dfc: TCP pure acks

Detects TCP pure acks so they can be put into the dedicated TX queues
even if they contains various options.

Change-Id: I6a9b714ccb58616ff49a150467d33a348d88ec64
Acked-by: Weiyi Chen <[email protected]>
Signed-off-by: Subash Abhinov Kasiviswanathan <[email protected]>

core/qmi_rmnet.c

@@ -19,6 +19,7 @@
 #include <linux/rtnetlink.h>
 #include <uapi/linux/rtnetlink.h>
 #include <net/pkt_sched.h>
+#include <net/tcp.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/ip.h>
@@ -873,16 +874,14 @@ void qmi_rmnet_burst_fc_check(struct net_device *dev,
 }
 EXPORT_SYMBOL(qmi_rmnet_burst_fc_check);
 
-static bool qmi_rmnet_is_tcp_ack(struct sk_buff *skb)
+static bool _qmi_rmnet_is_tcp_ack(struct sk_buff *skb)
 {
-	unsigned int len = skb->len;
-
 	switch (skb->protocol) {
 	/* TCPv4 ACKs */
 	case htons(ETH_P_IP):
 		if ((ip_hdr(skb)->protocol == IPPROTO_TCP) &&
-		    (ip_hdr(skb)->ihl == 5) &&
-		    (len == 40 || len == 52) &&
+		    (ntohs(ip_hdr(skb)->tot_len) - (ip_hdr(skb)->ihl << 2) ==
+		      tcp_hdr(skb)->doff << 2) &&
 		    ((tcp_flag_word(tcp_hdr(skb)) &
 		      cpu_to_be32(0x00FF0000)) == TCP_FLAG_ACK))
 			return true;
@@ -891,7 +890,8 @@ static bool qmi_rmnet_is_tcp_ack(struct sk_buff *skb)
 	/* TCPv6 ACKs */
 	case htons(ETH_P_IPV6):
 		if ((ipv6_hdr(skb)->nexthdr == IPPROTO_TCP) &&
-		    (len == 60 || len == 72) &&
+		    (ntohs(ipv6_hdr(skb)->payload_len) ==
+		      (tcp_hdr(skb)->doff) << 2) &&
 		    ((tcp_flag_word(tcp_hdr(skb)) &
 		      cpu_to_be32(0x00FF0000)) == TCP_FLAG_ACK))
 			return true;
@@ -901,6 +901,19 @@ static bool qmi_rmnet_is_tcp_ack(struct sk_buff *skb)
 	return false;
 }
 
+static inline bool qmi_rmnet_is_tcp_ack(struct sk_buff *skb)
+{
+	/* Locally generated TCP acks */
+	if (skb_is_tcp_pure_ack(skb))
+		return true;
+
+	/* Forwarded */
+	if (unlikely(_qmi_rmnet_is_tcp_ack(skb)))
+		return true;
+
+	return false;
+}
+
 static int qmi_rmnet_get_queue_sa(struct qos_info *qos, struct sk_buff *skb)
 {
 	struct rmnet_flow_map *itm;