Allow to turn off TCP window scale opt per route

Add and use no window scale bit in the features field.

Note that this is not the same as setting a window scale of 0
as would happen with window limit on route.

Signed-off-by: Gilad Ben-Yossef <gilad@codefidence.com>
Sigend-off-by: Ori Finkelman <ori@comsleep.com>
Sigend-off-by: Yony Amit <yony@comsleep.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 2ab8c75..6784b34 100644 (file)
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -380,6 +380,7 @@ enum
 #define RTAX_FEATURE_NO_SACK   0x00000002
 #define RTAX_FEATURE_NO_TSTAMP 0x00000004
 #define RTAX_FEATURE_ALLFRAG   0x00000008
+#define RTAX_FEATURE_NO_WSCALE 0x00000010
 
 struct rta_session
 {

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 6097491..393c569 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3739,7 +3739,8 @@ void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx,
                                break;
                        case TCPOPT_WINDOW:
                                if (opsize == TCPOLEN_WINDOW && th->syn &&
-                                   !estab && sysctl_tcp_window_scaling) {
+                                   !estab && sysctl_tcp_window_scaling &&
+                                   !dst_feature(dst, RTAX_FEATURE_NO_WSCALE)) {
                                        __u8 snd_wscale = *(__u8 *)ptr;
                                        opt_rx->wscale_ok = 1;
                                        if (snd_wscale > 14) {

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 8819eba..616c686 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -496,7 +496,8 @@ static unsigned tcp_syn_options(struct sock *sk, struct sk_buff *skb,
                opts->tsecr = tp->rx_opt.ts_recent;
                size += TCPOLEN_TSTAMP_ALIGNED;
        }
-       if (likely(sysctl_tcp_window_scaling)) {
+       if (likely(sysctl_tcp_window_scaling &&
+                  !dst_feature(dst, RTAX_FEATURE_NO_WSCALE))) {
                opts->ws = tp->rx_opt.rcv_wscale;
                opts->options |= OPTION_WSCALE;
                size += TCPOLEN_WSCALE_ALIGNED;
@@ -2347,7 +2348,8 @@ static void tcp_connect_init(struct sock *sk)
                                  tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
                                  &tp->rcv_wnd,
                                  &tp->window_clamp,
-                                 sysctl_tcp_window_scaling,
+                                 (sysctl_tcp_window_scaling &&
+                                  !dst_feature(dst, RTAX_FEATURE_NO_WSCALE)),
                                  &rcv_wscale);
 
        tp->rx_opt.rcv_wscale = rcv_wscale;