1 files changed, 35 insertions, 24 deletions

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 02bef6aa8b30..650cace2180d 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -18,8 +18,8 @@
 #include <net/tcp.h>
 #include <net/route.h>
 
-/* Timestamps: lowest 9 bits store TCP options */
-#define TSBITS 9
+/* Timestamps: lowest bits store TCP options */
+#define TSBITS 6
 #define TSMASK (((__u32)1 << TSBITS) - 1)
 
 extern int sysctl_tcp_syncookies;
@@ -58,7 +58,7 @@ static u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport,
 
 /*
  * when syncookies are in effect and tcp timestamps are enabled we encode
- * tcp options in the lowest 9 bits of the timestamp value that will be
+ * tcp options in the lower bits of the timestamp value that will be
  * sent in the syn-ack.
  * Since subsequent timestamps use the normal tcp_time_stamp value, we
  * must make sure that the resulting initial timestamp is <= tcp_time_stamp.
@@ -70,11 +70,10 @@ __u32 cookie_init_timestamp(struct request_sock *req)
 	u32 options = 0;
 
 	ireq = inet_rsk(req);
-	if (ireq->wscale_ok) {
-		options = ireq->snd_wscale;
-		options |= ireq->rcv_wscale << 4;
-	}
-	options |= ireq->sack_ok << 8;
+
+	options = ireq->wscale_ok ? ireq->snd_wscale : 0xf;
+	options |= ireq->sack_ok << 4;
+	options |= ireq->ecn_ok << 5;
 
 	ts = ts_now & ~TSMASK;
 	ts |= options;
@@ -227,26 +226,38 @@ static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb,
  * additional tcp options in the timestamp.
  * This extracts these options from the timestamp echo.
  *
- * The lowest 4 bits are for snd_wscale
- * The next 4 lsb are for rcv_wscale
- * The next lsb is for sack_ok
+ * The lowest 4 bits store snd_wscale.
+ * next 2 bits indicate SACK and ECN support.
+ *
+ * return false if we decode an option that should not be.
  */
-void cookie_check_timestamp(struct tcp_options_received *tcp_opt)
+bool cookie_check_timestamp(struct tcp_options_received *tcp_opt, bool *ecn_ok)
 {
-	/* echoed timestamp, 9 lowest bits contain options */
+	/* echoed timestamp, lowest bits contain options */
 	u32 options = tcp_opt->rcv_tsecr & TSMASK;
 
-	tcp_opt->snd_wscale = options & 0xf;
-	options >>= 4;
-	tcp_opt->rcv_wscale = options & 0xf;
+	if (!tcp_opt->saw_tstamp)  {
+		tcp_clear_options(tcp_opt);
+		return true;
+	}
+
+	if (!sysctl_tcp_timestamps)
+		return false;
 
 	tcp_opt->sack_ok = (options >> 4) & 0x1;
+	*ecn_ok = (options >> 5) & 1;
+	if (*ecn_ok && !sysctl_tcp_ecn)
+		return false;
+
+	if (tcp_opt->sack_ok && !sysctl_tcp_sack)
+		return false;
 
-	if (tcp_opt->sack_ok)
-		tcp_sack_reset(tcp_opt);
+	if ((options & 0xf) == 0xf)
+		return true; /* no window scaling */
 
-	if (tcp_opt->snd_wscale || tcp_opt->rcv_wscale)
-		tcp_opt->wscale_ok = 1;
+	tcp_opt->wscale_ok = 1;
+	tcp_opt->snd_wscale = options & 0xf;
+	return sysctl_tcp_window_scaling != 0;
 }
 EXPORT_SYMBOL(cookie_check_timestamp);
 
@@ -265,6 +276,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
 	int mss;
 	struct rtable *rt;
 	__u8 rcv_wscale;
+	bool ecn_ok;
 
 	if (!sysctl_tcp_syncookies || !th->ack || th->rst)
 		goto out;
@@ -281,8 +293,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
 	memset(&tcp_opt, 0, sizeof(tcp_opt));
 	tcp_parse_options(skb, &tcp_opt, &hash_location, 0);
 
-	if (tcp_opt.saw_tstamp)
-		cookie_check_timestamp(&tcp_opt);
+	if (!cookie_check_timestamp(&tcp_opt, &ecn_ok))
+		goto out;
 
 	ret = NULL;
 	req = inet_reqsk_alloc(&tcp_request_sock_ops); /* for safety */
@@ -298,9 +310,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
 	ireq->rmt_port		= th->source;
 	ireq->loc_addr		= ip_hdr(skb)->daddr;
 	ireq->rmt_addr		= ip_hdr(skb)->saddr;
-	ireq->ecn_ok		= 0;
+	ireq->ecn_ok		= ecn_ok;
 	ireq->snd_wscale	= tcp_opt.snd_wscale;
-	ireq->rcv_wscale	= tcp_opt.rcv_wscale;
 	ireq->sack_ok		= tcp_opt.sack_ok;
 	ireq->wscale_ok		= tcp_opt.wscale_ok;
 	ireq->tstamp_ok		= tcp_opt.saw_tstamp;