[PATCH v4 bpf-next 1/3] bpf: Add get_netns_id helper function for sock_ops

[Lingpeng Chen <forrest0579@gmail.com>]

Currently 5-tuple(sip+dip+sport+dport+proto) can't identify a
uniq connection because there may be multi net namespace.
For example, there may be a chance that netns a and netns b all
listen on 127.0.0.1:8080 and the client with same port 40782
connect to them. Without netns number, sock ops program
can't distinguish them.
Using bpf_get_netns_id helper to get current connection
netns id to distinguish connections.

Signed-off-by: Lingpeng Chen <forrest0579@gmail.com>
---
 include/uapi/linux/bpf.h |  9 ++++++++-
 net/core/filter.c        | 20 ++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 906e9f2752db..c53178f7585e 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2909,6 +2909,12 @@ union bpf_attr {
  *		of sizeof(struct perf_branch_entry).
  *
  *		**-ENOENT** if architecture does not support branch records.
+ *
+ * u64 bpf_get_netns_id(struct bpf_sock_ops *bpf_socket)
+ *  Description
+ *      Obtain netns id of sock
+ * Return
+ *      The current netns inum
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -3030,7 +3036,8 @@ union bpf_attr {
 	FN(tcp_send_ack),		\
 	FN(send_signal_thread),		\
 	FN(jiffies64),			\
-	FN(read_branch_records),
+	FN(read_branch_records),	\
+	FN(get_netns_id),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
diff --git a/net/core/filter.c b/net/core/filter.c
index 925b23de218b..98536b0eecb6 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4421,6 +4421,24 @@ static const struct bpf_func_proto bpf_sock_ops_cb_flags_set_proto = {
 	.arg2_type	= ARG_ANYTHING,
 };
 
+BPF_CALL_1(bpf_get_netns_id, struct bpf_sock_ops_kern *, bpf_sock)
+{
+#ifdef CONFIG_NET_NS
+	struct sock *sk = bpf_sock->sk;
+
+	return (u64)sk->sk_net.net->ns.inum;
+#else
+	return 0;
+#endif
+}
+
+static const struct bpf_func_proto bpf_get_netns_id_proto = {
+	.func		= bpf_get_netns_id,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+};
+
 const struct ipv6_bpf_stub *ipv6_bpf_stub __read_mostly;
 EXPORT_SYMBOL_GPL(ipv6_bpf_stub);
 
@@ -6218,6 +6236,8 @@ sock_ops_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_tcp_sock:
 		return &bpf_tcp_sock_proto;
 #endif /* CONFIG_INET */
+	case BPF_FUNC_get_netns_id:
+		return &bpf_get_netns_id_proto;
 	default:
 		return bpf_base_func_proto(func_id);
 	}
-- 
2.20.1