Re: [MPTCP] [RFC 8/9] Restructure TCP code so that it can be shared primarily with MPTCP

[Krystad, Peter <peter.krystad at intel.com>]

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On Thu, 2018-02-22 at 15:50 -0800, rao.shoaib(a)oracle.com wrote:
> From: Rao Shoaib <rao.shoaib(a)oracle.com>
> 
> Signed-off-by: Rao Shoaib <rao.shoaib(a)oracle.com>
> ---
>  include/net/inet_common.h |   2 +
>  include/net/tcp.h         | 106 ++++++++++++++++++++++++++++++++++++++++++++++
>  net/ipv4/af_inet.c        |   3 +-
>  net/ipv4/tcp.c            |  59 ++++++++++++++------------
>  net/ipv4/tcp_input.c      |  89 +++++++++++++++++++++++---------------
>  net/ipv4/tcp_ipv4.c       |  42 ++++++++++++------
>  net/ipv4/tcp_output.c     |  55 +++++++++++++-----------
>  net/ipv4/tcp_timer.c      |   9 ++--
>  net/ipv6/af_inet6.c       |   4 +-
>  net/ipv6/tcp_ipv6.c       |  63 ++++++++++++++-------------
>  10 files changed, 293 insertions(+), 139 deletions(-)
> 
> diff --git a/include/net/inet_common.h b/include/net/inet_common.h
> index 500f813..7b919c7 100644
> --- a/include/net/inet_common.h
> +++ b/include/net/inet_common.h
> @@ -14,6 +14,8 @@ struct sock;
>  struct sockaddr;
>  struct socket;
>  
> +int inet_create(struct net *net, struct socket *sock, int protocol, int kern);
> +int inet6_create(struct net *net, struct socket *sock, int protocol, int kern);
>  int inet_release(struct socket *sock);
>  int inet_stream_connect(struct socket *sock, struct sockaddr *uaddr,
>  			int addr_len, int flags);
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index f5d748a..3344b1d 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -314,6 +314,12 @@ static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
>  	return false;
>  }
>  
> +static inline void tcp_drop(struct sock *sk, struct sk_buff *skb)
> +{
> +	sk_drops_add(sk, skb);
> +	__kfree_skb(skb);
> +}
> +
>  bool tcp_check_oom(struct sock *sk, int shift);
>  
>  extern struct proto tcp_prot;
> @@ -2273,6 +2279,106 @@ static inline bool tcp_bpf_ca_needs_ecn(struct sock *sk)
>  	return (tcp_call_bpf(sk, BPF_SOCK_OPS_NEEDS_ECN, 0, NULL) == 1);
>  }
>  
> +/* MPTCP */
> +unsigned int tcp_xmit_size_goal(struct sock *sk, u32 mss_now,
> +				int large_allowed);
> +ssize_t tcp_sendpages_xmit(struct sock *sk, struct page *page, int offset,
> +			   size_t size, int flags);
> +ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
> +			 size_t size, int flags);
> +int tcp_close_state(struct sock *sk);
> +void tcp_enter_quickack_mode(struct sock *sk);
> +void tcp_sndbuf_expand_impl(struct sock *sk, u32 nr_segs);
> +bool tcp_check_rtt(struct sock *sk);
> +u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb);
> +void tcp_ack_probe(struct sock *sk);
> +bool tcp_may_update_window(const struct tcp_sock *tp, const u32 ack,
> +			   const u32 ack_seq, const u32 nwin);
> +bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
> +			     struct tcp_fastopen_cookie *cookie);
> +bool tcp_rcv_fastopen_synack_impl(struct sock *sk, struct sk_buff *synack,
> +				  struct tcp_fastopen_cookie *cookie,
> +				  bool rexmit);
> +void tcp_enter_quickack_mode(struct sock *sk);
> +void tcp_check_space(struct sock *sk);
> +int __must_check tcp_queue_rcv(struct sock *sk, struct sk_buff *skb, int hdrlen,
> +			       bool *fragstolen);
> +void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb);
> +void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags);
> +bool tcp_urg_mode(const struct tcp_sock *tp);
> +int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
> +		     gfp_t gfp_mask);
> +void tcp_queue_skb(struct sock *sk, struct sk_buff *skb);
> +void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now);
> +void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr);
> +int pskb_trim_head(struct sk_buff *skb, int len);
> +void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
> +			 const struct sk_buff *skb);
> +unsigned int tcp_mss_split_point(const struct sock *sk,
> +				 const struct sk_buff *skb,
> +				 unsigned int mss_now,
> +				 unsigned int max_segs,
> +				 int nonagle);
> +unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
> +			   const struct sk_buff *skb);
> +int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now);
> +bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
> +		    unsigned int cur_mss, int nonagle);
> +bool tcp_snd_wnd_test(const struct tcp_sock *tp, const struct sk_buff *skb,
> +		      unsigned int cur_mss);
> +int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib);
> +void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb);
> +void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
> +			   struct request_sock *req);
> +void tcp_v4_reqsk_destructor(struct request_sock *req);
> +struct sock *tcp_v4_cookie_check(struct sock *sk, struct sk_buff *skb);
> +void tcp_v4_fill_cb(struct sk_buff *skb, const struct iphdr *iph,
> +		    const struct tcphdr *th);
