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Commit 13d3b1eb authored by Lawrence Brakmo's avatar Lawrence Brakmo Committed by David S. Miller
Browse files

bpf: Support for setting initial receive window 



This patch adds suppport for setting the initial advertized window from
within a BPF_SOCK_OPS program. This can be used to support larger
initial cwnd values in environments where it is known to be safe.

Signed-off-by: default avatarLawrence Brakmo <brakmo@fb.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 61bc4d8d

include/net/tcp.h

+10 −0
Original line number Diff line number Diff line
@@ -2068,4 +2068,14 @@ static inline u32 tcp_timeout_init(struct sock *sk) 
	return timeout;

}



static inline u32 tcp_rwnd_init_bpf(struct sock *sk)

{

	int rwnd;



	rwnd = tcp_call_bpf(sk, BPF_SOCK_OPS_RWND_INIT);



	if (rwnd < 0)

		rwnd = 0;

	return rwnd;

}

#endif	/* _TCP_H */

include/uapi/linux/bpf.h

+4 −0
Original line number Diff line number Diff line
@@ -751,6 +751,10 @@ enum { 
	BPF_SOCK_OPS_TIMEOUT_INIT,	/* Should return SYN-RTO value to use or

					 * -1 if default value should be used

					 */

	BPF_SOCK_OPS_RWND_INIT,		/* Should return initial advertized

					 * window (in packets) or -1 if default

					 * value should be used

					 */

};



#endif /* _UAPI__LINUX_BPF_H__ */

net/ipv4/tcp_minisocks.c

+8 −1
Original line number Diff line number Diff line
@@ -351,6 +351,7 @@ void tcp_openreq_init_rwin(struct request_sock *req, 
	int full_space = tcp_full_space(sk_listener);

	u32 window_clamp;

	__u8 rcv_wscale;

	u32 rcv_wnd;

	int mss;



	mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
@@ -363,6 +364,12 @@ void tcp_openreq_init_rwin(struct request_sock *req, 
	    (req->rsk_window_clamp > full_space || req->rsk_window_clamp == 0))

		req->rsk_window_clamp = full_space;



	rcv_wnd = tcp_rwnd_init_bpf((struct sock *)req);

	if (rcv_wnd == 0)

		rcv_wnd = dst_metric(dst, RTAX_INITRWND);

	else if (full_space < rcv_wnd * mss)

		full_space = rcv_wnd * mss;



	/* tcp_full_space because it is guaranteed to be the first packet */

	tcp_select_initial_window(full_space,

		mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
@@ -370,7 +377,7 @@ void tcp_openreq_init_rwin(struct request_sock *req, 
		&req->rsk_window_clamp,

		ireq->wscale_ok,

		&rcv_wscale,

		dst_metric(dst, RTAX_INITRWND));

		rcv_wnd);

	ireq->rcv_wscale = rcv_wscale;

}

EXPORT_SYMBOL(tcp_openreq_init_rwin);

net/ipv4/tcp_output.c

+6 −1
Original line number Diff line number Diff line
@@ -3266,6 +3266,7 @@ static void tcp_connect_init(struct sock *sk) 
	const struct dst_entry *dst = __sk_dst_get(sk);

	struct tcp_sock *tp = tcp_sk(sk);

	__u8 rcv_wscale;

	u32 rcv_wnd;



	/* We'll fix this up when we get a response from the other end.

	 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
@@ -3299,13 +3300,17 @@ static void tcp_connect_init(struct sock *sk) 
	    (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))

		tp->window_clamp = tcp_full_space(sk);



	rcv_wnd = tcp_rwnd_init_bpf(sk);

	if (rcv_wnd == 0)

		rcv_wnd = dst_metric(dst, RTAX_INITRWND);



	tcp_select_initial_window(tcp_full_space(sk),

				  tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),

				  &tp->rcv_wnd,

				  &tp->window_clamp,

				  sock_net(sk)->ipv4.sysctl_tcp_window_scaling,

				  &rcv_wscale,

				  dst_metric(dst, RTAX_INITRWND));

				  rcv_wnd);



	tp->rx_opt.rcv_wscale = rcv_wscale;

	tp->rcv_ssthresh = tp->rcv_wnd;