netdev - [RFC PATCH net-next 14/15] bpf: Adds support for setting sndcwnd clamp

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Message-ID: <20170613180004.3008403-15-brakmo@fb.com>
Date:   Tue, 13 Jun 2017 11:00:03 -0700
From:   Lawrence Brakmo <brakmo@...com>
To:     netdev <netdev@...r.kernel.org>
CC:     Kernel Team <kernel-team@...com>, Blake Matheny <bmatheny@...com>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Ahern <dsa@...ulusnetworks.com>
Subject: [RFC PATCH net-next 14/15] bpf: Adds support for setting sndcwnd clamp

Adds a new bpf_setsockopt for TCP sockets, TCP_BPF_SNDCWND_CLAMP, which
sets the initial congestion window. It is useful to limit the sndcwnd
when the host are close to each other (small RTT).

Signed-off-by: Lawrence Brakmo <brakmo@...com>
---
 include/uapi/linux/bpf.h | 1 +
 net/core/filter.c        | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 9895672..6ca0aa2 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -735,5 +735,6 @@ enum {
 };
 
 #define TCP_BPF_IW		1001	/* Set TCP initial congestion window */
+#define TCP_BPF_SNDCWND_CLAMP	1002	/* Set sndcwnd_clamp */
 
 #endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/net/core/filter.c b/net/core/filter.c
index 7b4458d..bcd4495 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2715,6 +2715,13 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_socket_ops_kern *, bpf_socket,
 				else
 					tp->snd_cwnd = val;
 				break;
+			case TCP_BPF_SNDCWND_CLAMP:
+				if (val <= 0) {
+					ret = -EINVAL;
+				} else {
+					tp->snd_cwnd_clamp = val;
+					tp->snd_ssthresh = val;
+				}
 			default:
 				ret = -EINVAL;
 			}
-- 
2.9.3