When reacting upon the reception of an ADD_ADDR, the in-kernel PM first
looks for fullmesh endpoints. If there are some, it will pick them,
using their entry ID.

It should set the ID 0 when using the endpoint corresponding to the
initial subflow, it is a special case imposed by the MPTCP specs.

Note that msk->mpc_endpoint_id might not be set when receiving the first
ADD_ADDR from the server. So better to compare the addresses.

Fixes: 1a0d6136c5f0 ("mptcp: local addresses fullmesh")
Cc: [email protected]
Reviewed-by: Mat Martineau <[email protected]>
Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>
---
 net/mptcp/pm_netlink.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index d0a80f537fc3..a2e37ab1c40f 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -636,6 +636,7 @@ static unsigned int fill_local_addresses_vec(struct 
mptcp_sock *msk,
 {
        struct sock *sk = (struct sock *)msk;
        struct mptcp_pm_addr_entry *entry;
+       struct mptcp_addr_info mpc_addr;
        struct pm_nl_pernet *pernet;
        unsigned int subflows_max;
        int i = 0;
@@ -643,6 +644,8 @@ static unsigned int fill_local_addresses_vec(struct 
mptcp_sock *msk,
        pernet = pm_nl_get_pernet_from_msk(msk);
        subflows_max = mptcp_pm_get_subflows_max(msk);
 
+       mptcp_local_address((struct sock_common *)msk, &mpc_addr);
+
        rcu_read_lock();
        list_for_each_entry_rcu(entry, &pernet->local_addr_list, list) {
                if (!(entry->flags & MPTCP_PM_ADDR_FLAG_FULLMESH))
@@ -653,7 +656,13 @@ static unsigned int fill_local_addresses_vec(struct 
mptcp_sock *msk,
 
                if (msk->pm.subflows < subflows_max) {
                        msk->pm.subflows++;
-                       addrs[i++] = entry->addr;
+                       addrs[i] = entry->addr;
+
+                       /* Special case for ID0: set the correct ID */
+                       if (mptcp_addresses_equal(&entry->addr, &mpc_addr, 
entry->addr.port))
+                               addrs[i].id = 0;
+
+                       i++;
                }
        }
        rcu_read_unlock();

-- 
2.45.2


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