[RFC PATCH v4 net-next 3/4] tcp: add in_flight to tcp_skb_cb

[Lawrence Brakmo]

Add in_flight (bytes in flight when packet was sent) field
to tx component of tcp_skb_cb and make it available to
congestion modules' pkts_acked() function through the
ack_sample function argument.

Signed-off-by: Lawrence Brakmo <bra...@fb.com>
---
 include/net/tcp.h     | 2 ++
 net/ipv4/tcp_input.c  | 5 ++++-
 net/ipv4/tcp_output.c | 4 +++-
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 7c510ed..f850404 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -757,6 +757,7 @@ struct tcp_skb_cb {
        union {
                struct {
                        /* There is space for up to 20 bytes */
+                       __u32 in_flight;/* Bytes in flight when packet sent */
                } tx;   /* only used for outgoing skbs */
                union {
                        struct inet_skb_parm    h4;
@@ -842,6 +843,7 @@ union tcp_cc_info;
 struct ack_sample {
        u32 pkts_acked;
        s32 rtt_us;
+       u32 in_flight;
 };
 
 struct tcp_congestion_ops {
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 423d3af..3ab4178 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3068,6 +3068,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int 
prior_fackets,
        long ca_rtt_us = -1L;
        struct sk_buff *skb;
        u32 pkts_acked = 0;
+       u32 last_in_flight = 0;
        bool rtt_update;
        int flag = 0;
 
@@ -3107,6 +3108,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int 
prior_fackets,
                        if (!first_ackt.v64)
                                first_ackt = last_ackt;
 
+                       last_in_flight = TCP_SKB_CB(skb)->tx.in_flight;
                        reord = min(pkts_acked, reord);
                        if (!after(scb->end_seq, tp->high_seq))
                                flag |= FLAG_ORIG_SACK_ACKED;
@@ -3196,7 +3198,8 @@ static int tcp_clean_rtx_queue(struct sock *sk, int 
prior_fackets,
        }
 
        if (icsk->icsk_ca_ops->pkts_acked) {
-               struct ack_sample sample = {pkts_acked, ca_rtt_us};
+               struct ack_sample sample = {pkts_acked, ca_rtt_us,
+                                           last_in_flight};
 
                icsk->icsk_ca_ops->pkts_acked(sk, &sample);
        }
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 7105784..e9deab5 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -920,9 +920,12 @@ static int tcp_transmit_skb(struct sock *sk, struct 
sk_buff *skb, int clone_it,
        int err;
 
        BUG_ON(!skb || !tcp_skb_pcount(skb));
+       tp = tcp_sk(sk);
 
        if (clone_it) {
                skb_mstamp_get(&skb->skb_mstamp);
+               TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
+                       - tp->snd_una;
 
                if (unlikely(skb_cloned(skb)))
                        skb = pskb_copy(skb, gfp_mask);
@@ -933,7 +936,6 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff 
*skb, int clone_it,
        }
 
        inet = inet_sk(sk);
-       tp = tcp_sk(sk);
        tcb = TCP_SKB_CB(skb);
        memset(&opts, 0, sizeof(opts));
 
-- 
1.8.1

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