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mptcp: introduce implicit endpoints
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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>
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Paolo Abeni authored and Jakub Kicinski committed Mar 9, 2022
1 parent 6fa0174 commit d045b9e
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Showing 3 changed files with 47 additions and 19 deletions.
1 change: 1 addition & 0 deletions include/uapi/linux/mptcp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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,
Expand Down
61 changes: 44 additions & 17 deletions net/mptcp/pm_netlink.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;

Expand All @@ -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) {
Expand Down Expand Up @@ -938,6 +960,12 @@ static int mptcp_pm_nl_append_new_local_addr(struct pm_nl_pernet *pernet,

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;
}

Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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");
Expand Down Expand Up @@ -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);

Expand All @@ -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);
Expand All @@ -1367,14 +1402,6 @@ static int mptcp_nl_remove_subflow_and_signal_addr(struct net *net,
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)
{
Expand Down Expand Up @@ -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);

Expand Down
4 changes: 2 additions & 2 deletions tools/testing/selftests/net/mptcp/mptcp_join.sh
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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()
Expand Down

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