[PATCH 5.17 114/158] mptcp: strict local address ID selection

Greg Kroah-Hartman
2022-05-23T18:04:38Z

From: Paolo Abeni <pabeni@redhat.com>

[ Upstream commit 4cf86ae84c718333928fd2d43168a1e359a28329 ]

The address ID selection for MPJ subflows created in response
to incoming ADD_ADDR option is currently unreliable: it happens
at MPJ socket creation time, when the local address could be
unknown.

Additionally, if the no local endpoint is available for the local
address, a new dummy endpoint is created, confusing the user-land.

This change refactor the code to move the address ID selection inside
the rebuild_header() helper, when the local address eventually
selected by the route lookup is finally known. If the address used
is not mapped by any endpoint - and thus can't be advertised/removed
pick the id 0 instead of allocate a new endpoint.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/mptcp/pm_netlink.c | 13 --------
net/mptcp/protocol.c | 3 ++
net/mptcp/protocol.h | 3 +-
net/mptcp/subflow.c | 67 ++++++++++++++++++++++++++++++++++++------
4 files changed, 63 insertions(+), 23 deletions(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 4b5d795383cd..ec73bd4be0a8 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -83,16 +83,6 @@ static bool addresses_equal(const struct mptcp_addr_info *a,
return a->port == b->port;
}

-static bool address_zero(const struct mptcp_addr_info *addr)
-{
- struct mptcp_addr_info zero;
-
- memset(&zero, 0, sizeof(zero));
- zero.family = addr->family;
-
- return addresses_equal(addr, &zero, true);
-}
-
static void local_address(const struct sock_common *skc,
struct mptcp_addr_info *addr)
{
@@ -1011,9 +1001,6 @@ int mptcp_pm_nl_get_local_id(struct mptcp_sock *msk, struct sock_common *skc)
if (addresses_equal(&msk_local, &skc_local, false))
return 0;

- if (address_zero(&skc_local))
- return 0;
-
pernet = net_generic(sock_net((struct sock *)msk), pm_nl_pernet_id);

rcu_read_lock();
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 014c9d88f947..cb90941840b1 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -117,6 +117,9 @@ static int __mptcp_socket_create(struct mptcp_sock *msk)
list_add(&subflow->node, &msk->conn_list);
sock_hold(ssock->sk);
subflow->request_mptcp = 1;
+
+ /* This is the first subflow, always with id 0 */
+ subflow->local_id_valid = 1;
mptcp_sock_graft(msk->first, sk->sk_socket);

return 0;
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index aec767ee047a..e4413b3e50c2 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -442,7 +442,8 @@ struct mptcp_subflow_context {
rx_eof : 1,
can_ack : 1, /* only after processing the remote a key */
disposable : 1, /* ctx can be free at ulp release time */
- stale : 1; /* unable to snd/rcv data, do not use for xmit */
+ stale : 1, /* unable to snd/rcv data, do not use for xmit */
+ local_id_valid : 1; /* local_id is correctly initialized */
enum mptcp_data_avail data_avail;
u32 remote_nonce;
u64 thmac;
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 651f01d13191..e27574e9f969 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -483,6 +483,51 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
mptcp_subflow_reset(sk);
}

+static void subflow_set_local_id(struct mptcp_subflow_context *subflow, int local_id)
+{
+ subflow->local_id = local_id;
+ subflow->local_id_valid = 1;
+}
+
+static int subflow_chk_local_id(struct sock *sk)
+{
+ struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+ struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+ int err;
+
+ if (likely(subflow->local_id_valid))
+ return 0;
+
+ err = mptcp_pm_get_local_id(msk, (struct sock_common *)sk);
+ if (err < 0)
+ return err;
+
+ subflow_set_local_id(subflow, err);
+ return 0;
+}
+
+static int subflow_rebuild_header(struct sock *sk)
+{
+ int err = subflow_chk_local_id(sk);
+
+ if (unlikely(err < 0))
+ return err;
+
+ return inet_sk_rebuild_header(sk);
+}
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+static int subflow_v6_rebuild_header(struct sock *sk)
+{
+ int err = subflow_chk_local_id(sk);
+
+ if (unlikely(err < 0))
+ return err;
+
+ return inet6_sk_rebuild_header(sk);
+}
+#endif
+
struct request_sock_ops mptcp_subflow_request_sock_ops;
EXPORT_SYMBOL_GPL(mptcp_subflow_request_sock_ops);
static struct tcp_request_sock_ops subflow_request_sock_ipv4_ops;
@@ -1401,13 +1446,8 @@ int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_addr_info *loc,
get_random_bytes(&subflow->local_nonce, sizeof(u32));
} while (!subflow->local_nonce);

