tcp: remove TCP_SKB_CB(skb)->when

After commit 740b0f1841f6 ("tcp: switch rtt estimations to usec resolution"),
we no longer need to maintain timestamps in two different fields.

TCP_SKB_CB(skb)->when can be removed, as same information sits in skb_mstamp.stamp_jiffies

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 24 insertions, 30 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9c8b9f1dcf69..f97003ad0af5 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2967,7 +2967,8 @@ void tcp_rearm_rto(struct sock *sk)
                 if (icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
                     icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
                         struct sk_buff *skb = tcp_write_queue_head(sk);
-                        const u32 rto_time_stamp = TCP_SKB_CB(skb)->when + rto;
+                        const u32 rto_time_stamp =
+                                tcp_skb_timestamp(skb) + rto;
                         s32 delta = (s32)(rto_time_stamp - tcp_time_stamp);
                         /* delta may not be positive if the socket is locked
                          * when the retrans timer fires and is rescheduled.
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 02e6cd29ebf1..3f9bc3f0bba0 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -437,8 +437,9 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
                 skb = tcp_write_queue_head(sk);
                 BUG_ON(!skb);
 
-                remaining = icsk->icsk_rto - min(icsk->icsk_rto,
-                                tcp_time_stamp - TCP_SKB_CB(skb)->when);
+                remaining = icsk->icsk_rto -
+                            min(icsk->icsk_rto,
+                                tcp_time_stamp - tcp_skb_timestamp(skb));
 
                 if (remaining) {
                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 5a7c41fbc6d3..3b22dcb7bb5c 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -550,7 +550,7 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
 
         if (likely(sysctl_tcp_timestamps && *md5 == NULL)) {
                 opts->options |= OPTION_TS;
-                opts->tsval = TCP_SKB_CB(skb)->when + tp->tsoffset;
+                opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
                 opts->tsecr = tp->rx_opt.ts_recent;
                 remaining -= TCPOLEN_TSTAMP_ALIGNED;
         }
@@ -618,7 +618,7 @@ static unsigned int tcp_synack_options(struct sock *sk,
         }
         if (likely(ireq->tstamp_ok)) {
                 opts->options |= OPTION_TS;
-                opts->tsval = TCP_SKB_CB(skb)->when;
+                opts->tsval = tcp_skb_timestamp(skb);
                 opts->tsecr = req->ts_recent;
                 remaining -= TCPOLEN_TSTAMP_ALIGNED;
         }
@@ -647,7 +647,6 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
                                         struct tcp_out_options *opts,
                                         struct tcp_md5sig_key **md5)
 {
-        struct tcp_skb_cb *tcb = skb ? TCP_SKB_CB(skb) : NULL;
         struct tcp_sock *tp = tcp_sk(sk);
         unsigned int size = 0;
         unsigned int eff_sacks;
@@ -666,7 +665,7 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
 
         if (likely(tp->rx_opt.tstamp_ok)) {
                 opts->options |= OPTION_TS;
-                opts->tsval = tcb ? tcb->when + tp->tsoffset : 0;
+                opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
                 opts->tsecr = tp->rx_opt.ts_recent;
                 size += TCPOLEN_TSTAMP_ALIGNED;
         }
@@ -886,8 +885,6 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
                         skb = skb_clone(skb, gfp_mask);
                 if (unlikely(!skb))
                         return -ENOBUFS;
-                /* Our usage of tstamp should remain private */
-                skb->tstamp.tv64 = 0;
         }
 
         inet = inet_sk(sk);
@@ -975,7 +972,10 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
                 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
                               tcp_skb_pcount(skb));
 
+        /* Our usage of tstamp should remain private */
+        skb->tstamp.tv64 = 0;
         err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
+
         if (likely(err <= 0))
                 return err;
 
@@ -1149,7 +1149,6 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
         /* Looks stupid, but our code really uses when of
          * skbs, which it never sent before. --ANK
          */
-        TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when;
         buff->tstamp = skb->tstamp;
         tcp_fragment_tstamp(skb, buff);
 
@@ -1874,8 +1873,8 @@ static int tcp_mtu_probe(struct sock *sk)
         tcp_init_tso_segs(sk, nskb, nskb->len);
 
         /* We're ready to send.  If this fails, the probe will
-         * be resegmented into mss-sized pieces by tcp_write_xmit(). */
-        TCP_SKB_CB(nskb)->when = tcp_time_stamp;
+         * be resegmented into mss-sized pieces by tcp_write_xmit().
+         */
         if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
                 /* Decrement cwnd here because we are sending
                  * effectively two packets. */
@@ -1935,8 +1934,8 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
                 BUG_ON(!tso_segs);
 
                 if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
-                        /* "when" is used as a start point for the retransmit timer */
-                        TCP_SKB_CB(skb)->when = tcp_time_stamp;
+                        /* "skb_mstamp" is used as a start point for the retransmit timer */
+                        skb_mstamp_get(&skb->skb_mstamp);
                         goto repair; /* Skip network transmission */
                 }
 
