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Revert "tcp: enforce receive buffer memory limits by allowing the tcp window to shrink"

Browse Source 
This reverts commit 0796c53424 which is
commit b650d953cd391595e536153ce30b4aab385643ac upstream.

It breaks the Android ABI so revert it for now, if it is needed in the
future, it can be brought back in an ABI-safe way.

Bug: 161946584
Change-Id: I6d4865da903caac56dbca2c7c0cfca14622760d4
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
This commit is contained in:
Greg Kroah-Hartman 2023-11-02 15:24:40 +00:00
parent 3858124ea0
commit b0e44b2726
5 changed files with 9 additions and 78 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
Documentation/networking/ip-sysctl.rst
View File

@ -967,21 +967,6 @@ tcp_tw_reuse - INTEGER
tcp_window_scaling - BOOLEAN
Enable window scaling as defined in RFC1323.
tcp_shrink_window - BOOLEAN
This changes how the TCP receive window is calculated.
RFC 7323, section 2.4, says there are instances when a retracted
window can be offered, and that TCP implementations MUST ensure
that they handle a shrinking window, as specified in RFC 1122.
- 0 - Disabled. The window is never shrunk.
- 1 - Enabled. The window is shrunk when necessary to remain within
the memory limit set by autotuning (sk_rcvbuf).
This only occurs if a non-zero receive window
scaling factor is also in effect.
Default: 0
tcp_wmem - vector of 3 INTEGERs: min, default, max
min: Amount of memory reserved for send buffers for TCP sockets.
Each TCP socket has rights to use it due to fact of its birth.

1
include/net/netns/ipv4.h
View File

@ -65,7 +65,6 @@ struct netns_ipv4 {
#endif
bool fib_has_custom_local_routes;
bool fib_offload_disabled;
u8 sysctl_tcp_shrink_window;
#ifdef CONFIG_IP_ROUTE_CLASSID
atomic_t fib_num_tclassid_users;
#endif

9
net/ipv4/sysctl_net_ipv4.c
View File

@ -1387,15 +1387,6 @@ static struct ctl_table ipv4_net_table[] = {
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_TWO,
},
{
.procname = "tcp_shrink_window",
.data = &init_net.ipv4.sysctl_tcp_shrink_window,
.maxlen = sizeof(u8),
.mode = 0644,
.proc_handler = proc_dou8vec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
},
{ }
};

2
net/ipv4/tcp_ipv4.c
View File

@ -3221,8 +3221,6 @@ static int __net_init tcp_sk_init(struct net *net)
else
net->ipv4.tcp_congestion_control = &tcp_reno;
net->ipv4.sysctl_tcp_shrink_window = 0;
return 0;
}

60
net/ipv4/tcp_output.c
View File

@ -259,8 +259,8 @@ 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
@ -269,14 +269,11 @@ static u16 tcp_select_window(struct sock *sk)
*
* Relax Will Robinson.
*/
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);
}
if (new_win == 0)
NET_INC_STATS(sock_net(sk),
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;
@ -284,7 +281,7 @@ static u16 tcp_select_window(struct sock *sk)
* scaled window.
*/
if (!tp->rx_opt.rcv_wscale &&
READ_ONCE(net->ipv4.sysctl_tcp_workaround_signed_windows))
READ_ONCE(sock_net(sk)->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));
@ -296,9 +293,10 @@ static u16 tcp_select_window(struct sock *sk)
if (new_win == 0) {
tp->pred_flags = 0;
if (old_win)
NET_INC_STATS(net, LINUX_MIB_TCPTOZEROWINDOWADV);
NET_INC_STATS(sock_net(sk),
LINUX_MIB_TCPTOZEROWINDOWADV);
} else if (old_win == 0) {
NET_INC_STATS(net, LINUX_MIB_TCPFROMZEROWINDOWADV);
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV);
}
return new_win;
@ -2951,7 +2949,6 @@ 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
@ -2973,15 +2970,6 @@ 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;
@ -3036,36 +3024,6 @@ 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,