net/sched: Handle TC_ACT_REDIRECT from qdisc filter chains

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.

Jamal Hadi Salim committed 4 months ago

Commit ec48b3b1 parent 3f4920d15 files · +27 −17Browse files

Unified · Split

15 files

include/net/pkt_cls.h +13 −1
net/sched/cls_api.c +1 −3
net/sched/sch_cake.c +1 −1
net/sched/sch_drr.c +1 −1
net/sched/sch_dualpi2.c +1 −1
net/sched/sch_ets.c +1 −1
net/sched/sch_fq_codel.c +1 −1
net/sched/sch_fq_pie.c +1 −1
net/sched/sch_hfsc.c +1 −1
net/sched/sch_htb.c +1 −1
net/sched/sch_multiq.c +1 −1
net/sched/sch_prio.c +1 −1
net/sched/sch_qfq.c +1 −1
net/sched/sch_sfb.c +1 −1
net/sched/sch_sfq.c +1 −1

include/net/pkt_cls.h+13−1

@@ -156,8 +156,20 @@ static inline int tcf_classify(struct sk_buff *skb, · 155 unmodified lines
156	{	156	{
157	return TC_ACT_UNSPEC;	157	return TC_ACT_UNSPEC;
158	}	158	}
159
160	#endif	159	#endif
		160	static inline int tcf_classify_qdisc(struct sk_buff *skb,
		161	const struct tcf_proto *tp,
		162	struct tcf_result *res, bool compat_mode)
		163	{
		164	int ret = tcf_classify(skb, NULL, tp, res, compat_mode);
		165
		166	/* TC_ACT_REDIRECT from qdisc filter chains is not supported.
		167	* Use BPF via tcx or mirred redirect instead.
		168	*/
		169	if (unlikely(ret == TC_ACT_REDIRECT))
		170	ret = TC_ACT_SHOT;
		171	return ret;
		172	}
161		173
162	static inline unsigned long	174	static inline unsigned long
163	__cls_set_class(unsigned long *clp, unsigned long cl)	175	__cls_set_class(unsigned long *clp, unsigned long cl)

net/sched/cls_api.c+1−3

@@ -4045,9 +4045,7 @@ struct sk_buff tcf_qevent_handle(struct tcf_qevent qe, struct Qdisc *sch, stru · 4044 unmodified lines
4045		4045
4046	fl = rcu_dereference_bh(qe->filter_chain);	4046	fl = rcu_dereference_bh(qe->filter_chain);
4047		4047
4048	switch (tcf_classify(skb, NULL, fl, &cl_res, false)) {	4048	switch (tcf_classify_qdisc(skb, fl, &cl_res, false)) {
4049	case TC_ACT_REDIRECT:
4050	fallthrough;
4051	case TC_ACT_SHOT:	4049	case TC_ACT_SHOT:
4052	qdisc_qstats_drop(sch);	4050	qdisc_qstats_drop(sch);
4053	__qdisc_drop(skb, to_free);	4051	__qdisc_drop(skb, to_free);

net/sched/sch_cake.c+1−1

@@ -1727,7 +1727,7 @@ static u32 cake_classify(struct Qdisc sch, struct cake_tin_data *t, · 1726 unmodified lines
1727	goto hash;	1727	goto hash;
1728		1728
1729	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;	1729	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;
1730	result = tcf_classify(skb, NULL, filter, &res, false);	1730	result = tcf_classify_qdisc(skb, filter, &res, false);
1731		1731
1732	if (result >= 0) {	1732	if (result >= 0) {
1733	#ifdef CONFIG_NET_CLS_ACT	1733	#ifdef CONFIG_NET_CLS_ACT

net/sched/sch_drr.c+1−1

@@ -312,7 +312,7 @@ static struct drr_class drr_classify(struct sk_buff skb, struct Qdisc *sch, · 311 unmodified lines
312		312
313	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;	313	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;
314	fl = rcu_dereference_bh(q->filter_list);	314	fl = rcu_dereference_bh(q->filter_list);
315	result = tcf_classify(skb, NULL, fl, &res, false);	315	result = tcf_classify_qdisc(skb, fl, &res, false);
316	if (result >= 0) {	316	if (result >= 0) {
317	#ifdef CONFIG_NET_CLS_ACT	317	#ifdef CONFIG_NET_CLS_ACT
318	switch (result) {	318	switch (result) {