> +void tcp_v6_fill_cb(struct sk_buff *skb, const struct ipv6hdr *hdr,
> +		    const struct tcphdr *th);
> +void tcp_write_err(struct sock *sk);
> +bool retransmits_timed_out(struct sock *sk, unsigned int boundary,
> +			   unsigned int timeout);
> +int tcp_write_timeout(struct sock *sk);
> +struct request_sock *tcp_cookie_req_alloc(struct sock *sk,
> +					  struct sk_buff *skb,
> +					  struct tcp_options_received *tcp_opts,
> +					  __u32 cookie, int mss);
> +void inet_twsk_free(struct inet_timewait_sock *tw);
> +#if IS_ENABLED(CONFIG_IPV6)
> +void inet6_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
> +void tcp_v6_mtu_reduced(struct sock *sk);
> +void tcp_v6_reqsk_destructor(struct request_sock *req);
> +void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb);
> +void tcp_v6_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
> +			   struct request_sock *req);
> +struct sock *tcp_v6_cookie_check(struct sock *sk, struct sk_buff *skb);
> +int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb);
> +struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
> +				  struct request_sock *req,
> +				  struct dst_entry *dst,
> +				  struct request_sock *req_unhash,
> +				  bool *own_req);
> +int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb);
> +#endif
> +
> +static inline void tcp_data_snd_check(struct sock *sk)
> +{
> +	tcp_push_pending_frames(sk);
> +	tcp_check_space(sk);
> +}
> +
> +/* These states need RST on ABORT according to RFC793 */
> +
> +static inline bool tcp_need_reset(int state)
> +{
> +	return (1 << state) &
> +		(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT | TCPF_FIN_WAIT1 |
> +		TCPF_FIN_WAIT2 | TCPF_SYN_RECV);
> +}
> +
> +/* END MPTCP */
> +
>  #if IS_ENABLED(CONFIG_SMC)
>  extern struct static_key_false tcp_have_smc;
>  #endif
> diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> index e8c7fad..5d8ea09 100644
> --- a/net/ipv4/af_inet.c
> +++ b/net/ipv4/af_inet.c
> @@ -243,8 +243,7 @@ EXPORT_SYMBOL(inet_listen);
>   *	Create an inet socket.
>   */
>  
> -static int inet_create(struct net *net, struct socket *sock, int protocol,
> -		       int kern)
> +int inet_create(struct net *net, struct socket *sock, int protocol, int kern)
>  {
>  	struct sock *sk;
>  	struct inet_protosw *answer;
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index ea89a41..20a69eb 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -429,6 +429,7 @@ static const struct tcp_operational_ops __tcp_default_op_ops = {
>  	.sndbuf_expand			= tcp_sndbuf_expand,
>  	.shift_skb_data			= tcp_shift_skb_data,
>  	.grow_window			= tcp_grow_window,
> +	.check_rtt			= tcp_check_rtt,
>  	.try_coalesce			= tcp_try_coalesce,
>  	.try_rmem_schedule		= tcp_try_rmem_schedule,
>  	.collapse_one			= tcp_collapse_one,
> @@ -963,8 +964,7 @@ struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp,
>  	return NULL;
>  }
>  
> -static unsigned int tcp_xmit_size_goal(struct sock *sk, u32 mss_now,
> -				       int large_allowed)
> +unsigned int tcp_xmit_size_goal(struct sock *sk, u32 mss_now, int large_allowed)
>  {
>  	struct tcp_sock *tp = tcp_sk(sk);
>  	u32 new_size_goal, size_goal;
> @@ -998,8 +998,8 @@ int tcp_send_mss(struct sock *sk, int *size_goal, int flags)
>  	return mss_now;
>  }
>  
> -ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
> -			 size_t size, int flags)
> +ssize_t tcp_sendpages_xmit(struct sock *sk, struct page *page, int offset,
> +			   size_t size, int flags)
>  {
>  	struct tcp_sock *tp = tcp_sk(sk);
>  	int mss_now, size_goal;
> @@ -1007,25 +1007,12 @@ ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
>  	ssize_t copied;
>  	long timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
>  
> -	/* Wait for a connection to finish. One exception is TCP Fast Open
> -	 * (passive side) where data is allowed to be sent before a connection
> -	 * is fully established.
> -	 */
> -	if (((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) &&
> -	    !tcp_passive_fastopen(sk)) {
> -		err = sk_stream_wait_connect(sk, &timeo);
> -		if (err != 0)
> -			goto out_err;
> -	}
> -
>  	sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
>  
>  	mss_now = tp->op_ops->send_mss(sk, &size_goal, flags);
>  	copied = 0;
>  
>  	err = -EPIPE;
> -	if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
> -		goto out_err;
>  
>  	while (size > 0) {
>  		struct sk_buff *skb = tcp_write_queue_tail(sk);
> @@ -1120,6 +1107,33 @@ ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
>  do_error:
>  	if (copied)
>  		goto out;
> +	return err;
> +}
> +EXPORT_SYMBOL_GPL(tcp_sendpages_xmit);
> +
> +ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
> +			 size_t size, int flags)
> +{
> +	int err;
> +	long timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
> +
> +	/* Wait for a connection to finish. One exception is TCP Fast Open
> +	 * (passive side) where data is allowed to be sent before a connection
> +	 * is fully established.
