[TCP]: Remove TCPCB_URG & TCPCB_AT_TAIL as unnecessary

The snd_up check should be enough. I suspect this has been
there to provide a minor optimization in clean_rtx_queue which
used to have a small if (!->sacked) block which could skip
snd_up check among the other work.
Signed-off-by: NIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -578,10 +578,6 @@ struct tcp_skb_cb {
 #define TCPCB_EVER_RETRANS	0x80	/* Ever retransmitted frame	*/
 #define TCPCB_RETRANS		(TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS)
 
-#define TCPCB_URG		0x20	/* Urgent pointer advanced here	*/
-
-#define TCPCB_AT_TAIL		(TCPCB_URG)
-
 	__u16		urg_ptr;	/* Valid w/URG flags is set.	*/
 	__u32		ack_seq;	/* Sequence number ACK'd	*/
 };

net/ipv4/tcp.c

@@ -497,7 +497,6 @@ static inline void tcp_mark_urg(struct tcp_sock *tp, int flags,
 	if (flags & MSG_OOB) {
 		tp->urg_mode = 1;
 		tp->snd_up = tp->write_seq;
-		TCP_SKB_CB(skb)->sacked |= TCPCB_URG;
 	}
 }
 

net/ipv4/tcp_input.c

@@ -2821,8 +2821,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
 		if (sacked & TCPCB_LOST)
 			tp->lost_out -= acked_pcount;
 
-		if (unlikely((sacked & TCPCB_URG) && tp->urg_mode &&
-			     !before(end_seq, tp->snd_up)))
+		if (unlikely(tp->urg_mode && !before(end_seq, tp->snd_up)))
 			tp->urg_mode = 0;
 
 		tp->packets_out -= acked_pcount;

net/ipv4/tcp_output.c

@@ -711,7 +711,6 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss
 	TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH);
 	TCP_SKB_CB(buff)->flags = flags;
 	TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
-	TCP_SKB_CB(skb)->sacked &= ~TCPCB_AT_TAIL;
 
 	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
 		/* Copy and checksum data tail into the new buffer. */
@@ -1726,7 +1725,7 @@ static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, int m
 		/* All done, get rid of second SKB and account for it so
 		 * packet counting does not break.
 		 */
-		TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked&(TCPCB_EVER_RETRANS|TCPCB_AT_TAIL);
+		TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
 		if (TCP_SKB_CB(next_skb)->sacked&TCPCB_SACKED_RETRANS)
 			tp->retrans_out -= tcp_skb_pcount(next_skb);
 		if (TCP_SKB_CB(next_skb)->sacked&TCPCB_LOST)
@@ -2475,7 +2474,7 @@ static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
 	skb_reserve(skb, MAX_TCP_HEADER);
 	skb->csum = 0;
 	TCP_SKB_CB(skb)->flags = TCPCB_FLAG_ACK;
-	TCP_SKB_CB(skb)->sacked = urgent;
+	TCP_SKB_CB(skb)->sacked = 0;
 	skb_shinfo(skb)->gso_segs = 1;
 	skb_shinfo(skb)->gso_size = 0;
 	skb_shinfo(skb)->gso_type = 0;
@@ -2527,7 +2526,7 @@ int tcp_write_wakeup(struct sock *sk)
 		} else {
 			if (tp->urg_mode &&
 			    between(tp->snd_up, tp->snd_una+1, tp->snd_una+0xFFFF))
-				tcp_xmit_probe_skb(sk, TCPCB_URG);
+				tcp_xmit_probe_skb(sk, 1);
 			return tcp_xmit_probe_skb(sk, 0);
 		}
 	}