[ovs-dev] [PATCH] ofproto-dpif-xlate: makes OVS native tunneling honor tunnel-specified source addresses

Ben Pfaff blp at ovn.org
Tue Apr 17 15:04:24 UTC 2018


On Tue, Apr 17, 2018 at 10:54:29AM +0800, wenxu wrote:
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> At 2018-04-17 04:40:26, "Ben Pfaff" <blp at ovn.org> wrote:
> >On Mon, Apr 16, 2018 at 03:35:57PM +0800, wenxu at ucloud.cn wrote:
> >> From: wenxu <wenxu at ucloud.cn>
> >> 
> >> It makes OVS native tunneling honor tunnel-specified source addresses,
> >> in the same way that Linux kernel tunneling honors them.
> >> 
> >> This patch made valid tun_src specified by flow-action can be used for
> >> tunnel_src of packet. add a "local" property for a route entry.
> >> Like the kernel space when lookup the route, if there are tun_src specified
> >> by flow-action or port options. Check the tun_src wheather is a local
> >> address, then lookup the route.
> >> 
> >> Signed-off-by: wenxu <wenxu at ucloud.cn>
> >
> >Thanks for v2.  It resolves the portability issue.  I hope I may ask
> >some more questions, because there are some pieces that I do not
> >understand yet.
> >
> >I think that there is a redundant assignment to change->rd.rtm_dst_len
> >in route_table_parse().  I think that the first assignment here may be
> >removed:
> >
> >        change->rd.rtm_dst_len = rtm->rtm_dst_len + (ipv4 ? 96 : 0);
> >        if (rtm->rtm_type == RTN_LOCAL) {
> >            dst_len_off += 64;
> >            change->rd.local = true;
> >        } else {
> >            change->rd.local = false;
> >        }
> >        change->rd.rtm_dst_len = rtm->rtm_dst_len + (ipv4 ? dst_len_off : 0);
> >
> >I do not understand dst_len_off yet.  It is normally 96, but for local
> >addresses it increases by 64, to 160.  Then, only for IPv4, it gets
> >added to the prefix length.  I don't understand how a prefix length
> >greater than 128 is to be interpreted, since an IPv6 address is only 128
> >bits long.  (Without the addition of 64, I understand: it is because
> >32-bit IPv4 addresses are mapped into 128-bit IPv6 addresses and 96 =
> >128 - 32.)  rd.rtm_dst_len eventually gets passed to ovs_router_insert()
> >as plen, then to rt_init_match() as plen, and then that is used to
> >create a IPv6 address mask, so it seems like the value should be 128 or
> >less, not 160 or more.
> 
> I want to improve the priority of the local route higher than userdef route
> in the ovs_router_add : the priority of userdef route  is alway higheer than cached route
> ovs_router_insert__(mark, plen + 32, &ip6, plen, argv[2], &gw6);
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> I think I should only enhance the priority of the local route is fine, but not dst_len

That sounds right to me.  Thanks!


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