> +	 */
> +	if (((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) &&
> +	    !tcp_passive_fastopen(sk)) {
> +		err = sk_stream_wait_connect(sk, &timeo);
> +		if (err != 0)
> +			goto out_err;
> +	}
> +
> +	if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
> +		goto out_err;
> +
> +	err = tcp_sendpages_xmit(sk, page, offset, size, flags);
> +	if (err >= 0)
> +		return(err);
>  out_err:
>  	/* make sure we wake any epoll edge trigger waiter */
>  	if (unlikely(skb_queue_len(&sk->sk_write_queue) == 0 &&
> @@ -2193,7 +2207,7 @@ static const unsigned char new_state[16] = {
>    [TCP_NEW_SYN_RECV]	= TCP_CLOSE,	/* should not happen ! */
>  };
>  
> -static int tcp_close_state(struct sock *sk)
> +int tcp_close_state(struct sock *sk)
>  {
>  	int next = (int)new_state[sk->sk_state];
>  	int ns = next & TCP_STATE_MASK;
> @@ -2419,15 +2433,6 @@ void tcp_close(struct sock *sk, long timeout)
>  }
>  EXPORT_SYMBOL(tcp_close);
>  
> -/* These states need RST on ABORT according to RFC793 */
> -
> -static inline bool tcp_need_reset(int state)
> -{
> -	return (1 << state) &
> -	       (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT | TCPF_FIN_WAIT1 |
> -		TCPF_FIN_WAIT2 | TCPF_SYN_RECV);
> -}
> -
>  static void tcp_rtx_queue_purge(struct sock *sk)
>  {
>  	struct rb_node *p = rb_first(&sk->tcp_rtx_queue);
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index 8cc48bb..398505e 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -195,7 +195,7 @@ static void tcp_incr_quickack(struct sock *sk)
>  		icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
>  }
>  
> -static void tcp_enter_quickack_mode(struct sock *sk)
> +void tcp_enter_quickack_mode(struct sock *sk)
>  {
>  	struct inet_connection_sock *icsk = inet_csk(sk);
>  	tcp_incr_quickack(sk);
> @@ -293,12 +293,11 @@ static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr
>   * 1. Tuning sk->sk_sndbuf, when connection enters established state.
>   */
>  
> -void tcp_sndbuf_expand(struct sock *sk)
> +void tcp_sndbuf_expand_impl(struct sock *sk, u32 nr_segs)
>  {
>  	const struct tcp_sock *tp = tcp_sk(sk);
>  	const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
>  	int sndmem, per_mss;
> -	u32 nr_segs;
>  
>  	/* Worst case is non GSO/TSO : each frame consumes one skb
>  	 * and skb->head is kmalloced using power of two area of memory
> @@ -310,8 +309,10 @@ void tcp_sndbuf_expand(struct sock *sk)
>  	per_mss = roundup_pow_of_two(per_mss) +
>  		  SKB_DATA_ALIGN(sizeof(struct sk_buff));
>  
> -	nr_segs = max_t(u32, TCP_INIT_CWND, tp->snd_cwnd);
> -	nr_segs = max_t(u32, nr_segs, tp->reordering + 1);
> +	if (nr_segs <= 0) {
> +		nr_segs = max_t(u32, TCP_INIT_CWND, tp->snd_cwnd);
> +		nr_segs = max_t(u32, nr_segs, tp->reordering + 1);
> +	}
>  
>  	/* Fast Recovery (RFC 5681 3.2) :
>  	 * Cubic needs 1.7 factor, rounded to 2 to include
> @@ -324,6 +325,11 @@ void tcp_sndbuf_expand(struct sock *sk)
>  		sk->sk_sndbuf = min(sndmem, sock_net(sk)->ipv4.sysctl_tcp_wmem[2]);
>  }
>  
> +void tcp_sndbuf_expand(struct sock *sk)
> +{
> +	tcp_sndbuf_expand_impl(sk, 0);
> +}
> +
>  /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
>   *
>   * All tcp_full_space() is split to two parts: "network" buffer, allocated
> @@ -572,6 +578,17 @@ static inline void tcp_rcv_rtt_measure_ts(struct sock *sk,
>  	}
>  }
>  
> +bool tcp_check_rtt(struct sock *sk)
> +{
> +	struct tcp_sock *tp = tcp_sk(sk);
> +	int time;
> +
> +	time = tcp_stamp_us_delta(tp->tcp_mstamp, tp->rcvq_space.time);
> +
> +	if (time < (tp->rcv_rtt_est.rtt_us >> 3) || tp->rcv_rtt_est.rtt_us == 0)
> +		return (true);
> +	return false;
> +}
>  /*
>   * This function should be called every time data is copied to user space.
>   * It calculates the appropriate TCP receive buffer space.
