tcp: allow effective reduction of TCP's rcv-buffer via setsockopt

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / net / ipv4 / tcp_output.c

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index de3bd84585881f99f8a23eb28fa9f380516d087c..01b94b8d9ec9459c9f463842f25c913e6667e6c1 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2429,6 +2429,12 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
                __u8 rcv_wscale;
                /* Set this up on the first call only */
                req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
+
+               /* limit the window selection if the user enforce a smaller rx buffer */
+               if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
+                   (req->window_clamp > tcp_full_space(sk) || req->window_clamp == 0))
+                       req->window_clamp = tcp_full_space(sk);
+
                /* tcp_full_space because it is guaranteed to be the first packet */
                tcp_select_initial_window(tcp_full_space(sk),
                        mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
@@ -2555,6 +2561,11 @@ static void tcp_connect_init(struct sock *sk)
 
        tcp_initialize_rcv_mss(sk);
 
+       /* limit the window selection if the user enforce a smaller rx buffer */
+       if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
+           (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
+               tp->window_clamp = tcp_full_space(sk);
+
        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,