net/sched/sch_dualpi2.c+1−1

@@ -364,7 +364,7 @@ static int dualpi2_skb_classify(struct dualpi2_sched_data *q, · 363 unmodified lines
364	if (!fl)	364	if (!fl)
365	return NET_XMIT_SUCCESS;	365	return NET_XMIT_SUCCESS;
366		366
367	result = tcf_classify(skb, NULL, fl, &res, false);	367	result = tcf_classify_qdisc(skb, fl, &res, false);
368	if (result >= 0) {	368	if (result >= 0) {
369	#ifdef CONFIG_NET_CLS_ACT	369	#ifdef CONFIG_NET_CLS_ACT
370	switch (result) {	370	switch (result) {

net/sched/sch_ets.c+1−1

@@ -391,7 +391,7 @@ static struct ets_class ets_classify(struct sk_buff skb, struct Qdisc *sch, · 390 unmodified lines
391	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;	391	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;
392	if (TC_H_MAJ(skb->priority) != sch->handle) {	392	if (TC_H_MAJ(skb->priority) != sch->handle) {
393	fl = rcu_dereference_bh(q->filter_list);	393	fl = rcu_dereference_bh(q->filter_list);
394	err = tcf_classify(skb, NULL, fl, &res, false);	394	err = tcf_classify_qdisc(skb, fl, &res, false);
395	#ifdef CONFIG_NET_CLS_ACT	395	#ifdef CONFIG_NET_CLS_ACT
396	switch (err) {	396	switch (err) {
397	case TC_ACT_STOLEN:	397	case TC_ACT_STOLEN:

net/sched/sch_fq_codel.c+1−1

@@ -91,7 +91,7 @@ static unsigned int fq_codel_classify(struct sk_buff skb, struct Qdisc sch, · 90 unmodified lines
91	return fq_codel_hash(q, skb) + 1;	91	return fq_codel_hash(q, skb) + 1;
92		92
93	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;	93	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;
94	result = tcf_classify(skb, NULL, filter, &res, false);	94	result = tcf_classify_qdisc(skb, filter, &res, false);
95	if (result >= 0) {	95	if (result >= 0) {
96	#ifdef CONFIG_NET_CLS_ACT	96	#ifdef CONFIG_NET_CLS_ACT
97	switch (result) {	97	switch (result) {

net/sched/sch_fq_pie.c+1−1

@@ -96,7 +96,7 @@ static unsigned int fq_pie_classify(struct sk_buff skb, struct Qdisc sch, · 95 unmodified lines
96	return fq_pie_hash(q, skb) + 1;	96	return fq_pie_hash(q, skb) + 1;
97		97
98	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;	98	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;
99	result = tcf_classify(skb, NULL, filter, &res, false);	99	result = tcf_classify_qdisc(skb, filter, &res, false);
100	if (result >= 0) {	100	if (result >= 0) {
101	#ifdef CONFIG_NET_CLS_ACT	101	#ifdef CONFIG_NET_CLS_ACT
102	switch (result) {	102	switch (result) {

net/sched/sch_hfsc.c+1−1

@@ -1143,7 +1143,7 @@ hfsc_classify(struct sk_buff skb, struct Qdisc sch, int *qerr) · 1142 unmodified lines
1143	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;	1143	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;
1144	head = &q->root;	1144	head = &q->root;
1145	tcf = rcu_dereference_bh(q->root.filter_list);	1145	tcf = rcu_dereference_bh(q->root.filter_list);
1146	while (tcf && (result = tcf_classify(skb, NULL, tcf, &res, false)) >= 0) {	1146	while (tcf && (result = tcf_classify_qdisc(skb, tcf, &res, false)) >= 0) {
1147	#ifdef CONFIG_NET_CLS_ACT	1147	#ifdef CONFIG_NET_CLS_ACT
1148	switch (result) {	1148	switch (result) {
1149	case TC_ACT_QUEUED:	1149	case TC_ACT_QUEUED:

