netlink: provide an ability to set default extack message

In netdev common pattern, extack pointer is forwarded to the drivers
to be filled with error message. However, the caller can easily
overwrite the filled message.

Instead of adding multiple "if (!extack->_msg)" checks before any
NL_SET_ERR_MSG() call, which appears after call to the driver, let's
add new macro to common code.

[1] https://lore.kernel.org/all/Y9Irgrgf3uxOjwUm@unreal
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Link: https://lore.kernel.org/r/6993fac557a40a1973dfa0095107c3d03d40bec1.1675171790.git.leon@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index fa4d86da0ec7d32cc97f9ef151731970de1dcc8c..c43ac7690eca1bc8f945d39d4c5de806856b0bc2 100644 (file)
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -130,6 +130,16 @@ struct netlink_ext_ack {
 #define NL_SET_ERR_MSG_FMT_MOD(extack, fmt, args...)   \
        NL_SET_ERR_MSG_FMT((extack), KBUILD_MODNAME ": " fmt, ##args)
 
+#define NL_SET_ERR_MSG_WEAK(extack, msg) do {          \
+       if ((extack) && !(extack)->_msg)                \
+               NL_SET_ERR_MSG((extack), msg);          \
+} while (0)
+
+#define NL_SET_ERR_MSG_WEAK_MOD(extack, msg) do {      \
+       if ((extack) && !(extack)->_msg)                \
+               NL_SET_ERR_MSG_MOD((extack), msg);      \
+} while (0)
+
 #define NL_SET_BAD_ATTR_POLICY(extack, attr, pol) do { \
        if ((extack)) {                                 \
                (extack)->bad_attr = (attr);            \

diff --git a/net/bridge/br_switchdev.c b/net/bridge/br_switchdev.c
index 7eb6fd5bb917aa8761fc67bbf6f6276e5d7ec019..de18e9c1d7a784dcc89a514f91ad7ed8a0aa6b71 100644 (file)
--- a/net/bridge/br_switchdev.c
+++ b/net/bridge/br_switchdev.c
@@ -104,9 +104,8 @@ int br_switchdev_set_port_flag(struct net_bridge_port *p,
                return 0;
 
        if (err) {
-               if (extack && !extack->_msg)
-                       NL_SET_ERR_MSG_MOD(extack,
-                                          "bridge flag offload is not supported");
+               NL_SET_ERR_MSG_WEAK_MOD(extack,
+                                       "bridge flag offload is not supported");
                return -EOPNOTSUPP;
        }
 
@@ -115,9 +114,8 @@ int br_switchdev_set_port_flag(struct net_bridge_port *p,
 
        err = switchdev_port_attr_set(p->dev, &attr, extack);
        if (err) {
-               if (extack && !extack->_msg)
-                       NL_SET_ERR_MSG_MOD(extack,
-                                          "error setting offload flag on port");
+               NL_SET_ERR_MSG_WEAK_MOD(extack,
+                                       "error setting offload flag on port");
                return err;
        }
 

diff --git a/net/dsa/master.c b/net/dsa/master.c
index 26d90140d271fb5ebf2375a9305405c2a2c99aa0..1507b8cdb3604015495cd13510138ab89b6eee51 100644 (file)
--- a/net/dsa/master.c
+++ b/net/dsa/master.c
@@ -464,9 +464,7 @@ int dsa_master_lag_setup(struct net_device *lag_dev, struct dsa_port *cpu_dp,
 
        err = dsa_port_lag_join(cpu_dp, lag_dev, uinfo, extack);
        if (err) {
-               if (extack && !extack->_msg)
-                       NL_SET_ERR_MSG_MOD(extack,
-                                          "CPU port failed to join LAG");
+               NL_SET_ERR_MSG_WEAK_MOD(extack, "CPU port failed to join LAG");
                goto out_master_teardown;
        }
 

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 6014ac3aad34c133d64a49c5a9a14b598118329c..26c458f50ac6cf652da0f37fdcc8d960324213ad 100644 (file)
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -2692,9 +2692,7 @@ static int dsa_slave_changeupper(struct net_device *dev,
                        if (!err)
                                dsa_bridge_mtu_normalization(dp);
                        if (err == -EOPNOTSUPP) {
-                               if (extack && !extack->_msg)
-                                       NL_SET_ERR_MSG_MOD(extack,
-                                                          "Offloading not supported");
+                               NL_SET_ERR_MSG_WEAK_MOD(extack, "Offloading not supported");
                                err = 0;
                        }
                        err = notifier_from_errno(err);

diff --git a/net/xfrm/xfrm_device.c b/net/xfrm/xfrm_device.c
index 562b9d9515988e0ffe0876431d224f846fb71d57..95f1436bf6a2e3d46bf626c784c952bd845856e5 100644 (file)
--- a/net/xfrm/xfrm_device.c
+++ b/net/xfrm/xfrm_device.c
@@ -325,8 +325,10 @@ int xfrm_dev_state_add(struct net *net, struct xfrm_state *x,
                 * authors to do not return -EOPNOTSUPP in packet offload mode.
                 */
                WARN_ON(err == -EOPNOTSUPP && is_packet_offload);
-               if (err != -EOPNOTSUPP || is_packet_offload)
+               if (err != -EOPNOTSUPP || is_packet_offload) {
+                       NL_SET_ERR_MSG_WEAK(extack, "Device failed to offload this state");
                        return err;
+               }
        }
 
        return 0;
@@ -388,6 +390,7 @@ int xfrm_dev_policy_add(struct net *net, struct xfrm_policy *xp,
                xdo->type = XFRM_DEV_OFFLOAD_UNSPECIFIED;
                xdo->dir = 0;
                netdev_put(dev, &xdo->dev_tracker);
+               NL_SET_ERR_MSG_WEAK(extack, "Device failed to offload this policy");
                return err;
        }