> @@ -580,11 +597,9 @@ void tcp_rcv_space_adjust(struct sock *sk)
>  {
>  	struct tcp_sock *tp = tcp_sk(sk);
>  	u32 copied;
> -	int time;
>  
>  	tcp_mstamp_refresh(tp);
> -	time = tcp_stamp_us_delta(tp->tcp_mstamp, tp->rcvq_space.time);
> -	if (time < (tp->rcv_rtt_est.rtt_us >> 3) || tp->rcv_rtt_est.rtt_us == 0)
> +	if (tp->op_ops->check_rtt(sk))
>  		return;
>  
>  	/* Number of bytes copied to user in last RTT */
> @@ -2966,7 +2981,7 @@ static void tcp_set_xmit_timer(struct sock *sk)
>  }
>  
>  /* If we get here, the whole TSO packet has not been acked. */
> -static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
> +u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
>  {
>  	struct tcp_sock *tp = tcp_sk(sk);
>  	u32 packets_acked;
> @@ -3201,7 +3216,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, u32 prior_fack,
>  	return flag;
>  }
>  
> -static void tcp_ack_probe(struct sock *sk)
> +void tcp_ack_probe(struct sock *sk)
>  {
>  	struct inet_connection_sock *icsk = inet_csk(sk);
>  	struct sk_buff *head = tcp_send_head(sk);
> @@ -3273,7 +3288,7 @@ static void tcp_cong_control(struct sock *sk, u32 ack, u32 acked_sacked,
>  /* Check that window update is acceptable.
>   * The function assumes that snd_una<=ack<=snd_next.
>   */
> -static inline bool tcp_may_update_window(const struct tcp_sock *tp,
> +inline bool tcp_may_update_window(const struct tcp_sock *tp,
>  					const u32 ack, const u32 ack_seq,
>  					const u32 nwin)
>  {
> @@ -4290,12 +4305,6 @@ bool tcp_try_coalesce(struct sock *sk,
>  	return true;
>  }
>  
> -static void tcp_drop(struct sock *sk, struct sk_buff *skb)
> -{
> -	sk_drops_add(sk, skb);
> -	__kfree_skb(skb);
> -}
> -
>  /* This one checks to see if we can put data from the
>   * out_of_order queue into the receive_queue.
>   */
> @@ -4505,8 +4514,8 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
>  	}
>  }
>  
> -static int __must_check tcp_queue_rcv(struct sock *sk, struct sk_buff *skb, int hdrlen,
> -		  bool *fragstolen)
> +int __must_check tcp_queue_rcv(struct sock *sk, struct sk_buff *skb, int hdrlen,
> +			       bool *fragstolen)
>  {
>  	int eaten;
>  	struct sk_buff *tail = skb_peek_tail(&sk->sk_receive_queue);
> @@ -4580,7 +4589,11 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
>  	int eaten;
>  
>  	if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
> -		__kfree_skb(skb);
> +		/* options that a layer above might be interested in */
> +		if (unlikely(tp->op_ops->ack_only))
> +			tp->op_ops->ack_only(sk, skb);
> +		else
> +			__kfree_skb(skb);

If it is a possibility that ack_only() does not call __kfree_skb(skb)
what is the consequence? I don't have enough context here.

Peter. 
 
>  		return;
>  	}
>  	skb_dst_drop(skb);
> @@ -4995,7 +5008,7 @@ static void tcp_new_space(struct sock *sk)
>  	sk->sk_write_space(sk);
>  }
>  
> -static void tcp_check_space(struct sock *sk)
> +void tcp_check_space(struct sock *sk)
>  {
>  	if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
>  		sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
> @@ -5010,12 +5023,6 @@ static void tcp_check_space(struct sock *sk)
>  	}
>  }
>  
> -static inline void tcp_data_snd_check(struct sock *sk)
> -{
> -	tcp_push_pending_frames(sk);
> -	tcp_check_space(sk);
> -}
> -
>  /*
>   * Check if sending an ack is needed.
>   */
> @@ -5504,8 +5511,9 @@ void tcp_finish_connect(struct sock *sk, struct sk_buff *skb)
>  		tp->pred_flags = 0;
>  }
>  
> -bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
> -			     struct tcp_fastopen_cookie *cookie)
> +bool tcp_rcv_fastopen_synack_impl(struct sock *sk, struct sk_buff *synack,
> +				  struct tcp_fastopen_cookie *cookie,
> +				  bool rexmit)
>  {
>  	struct tcp_sock *tp = tcp_sk(sk);
>  	struct sk_buff *data = tp->syn_data ? tcp_rtx_queue_head(sk) : NULL;
> @@ -5542,7 +5550,7 @@ bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
>  
>  	tcp_fastopen_cache_set(sk, mss, cookie, syn_drop, try_exp);
>  
> -	if (data) { /* Retransmit unacked data in SYN */
> +	if (data && rexmit) { /* Retransmit unacked data in SYN */
>  		skb_rbtree_walk_from(data) {
>  			if (__tcp_retransmit_skb(sk, data, 1))
>  				break;
> @@ -5562,6 +5570,12 @@ bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
>  	return false;
>  }
>  
> +bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
> +			     struct tcp_fastopen_cookie *cookie)
> +{
> +	return tcp_rcv_fastopen_synack_impl(sk, synack, cookie, true);
> +}
> +
>  static void smc_check_reset_syn(struct tcp_sock *tp)
>  {
>  #if IS_ENABLED(CONFIG_SMC)
> @@ -5581,6 +5595,9 @@ int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
>  	int saved_clamp = tp->rx_opt.mss_clamp;
>  	bool fastopen_fail;
>  
> +	tp->rx_opt.saw_tstamp = 0;
> +	tcp_mstamp_refresh(tp);
> +
>  	tcp_parse_options(sock_net(sk), skb, &tp->rx_opt, 0, &foc);
>  	if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
>  		tp->rx_opt.rcv_tsecr -= tp->tsoffset;
> @@ -5682,7 +5699,7 @@ int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
>  		tcp_finish_connect(sk, skb);
>  
>  		fastopen_fail = (tp->syn_fastopen || tp->syn_data) &&
