.
> >> The reason for this simplify job is because guest kernel will track
> >> the TCP status and wait 2MSL time too, if client resend the FIN packet,
> >> guest will resend the last ACK, so we needn't wait 2MSL time in
> filter-rewriter.
> >>
> >> After a net connection is closed, we didn't clear its related resources
> >> in connection_track_table, which will lead to memory leak.
> >>
> >> Let's track the state of net connection, if it is closed, its related
> >> resources will be cleared up.
> > Hi. Coverity (CID 1396477) points out that here:
> >
> >> +        /*
> >> +         * Active close step 2.
> >> +         */
> >> +        if (conn->tcp_state == TCPS_FIN_WAIT_1) {
> >> +            conn->tcp_state = TCPS_TIME_WAIT;
> > ...this assignment to conn->tcp_state has no effect, because...
> >
> >> +            /*
> >> +             * For simplify implementation, we needn't wait 2MSL time
> >> +             * in filter rewriter. Because guest kernel will track the
> >> +             * TCP status and wait 2MSL time, if client resend the FIN
> >> +             * packet, guest will apply the last ACK too.
> >> +             */
> >> +            conn->tcp_state = TCPS_CLOSED;
> > ...we immediately overwrite it with a different value.
> >
> >> +            g_hash_table_remove(rf->connection_track_table, key);
> >> +        }
> >>       }
> > What was the intention of the code here?
> >
> > thanks
> > -- PMM
>
>
> Looks not.
>
> Chen, can you please send a patch to fix this?
>
>
Sure, I will send a patch for this issue.

Thanks
Zhang Chen


> Thanks
>
>