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

Ben Pfaff blp at ovn.org
Mon Apr 16 20:40:26 UTC 2018

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

        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.



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