[PATCH 5.10.y 2/2] mptcp: pm: fix backup support in signal endpoints

Matthieu Baerts (NGI0)
2024-08-09T10:55:54Z

commit 6834097fc38c5416701c793da94558cea49c0a1f upstream.

There was a support for signal endpoints, but only when the endpoint's
flag was changed during a connection. If an endpoint with the signal and
backup was already present, the MP_JOIN reply was not containing the
backup flag as expected.

That's confusing to have this inconsistent behaviour. On the other hand,
the infrastructure to set the backup flag in the SYN + ACK + MP_JOIN was
already there, it was just never set before. Now when requesting the
local ID from the path-manager, the backup status is also requested.

Note that when the userspace PM is used, the backup flag can be set if
the local address was already used before with a backup flag, e.g. if
the address was announced with the 'backup' flag, or a subflow was
created with the 'backup' flag.

Fixes: 4596a2c1b7f5 ("mptcp: allow creating non-backup subflows")
Cc: stable@vger.kernel.org
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/507
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
[ Conflicts in pm_userspace.c because the context has changed in commit
1e07938e29c5 ("net: mptcp: rename netlink handlers to
mptcp_pm_nl_<blah>_{doit,dumpit}") which is not in this version. This
commit is unrelated to this modification.
Conflicts in protocol.h because the context has changed in commit
9ae7846c4b6b ("mptcp: dump addrs in userspace pm list") which is not
in this version. This commit is unrelated to this modification.
Conflicts in pm.c because the context has changed in commit
f40be0db0b76 ("mptcp: unify pm get_flags_and_ifindex_by_id") and
commit 71b7dec27f34 ("mptcp: less aggressive retransmission strategy")
which are not in this version. These commits are unrelated to this
modification.
Conflicts in subflow.c, because the commit 4cf86ae84c71 ("mptcp:
strict local address ID selection") is not in this version. It is then
not needed to modify the subflow_chk_local_id() helper, which is not
in this version.
Also, in this version, there is no pm_userspace.c, because this PM has
been added in v5.19, which also causes conflicts in protocol.h, and
pm_netlink.c. Plus the code in pm.c can be simplified, as there is no
userspace PM. And the code in pm_netlink.c needs to use
addresses_equal() instead of mptcp_addresses_equal(), see commit
4638de5aefe5 ("mptcp: handle local addrs announced by userspace PMs").
The code in pm_netlink.c also needs to be adapted because the
pm_nl_get_pernet_from_msk() helper is not in this version, introduced
later in commit c682bf536cf4 ("mptcp: add pm_nl_pernet helpers"), and
also because the 'flags' are in mptcp_addr_info structure, see commit
daa83ab03954 ("mptcp: move flags and ifindex out of
mptcp_addr_info"). ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
net/mptcp/pm.c | 9 +++++++++
net/mptcp/pm_netlink.c | 20 ++++++++++++++++++++
net/mptcp/protocol.h | 2 ++
net/mptcp/subflow.c | 1 +
4 files changed, 32 insertions(+)

diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
index e19e1525ecbb..1f310abbf1ed 100644
--- a/net/mptcp/pm.c
+++ b/net/mptcp/pm.c
@@ -225,6 +225,15 @@ int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc)
return mptcp_pm_nl_get_local_id(msk, skc);
}

+bool mptcp_pm_is_backup(struct mptcp_sock *msk, struct sock_common *skc)
+{
+ struct mptcp_addr_info skc_local;
+
+ mptcp_local_address((struct sock_common *)skc, &skc_local);
+
+ return mptcp_pm_nl_is_backup(msk, &skc_local);
+}
+
void mptcp_pm_data_init(struct mptcp_sock *msk)
{
msk->pm.add_addr_signaled = 0;
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 6a0079d42dc4..ca57d856d5df 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -568,6 +568,26 @@ int mptcp_pm_nl_get_local_id(struct mptcp_sock *msk, struct sock_common *skc)
return ret;
}

+bool mptcp_pm_nl_is_backup(struct mptcp_sock *msk, struct mptcp_addr_info *skc)
+{
+ struct mptcp_pm_addr_entry *entry;
+ struct pm_nl_pernet *pernet;
+ bool backup = false;
+
+ pernet = net_generic(sock_net((struct sock *)msk), pm_nl_pernet_id);
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(entry, &pernet->local_addr_list, list) {
+ if (addresses_equal(&entry->addr, skc, entry->addr.port)) {
+ backup = !!(entry->addr.flags & MPTCP_PM_ADDR_FLAG_BACKUP);
+ break;
+ }
+ }
+ rcu_read_unlock();
+
+ return backup;
+}
+
void mptcp_pm_nl_data_init(struct mptcp_sock *msk)
{
struct mptcp_pm_data *pm = &msk->pm;
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index ddfc7bde8c90..4348bccb982f 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -481,6 +481,7 @@ bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
bool mptcp_pm_rm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
u8 *rm_id);
int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);
+bool mptcp_pm_is_backup(struct mptcp_sock *msk, struct sock_common *skc);

void __init mptcp_pm_nl_init(void);
void mptcp_pm_nl_data_init(struct mptcp_sock *msk);
@@ -490,6 +491,7 @@ void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk);
void mptcp_pm_nl_rm_addr_received(struct mptcp_sock *msk);
void mptcp_pm_nl_rm_subflow_received(struct mptcp_sock *msk, u8 rm_id);
int mptcp_pm_nl_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);
+bool mptcp_pm_nl_is_backup(struct mptcp_sock *msk, struct mptcp_addr_info *skc);

static inline struct mptcp_ext *mptcp_get_ext(struct sk_buff *skb)
{
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index f4067484727e..ba86cb06d6d8 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -80,6 +80,7 @@ static struct mptcp_sock *subflow_token_join_request(struct request_sock *req,
return NULL;
}
subflow_req->local_id = local_id;
+ subflow_req->request_bkup = mptcp_pm_is_backup(msk, (struct sock_common *)req);

get_random_bytes(&subflow_req->local_nonce, sizeof(u32));

--
2.45.2