netdev - [PATCH bpf-next v3 06/12] bpf, sockmap: Don't set up sockmap progs for listening sockets

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Message-Id: <20200122130549.832236-7-jakub@cloudflare.com>
Date:   Wed, 22 Jan 2020 14:05:43 +0100
From:   Jakub Sitnicki <jakub@...udflare.com>
To:     bpf@...r.kernel.org
Cc:     netdev@...r.kernel.org, kernel-team@...udflare.com,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Lorenz Bauer <lmb@...udflare.com>, Martin Lau <kafai@...com>
Subject: [PATCH bpf-next v3 06/12] bpf, sockmap: Don't set up sockmap progs for listening sockets

Now that sockmap can hold listening sockets, when setting up the psock we
will (i) grab references to verdict/parser progs, and (2) override socket
upcalls sk_data_ready and sk_write_space.

We cannot redirect to listening sockets so we don't need to link the socket
to the BPF progs, but more importantly we don't want the listening socket
to have overridden upcalls because they would get inherited by child
sockets cloned from it.

Introduce a separate initialization path for listening sockets that does
not change the upcalls and ignores the BPF progs.

Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
---
 net/core/sock_map.c | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 97bdceb29f09..439f1e0b995e 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -228,6 +228,30 @@ static int sock_map_link(struct bpf_map *map, struct sk_psock_progs *progs,
 	return ret;
 }
 
+static int sock_map_link_no_progs(struct bpf_map *map, struct sock *sk)
+{
+	struct sk_psock *psock;
+	int ret;
+
+	psock = sk_psock_get_checked(sk);
+	if (IS_ERR(psock))
+		return PTR_ERR(psock);
+
+	if (psock) {
+		tcp_bpf_reinit(sk);
+		return 0;
+	}
+
+	psock = sk_psock_init(sk, map->numa_node);
+	if (!psock)
+		return -ENOMEM;
+
+	ret = tcp_bpf_init(sk);
+	if (ret < 0)
+		sk_psock_put(sk, psock);
+	return ret;
+}
+
 static void sock_map_free(struct bpf_map *map)
 {
 	struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
@@ -352,7 +376,15 @@ static int sock_map_update_common(struct bpf_map *map, u32 idx,
 	if (!link)
 		return -ENOMEM;
 
-	ret = sock_map_link(map, &stab->progs, sk);
+	/* Only established or almost established sockets leaving
+	 * SYN_RECV state need to hold refs to parser/verdict progs
+	 * and have their sk_data_ready and sk_write_space callbacks
+	 * overridden.
+	 */
+	if (sk->sk_state == TCP_LISTEN)
+		ret = sock_map_link_no_progs(map, sk);
+	else
+		ret = sock_map_link(map, &stab->progs, sk);
 	if (ret < 0)
 		goto out_free;
 
-- 
2.24.1