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([2a0d:3344:5521:6b10:58fd:68f:7756:389d]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-493c63bfba1sm406103625e9.15.2026.07.06.02.01.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Jul 2026 02:01:41 -0700 (PDT) Message-ID: <43c79a50-eea1-47b4-9a4c-5c61e611c059@redhat.com> Date: Mon, 6 Jul 2026 11:01:40 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net 2/3] net/sched: Handle TC_ACT_REDIRECT from qdisc filter chains To: Daniel Borkmann , kuba@kernel.org Cc: jhs@mojatatu.com, bigeasy@linutronix.de, andrii@kernel.org, memxor@gmail.com, bpf@vger.kernel.org, netdev@vger.kernel.org, Victor Nogueira References: <20260630123331.186840-1-daniel@iogearbox.net> <20260630123331.186840-3-daniel@iogearbox.net> From: Paolo Abeni Content-Language: en-US In-Reply-To: <20260630123331.186840-3-daniel@iogearbox.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/30/26 2:33 PM, Daniel Borkmann wrote: > From: Jamal Hadi Salim > > When a TC filter attached to a qdisc filter chain returns > TC_ACT_REDIRECT (ex: via an eBPF program calling bpf_redirect() or an > act_bpf action), the redirect was silently lost i.e no qdisc classify > function handled TC_ACT_REDIRECT, so the packet fell through the > switch and was enqueued normally instead of being redirected. > > This has been broken since bpf_redirect() was introduced for TC in > commit 27b29f63058d ("bpf: add bpf_redirect() helper"). We got lucky > for a long time because bpf_net_context was a per-CPU variable that > was always available. > > commit 401cb7dae813 ("net: Reference bpf_redirect_info via task_struct > on PREEMPT_RT.") turned bpf_net_context into a task_struct member that > is only set up by explicit callers. Without a caller setting it up, > bpf_redirect() itself crashes with a NULL pointer dereference in > bpf_net_ctx_get_ri(). However, even with bpf_net_context available, > TC_ACT_REDIRECT from qdisc filter chains cannot be honored without > adding skb_do_redirect() calls to every qdisc classify function, which > would require changes across net/sched/. Isolate it to ebpf core where > it belongs. > > Instead, add a tcf_classify_qdisc() inline helper in pkt_cls.h, as a > wrapper around tcf_classify() for use by qdisc classify functions and > tcf_qevent_handle(). When the classify verdict is TC_ACT_REDIRECT, > the wrapper converts it to TC_ACT_SHOT, dropping the packet rather > than letting it continue silently. Dropping is preferred over > letting the packet through because the user immediately sees packet > loss. Silently passing the packet through would hide the problem and > leave the user wondering why their redirect is not working. > > The clsact fast path, tc_run() continues to call tcf_classify() directly > and is unaffected: TC_ACT_REDIRECT is returned as-is and handled by > sch_handle_egress/ingress() calling skb_do_redirect() as before. > > Fixes: 27b29f63058d ("bpf: add bpf_redirect() helper") > Fixes: 401cb7dae813 ("net: Reference bpf_redirect_info via task_struct on PREEMPT_RT.") > Tested-by: Victor Nogueira > Signed-off-by: Jamal Hadi Salim > Signed-off-by: Daniel Borkmann I'm sorry, this does not apply cleanly anymore. Could you please rebase and repost? Thanks! Paolo