[PATCH bpf-next 1/2] bpf: Add support for {set|get} socket options from setsockopt BPF

[Prankur gupta <prankgup@fb.com>]

Add logic to call bpf_setsockopt and bpf_getsockopt from
setsockopt BPF programs.
Example use case, when the user sets the IPV6_TCLASS socket option
we would also like to change the tcp-cc for that socket.
We don't have any use case for calling bpf_setsockopt from
supposedly read-only sys_getsockopti, so it is made available to
BPF_CGROUP_SETSOCKOPT only.

Signed-off-by: Prankur gupta <prankgup@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
---
 kernel/bpf/cgroup.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 9f35928bab0a..8e9d99e2ade4 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1873,6 +1873,14 @@ cg_sockopt_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_sk_storage_get_proto;
 	case BPF_FUNC_sk_storage_delete:
 		return &bpf_sk_storage_delete_proto;
+	case BPF_FUNC_setsockopt:
+		if (prog->expected_attach_type == BPF_CGROUP_SETSOCKOPT)
+			return &bpf_sk_setsockopt_proto;
+		return NULL;
+	case BPF_FUNC_getsockopt:
+		if (prog->expected_attach_type == BPF_CGROUP_SETSOCKOPT)
+			return &bpf_sk_getsockopt_proto;
+		return NULL;
 #endif
 #ifdef CONFIG_INET
 	case BPF_FUNC_tcp_sock:
-- 
2.30.2