net/sched/sch_htb.c+1−1

@@ -243,7 +243,7 @@ static struct htb_class htb_classify(struct sk_buff skb, struct Qdisc *sch, · 242 unmodified lines
243	}	243	}
244		244
245	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;	245	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;
246	while (tcf && (result = tcf_classify(skb, NULL, tcf, &res, false)) >= 0) {	246	while (tcf && (result = tcf_classify_qdisc(skb, tcf, &res, false)) >= 0) {
247	#ifdef CONFIG_NET_CLS_ACT	247	#ifdef CONFIG_NET_CLS_ACT
248	switch (result) {	248	switch (result) {
249	case TC_ACT_QUEUED:	249	case TC_ACT_QUEUED:

net/sched/sch_multiq.c+1−1

@@ -36,7 +36,7 @@ multiq_classify(struct sk_buff skb, struct Qdisc sch, int *qerr) · 35 unmodified lines
36	int err;	36	int err;
37		37
38	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;	38	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;
39	err = tcf_classify(skb, NULL, fl, &res, false);	39	err = tcf_classify_qdisc(skb, fl, &res, false);
40	#ifdef CONFIG_NET_CLS_ACT	40	#ifdef CONFIG_NET_CLS_ACT
41	switch (err) {	41	switch (err) {
42	case TC_ACT_STOLEN:	42	case TC_ACT_STOLEN:

net/sched/sch_prio.c+1−1

@@ -39,7 +39,7 @@ prio_classify(struct sk_buff skb, struct Qdisc sch, int *qerr) · 38 unmodified lines
39	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;	39	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;
40	if (TC_H_MAJ(skb->priority) != sch->handle) {	40	if (TC_H_MAJ(skb->priority) != sch->handle) {
41	fl = rcu_dereference_bh(q->filter_list);	41	fl = rcu_dereference_bh(q->filter_list);
42	err = tcf_classify(skb, NULL, fl, &res, false);	42	err = tcf_classify_qdisc(skb, fl, &res, false);
43	#ifdef CONFIG_NET_CLS_ACT	43	#ifdef CONFIG_NET_CLS_ACT
44	switch (err) {	44	switch (err) {
45	case TC_ACT_STOLEN:	45	case TC_ACT_STOLEN:

net/sched/sch_qfq.c+1−1

@@ -709,7 +709,7 @@ static struct qfq_class qfq_classify(struct sk_buff skb, struct Qdisc *sch, · 708 unmodified lines
709		709
710	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;	710	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;
711	fl = rcu_dereference_bh(q->filter_list);	711	fl = rcu_dereference_bh(q->filter_list);
712	result = tcf_classify(skb, NULL, fl, &res, false);	712	result = tcf_classify_qdisc(skb, fl, &res, false);
713	if (result >= 0) {	713	if (result >= 0) {
714	#ifdef CONFIG_NET_CLS_ACT	714	#ifdef CONFIG_NET_CLS_ACT
715	switch (result) {	715	switch (result) {

net/sched/sch_sfb.c+1−1

@@ -260,7 +260,7 @@ static bool sfb_classify(struct sk_buff skb, struct tcf_proto fl, · 259 unmodified lines
260	struct tcf_result res;	260	struct tcf_result res;
261	int result;	261	int result;
262		262
263	result = tcf_classify(skb, NULL, fl, &res, false);	263	result = tcf_classify_qdisc(skb, fl, &res, false);
264	if (result >= 0) {	264	if (result >= 0) {
265	#ifdef CONFIG_NET_CLS_ACT	265	#ifdef CONFIG_NET_CLS_ACT
266	switch (result) {	266	switch (result) {

net/sched/sch_sfq.c+1−1

@@ -171,7 +171,7 @@ static unsigned int sfq_classify(struct sk_buff skb, struct Qdisc sch, · 170 unmodified lines
171	return sfq_hash(q, skb) + 1;	171	return sfq_hash(q, skb) + 1;
172		172
173	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;	173	*qerr = NET_XMIT_SUCCESS \| __NET_XMIT_BYPASS;
174	result = tcf_classify(skb, NULL, fl, &res, false);	174	result = tcf_classify_qdisc(skb, fl, &res, false);
175	if (result >= 0) {	175	if (result >= 0) {
176	#ifdef CONFIG_NET_CLS_ACT	176	#ifdef CONFIG_NET_CLS_ACT
177	switch (result) {	177	switch (result) {

net/sched: Handle TC_ACT_REDIRECT from qdisc filter chains

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