IPV4_DEVCONF_ALL
IPV4_DEVCONF_ALL(dev_net(ovpn->dev), SEND_REDIRECTS) = false;
IPV4_DEVCONF_ALL(dev_net(dev), SEND_REDIRECTS) = false;
#define IPV4_DEVCONF_ALL_RO(net, attr) READ_ONCE(IPV4_DEVCONF_ALL(net, attr))
IPV4_DEVCONF_ALL(net, PROXY_ARP) = on;
int on = IPV4_DEVCONF_ALL(net, FORWARDING);
IPV4_DEVCONF_ALL(net, ACCEPT_REDIRECTS) = !on;
if (valp == &IPV4_DEVCONF_ALL(net, FORWARDING)) {
IPV4_DEVCONF_ALL(net, MC_FORWARDING)--;
IPV4_DEVCONF_ALL(net, MC_FORWARDING)++;