[PATCH net-next v6 14/16] bpf: Adds support for setting sndcwnd clamp

[Lawrence Brakmo]

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 <bra...@fb.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 32755b5..a6a91e5 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -784,5 +784,6 @@ 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 794be0a..523b91d 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2746,6 +2746,13 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, 
bpf_sock,
                                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