1 files changed, 31 insertions, 19 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 990a58493235..fe3b4bdfd251 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -362,6 +362,17 @@ struct tcp_out_options {
 	__u32 tsval, tsecr;	/* need to include OPTION_TS */
 };
 
+/* Beware: Something in the Internet is very sensitive to the ordering of
+ * TCP options, we learned this through the hard way, so be careful here.
+ * Luckily we can at least blame others for their non-compliance but from
+ * inter-operatibility perspective it seems that we're somewhat stuck with
+ * the ordering which we have been using if we want to keep working with
+ * those broken things (not that it currently hurts anybody as there isn't
+ * particular reason why the ordering would need to be changed).
+ *
+ * At least SACK_PERM as the first option is known to lead to a disaster
+ * (but it may well be that other scenarios fail similarly).
+ */
 static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
 			      const struct tcp_out_options *opts,
 			      __u8 **md5_hash) {
@@ -376,6 +387,12 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
 		*md5_hash = NULL;
 	}
 
+	if (unlikely(opts->mss)) {
+		*ptr++ = htonl((TCPOPT_MSS << 24) |
+			       (TCPOLEN_MSS << 16) |
+			       opts->mss);
+	}
+
 	if (likely(OPTION_TS & opts->options)) {
 		if (unlikely(OPTION_SACK_ADVERTISE & opts->options)) {
 			*ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
@@ -392,12 +409,6 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
 		*ptr++ = htonl(opts->tsecr);
 	}
 
-	if (unlikely(opts->mss)) {
-		*ptr++ = htonl((TCPOPT_MSS << 24) |
-			       (TCPOLEN_MSS << 16) |
-			       opts->mss);
-	}
-
 	if (unlikely(OPTION_SACK_ADVERTISE & opts->options &&
 		     !(OPTION_TS & opts->options))) {
 		*ptr++ = htonl((TCPOPT_NOP << 24) |
@@ -432,7 +443,7 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
 
 		if (tp->rx_opt.dsack) {
 			tp->rx_opt.dsack = 0;
-			tp->rx_opt.eff_sacks--;
+			tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks;
 		}
 	}
 }
@@ -1017,10 +1028,6 @@ unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
 
 /* Compute the current effective MSS, taking SACKs and IP options,
  * and even PMTU discovery events into account.
- *
- * LARGESEND note: !tcp_urg_mode is overkill, only frames up to snd_up
- * cannot be large. However, taking into account rare use of URG, this
- * is not a big flaw.
  */
 unsigned int tcp_current_mss(struct sock *sk, int large_allowed)
 {
@@ -1035,7 +1042,7 @@ unsigned int tcp_current_mss(struct sock *sk, int large_allowed)
 
 	mss_now = tp->mss_cache;
 
-	if (large_allowed && sk_can_gso(sk) && !tcp_urg_mode(tp))
+	if (large_allowed && sk_can_gso(sk))
 		doing_tso = 1;
 
 	if (dst) {
@@ -1505,6 +1512,10 @@ static int tcp_mtu_probe(struct sock *sk)
  * send_head.  This happens as incoming acks open up the remote
  * window for us.
  *
+ * LARGESEND note: !tcp_urg_mode is overkill, only frames between
+ * snd_up-64k-mss .. snd_up cannot be large. However, taking into
+ * account rare use of URG, this is not a big flaw.
+ *
  * Returns 1, if no segments are in flight and we have queued segments, but
  * cannot send anything now because of SWS or another problem.
  */
@@ -1556,7 +1567,7 @@ static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
 		}
 
 		limit = mss_now;
-		if (tso_segs > 1)
+		if (tso_segs > 1 && !tcp_urg_mode(tp))
 			limit = tcp_mss_split_point(sk, skb, mss_now,
 						    cwnd_quota);
 
@@ -1605,6 +1616,7 @@ void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
  */
 void tcp_push_one(struct sock *sk, unsigned int mss_now)
 {
+	struct tcp_sock *tp = tcp_sk(sk);
 	struct sk_buff *skb = tcp_send_head(sk);
 	unsigned int tso_segs, cwnd_quota;
 
@@ -1619,7 +1631,7 @@ void tcp_push_one(struct sock *sk, unsigned int mss_now)
 		BUG_ON(!tso_segs);
 
 		limit = mss_now;
-		if (tso_segs > 1)
+		if (tso_segs > 1 && !tcp_urg_mode(tp))
 			limit = tcp_mss_split_point(sk, skb, mss_now,
 						    cwnd_quota);
 
@@ -2268,6 +2280,11 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
 	}
 
 	memset(&opts, 0, sizeof(opts));
+#ifdef CONFIG_SYN_COOKIES
+	if (unlikely(req->cookie_ts))
+		TCP_SKB_CB(skb)->when = cookie_init_timestamp(req);
+	else
+#endif
 	TCP_SKB_CB(skb)->when = tcp_time_stamp;
 	tcp_header_size = tcp_synack_options(sk, req, mss,
 					     skb, &opts, &md5) +
@@ -2293,11 +2310,6 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
 
 	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
 	th->window = htons(min(req->rcv_wnd, 65535U));
-#ifdef CONFIG_SYN_COOKIES
-	if (unlikely(req->cookie_ts))
-		TCP_SKB_CB(skb)->when = cookie_init_timestamp(req);
-	else
-#endif
 	tcp_options_write((__be32 *)(th + 1), tp, &opts, &md5_hash_location);
 	th->doff = (tcp_header_size >> 2);
 	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);