1 files changed, 15 insertions, 12 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index c53b7f35c51d..eeaac399420d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -671,6 +671,7 @@ static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
 {
         struct tcp_sock *tp = tcp_sk(sk);
         long m = mrtt; /* RTT */
+        u32 srtt = tp->srtt;
 
         /*      The following amusing code comes from Jacobson's
          *      article in SIGCOMM '88.  Note that rtt and mdev
@@ -688,11 +689,9 @@ static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
          * does not matter how to _calculate_ it. Seems, it was trap
          * that VJ failed to avoid. 8)
          */
-        if (m == 0)
-                m = 1;
-        if (tp->srtt != 0) {
-                m -= (tp->srtt >> 3);   /* m is now error in rtt est */
-                tp->srtt += m;          /* rtt = 7/8 rtt + 1/8 new */
+        if (srtt != 0) {
+                m -= (srtt >> 3);       /* m is now error in rtt est */
+                srtt += m;              /* rtt = 7/8 rtt + 1/8 new */
                 if (m < 0) {
                         m = -m;         /* m is now abs(error) */
                         m -= (tp->mdev >> 2);   /* similar update on mdev */
@@ -723,11 +722,12 @@ static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
                 }
         } else {
                 /* no previous measure. */
-                tp->srtt = m << 3;      /* take the measured time to be rtt */
+                srtt = m << 3;          /* take the measured time to be rtt */
                 tp->mdev = m << 1;      /* make sure rto = 3*rtt */
                 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
                 tp->rtt_seq = tp->snd_nxt;
         }
+        tp->srtt = max(1U, srtt);
 }
 
 /* Set the sk_pacing_rate to allow proper sizing of TSO packets.
@@ -746,8 +746,10 @@ static void tcp_update_pacing_rate(struct sock *sk)
 
         rate *= max(tp->snd_cwnd, tp->packets_out);
 
-        /* Correction for small srtt : minimum srtt being 8 (1 jiffy << 3),
-         * be conservative and assume srtt = 1 (125 us instead of 1.25 ms)
+        /* Correction for small srtt and scheduling constraints.
+         * For small rtt, consider noise is too high, and use
+         * the minimal value (srtt = 1 -> 125 us for HZ=1000)
+         *
          * We probably need usec resolution in the future.
          * Note: This also takes care of possible srtt=0 case,
          * when tcp_rtt_estimator() was not yet called.
@@ -766,7 +768,7 @@ static void tcp_update_pacing_rate(struct sock *sk)
 /* Calculate rto without backoff.  This is the second half of Van Jacobson's
  * routine referred to above.
  */
-void tcp_set_rto(struct sock *sk)
+static void tcp_set_rto(struct sock *sk)
 {
         const struct tcp_sock *tp = tcp_sk(sk);
         /* Old crap is replaced with new one. 8)
@@ -1943,8 +1945,9 @@ void tcp_enter_loss(struct sock *sk, int how)
                 if (skb == tcp_send_head(sk))
                         break;
 
-                if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
+                if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
                         tp->undo_marker = 0;
+
                 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
                         TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
@@ -3686,7 +3689,7 @@ const u8 *tcp_parse_md5sig_option(const struct tcphdr *th)
                 int opcode = *ptr++;
                 int opsize;
 
-                switch(opcode) {
+                switch (opcode) {
                 case TCPOPT_EOL:
                         return NULL;
                 case TCPOPT_NOP:
@@ -4046,7 +4049,7 @@ static void tcp_sack_remove(struct tcp_sock *tp)
                         WARN_ON(before(tp->rcv_nxt, sp->end_seq));
 
                         /* Zap this SACK, by moving forward any other SACKS. */
-                        for (i=this_sack+1; i < num_sacks; i++)
+                        for (i = this_sack+1; i < num_sacks; i++)
                                 tp->selective_acks[i-1] = tp->selective_acks[i];
                         num_sacks--;
                         continue;