@@ -303,6 +303,7 @@ void mptcp_rcv_synsent(struct sock *sk)
pr_debug("subflow=%p", subflow);
if (subflow->request_mptcp && tp->rx_opt.mptcp.mp_capable) {
subflow->mp_capable = 1;
+ subflow->can_ack = 1;
subflow->remote_key = tp->rx_opt.mptcp.sndr_key;
}
}
@@ -421,6 +422,11 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
mptcp_write_data_fin(subflow, &opts->ext_copy);
}
+ opts->ext_copy.use_ack = 0;
+ msk = mptcp_sk(subflow->conn);
+ if (!msk || !READ_ONCE(msk->can_ack))
+ return false;
+
ack_size = TCPOLEN_MPTCP_DSS_ACK64;
/* Add kind/length/subtype/flag overhead if mapping is not populated */
@@ -429,15 +435,7 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
dss_size += ack_size;
- msk = mptcp_sk(mptcp_subflow_ctx(sk)->conn);
- if (msk) {
- opts->ext_copy.data_ack = msk->ack_seq;
- } else {
- mptcp_crypto_key_sha(mptcp_subflow_ctx(sk)->remote_key,
- NULL, &opts->ext_copy.data_ack);
- opts->ext_copy.data_ack++;
- }
-
+ opts->ext_copy.data_ack = msk->ack_seq;
opts->ext_copy.ack64 = 1;
opts->ext_copy.use_ack = 1;
@@ -489,6 +487,35 @@ bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
return false;
}
+static bool check_fourth_ack(struct mptcp_subflow_context *subflow,
+ struct sk_buff *skb,
+ struct mptcp_options_received *mp_opt)
+{
+ /* here we can process OoO, in-window pkts, only in-sequence 4th ack
+ * are relevant
+ */
+ if (likely(subflow->fourth_ack ||
+ TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1))
+ return true;
+
+ if (mp_opt->use_ack)
+ subflow->fourth_ack = 1;
+
+ if (subflow->can_ack)
+ return true;
+
+ /* If the first established packet does not contain MP_CAPABLE + data
+ * then fallback to TCP
+ */
+ if (!mp_opt->mp_capable) {
+ subflow->mp_capable = 0;
+ return false;
+ }
+ subflow->remote_key = mp_opt->sndr_key;
+ subflow->can_ack = 1;
+ return true;
+}
+
void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb,
struct tcp_options_received *opt_rx)
{
@@ -500,6 +527,8 @@ void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb,
return;
mp_opt = &opt_rx->mptcp;
+ if (!check_fourth_ack(subflow, skb, mp_opt))
+ return;
if (!mp_opt->dss)
return;
@@ -347,6 +347,12 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
lock_sock(ssk);
while (mptcp_subflow_data_available(ssk) && !done) {
+ if (unlikely(!msk->can_ack)) {
+ msk->remote_key = subflow->remote_key;
+ msk->ack_seq = subflow->map_seq;
+ msk->can_ack = true;
+ }
+
/* try to read as much data as available */
map_remaining = subflow->map_data_len -
mptcp_subflow_get_map_offset(subflow);
@@ -505,17 +511,20 @@ static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
__mptcp_init_sock(new_mptcp_sock);
msk = mptcp_sk(new_mptcp_sock);
- msk->remote_key = subflow->remote_key;
msk->local_key = subflow->local_key;
msk->token = subflow->token;
mptcp_token_update_accept(new_sock->sk, new_mptcp_sock);
msk->subflow = NULL;
- mptcp_crypto_key_sha(msk->remote_key, NULL, &ack_seq);
msk->write_seq = subflow->idsn + 1;
- ack_seq++;
- msk->ack_seq = ack_seq;
+ if (subflow->can_ack) {
+ msk->can_ack = true;
+ msk->remote_key = subflow->remote_key;
+ mptcp_crypto_key_sha(msk->remote_key, NULL, &ack_seq);
+ ack_seq++;
+ msk->ack_seq = ack_seq;
+ }
newsk = new_mptcp_sock;
list_add(&subflow->node, &msk->conn_list);
bh_unlock_sock(new_mptcp_sock);
@@ -527,8 +536,6 @@ static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
* the receive path and process the pending ones
*/
lock_sock(new_sock->sk);
- subflow->map_seq = ack_seq;
- subflow->map_subflow_seq = 1;
subflow->rel_write_seq = 1;
subflow->tcp_sock = new_sock;
subflow->conn = new_mptcp_sock;
@@ -656,6 +663,7 @@ void mptcp_finish_connect(struct sock *sk, int mp_capable)
msk->write_seq = subflow->idsn + 1;
ack_seq++;
msk->ack_seq = ack_seq;
+ msk->can_ack = 1;
subflow->map_seq = ack_seq;
subflow->map_subflow_seq = 1;
subflow->rel_write_seq = 1;
@@ -68,6 +68,7 @@ struct mptcp_sock {
u64 ack_seq;
u32 token;
unsigned long flags;
+ bool can_ack;
struct list_head conn_list;
struct socket *subflow; /* outgoing connect/listener/!mp_capable */
};
@@ -82,9 +83,10 @@ static inline struct mptcp_sock *mptcp_sk(const struct sock *sk)
struct mptcp_subflow_request_sock {
struct tcp_request_sock sk;
- u8 mp_capable : 1,
+ u16 mp_capable : 1,
mp_join : 1,
backup : 1,
+ remote_key_valid : 1,
version : 4;
u64 local_key;
u64 remote_key;
