[PATCH bpf-next V5 5/5] bpf: make it possible to identify BPF redirected SKBs
From: Jesper Dangaard Brouer <hidden>
Date: 2020-10-30 16:51:26
Also in:
bpf
Subsystem:
networking [general], tc subsystem, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Jamal Hadi Salim, Jiri Pirko, Linus Torvalds
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 <redacted> --- net/core/dev.c | 2 ++ net/sched/Kconfig | 1 + 2 files changed, 3 insertions(+)
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; case TC_ACT_REDIRECT: /* No need to push/pop skb's mac_header here on egress! */ + skb_set_redirected(skb, false); skb_do_redirect(skb); *ret = NET_XMIT_SUCCESS; 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 + select NET_REDIRECT help 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,