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[bpf-next,V5,5/5] bpf: make it possible to identify BPF redirected SKBs

Message ID 160407667257.1525159.8494441828025036187.stgit@firesoul
State Not Applicable
Delegated to: BPF Maintainers
Headers show
Series Subj: bpf: New approach for BPF MTU handling | expand


Context Check Description
jkicinski/cover_letter success Link
jkicinski/fixes_present success Link
jkicinski/patch_count success Link
jkicinski/tree_selection success Clearly marked for bpf-next
jkicinski/subject_prefix success Link
jkicinski/source_inline success Was 0 now: 0
jkicinski/verify_signedoff success Link
jkicinski/module_param success Was 0 now: 0
jkicinski/build_32bit fail Errors and warnings before: 14 this patch: 14
jkicinski/kdoc success Errors and warnings before: 0 this patch: 0
jkicinski/verify_fixes success Link
jkicinski/checkpatch fail Link
jkicinski/build_allmodconfig_warn success Errors and warnings before: 10 this patch: 10
jkicinski/header_inline success Link
jkicinski/stable success Stable not CCed

Commit Message

Jesper Dangaard Brouer Oct. 30, 2020, 4:51 p.m. UTC
This change makes it possible to identify SKBs that have been redirected
by TC-BPF (cls_act). This is needed for a number of cases.

(1) For collaborating with driver ifb net_devices.
(2) For avoiding starting generic-XDP prog on TC ingress redirect.

It is most important to fix XDP case(2), because this can break userspace
when a driver gets support for native-XDP. Imagine userspace loads XDP
prog on eth0, which fallback to generic-XDP, and it process TC-redirected
packets. When kernel is updated with native-XDP support for eth0, then the
program no-longer see the TC-redirected packets. Therefore it is important
to keep the order intact; that XDP runs before TC-BPF.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
 net/core/dev.c    |    2 ++
 net/sched/Kconfig |    1 +
 2 files changed, 3 insertions(+)
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diff --git a/net/core/dev.c b/net/core/dev.c
index 445ccf92c149..930c165a607e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3870,6 +3870,7 @@  sch_handle_egress(struct sk_buff *skb, int *ret, struct net_device *dev)
 		return NULL;
 		/* No need to push/pop skb's mac_header here on egress! */
+		skb_set_redirected(skb, false);
 		return NULL;
@@ -4959,6 +4960,7 @@  sch_handle_ingress(struct sk_buff *skb, struct packet_type **pt_prev, int *ret,
 		 * redirecting to another netdev
 		__skb_push(skb, skb->mac_len);
+		skb_set_redirected(skb, true);
 		if (skb_do_redirect(skb) == -EAGAIN) {
 			__skb_pull(skb, skb->mac_len);
 			*another = true;
diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index a3b37d88800e..a1bbaa8fd054 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -384,6 +384,7 @@  config NET_SCH_INGRESS
 	depends on NET_CLS_ACT
 	select NET_INGRESS
 	select NET_EGRESS
 	  Say Y here if you want to use classifiers for incoming and/or outgoing
 	  packets. This qdisc doesn't do anything else besides running classifiers,