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bpf: Support for setting initial receive window

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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: Lawrence Brakmo <brakmo@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Lawrence Brakmo 2017-06-30 20:02:44 -07:00 committed by David S. Miller
parent 61bc4d8daa
commit 13d3b1ebe2
4 changed files with 28 additions and 2 deletions
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10
include/net/tcp.h
View File

@ -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 */

4
include/uapi/linux/bpf.h
View File

@ -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__ */

9
net/ipv4/tcp_minisocks.c
View File

@ -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);

7
net/ipv4/tcp_output.c
View File

@ -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;