> -				tcp_rcv_fastopen_synack(sk, skb, &foc);
> +				 tp->op_ops->fastopen_synack(sk, skb, &foc);
>  
>  		if (!sock_flag(sk, SOCK_DEAD)) {
>  			sk->sk_state_change(sk);
> @@ -5842,9 +5859,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
>  		goto discard;
>  
>  	case TCP_SYN_SENT:
> -		tp->rx_opt.saw_tstamp = 0;
> -		tcp_mstamp_refresh(tp);
> -		queued = tcp_rcv_synsent_state_process(sk, skb, th);
> +		queued = tp->state_ops->synsent(sk, skb, th);
>  		if (queued >= 0)
>  			return queued;
>  
> @@ -6052,8 +6067,12 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
>  	}
>  
>  	if (!queued) {
> +		/* options that a layer above might be interested in */
> +		if (unlikely(tp->op_ops && tp->op_ops->ack_only))
> +			tp->op_ops->ack_only(sk, skb);
> +		else
>  discard:
> -		tcp_drop(sk, skb);
> +			tcp_drop(sk, skb);
>  	}
>  	return 0;
>  }
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index 482ca15..95d4c1f 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -595,7 +595,7 @@ EXPORT_SYMBOL(tcp_v4_send_check);
>   *	Exception: precedence violation. We do not implement it in any case.
>   */
>  
> -static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
> +void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
>  {
>  	const struct tcphdr *th = tcp_hdr(skb);
>  	struct {
> @@ -829,8 +829,8 @@ static void tcp_v4_timewait_ack(struct sock *sk, struct sk_buff *skb)
>  	inet_twsk_put(tw);
>  }
>  
> -static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
> -				  struct request_sock *req)
> +void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
> +			   struct request_sock *req)
>  {
>  	/* sk->sk_state == TCP_LISTEN -> for regular TCP_SYN_RECV
>  	 * sk->sk_state == TCP_SYN_RECV -> for Fast Open.
> @@ -892,7 +892,7 @@ static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst,
>  /*
>   *	IPv4 request_sock destructor.
>   */
> -static void tcp_v4_reqsk_destructor(struct request_sock *req)
> +void tcp_v4_reqsk_destructor(struct request_sock *req)
>  {
>  	kfree(rcu_dereference_protected(inet_rsk(req)->ireq_opt, 1));
>  }
> @@ -1431,7 +1431,7 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
>  }
>  EXPORT_SYMBOL(tcp_v4_syn_recv_sock);
>  
> -static struct sock *tcp_v4_cookie_check(struct sock *sk, struct sk_buff *skb)
> +struct sock *tcp_v4_cookie_check(struct sock *sk, struct sk_buff *skb)
>  {
>  #ifdef CONFIG_SYN_COOKIES
>  	const struct tcphdr *th = tcp_hdr(skb);
> @@ -1598,8 +1598,8 @@ static void tcp_v4_restore_cb(struct sk_buff *skb)
>  		sizeof(struct inet_skb_parm));
>  }
>  
> -static void tcp_v4_fill_cb(struct sk_buff *skb, const struct iphdr *iph,
> -			   const struct tcphdr *th)
> +void tcp_v4_fill_cb(struct sk_buff *skb, const struct iphdr *iph,
> +		    const struct tcphdr *th)
>  {
>  	/* This is tricky : We move IPCB at its correct location into TCP_SKB_CB()
>  	 * barrier() makes sure compiler wont play fool^Waliasing games.
> @@ -1620,6 +1620,9 @@ static void tcp_v4_fill_cb(struct sk_buff *skb, const struct iphdr *iph,
>  			skb->tstamp || skb_hwtstamps(skb)->hwtstamp;
>  }
>  
> +process_unclaimed tcp_process_unclaimed;
> +EXPORT_SYMBOL(tcp_process_unclaimed);
> +
>  /*
>   *	From tcp_input.c
>   */
> @@ -1750,13 +1753,16 @@ int tcp_v4_rcv(struct sk_buff *skb)
>  
>  	sk_incoming_cpu_update(sk);
>  
> -	bh_lock_sock_nested(sk);
> -	tcp_segs_in(tcp_sk(sk), skb);
> -	ret = 0;
> -	if (!sock_owned_by_user(sk)) {
> -		ret = tcp_v4_do_rcv(sk, skb);
> -	} else if (tcp_add_backlog(sk, skb)) {
> -		goto discard_and_relse;
> +	if (likely(!tcp_sk(sk)->op_ops->rx)) {
> +		bh_lock_sock_nested(sk);
> +		tcp_segs_in(tcp_sk(sk), skb);
> +		ret = 0;
> +		if (!sock_owned_by_user(sk))
> +			ret = tcp_v4_do_rcv(sk, skb);
> +		else if (tcp_add_backlog(sk, skb))
> +			goto discard_and_relse;
> +	} else {
> +		return(tcp_sk(sk)->op_ops->rx(sk, skb, refcounted));
>  	}
>  	bh_unlock_sock(sk);
>  
> @@ -1778,6 +1784,10 @@ int tcp_v4_rcv(struct sk_buff *skb)
>  bad_packet:
>  		__TCP_INC_STATS(net, TCP_MIB_INERRS);
>  	} else {
> +		if (unlikely(tcp_process_unclaimed)) {
> +			if (tcp_process_unclaimed(sk, skb))
> +				return (0);
> +		}
>  		tcp_v4_send_reset(NULL, skb);
>  	}
>  
> @@ -1820,6 +1830,10 @@ int tcp_v4_rcv(struct sk_buff *skb)
>  			refcounted = false;
>  			goto process;
>  		}
> +		if (unlikely(tcp_process_unclaimed)) {
> +			if (tcp_process_unclaimed(sk, skb))
> +				return 0;
> +		}
>  	}
>  		/* to ACK */
>  		/* fall through */
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 2fa5c05..72b494a 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -46,7 +46,7 @@
>  #include <trace/events/tcp.h>
>  
>  /* Account for new data that has been sent to the network. */
> -static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
> +void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
>  {
>  	struct inet_connection_sock *icsk = inet_csk(sk);
>  	struct tcp_sock *tp = tcp_sk(sk);
> @@ -375,7 +375,7 @@ static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
>  /* Constructs common control bits of non-data skb. If SYN/FIN is present,
>   * auto increment end seqno.
