diff options
Diffstat (limited to 'net/ipv4/tcp_output.c')
| -rw-r--r-- | net/ipv4/tcp_output.c | 60 |
1 files changed, 51 insertions, 9 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 660eac4bf2a7..2cb39b6dad02 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -260,8 +260,8 @@ static u16 tcp_select_window(struct sock *sk) u32 old_win = tp->rcv_wnd; u32 cur_win = tcp_receive_window(tp); u32 new_win = __tcp_select_window(sk); + struct net *net = sock_net(sk); - /* Never shrink the offered window */ if (new_win < cur_win) { /* Danger Will Robinson! * Don't update rcv_wup/rcv_wnd here or else @@ -270,11 +270,14 @@ static u16 tcp_select_window(struct sock *sk) * * Relax Will Robinson. */ - if (new_win == 0) - NET_INC_STATS(sock_net(sk), - LINUX_MIB_TCPWANTZEROWINDOWADV); - new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale); + if (!READ_ONCE(net->ipv4.sysctl_tcp_shrink_window) || !tp->rx_opt.rcv_wscale) { + /* Never shrink the offered window */ + if (new_win == 0) + NET_INC_STATS(net, LINUX_MIB_TCPWANTZEROWINDOWADV); + new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale); + } } + tp->rcv_wnd = new_win; tp->rcv_wup = tp->rcv_nxt; @@ -282,7 +285,7 @@ static u16 tcp_select_window(struct sock *sk) * scaled window. */ if (!tp->rx_opt.rcv_wscale && - READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)) + READ_ONCE(net->ipv4.sysctl_tcp_workaround_signed_windows)) new_win = min(new_win, MAX_TCP_WINDOW); else new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale)); @@ -294,10 +297,9 @@ static u16 tcp_select_window(struct sock *sk) if (new_win == 0) { tp->pred_flags = 0; if (old_win) - NET_INC_STATS(sock_net(sk), - LINUX_MIB_TCPTOZEROWINDOWADV); + NET_INC_STATS(net, LINUX_MIB_TCPTOZEROWINDOWADV); } else if (old_win == 0) { - NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV); + NET_INC_STATS(net, LINUX_MIB_TCPFROMZEROWINDOWADV); } return new_win; @@ -2987,6 +2989,7 @@ u32 __tcp_select_window(struct sock *sk) { struct inet_connection_sock *icsk = inet_csk(sk); struct tcp_sock *tp = tcp_sk(sk); + struct net *net = sock_net(sk); /* MSS for the peer's data. Previous versions used mss_clamp * here. I don't know if the value based on our guesses * of peer's MSS is better for the performance. It's more correct @@ -3008,6 +3011,15 @@ u32 __tcp_select_window(struct sock *sk) if (mss <= 0) return 0; } + + /* Only allow window shrink if the sysctl is enabled and we have + * a non-zero scaling factor in effect. + */ + if (READ_ONCE(net->ipv4.sysctl_tcp_shrink_window) && tp->rx_opt.rcv_wscale) + goto shrink_window_allowed; + + /* do not allow window to shrink */ + if (free_space < (full_space >> 1)) { icsk->icsk_ack.quick = 0; @@ -3062,6 +3074,36 @@ u32 __tcp_select_window(struct sock *sk) } return window; + +shrink_window_allowed: + /* new window should always be an exact multiple of scaling factor */ + free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale); + + if (free_space < (full_space >> 1)) { + icsk->icsk_ack.quick = 0; + + if (tcp_under_memory_pressure(sk)) + tcp_adjust_rcv_ssthresh(sk); + + /* if free space is too low, return a zero window */ + if (free_space < (allowed_space >> 4) || free_space < mss || + free_space < (1 << tp->rx_opt.rcv_wscale)) + return 0; + } + + if (free_space > tp->rcv_ssthresh) { + free_space = tp->rcv_ssthresh; + /* new window should always be an exact multiple of scaling factor + * + * For this case, we ALIGN "up" (increase free_space) because + * we know free_space is not zero here, it has been reduced from + * the memory-based limit, and rcv_ssthresh is not a hard limit + * (unlike sk_rcvbuf). + */ + free_space = ALIGN(free_space, (1 << tp->rx_opt.rcv_wscale)); + } + + return free_space; } void tcp_skb_collapse_tstamp(struct sk_buff *skb, |