netdev - [PATCH bpf-next 3/4] bpf: Support socket lookup in CGROUP_SOCK

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Message-ID: <56e95bcb5c99a4547cb896b1e7e732d7926d23e1.1541695683.git.rdna@fb.com>
Date:   Thu, 8 Nov 2018 08:54:24 -0800
From:   Andrey Ignatov <rdna@...com>
To:     <netdev@...r.kernel.org>
CC:     Andrey Ignatov <rdna@...com>, <ast@...nel.org>,
        <daniel@...earbox.net>, <joe@...d.net.nz>, <kernel-team@...com>
Subject: [PATCH bpf-next 3/4] bpf: Support socket lookup in CGROUP_SOCK_ADDR progs

Make bpf_sk_lookup_tcp, bpf_sk_lookup_udp and bpf_sk_release helpers
available in programs of type BPF_PROG_TYPE_CGROUP_SOCK_ADDR.

Such programs operate on sockets and have access to socket and struct
sockaddr passed by user to system calls such as sys_bind, sys_connect,
sys_sendmsg.

It's useful to be able to lookup other sockets from these programs.
E.g. sys_connect may lookup IP:port endpoint and if there is a server
socket bound to that endpoint ("server" can be defined by saddr & sport
being zero), redirect client connection to it by rewriting IP:port in
sockaddr passed to sys_connect.

Signed-off-by: Andrey Ignatov <rdna@...com>
Acked-by: Alexei Starovoitov <ast@...nel.org>
---
 net/core/filter.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/net/core/filter.c b/net/core/filter.c
index dc0f86a707b7..2e8575a34a1e 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4971,6 +4971,51 @@ static const struct bpf_func_proto bpf_sk_release_proto = {
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_SOCKET,
 };
+
+static unsigned long
+bpf_sock_addr_sk_lookup(struct sock *sk, struct bpf_sock_tuple *tuple, u32 len,
+			u8 proto, u64 netns_id, u64 flags)
+{
+	return __bpf_sk_lookup(NULL, tuple, len, proto, netns_id, sock_net(sk),
+			       0, flags);
+}
+
+BPF_CALL_5(bpf_sock_addr_sk_lookup_tcp, struct bpf_sock_addr_kern *, ctx,
+	   struct bpf_sock_tuple *, tuple, u32, len, u64, netns_id, u64, flags)
+{
+	return bpf_sock_addr_sk_lookup(ctx->sk, tuple, len, IPPROTO_TCP,
+				       netns_id, flags);
+}
+
+static const struct bpf_func_proto bpf_sock_addr_sk_lookup_tcp_proto = {
+	.func		= bpf_sock_addr_sk_lookup_tcp,
+	.gpl_only	= false,
+	.ret_type	= RET_PTR_TO_SOCKET_OR_NULL,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_PTR_TO_MEM,
+	.arg3_type	= ARG_CONST_SIZE,
+	.arg4_type	= ARG_ANYTHING,
+	.arg5_type	= ARG_ANYTHING,
+};
+
+BPF_CALL_5(bpf_sock_addr_sk_lookup_udp, struct bpf_sock_addr_kern *, ctx,
+	   struct bpf_sock_tuple *, tuple, u32, len, u64, netns_id, u64, flags)
+{
+	return bpf_sock_addr_sk_lookup(ctx->sk, tuple, len, IPPROTO_UDP,
+				       netns_id, flags);
+}
+
+static const struct bpf_func_proto bpf_sock_addr_sk_lookup_udp_proto = {
+	.func		= bpf_sock_addr_sk_lookup_udp,
+	.gpl_only	= false,
+	.ret_type	= RET_PTR_TO_SOCKET_OR_NULL,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_PTR_TO_MEM,
+	.arg3_type	= ARG_CONST_SIZE,
+	.arg4_type	= ARG_ANYTHING,
+	.arg5_type	= ARG_ANYTHING,
+};
+
 #endif /* CONFIG_INET */
 
 bool bpf_helper_changes_pkt_data(void *func)
@@ -5077,6 +5122,14 @@ sock_addr_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_get_socket_cookie_sock_addr_proto;
 	case BPF_FUNC_get_local_storage:
 		return &bpf_get_local_storage_proto;
+#ifdef CONFIG_INET
+	case BPF_FUNC_sk_lookup_tcp:
+		return &bpf_sock_addr_sk_lookup_tcp_proto;
+	case BPF_FUNC_sk_lookup_udp:
+		return &bpf_sock_addr_sk_lookup_udp_proto;
+	case BPF_FUNC_sk_release:
+		return &bpf_sk_release_proto;
+#endif /* CONFIG_INET */
 	default:
 		return bpf_base_func_proto(func_id);
 	}
-- 
2.17.1