@@ -118,8 +120,10 @@ struct mptcp_subflow_context {
fourth_ack : 1, /* send initial DSS */
conn_finished : 1,
map_valid : 1,
+ mpc_map : 1,
data_avail : 1,
- rx_eof : 1;
+ rx_eof : 1,
+ can_ack : 1; /* only after processing the remote a key */
struct socket *tcp_sock; /* underlying tcp_sock */
struct sock *conn; /* parent mptcp_sock */
@@ -61,6 +61,7 @@ static void subflow_init_req(struct request_sock *req,
mptcp_get_options(skb, &rx_opt);
subflow_req->mp_capable = 0;
+ subflow_req->remote_key_valid = 0;
#ifdef CONFIG_TCP_MD5SIG
/* no MPTCP if MD5SIG is enabled on this socket or we may run out of
@@ -188,17 +189,28 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
pr_debug("listener=%p, req=%p, conn=%p", listener, req, listener->conn);
- /* if the sk is MP_CAPABLE, we need to fetch the client key */
+ /* if the sk is MP_CAPABLE, we try to fetch the client key */
subflow_req = mptcp_subflow_rsk(req);
if (subflow_req->mp_capable) {
+ if (TCP_SKB_CB(skb)->seq != subflow_req->ssn_offset + 1) {
+ /* here we can receive and accept an in-window,
+ * out-of-order pkt, which will not carry the MP_CAPABLE
+ * opt even on mptcp enabled paths
+ */
+ goto create_child;
+ }
+
opt_rx.mptcp.mp_capable = 0;
mptcp_get_options(skb, &opt_rx);
- if (!opt_rx.mptcp.mp_capable)
- subflow_req->mp_capable = 0;
- else
+ if (opt_rx.mptcp.mp_capable) {
subflow_req->remote_key = opt_rx.mptcp.sndr_key;
+ subflow_req->remote_key_valid = 1;
+ } else {
+ subflow_req->mp_capable = 0;
+ }
}
+create_child:
child = listener->icsk_af_ops->syn_recv_sock(sk, skb, req, dst,
req_unhash, own_req);
@@ -377,6 +389,7 @@ static enum mapping_status get_mapping_status(struct sock *ssk)
subflow->map_subflow_seq = mpext->subflow_seq;
subflow->map_data_len = data_len;
subflow->map_valid = 1;
+ subflow->mpc_map = mpext->mpc_map;
pr_debug("new map seq=%llu subflow_seq=%u data_len=%u",
subflow->map_seq, subflow->map_subflow_seq,
subflow->map_data_len);
@@ -428,6 +441,16 @@ static bool subflow_check_data_avail(struct sock *ssk)
if (WARN_ON_ONCE(!skb))
return false;
+ /* if msk lacks the remote key, this subflow must provide an
+ * MP_CAPABLE-based mapping
+ */
+ if (unlikely(!READ_ONCE(msk->ack_seq))) {
+ if (subflow->mpc_map)
+ break;
+ ssk->sk_err = EBADMSG;
+ goto fatal;
+ }
+
old_ack = READ_ONCE(msk->ack_seq);
ack_seq = mptcp_subflow_get_mapped_dsn(subflow);
pr_debug("msk ack_seq=%llx subflow ack_seq=%llx", old_ack,
@@ -665,8 +688,12 @@ static void subflow_ulp_clone(const struct request_sock *req,
new_ctx->tcp_sk_data_ready = old_ctx->tcp_sk_data_ready;
if (subflow_req->mp_capable) {
+ /* see comments in subflow_syn_recv_sock(), MPTCP connection
+ * is fully established only after we receive the remote key
+ */
new_ctx->mp_capable = 1;
- new_ctx->fourth_ack = 1;
+ new_ctx->fourth_ack = subflow_req->remote_key_valid;
+ new_ctx->can_ack = subflow_req->remote_key_valid;
new_ctx->remote_key = subflow_req->remote_key;
new_ctx->local_key = subflow_req->local_key;
new_ctx->token = subflow_req->token;
This patch implement the handling of MP_CAPABLE + data option, as per RFC 6824 bis - MPTCP v1. On the server side we can receive the remote key after that the connection is established. We need to explicitly track the 'missing remote key' status and avoid emtting mptcp ack till we get such info. When a late/retransmitted/OoO pkt carrying MP_CAPABLE[+data] option is received, we have to propagate the mptcp seq number info to the msk socket. To avoid ABBA locking issue, explicitly check for that in recvmsg(), where we own msk and subflow sock locks. The above also means that an established mp_capable subflow - still waiting for the remote key - can be 'downgraded' to plain TCP. Such change could potentially block forever reader waiting for new data - as they hook to msk, while later wake-up after the downgrade will be on subflow only. The above issue is not handled here, we likely have to get rid of msk->fallback to handle that cleanly. v1 -> v2: - mp_capable_map -> mpc_map - comment fix Signed-off-by: Christoph Paasch <cpaasch@apple.com> --- net/mptcp/options.c | 47 +++++++++++++++++++++++++++++++++++--------- net/mptcp/protocol.c | 20 +++++++++++++------ net/mptcp/protocol.h | 8 ++++++-- net/mptcp/subflow.c | 37 +++++++++++++++++++++++++++++----- 4 files changed, 90 insertions(+), 22 deletions(-)