>   */
> -static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
> +void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
>  {
>  	skb->ip_summed = CHECKSUM_PARTIAL;
>  
> @@ -390,7 +390,7 @@ static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
>  	TCP_SKB_CB(skb)->end_seq = seq;
>  }
>  
> -static inline bool tcp_urg_mode(const struct tcp_sock *tp)
> +inline bool tcp_urg_mode(const struct tcp_sock *tp)
>  {
>  	return tp->snd_una != tp->snd_up;
>  }
> @@ -1031,8 +1031,8 @@ static void tcp_update_skb_after_send(struct tcp_sock *tp, struct sk_buff *skb)
>   * We are working here with either a clone of the original
>   * SKB, or a fresh unique copy made by the retransmit engine.
>   */
> -static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
> -			    gfp_t gfp_mask)
> +int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
> +		     gfp_t gfp_mask)
>  {
>  	const struct inet_connection_sock *icsk = inet_csk(sk);
>  	struct inet_sock *inet;
> @@ -1193,7 +1193,7 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
>   * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
>   * otherwise socket can stall.
>   */
> -static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
> +void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
>  {
>  	struct tcp_sock *tp = tcp_sk(sk);
>  
> @@ -1206,7 +1206,7 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
>  }
>  
>  /* Initialize TSO segments for a packet. */
> -static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
> +void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
>  {
>  	if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
>  		/* Avoid the costly divide in the normal
> @@ -1223,7 +1223,7 @@ static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
>  /* Pcount in the middle of the write queue got changed, we need to do various
>   * tweaks to fix counters
>   */
> -static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
> +void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
>  {
>  	struct tcp_sock *tp = tcp_sk(sk);
>  
> @@ -1426,6 +1426,11 @@ static int __pskb_trim_head(struct sk_buff *skb, int len)
>  	return len;
>  }
>  
> +int pskb_trim_head(struct sk_buff *skb, int len)
> +{
> +	return __pskb_trim_head(skb, len);
> +}
> +
>  /* Remove acked data from a packet in the transmit queue. */
>  int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
>  {
> @@ -1434,7 +1439,7 @@ int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
>  	if (skb_unclone(skb, GFP_ATOMIC))
>  		return -ENOMEM;
>  
> -	delta_truesize = __pskb_trim_head(skb, len);
> +	delta_truesize = pskb_trim_head(skb, len);
>  
>  	TCP_SKB_CB(skb)->seq += len;
>  	skb->ip_summed = CHECKSUM_PARTIAL;
> @@ -1693,8 +1698,8 @@ static bool tcp_minshall_check(const struct tcp_sock *tp)
>   * But we can avoid doing the divide again given we already have
>   *  skb_pcount = skb->len / mss_now
>   */
> -static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
> -				const struct sk_buff *skb)
> +void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
> +			 const struct sk_buff *skb)
>  {
>  	if (skb->len < tcp_skb_pcount(skb) * mss_now)
>  		tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
> @@ -1751,11 +1756,11 @@ static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now)
>  }
>  
>  /* Returns the portion of skb which can be sent right away */
> -static unsigned int tcp_mss_split_point(const struct sock *sk,
> -					const struct sk_buff *skb,
> -					unsigned int mss_now,
> -					unsigned int max_segs,
> -					int nonagle)
> +unsigned int tcp_mss_split_point(const struct sock *sk,
> +				 const struct sk_buff *skb,
> +				 unsigned int mss_now,
> +				 unsigned int max_segs,
> +				 int nonagle)
>  {
>  	const struct tcp_sock *tp = tcp_sk(sk);
>  	u32 partial, needed, window, max_len;
> @@ -1785,7 +1790,7 @@ static unsigned int tcp_mss_split_point(const struct sock *sk,
>  /* Can at least one segment of SKB be sent right now, according to the
>   * congestion window rules?  If so, return how many segments are allowed.
