Before this patch, receiving an ADD_ADDR echo on the just connected MP_JOIN subflow -- initiator side, after the MP_JOIN 3WHS -- was resulting in an MP_RESET. That's because only ACKs with a DSS or ADD_ADDRs without the echo bit were allowed.

Not allowing the ADD_ADDR echo after an MP_CAPABLE 3WHS makes sense, as we are not supposed to send an ADD_ADDR before because it requires to be in full established mode first. For the MP_JOIN 3WHS, that's different: the ADD_ADDR can be sent on a previous subflow, and the ADD_ADDR echo can be received on the recently created one. The other peer will already be in fully established, so it is allowed to send that.

We can then relax the conditions here to accept the ADD_ADDR echo for MPJ subflows.

Fixes: 67b12f792d5e ("mptcp: full fully established support after ADD_ADDR") Cc: stable@vger.kernel.org Reviewed-by: Mat Martineau martineau@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org --- net/mptcp/options.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/options.c b/net/mptcp/options.c index 8a68382a4fe9..ac2f1a54cc43 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -958,7 +958,8 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,

if (subflow->remote_key_valid && (((mp_opt->suboptions & OPTION_MPTCP_DSS) && mp_opt->use_ack) || - ((mp_opt->suboptions & OPTION_MPTCP_ADD_ADDR) && !mp_opt->echo))) { + ((mp_opt->suboptions & OPTION_MPTCP_ADD_ADDR) && + (!mp_opt->echo || subflow->mp_join)))) { /* subflows are fully established as soon as we get any * additional ack, including ADD_ADDR. */

That will simplify the following commits.

No functional changes intended.

Suggested-by: Paolo Abeni pabeni@redhat.com Reviewed-by: Mat Martineau martineau@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org --- net/mptcp/pm_netlink.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c index c921d07e5940..780f4cca165c 100644 --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -567,16 +567,19 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk) if (msk->pm.addr_signal & BIT(MPTCP_ADD_ADDR_SIGNAL)) return;

- if (local) { - if (mptcp_pm_alloc_anno_list(msk, &local->addr)) { - __clear_bit(local->addr.id, msk->pm.id_avail_bitmap); - msk->pm.add_addr_signaled++; - mptcp_pm_announce_addr(msk, &local->addr, false); - mptcp_pm_nl_addr_send_ack(msk); - } - } + if (!local) + goto subflow; + + if (!mptcp_pm_alloc_anno_list(msk, &local->addr)) + goto subflow; + + __clear_bit(local->addr.id, msk->pm.id_avail_bitmap); + msk->pm.add_addr_signaled++; + mptcp_pm_announce_addr(msk, &local->addr, false); + mptcp_pm_nl_addr_send_ack(msk); }

+subflow: /* check if should create a new subflow */ while (msk->pm.local_addr_used < local_addr_max && msk->pm.subflows < subflows_max) {

Up to the 'Fixes' commit, having an endpoint with both the 'signal' and 'subflow' flags, resulted in the creation of a subflow and an address announcement using the address linked to this endpoint. After this commit, only the address announcement was done, ignoring the 'subflow' flag.

That's because the same bitmap is used for the two flags. It is OK to keep this single bitmap, the already selected local endpoint simply have to be re-used, but not via select_local_address() not to look at the just modified bitmap.

Note that it is unusual to set the two flags together: creating a new subflow using a new local address will implicitly advertise it to the other peer. So in theory, no need to advertise it explicitly as well. Maybe there are use-cases -- the subflow might not reach the other peer that way, we can ask the other peer to try initiating the new subflow without delay -- or very likely the user is confused, and put both flags "just to be sure at least the right one is set". Still, if it is allowed, the kernel should do what has been asked: using this endpoint to announce the address and to create a new subflow from it.

An alternative is to forbid the use of the two flags together, but that's probably too late, there are maybe use-cases, and it was working before. This patch will avoid people complaining subflows are not created using the endpoint they added with the 'subflow' and 'signal' flag.

