diff options
| -rw-r--r-- | Documentation/networking/ip-sysctl.txt | 7 | ||||
| -rw-r--r-- | include/linux/sysctl.h | 1 | ||||
| -rw-r--r-- | include/net/tcp.h | 1 | ||||
| -rw-r--r-- | net/ipv4/sysctl_net_ipv4.c | 9 | ||||
| -rw-r--r-- | net/ipv4/tcp_output.c | 23 |
5 files changed, 34 insertions, 7 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 651298ba019a8..f12007b80a466 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -355,6 +355,13 @@ somaxconn - INTEGER Defaults to 128. See also tcp_max_syn_backlog for additional tuning for TCP sockets. +tcp_workaround_signed_windows - BOOLEAN + If set, assume no receipt of a window scaling option means the + remote TCP is broken and treats the window as a signed quantity. + If unset, assume the remote TCP is not broken even if we do + not receive a window scaling option from them. + Default: 0 + IP Variables: ip_local_port_range - 2 INTEGERS diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index 8754568a75d79..76eaeff76f82d 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -402,6 +402,7 @@ enum NET_IPV4_IPFRAG_MAX_DIST=112, NET_TCP_MTU_PROBING=113, NET_TCP_BASE_MSS=114, + NET_IPV4_TCP_WORKAROUND_SIGNED_WINDOWS=115, }; enum { diff --git a/include/net/tcp.h b/include/net/tcp.h index 16879fa560de0..457e224de4688 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -224,6 +224,7 @@ extern int sysctl_tcp_tso_win_divisor; extern int sysctl_tcp_abc; extern int sysctl_tcp_mtu_probing; extern int sysctl_tcp_base_mss; +extern int sysctl_tcp_workaround_signed_windows; extern atomic_t tcp_memory_allocated; extern atomic_t tcp_sockets_allocated; diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index ebf2e0b363c4c..6b6c3adfcf009 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -680,7 +680,14 @@ ctl_table ipv4_table[] = { .mode = 0644, .proc_handler = &proc_dointvec, }, - + { + .ctl_name = NET_IPV4_TCP_WORKAROUND_SIGNED_WINDOWS, + .procname = "tcp_workaround_signed_windows", + .data = &sysctl_tcp_workaround_signed_windows, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = &proc_dointvec + }, { .ctl_name = 0 } }; diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 518e568b53f32..9d79546d384ef 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -45,6 +45,11 @@ /* People can turn this off for buggy TCP's found in printers etc. */ int sysctl_tcp_retrans_collapse = 1; +/* People can turn this on to work with those rare, broken TCPs that + * interpret the window field as a signed quantity. + */ +int sysctl_tcp_workaround_signed_windows = 0; + /* This limits the percentage of the congestion window which we * will allow a single TSO frame to consume. Building TSO frames * which are too large can cause TCP streams to be bursty. @@ -177,12 +182,18 @@ void tcp_select_initial_window(int __space, __u32 mss, space = (space / mss) * mss; /* NOTE: offering an initial window larger than 32767 - * will break some buggy TCP stacks. We try to be nice. - * If we are not window scaling, then this truncates - * our initial window offering to 32k. There should also - * be a sysctl option to stop being nice. + * will break some buggy TCP stacks. If the admin tells us + * it is likely we could be speaking with such a buggy stack + * we will truncate our initial window offering to 32K-1 + * unless the remote has sent us a window scaling option, + * which we interpret as a sign the remote TCP is not + * misinterpreting the window field as a signed quantity. */ - (*rcv_wnd) = min(space, MAX_TCP_WINDOW); + if (sysctl_tcp_workaround_signed_windows) + (*rcv_wnd) = min(space, MAX_TCP_WINDOW); + else + (*rcv_wnd) = space; + (*rcv_wscale) = 0; if (wscale_ok) { /* Set window scaling on max possible window @@ -241,7 +252,7 @@ static u16 tcp_select_window(struct sock *sk) /* Make sure we do not exceed the maximum possible * scaled window. */ - if (!tp->rx_opt.rcv_wscale) + if (!tp->rx_opt.rcv_wscale && 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)); |