[PATCH net-next v3 1/5] tc/act: user space can't use TC_ACT_REDIRECT directly

[Paolo Abeni]

Only cls_bpf and act_bpf can safely use such value. If a generic
action is configured by user space to return TC_ACT_REDIRECT,
the usually visible behavior is passing the skb up the stack - as
for unknown action, but, with complex configuration, more random
results can be obtained.

This patch forcefully converts TC_ACT_REDIRECT to TC_ACT_UNSPEC
at action init time, making the kernel behavior more consistent.

v1 -> v3: use TC_ACT_UNSPEC instead of a newly definied act value

Signed-off-by: Paolo Abeni <pab...@redhat.com>
---
 net/sched/act_api.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 148a89ab789b..24b5534967fe 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -895,6 +895,11 @@ struct tc_action *tcf_action_init_1(struct net *net, 
struct tcf_proto *tp,
                }
        }
 
+       if (a->tcfa_action == TC_ACT_REDIRECT) {
+               net_warn_ratelimited("TC_ACT_REDIRECT can't be used directly");
+               a->tcfa_action = TC_ACT_UNSPEC;
+       }
+
        return a;
 
 err_mod:
-- 
2.17.1