Note that with the current patch, the subflow might not be created in some corner cases, e.g. if the 'subflows' limit was reached when sending the ADD_ADDR, but changed later on. It is probably not worth splitting id_avail_bitmap per target ('signal', 'subflow'), which will add another large field to the msk "just" to track (again) endpoints. Anyway, currently when the limits are changed, the kernel doesn't check if new subflows can be created or removed, because we would need to keep track of the received ADD_ADDR, and more. It sounds OK to assume that the limits should be properly configured before establishing new connections.

Fixes: 86e39e04482b ("mptcp: keep track of local endpoint still available for each msk") Cc: stable@vger.kernel.org Suggested-by: Paolo Abeni pabeni@redhat.com Reviewed-by: Mat Martineau martineau@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org --- net/mptcp/pm_netlink.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c index 2be7af377cda..4cae2aa7be5c 100644 --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -512,8 +512,8 @@ __lookup_addr(struct pm_nl_pernet *pernet, const struct mptcp_addr_info *info)

static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk) { + struct mptcp_pm_addr_entry *local, *signal_and_subflow = NULL; struct sock *sk = (struct sock *)msk; - struct mptcp_pm_addr_entry *local; unsigned int add_addr_signal_max; unsigned int local_addr_max; struct pm_nl_pernet *pernet; @@ -579,6 +579,9 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk) msk->pm.add_addr_signaled++; mptcp_pm_announce_addr(msk, &local->addr, false); mptcp_pm_nl_addr_send_ack(msk); + + if (local->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW) + signal_and_subflow = local; }

subflow: @@ -589,9 +592,14 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk) bool fullmesh; int i, nr;

- local = select_local_address(pernet, msk); - if (!local) - break; + if (signal_and_subflow) { + local = signal_and_subflow; + signal_and_subflow = NULL; + } else { + local = select_local_address(pernet, msk); + if (!local) + break; + }

fullmesh = !!(local->flags & MPTCP_PM_ADDR_FLAG_FULLMESH);

It should be quite uncommon to set both the subflow and the signal flags: the initiator of the connection is typically the one creating new subflows, not the other peer, then no need to announce additional local addresses, and use it to create subflows.

But some people might be confused about the flags, and set both "just to be sure at least the right one is set". To verify the previous fix, and avoid future regressions, this specific case is now validated: the client announces a new address, and initiates a new subflow from the same address.

While working on this, another bug has been noticed, where the client reset the new subflow because an ADD_ADDR echo got received as the 3rd ACK: this new test also explicitly checks that no RST have been sent by the client and server.

The 'Fixes' tag here below is the same as the one from the previous commit: this patch here is not fixing anything wrong in the selftests, but it validates the previous fix for an issue introduced by this commit ID.

Fixes: 86e39e04482b ("mptcp: keep track of local endpoint still available for each msk") Reviewed-by: Mat Martineau martineau@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org --- tools/testing/selftests/net/mptcp/mptcp_join.sh | 15 +++++++++++++++ 1 file changed, 15 insertions(+)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh index 52a25ac43d10..9ea6d698e9d3 100755 --- a/tools/testing/selftests/net/mptcp/mptcp_join.sh +++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh @@ -1989,6 +1989,21 @@ signal_address_tests() chk_add_nr 1 1 fi

+ # uncommon: subflow and signal flags on the same endpoint + # or because the user wrongly picked both, but still expects the client + # to create additional subflows + if reset "subflow and signal together"; then + pm_nl_set_limits $ns1 0 2 + pm_nl_set_limits $ns2 0 2 + pm_nl_add_endpoint $ns2 10.0.3.2 flags signal,subflow + run_tests $ns1 $ns2 10.0.1.1 + chk_join_nr 1 1 1 + chk_add_nr 1 1 0 invert # only initiated by ns2 + chk_add_nr 0 0 0 # none initiated by ns1 + chk_rst_nr 0 0 invert # no RST sent by the client + chk_rst_nr 0 0 # no RST sent by the server + fi + # accept and use add_addr with additional subflows if reset "multiple subflows and signal"; then pm_nl_set_limits $ns1 0 3