>   */
> -static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
> +inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
>  					 const struct sk_buff *skb)
>  {
>  	u32 in_flight, cwnd, halfcwnd;
> @@ -1811,7 +1816,7 @@ static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
>   * This must be invoked the first time we consider transmitting
>   * SKB onto the wire.
>   */
> -static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
> +int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
>  {
>  	int tso_segs = tcp_skb_pcount(skb);
>  
> @@ -1826,8 +1831,8 @@ static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
>  /* Return true if the Nagle test allows this packet to be
>   * sent now.
>   */
> -static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
> -				  unsigned int cur_mss, int nonagle)
> +inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
> +			   unsigned int cur_mss, int nonagle)
>  {
>  	/* Nagle rule does not apply to frames, which sit in the middle of the
>  	 * write_queue (they have no chances to get new data).
> @@ -1849,9 +1854,9 @@ static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buf
>  }
>  
>  /* Does at least the first segment of SKB fit into the send window? */
> -static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
> -			     const struct sk_buff *skb,
> -			     unsigned int cur_mss)
> +bool tcp_snd_wnd_test(const struct tcp_sock *tp,
> +		      const struct sk_buff *skb,
> +		      unsigned int cur_mss)
>  {
>  	u32 end_seq = TCP_SKB_CB(skb)->end_seq;
>  
> @@ -2148,7 +2153,7 @@ int tcp_mtu_probe(struct sock *sk)
>  					skb->csum = csum_partial(skb->data,
>  								 skb->len, 0);
>  			} else {
> -				__pskb_trim_head(skb, copy);
> +				pskb_trim_head(skb, copy);
>  				tcp_set_skb_tso_segs(skb, mss_now);
>  			}
>  			TCP_SKB_CB(skb)->seq += copy;
> @@ -3639,7 +3644,7 @@ EXPORT_SYMBOL_GPL(tcp_send_ack);
>   * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
>   * out-of-date with SND.UNA-1 to probe window.
>   */
> -static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
> +int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
>  {
>  	struct tcp_sock *tp = tcp_sk(sk);
>  	struct sk_buff *skb;
> diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
> index beaba7a..dbf284d 100644
> --- a/net/ipv4/tcp_timer.c
> +++ b/net/ipv4/tcp_timer.c
> @@ -29,7 +29,7 @@
>   *  Returns: Nothing (void)
>   */
>  
> -static void tcp_write_err(struct sock *sk)
> +void tcp_write_err(struct sock *sk)
>  {
>  	sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
>  	sk->sk_error_report(sk);
> @@ -155,9 +155,8 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
>   * after "boundary" unsuccessful, exponentially backed-off
>   * retransmissions with an initial RTO of TCP_RTO_MIN.
>   */
> -static bool retransmits_timed_out(struct sock *sk,
> -				  unsigned int boundary,
> -				  unsigned int timeout)
> +bool retransmits_timed_out(struct sock *sk, unsigned int boundary,
> +			   unsigned int timeout)
>  {
>  	const unsigned int rto_base = TCP_RTO_MIN;
>  	unsigned int linear_backoff_thresh, start_ts;
> @@ -187,7 +186,7 @@ static bool retransmits_timed_out(struct sock *sk,
>  }
>  
>  /* A write timeout has occurred. Process the after effects. */
> -static int tcp_write_timeout(struct sock *sk)
> +int tcp_write_timeout(struct sock *sk)
>  {
>  	struct inet_connection_sock *icsk = inet_csk(sk);
>  	struct tcp_sock *tp = tcp_sk(sk);
> diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
> index c1e292d..9a242a5 100644
> --- a/net/ipv6/af_inet6.c
> +++ b/net/ipv6/af_inet6.c
> @@ -107,8 +107,8 @@ static __inline__ struct ipv6_pinfo *inet6_sk_generic(struct sock *sk)
>  	return (struct ipv6_pinfo *)(((u8 *)sk) + offset);
>  }
>  
> -static int inet6_create(struct net *net, struct socket *sock, int protocol,
> -			int kern)
> +int inet6_create(struct net *net, struct socket *sock, int protocol,
> +		 int kern)
>  {
>  	struct inet_sock *inet;
>  	struct ipv6_pinfo *np;
> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index 293bdc8..c226cf6 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -71,12 +71,6 @@
>  
>  #include <trace/events/tcp.h>
>  
> -static void	tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb);
> -static void	tcp_v6_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
> -				      struct request_sock *req);
> -
> -static int	tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb);
> -
>  #ifdef CONFIG_TCP_MD5SIG
>  static const struct tcp_sock_af_ops tcp_sock_ipv6_specific;
>  static const struct tcp_sock_af_ops tcp_sock_ipv6_mapped_specific;
> @@ -88,7 +82,7 @@ static struct tcp_md5sig_key *tcp_v6_md5_do_lookup(const struct sock *sk,
>  }
>  #endif
>  
> -static void inet6_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
> +void inet6_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
>  {
>  	struct dst_entry *dst = skb_dst(skb);
>  
> @@ -315,7 +309,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
>  	return err;
>  }
>  
> -static void tcp_v6_mtu_reduced(struct sock *sk)
> +void tcp_v6_mtu_reduced(struct sock *sk)
>  {
>  	struct dst_entry *dst;
>  
> @@ -495,7 +489,7 @@ static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
>  }
>  
>  
> -static void tcp_v6_reqsk_destructor(struct request_sock *req)
> +void tcp_v6_reqsk_destructor(struct request_sock *req)
>  {
>  	kfree(inet_rsk(req)->ipv6_opt);
>  	kfree_skb(inet_rsk(req)->pktopts);
> @@ -877,7 +871,7 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
>  	kfree_skb(buff);
>  }
>  
> -static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
> +void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
>  {
>  	const struct tcphdr *th = tcp_hdr(skb);
>  	u32 seq = 0, ack_seq = 0;
> @@ -975,8 +969,8 @@ static void tcp_v6_timewait_ack(struct sock *sk, struct sk_buff *skb)
>  	inet_twsk_put(tw);
>  }
>  
> -static void tcp_v6_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
> -				  struct request_sock *req)
> +void tcp_v6_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
> +			   struct request_sock *req)
>  {
>  	/* sk->sk_state == TCP_LISTEN -> for regular TCP_SYN_RECV
>  	 * sk->sk_state == TCP_SYN_RECV -> for Fast Open.
