[PATCH v9 4/6] net: filter: run cgroup eBPF ingress programs

If the cgroup associated with the receiving socket has an eBPF
programs installed, run them from sk_filter_trim_cap().

eBPF programs used in this context are expected to either return 1 to
let the packet pass, or != 1 to drop them. The programs have access to
the skb through bpf_skb_load_bytes(), and the payload starts at the
network headers (L3).

Note that cgroup_bpf_run_filter() is stubbed out as static inline nop
for !CONFIG_CGROUP_BPF, and is otherwise guarded by a static key if
the feature is unused.

Signed-off-by: Daniel Mack <redacted>
Acked-by: Alexei Starovoitov <redacted>
---
 net/core/filter.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/core/filter.c b/net/core/filter.c
index e3813d6..474b486 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c

@@ -78,6 +78,10 @@ int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap)
 	if (skb_pfmemalloc(skb) && !sock_flag(sk, SOCK_MEMALLOC))
 		return -ENOMEM;
 
+	err = BPF_CGROUP_RUN_PROG_INET_INGRESS(sk, skb);
+	if (err)
+		return err;
+
 	err = security_sock_rcv_skb(sk, skb);
 	if (err)
 		return err;

-- 
2.7.4