Perhaps the following (NOT TESTED) kernel patch will show you how such error
messages
could be added.
Note: requires trickling down the extack parameter, but that is a good thing
because
other place like devconf could use it as well.
diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index 4da61c950e93..479f60ef54c0 100644
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -147,8 +147,8 @@ struct rtnl_af_ops {
int (*validate_link_af)(const struct net_device
*dev,
const struct nlattr *attr);
int (*set_link_af)(struct net_device *dev,
- const struct nlattr *attr);
-
+ const struct nlattr *attr,
+ struct netlink_ext_ack *extack);
int (*fill_stats_af)(struct sk_buff *skb,
const struct net_device *dev);
size_t (*get_stats_af_size)(const struct net_device
*dev);
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 1bdcb33fb561..3485b16a7ff3 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2863,7 +2863,7 @@ static int do_setlink(const struct sk_buff *skb,
BUG_ON(!(af_ops = rtnl_af_lookup(nla_type(af))));
- err = af_ops->set_link_af(dev, af);
+ err = af_ops->set_link_af(dev, af, extack);
if (err < 0) {
rcu_read_unlock();
goto errout;
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 75f67994fc85..2e35f68da40a 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1978,7 +1978,8 @@ static int inet_validate_link_af(const struct net_device
*dev,
return 0;
}
-static int inet_set_link_af(struct net_device *dev, const struct nlattr *nla)
+static int inet_set_link_af(struct net_device *dev, const struct nlattr *nla,
+ struct netlink_ext_ack *extack)
{
struct in_device *in_dev = __in_dev_get_rcu(dev);
struct nlattr *a, *tb[IFLA_INET_MAX+1];
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 120073ffb666..b817086fbf42 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -5672,7 +5672,8 @@ static int inet6_fill_link_af(struct sk_buff *skb, const
struct net_device *dev,
return 0;
}
-static int inet6_set_iftoken(struct inet6_dev *idev, struct in6_addr *token)
+static int inet6_set_iftoken(struct inet6_dev *idev, struct in6_addr *token,
+ struct netlink_ext_ack *extack)
{
struct inet6_ifaddr *ifp;
struct net_device *dev = idev->dev;
@@ -5681,14 +5682,29 @@ static int inet6_set_iftoken(struct inet6_dev *idev,
struct in6_addr *token)
ASSERT_RTNL();
- if (!token)
+ if (!token) {
return -EINVAL;
- if (dev->flags & (IFF_LOOPBACK | IFF_NOARP))
+ }
+
+ if (dev->flags & IFF_LOOPBACK) {
+ NL_SET_ERR_MSG_MOD(extack, "Device is loopback");
return -EINVAL;
- if (!ipv6_accept_ra(idev))
+ }
+
+ if (dev->flags & IFF_NOARP) {
+ NL_SET_ERR_MSG_MOD(extack, "Device does not do discovery");
return -EINVAL;
- if (idev->cnf.rtr_solicits == 0)
+ }
+
+ if (!ipv6_accept_ra(idev)) {
+ NL_SET_ERR_MSG_MOD(extack, "Device does accept route adverts");
+ return -EINVAL;
+ }
+
+ if (idev->cnf.rtr_solicits == 0) {
+ NL_SET_ERR_MSG(extack, "Device has disabled router
solicitation");
return -EINVAL;
+ }
write_lock_bh(&idev->lock);
@@ -5796,7 +5812,8 @@ static int inet6_validate_link_af(const struct net_device
*dev,
return 0;
}
-static int inet6_set_link_af(struct net_device *dev, const struct nlattr *nla)
+static int inet6_set_link_af(struct net_device *dev, const struct nlattr *nla,
+ struct netlink_ext_ack *extack)
{
struct inet6_dev *idev = __in6_dev_get(dev);
struct nlattr *tb[IFLA_INET6_MAX + 1];
@@ -5809,7 +5826,8 @@ static int inet6_set_link_af(struct net_device *dev,
const struct nlattr *nla)
BUG();
if (tb[IFLA_INET6_TOKEN]) {
- err = inet6_set_iftoken(idev, nla_data(tb[IFLA_INET6_TOKEN]));
+ err = inet6_set_iftoken(idev, nla_data(tb[IFLA_INET6_TOKEN]),
+ extack);
if (err)
return err;
}