@@ -2000,8 +1999,6 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
                     unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
                         break;
 
-                TCP_SKB_CB(skb)->when = tcp_time_stamp;
-
                 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
                         break;
 
@@ -2499,7 +2496,6 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
         /* Make a copy, if the first transmission SKB clone we made
          * is still in somebody's hands, else make a clone.
          */
-        TCP_SKB_CB(skb)->when = tcp_time_stamp;
 
         /* make sure skb->data is aligned on arches that require it
          * and check if ack-trimming & collapsing extended the headroom
@@ -2544,7 +2540,7 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
 
                 /* Save stamp of the first retransmit. */
                 if (!tp->retrans_stamp)
-                        tp->retrans_stamp = TCP_SKB_CB(skb)->when;
+                        tp->retrans_stamp = tcp_skb_timestamp(skb);
 
                 /* snd_nxt is stored to detect loss of retransmitted segment,
                  * see tcp_input.c tcp_sacktag_write_queue().
@@ -2752,7 +2748,6 @@ void tcp_send_active_reset(struct sock *sk, gfp_t priority)
         tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
                              TCPHDR_ACK | TCPHDR_RST);
         /* Send it off. */
-        TCP_SKB_CB(skb)->when = tcp_time_stamp;
         if (tcp_transmit_skb(sk, skb, 0, priority))
                 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
 
@@ -2791,7 +2786,6 @@ int tcp_send_synack(struct sock *sk)
                 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
                 TCP_ECN_send_synack(tcp_sk(sk), skb);
         }
-        TCP_SKB_CB(skb)->when = tcp_time_stamp;
         return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
 }
 
@@ -2835,10 +2829,10 @@ 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);
+                skb->skb_mstamp.stamp_jiffies = cookie_init_timestamp(req);
         else
 #endif
-        TCP_SKB_CB(skb)->when = tcp_time_stamp;
+        skb_mstamp_get(&skb->skb_mstamp);
         tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, &md5,
                                              foc) + sizeof(*th);
 
@@ -3086,7 +3080,7 @@ int tcp_connect(struct sock *sk)
         skb_reserve(buff, MAX_TCP_HEADER);
 
         tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
-        tp->retrans_stamp = TCP_SKB_CB(buff)->when = tcp_time_stamp;
+        tp->retrans_stamp = tcp_time_stamp;
         tcp_connect_queue_skb(sk, buff);
         TCP_ECN_send_syn(sk, buff);
 
@@ -3194,7 +3188,7 @@ void tcp_send_ack(struct sock *sk)
         tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
 
         /* Send it off, this clears delayed acks for us. */
-        TCP_SKB_CB(buff)->when = tcp_time_stamp;
+        skb_mstamp_get(&buff->skb_mstamp);
         tcp_transmit_skb(sk, buff, 0, sk_gfp_atomic(sk, GFP_ATOMIC));
 }
 
@@ -3226,7 +3220,7 @@ static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
          * send it.
          */
         tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
-        TCP_SKB_CB(skb)->when = tcp_time_stamp;
+        skb_mstamp_get(&skb->skb_mstamp);
         return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC);
 }
 
@@ -3270,7 +3264,6 @@ int tcp_write_wakeup(struct sock *sk)
                         tcp_set_skb_tso_segs(sk, skb, mss);
 
                 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
-                TCP_SKB_CB(skb)->when = tcp_time_stamp;
                 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
                 if (!err)
                         tcp_event_new_data_sent(sk, skb);
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index df90cd1ce37f..a339e7ba05a4 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -135,10 +135,9 @@ static bool retransmits_timed_out(struct sock *sk,
         if (!inet_csk(sk)->icsk_retransmits)
                 return false;
 
-        if (unlikely(!tcp_sk(sk)->retrans_stamp))
-                start_ts = TCP_SKB_CB(tcp_write_queue_head(sk))->when;
-        else
-                start_ts = tcp_sk(sk)->retrans_stamp;
+        start_ts = tcp_sk(sk)->retrans_stamp;
+        if (unlikely(!start_ts))
+                start_ts = tcp_skb_timestamp(tcp_write_queue_head(sk));
 
         if (likely(timeout == 0)) {
                 linear_backoff_thresh = ilog2(TCP_RTO_MAX/rto_base);