mptcp: introduce implicit endpoints

In some edge scenarios, an MPTCP subflows can use a local address
mapped by a "implicit" endpoint created by the in-kernel path manager.

Such endpoints presence can be confusing, as it's creation is hard
to track and will prevent the later endpoint creation from the user-space
using the same address.

Define a new endpoint flag to mark implicit endpoints and allow the
user-space to replace implicit them with user-provided data at endpoint
creation time.

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>

diff --git a/include/uapi/linux/mptcp.h b/include/uapi/linux/mptcp.h
index f106a39..9690efe 100644 (file)
--- a/include/uapi/linux/mptcp.h
+++ b/include/uapi/linux/mptcp.h
@@ -81,6 +81,7 @@ enum {
 #define MPTCP_PM_ADDR_FLAG_SUBFLOW                     (1 << 1)
 #define MPTCP_PM_ADDR_FLAG_BACKUP                      (1 << 2)
 #define MPTCP_PM_ADDR_FLAG_FULLMESH                    (1 << 3)
+#define MPTCP_PM_ADDR_FLAG_IMPLICIT                    (1 << 4)
 
 enum {
        MPTCP_PM_CMD_UNSPEC,

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 91b77d1..10368a4 100644 (file)
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -877,10 +877,18 @@ static bool address_use_port(struct mptcp_pm_addr_entry *entry)
                MPTCP_PM_ADDR_FLAG_SIGNAL;
 }
 
+/* caller must ensure the RCU grace period is already elapsed */
+static void __mptcp_pm_release_addr_entry(struct mptcp_pm_addr_entry *entry)
+{
+       if (entry->lsk)
+               sock_release(entry->lsk);
+       kfree(entry);
+}
+
 static int mptcp_pm_nl_append_new_local_addr(struct pm_nl_pernet *pernet,
                                             struct mptcp_pm_addr_entry *entry)
 {
-       struct mptcp_pm_addr_entry *cur;
+       struct mptcp_pm_addr_entry *cur, *del_entry = NULL;
        unsigned int addr_max;
        int ret = -EINVAL;
 
@@ -901,8 +909,22 @@ static int mptcp_pm_nl_append_new_local_addr(struct pm_nl_pernet *pernet,
        list_for_each_entry(cur, &pernet->local_addr_list, list) {
                if (addresses_equal(&cur->addr, &entry->addr,
                                    address_use_port(entry) &&
-                                   address_use_port(cur)))
-                       goto out;
+                                   address_use_port(cur))) {
+                       /* allow replacing the exiting endpoint only if such
+                        * endpoint is an implicit one and the user-space
+                        * did not provide an endpoint id
+                        */
+                       if (!(cur->flags & MPTCP_PM_ADDR_FLAG_IMPLICIT))
+                               goto out;
+                       if (entry->addr.id)
+                               goto out;
+
+                       pernet->addrs--;
+                       entry->addr.id = cur->addr.id;
+                       list_del_rcu(&cur->list);
+                       del_entry = cur;
+                       break;
+               }
        }
 
        if (!entry->addr.id) {
@@ -938,6 +960,12 @@ find_next:
 
 out:
        spin_unlock_bh(&pernet->lock);
+
+       /* just replaced an existing entry, free it */
+       if (del_entry) {
+               synchronize_rcu();
+               __mptcp_pm_release_addr_entry(del_entry);
+       }
        return ret;
 }
 
@@ -1036,7 +1064,7 @@ int mptcp_pm_nl_get_local_id(struct mptcp_sock *msk, struct sock_common *skc)
        entry->addr.id = 0;
        entry->addr.port = 0;
        entry->ifindex = 0;
-       entry->flags = 0;
+       entry->flags = MPTCP_PM_ADDR_FLAG_IMPLICIT;
        entry->lsk = NULL;
        ret = mptcp_pm_nl_append_new_local_addr(pernet, entry);
        if (ret < 0)
@@ -1249,6 +1277,11 @@ static int mptcp_nl_cmd_add_addr(struct sk_buff *skb, struct genl_info *info)
                return -EINVAL;
        }
 
+       if (addr.flags & MPTCP_PM_ADDR_FLAG_IMPLICIT) {
+               GENL_SET_ERR_MSG(info, "can't create IMPLICIT endpoint");
+               return -EINVAL;
+       }
+
        entry = kmalloc(sizeof(*entry), GFP_KERNEL);
        if (!entry) {
                GENL_SET_ERR_MSG(info, "can't allocate addr");
@@ -1333,11 +1366,12 @@ static bool mptcp_pm_remove_anno_addr(struct mptcp_sock *msk,
 }
 
 static int mptcp_nl_remove_subflow_and_signal_addr(struct net *net,
-                                                  struct mptcp_addr_info *addr)
+                                                  const struct mptcp_pm_addr_entry *entry)
 {
-       struct mptcp_sock *msk;
-       long s_slot = 0, s_num = 0;
+       const struct mptcp_addr_info *addr = &entry->addr;
        struct mptcp_rm_list list = { .nr = 0 };
+       long s_slot = 0, s_num = 0;
+       struct mptcp_sock *msk;
 
        pr_debug("remove_id=%d", addr->id);
 
@@ -1354,7 +1388,8 @@ static int mptcp_nl_remove_subflow_and_signal_addr(struct net *net,
 
                lock_sock(sk);
                remove_subflow = lookup_subflow_by_saddr(&msk->conn_list, addr);
-               mptcp_pm_remove_anno_addr(msk, addr, remove_subflow);
+               mptcp_pm_remove_anno_addr(msk, addr, remove_subflow &&
+                                         !(entry->flags & MPTCP_PM_ADDR_FLAG_IMPLICIT));
                if (remove_subflow)
                        mptcp_pm_remove_subflow(msk, &list);
                release_sock(sk);
@@ -1367,14 +1402,6 @@ next:
        return 0;
 }
 
-/* caller must ensure the RCU grace period is already elapsed */
-static void __mptcp_pm_release_addr_entry(struct mptcp_pm_addr_entry *entry)
-{
-       if (entry->lsk)
-               sock_release(entry->lsk);
-       kfree(entry);
-}
-
 static int mptcp_nl_remove_id_zero_address(struct net *net,
                                           struct mptcp_addr_info *addr)
 {
@@ -1451,7 +1478,7 @@ static int mptcp_nl_cmd_del_addr(struct sk_buff *skb, struct genl_info *info)
        __clear_bit(entry->addr.id, pernet->id_bitmap);
        spin_unlock_bh(&pernet->lock);
 
-       mptcp_nl_remove_subflow_and_signal_addr(sock_net(skb->sk), &entry->addr);
+       mptcp_nl_remove_subflow_and_signal_addr(sock_net(skb->sk), entry);
        synchronize_rcu();
        __mptcp_pm_release_addr_entry(entry);
 

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index 02bab8a..1e2e8dd 100755 (executable)
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -1938,7 +1938,7 @@ backup_tests()
        run_tests $ns1 $ns2 10.0.1.1 0 0 0 slow backup
        chk_join_nr "single address, backup" 1 1 1
        chk_add_nr 1 1
-       chk_prio_nr 1 0
+       chk_prio_nr 1 1
 
        # single address with port, backup
        reset
@@ -1948,7 +1948,7 @@ backup_tests()
        run_tests $ns1 $ns2 10.0.1.1 0 0 0 slow backup
        chk_join_nr "single address with port, backup" 1 1 1
        chk_add_nr 1 1
-       chk_prio_nr 1 0
+       chk_prio_nr 1 1
 }
 
 add_addr_ports_tests()