> @@ -997,7 +991,7 @@ static void tcp_v6_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
>  }
>  
>  
> -static struct sock *tcp_v6_cookie_check(struct sock *sk, struct sk_buff *skb)
> +struct sock *tcp_v6_cookie_check(struct sock *sk, struct sk_buff *skb)
>  {
>  #ifdef CONFIG_SYN_COOKIES
>  	const struct tcphdr *th = tcp_hdr(skb);
> @@ -1008,7 +1002,7 @@ static struct sock *tcp_v6_cookie_check(struct sock *sk, struct sk_buff *skb)
>  	return sk;
>  }
>  
> -static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
> +int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
>  {
>  	if (skb->protocol == htons(ETH_P_IP))
>  		return tcp_v4_conn_request(sk, skb);
> @@ -1034,11 +1028,11 @@ static void tcp_v6_restore_cb(struct sk_buff *skb)
>  		sizeof(struct inet6_skb_parm));
>  }
>  
> -static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
> -					 struct request_sock *req,
> -					 struct dst_entry *dst,
> -					 struct request_sock *req_unhash,
> -					 bool *own_req)
> +struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
> +				  struct request_sock *req,
> +				  struct dst_entry *dst,
> +				  struct request_sock *req_unhash,
> +				  bool *own_req)
>  {
>  	struct inet_request_sock *ireq;
>  	struct ipv6_pinfo *newnp;
> @@ -1250,7 +1244,7 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *
>   * This is because we cannot sleep with the original spinlock
>   * held.
>   */
> -static int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
> +int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
>  {
>  	struct ipv6_pinfo *np = inet6_sk(sk);
>  	struct tcp_sock *tp;
> @@ -1378,8 +1372,8 @@ static int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
>  	return 0;
>  }
>  
> -static void tcp_v6_fill_cb(struct sk_buff *skb, const struct ipv6hdr *hdr,
> -			   const struct tcphdr *th)
> +void tcp_v6_fill_cb(struct sk_buff *skb, const struct ipv6hdr *hdr,
> +		    const struct tcphdr *th)
>  {
>  	/* This is tricky: we move IP6CB at its correct location into
>  	 * TCP_SKB_CB(). It must be done after xfrm6_policy_check(), because
> @@ -1522,13 +1516,16 @@ static int tcp_v6_rcv(struct sk_buff *skb)
>  
>  	sk_incoming_cpu_update(sk);
>  
> -	bh_lock_sock_nested(sk);
> -	tcp_segs_in(tcp_sk(sk), skb);
> -	ret = 0;
> -	if (!sock_owned_by_user(sk)) {
> -		ret = tcp_v6_do_rcv(sk, skb);
> -	} else if (tcp_add_backlog(sk, skb)) {
> -		goto discard_and_relse;
> +	if (likely(!tcp_sk(sk)->op_ops->rx)) {
> +		bh_lock_sock_nested(sk);
> +		tcp_segs_in(tcp_sk(sk), skb);
> +		ret = 0;
> +		if (!sock_owned_by_user(sk))
> +			ret = tcp_v6_do_rcv(sk, skb);
> +		else if (tcp_add_backlog(sk, skb))
> +			goto discard_and_relse;
> +	} else {
> +		return(tcp_sk(sk)->op_ops->rx(sk, skb, refcounted));
>  	}
>  	bh_unlock_sock(sk);
>  
> @@ -1549,6 +1546,10 @@ static int tcp_v6_rcv(struct sk_buff *skb)
>  bad_packet:
>  		__TCP_INC_STATS(net, TCP_MIB_INERRS);
>  	} else {
> +		if (unlikely(tcp_process_unclaimed)) {
> +			if (tcp_process_unclaimed(sk, skb))
> +				return(0);
> +		}
>  		tcp_v6_send_reset(NULL, skb);
>  	}
>  
> @@ -1594,6 +1595,10 @@ static int tcp_v6_rcv(struct sk_buff *skb)
>  			refcounted = false;
>  			goto process;
>  		}
> +		if (unlikely(tcp_process_unclaimed)) {
> +			if (tcp_process_unclaimed(sk, skb))
> +				return 0;
> +		}
>  	}
>  		/* to ACK */
>  		/* fall through */