Re: [PATCH net-next] geneve: add rtnl changelink support

[Girish Moodalbail]

On 5/16/17 12:31 PM, David Miller wrote:
From: Girish Moodalbail <girish.moodalb...@oracle.com>
Date: Mon, 15 May 2017 10:47:04 -0700
        if (data[IFLA_GENEVE_REMOTE]) {
-               info.key.u.ipv4.dst =
+               info->key.u.ipv4.dst =
                        nla_get_in_addr(data[IFLA_GENEVE_REMOTE]);

-               if (IN_MULTICAST(ntohl(info.key.u.ipv4.dst))) {
+               if (IN_MULTICAST(ntohl(info->key.u.ipv4.dst))) {
                        netdev_dbg(dev, "multicast remote is unsupported\n");
                        return -EINVAL;
                }
+               if (changelink &&
+                   ip_tunnel_info_af(&geneve->info) == AF_INET6) {
+                       info->mode &= ~IP_TUNNEL_INFO_IPV6;
+                       info->key.tun_flags &= ~TUNNEL_CSUM;
+                       *use_udp6_rx_checksums = false;
+               }
        }

I don't understand this "changelink" guarded code, why do you need to
clear all of this state out if the existing tunnel type if AF_INET6
and only when doing a changelink?

In any event, I think you need to add a comment explaining it.


If geneve link was overlayed over IPv6 network and now the user modifies the 
link to be over IPv4 network by doing

# ip link set gen0 type geneve id 100 remote 192.168.13.2

Then we will need to

 - reset info->mode to be not IPv6 type
 - the default for UDP checksum over IPv4 is 'no', so reset that and
 - set use_udp6_rx_checksums to its default value which is false.

I will capture the above information concisely in a comment around that 
'changelink' guard.

thanks,
~Girish