[PATCH bpf-next 1/2] bpf: Adds support for setting window clamp

[Prankur gupta]

Adds a new bpf_setsockopt for TCP sockets, TCP_BPF_WINDOW_CLAMP,
which sets the maximum receiver window size. It will be useful for
limiting receiver window based on RTT.

Signed-off-by: Prankur gupta <prank...@fb.com>
---
 net/core/filter.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/net/core/filter.c b/net/core/filter.c
index 2ca5eecebacf..8c52ffae7b0c 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4910,6 +4910,19 @@ static int _bpf_setsockopt(struct sock *sk, int level, 
int optname,
                                tp->notsent_lowat = val;
                                sk->sk_write_space(sk);
                                break;
+                       case TCP_WINDOW_CLAMP:
+                               if (!val) {
+                                       if (sk->sk_state != TCP_CLOSE) {
+                                               ret = -EINVAL;
+                                               break;
+                                       }
+                                       tp->window_clamp = 0;
+                               } else {
+                                       tp->window_clamp =
+                                               val < SOCK_MIN_RCVBUF / 2 ?
+                                               SOCK_MIN_RCVBUF / 2 : val;
+                               }
+                               break;
                        default:
                                ret = -EINVAL;
                        }
-- 
2.24.1