- if (!local_id) {
- err = mptcp_pm_get_local_id(msk, (struct sock_common *)ssk);
- if (err < 0)
- goto failed;
-
- local_id = err;
- }
+ if (local_id)
+ subflow_set_local_id(subflow, local_id);

mptcp_pm_get_flags_and_ifindex_by_id(sock_net(sk), local_id,
&flags, &ifindex);
@@ -1432,7 +1472,6 @@ int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_addr_info *loc,
pr_debug("msk=%p remote_token=%u local_id=%d remote_id=%d", msk,
remote_token, local_id, remote_id);
subflow->remote_token = remote_token;
- subflow->local_id = local_id;
subflow->remote_id = remote_id;
subflow->request_join = 1;
subflow->request_bkup = !!(flags & MPTCP_PM_ADDR_FLAG_BACKUP);
@@ -1737,15 +1776,22 @@ static void subflow_ulp_clone(const struct request_sock *req,
new_ctx->token = subflow_req->token;
new_ctx->ssn_offset = subflow_req->ssn_offset;
new_ctx->idsn = subflow_req->idsn;
+
+ /* this is the first subflow, id is always 0 */
+ new_ctx->local_id_valid = 1;
} else if (subflow_req->mp_join) {
new_ctx->ssn_offset = subflow_req->ssn_offset;
new_ctx->mp_join = 1;
new_ctx->fully_established = 1;
new_ctx->backup = subflow_req->backup;
- new_ctx->local_id = subflow_req->local_id;
new_ctx->remote_id = subflow_req->remote_id;
new_ctx->token = subflow_req->token;
new_ctx->thmac = subflow_req->thmac;
+
+ /* the subflow req id is valid, fetched via subflow_check_req()
+ * and subflow_token_join_request()
+ */
+ subflow_set_local_id(new_ctx, subflow_req->local_id);
}
}

@@ -1798,6 +1844,7 @@ void __init mptcp_subflow_init(void)
subflow_specific.conn_request = subflow_v4_conn_request;
subflow_specific.syn_recv_sock = subflow_syn_recv_sock;
subflow_specific.sk_rx_dst_set = subflow_finish_connect;
+ subflow_specific.rebuild_header = subflow_rebuild_header;

tcp_prot_override = tcp_prot;
tcp_prot_override.release_cb = tcp_release_cb_override;
@@ -1810,6 +1857,7 @@ void __init mptcp_subflow_init(void)
subflow_v6_specific.conn_request = subflow_v6_conn_request;
subflow_v6_specific.syn_recv_sock = subflow_syn_recv_sock;
subflow_v6_specific.sk_rx_dst_set = subflow_finish_connect;
+ subflow_v6_specific.rebuild_header = subflow_v6_rebuild_header;

subflow_v6m_specific = subflow_v6_specific;
subflow_v6m_specific.queue_xmit = ipv4_specific.queue_xmit;
@@ -1817,6 +1865,7 @@ void __init mptcp_subflow_init(void)
subflow_v6m_specific.net_header_len = ipv4_specific.net_header_len;
subflow_v6m_specific.mtu_reduced = ipv4_specific.mtu_reduced;
subflow_v6m_specific.net_frag_header_len = 0;
+ subflow_v6m_specific.rebuild_header = subflow_rebuild_header;

tcpv6_prot_override = tcpv6_prot;
tcpv6_prot_override.release_cb = tcp_release_cb_override;
--
2.35.1