Commit 90bf4513 authored by Paolo Abeni's avatar Paolo Abeni Committed by David S. Miller
Browse files

mptcp: add new sock flag to deal with join subflows 



MP_JOIN subflows must not land into the accept queue.
Currently tcp_check_req() calls an mptcp specific helper
to detect such scenario.

Such helper leverages the subflow context to check for
MP_JOIN subflows. We need to deal also with MP JOIN
failures, even when the subflow context is not available
due allocation failure.

A possible solution would be changing the syn_recv_sock()
signature to allow returning a more descriptive action/
error code and deal with that in tcp_check_req().

Since the above need is MPTCP specific, this patch instead
uses a TCP request socket hole to add a MPTCP specific flag.
Such flag is used by the MPTCP syn_recv_sock() to tell
tcp_check_req() how to deal with the request socket.

This change is a no-op for !MPTCP build, and makes the
MPTCP code simpler. It allows also the next patch to deal
correctly with MP JOIN failure.

v1 -> v2:
 - be more conservative on drop_req initialization (Mat)

RFC -> v1:
 - move the drop_req bit inside tcp_request_sock (Eric)

Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Reviewed-by: default avatarMat Martineau <mathew.j.martineau@linux.intel.com>
Reviewed-by: default avatarChristoph Paasch <cpaasch@apple.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ca1c933b

include/linux/tcp.h

+3 −0
Original line number Diff line number Diff line
@@ -120,6 +120,9 @@ struct tcp_request_sock { 
	u64				snt_synack; /* first SYNACK sent time */

	bool				tfo_listener;

	bool				is_mptcp;

#if IS_ENABLED(CONFIG_MPTCP)

	bool				drop_req;

#endif

	u32				txhash;

	u32				rcv_isn;

	u32				snt_isn;

include/net/mptcp.h

+10 −7
Original line number Diff line number Diff line
@@ -68,6 +68,11 @@ static inline bool rsk_is_mptcp(const struct request_sock *req) 
	return tcp_rsk(req)->is_mptcp;

}



static inline bool rsk_drop_req(const struct request_sock *req)

{

	return tcp_rsk(req)->is_mptcp && tcp_rsk(req)->drop_req;

}



void mptcp_space(const struct sock *ssk, int *space, int *full_space);

bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,

		       unsigned int *size, struct mptcp_out_options *opts);
@@ -121,8 +126,6 @@ static inline bool mptcp_skb_can_collapse(const struct sk_buff *to, 
				 skb_ext_find(from, SKB_EXT_MPTCP));

}



bool mptcp_sk_is_subflow(const struct sock *sk);



void mptcp_seq_show(struct seq_file *seq);

#else
@@ -140,6 +143,11 @@ static inline bool rsk_is_mptcp(const struct request_sock *req) 
	return false;

}



static inline bool rsk_drop_req(const struct request_sock *req)

{

	return false;

}



static inline void mptcp_parse_option(const struct sk_buff *skb,

				      const unsigned char *ptr, int opsize,

				      struct tcp_options_received *opt_rx)
@@ -190,11 +198,6 @@ static inline bool mptcp_skb_can_collapse(const struct sk_buff *to, 
	return true;

}



static inline bool mptcp_sk_is_subflow(const struct sock *sk)

{

	return false;

}



static inline void mptcp_space(const struct sock *ssk, int *s, int *fs) { }

static inline void mptcp_seq_show(struct seq_file *seq) { }

#endif /* CONFIG_MPTCP */

net/ipv4/tcp_minisocks.c

+1 −1
Original line number Diff line number Diff line
@@ -774,7 +774,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb, 
	if (!child)

		goto listen_overflow;



	if (own_req && sk_is_mptcp(child) && mptcp_sk_is_subflow(child)) {

	if (own_req && rsk_drop_req(req)) {

		reqsk_queue_removed(&inet_csk(sk)->icsk_accept_queue, req);

		inet_csk_reqsk_queue_drop_and_put(sk, req);

		return child;

net/mptcp/protocol.c

+0 −7
Original line number Diff line number Diff line
@@ -1638,13 +1638,6 @@ bool mptcp_finish_join(struct sock *sk) 
	return ret;

}



bool mptcp_sk_is_subflow(const struct sock *sk)

{

	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);



	return subflow->mp_join == 1;

}



static bool mptcp_memory_free(const struct sock *sk, int wake)

{

	struct mptcp_sock *msk = mptcp_sk(sk);

net/mptcp/subflow.c

+3 −0
Original line number Diff line number Diff line
@@ -470,6 +470,8 @@ create_child: 
	if (child && *own_req) {

		struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(child);



		tcp_rsk(req)->drop_req = false;



		/* we need to fallback on ctx allocation failure and on pre-reqs

		 * checking above. In the latter scenario we additionally need

		 * to reset the context to non MPTCP status.
@@ -512,6 +514,7 @@ create_child: 
				goto close_child;



			SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKRX);

			tcp_rsk(req)->drop_req = true;

		}

	}

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